Friday, September 30, 2011



A Beverage antenna is probably one of the simplest and cheapest antennas one can build but it does have one-draw back in that you need a lot of space or a very long thin garden. Ideally the wire-needs to be at least half a wavelength long and for MW that means > 100 metres (ideally you need 200-500 metres). It is undoubtedly the best antenna around for use (for reception only) at frequencies below approx 5MHz, so a scaled down version will still work fine on the 60m and 90m tropical bands if you don't have enough space for MW.

Its nice to live in the countryside where there is more space but even in town the Beverage need not be ruled out if you apply your imagination. For example, if there is a long fence at the bottom of your garden that separates two rows of back-to-back houses and gardens you can run an unobtrusive wire along it. Obviously you have little say in which direction the aerial points but if you are lucky it may point somewhere interesting. Your neighbours need not know about the wire since it can be almost invisible!

Basically the Beverage is a travelling wave antenna made of a length of wire a small height (relative to the wavelength of interest) above earth. It can be terminated for unidirectional reception or left unterminated for bi-directional reception. The schematic of a terminated example is shown in Fig 1:

The components are all pretty basic, cheap, non-critical and easy to obtain as discussed below:

Wire and supports: Insulated 7 strand tinned copper wire (or similar) is fine and cheap with a 500metre roll of 7/0.2mm wire available from STC Electronic supplies for under ?12. Anything heavier is likely to sag, and lighter may break in the wind. The wire is best supported on bamboo gardening canes with a slit or split, made with a penknife or small hacksaw, in the top end to trap the wire. Canes can be between 1.5m and 2m long and one is needed every 8-10 metres along the wire. Take care to place the canes in a straight line as you insert them into the ground. Canes don't last for ever as they can rot in the ground (it might be worthwhile dipping the canes in varnish to protect one end) but they cost between 10-20 pence and are quite flexible to the wind. Alternative supports can be plastic support stakes used by farmers for temporary electric fences or anything non-metal that comes to hand. Indeed no support is needed at all if the wire can be unobtrusively slung along a hedgerow or run along a fence. Beverages will even work with an insulated wire just laid directly on the ground BOG - Beverage On the Ground

Terminating Resistor: This resistor can be a fixed value component of around 500-600 Ohms for simplicity. Or you can use a variable resistor which is carefully adjusted to an optimum value that minimises unwanted reception of signals off the back of the aerial. In both cases the resistor must be kept dry in its outdoor environment which is not always an easy task. The task of optimising the termination can be a bit time consuming and for a basic antenna needs two people linked by VHF radio or CB. One person adjusts the resistor whilst the other monitors the receiver. This activity needs to be done on stable ground wave signals since ionospheric fading makes the job nearly impossible. The best time of day is around solar noon but during short winter days late morning is good for westerly pointing aerials and early afternoon is good for easterly pointing antennas.

Earths: Good earths are essential at each end of the long wire and ideally the last bamboo stake, onto which the terminating resistor has been taped, has to be within a metre of the earth. This is to minimise the length of wire that is not part of the actual longwire. Earths can take many forms but I favour 22 mm diameter copper pipe in metre lengths pushed or hammered into wet soil (e.g. floor of a ditch or a stream). To join wires to a pipe like this is difficult. It is best to use very heavy duty copper wire (even thick braiding) clamped very tightly to the cleaned copper pipe using two Jubilee clips (i.e. metal hose clamps). Instead of Jubilee clips you can use purpose designed clamps for domestic mains electrical earths. This heavy duty wire forms the short link from earth to terminating resistor.

Transformer: This is not essential since it is quite possible to connect the longwire straight to your receiver, especially if it has a medium impedance input socket and the aerial wire makes a fairly straight run into the house to your radio. For the first few DX-peditions to Sheigra the antenna wire was connected directly to the receiver and often to several receivers in parallel. However, the transformer is useful if your radio has a low impedance input (often marked Low-Z, 75 ohm or 50 ohm) to avoid loss of signal strength, and it serves an additional purpose in that it helps discharge static build up on the longwire which could damage a sensitive receiver. Many designs for transformers have been published but my tried and tested low loss design uses a Seimens ferrite ring core (Type B6429QK618X830) obtained from Electrovalue (Phone 0784-433603 for catalogue and telephone credit card orders; Electrovalue stock number 2901448K @59pence) wound with the same type of multi-strand wire was used for my aerial. The primary should have 11 turns and, with a separate piece of wire, add four turns for the secondary or receiver side. These turns ratios are suitable for a 75 Ohm receiver input impedance, but the primary can be increased to 14 turns if a 50 Ohm receiver input is in use.

The transformer allows the addition of a length of coaxial cable to the receiver which does not (should not!) form part of the receiving antenna. This allows the longwire to keep a straight line and avoids kinks or bends at the house end as you try to bring the wire into the listening post. Ideally the coax run should be short ( <20m) to minimise extraneous pickup on it that could disturb the directional pattern of the main Beverage. In the earlier example of an urban Beverage, the use of a dog-leg to reach your listening post is undesirable, so if you build an antenna along a fence it is best to put a transformer at the end of the wire on the fence and then run coax cable hack to the house. (Fig 3)

Technical Tip 1:-How to measure earth resistance
Once you've erected your Beverage antenna there is one measurement that is worth doing on fairly regular basis. Since the antenna is outdoors and exposed to the elements it could suffer damage to the wire (e.g. a break due to fatigue damage) or damage to the termination resistor and its connections (e.g. corrosion) or damage to the earth (e.g. corrosion and high earth resistance). A simple continuity test using a pocket multi meter will quickly give a GO/NO-GO indication of antenna health and save you having to walk the line for a visual inspection. Apply your multirneter, set to measure resistance or continuity, to the receive end of the long wire as shown in Fig 4. If you cannot detect continuity, or resistance indicates an open circuit, you have a problem that needs investigation. Actually measuring the DC resistance of the antenna this way is usually difficult and you most likely will find that you can get two different readings according to tile polarity of the connections to your meter (just swap the two meter leads to see this effect). This is caused by corrosion of the earth stakes in the ground acting like a low power voltaic cell or battery. However you can exploit this phenomenon to more accurately measure your earth resistance. Still applying the meter in the same way, switch it to read voltage on a 0-2V scale; this is measuring the potential of the "battery". Record this figure and lets refer to it as "V". Now switch your meter to read current on a 0-2mA scale and record this short-circuit current figure "I".

Now Ohm's law tells us that the ratio of V/I gives us the total resistance of the antenna system "R". However "R" is the sum of the terminating resistor, the two earth resistance and the resistance of the wire itself. The latter is generally negligible unless the wire has been seriously damaged but not yet broken. Since we know the terminating resistance, subtracting this figure from "R" leaves us with the total earth resistance; the lower this is the better. Regular measurement of the earth resistance will indicate if a problem develops with the antenna.

As a practical example let's look at the figures from my Beverage; I recorded "V" as 0.56V and "I" as 0.85mA. Thus V/1 =659 Ohms and since I knew that my terminating resistor was exactly 500 Ohms and the wire resistance was about 30 Ohms this gives a total resistance of 129 Ohms for two earths (ie about 65 Ohms per earth), which is not a bad figure for my simple arrangement of copper pipes.

Another reason for knowing the earth resistance is that it allows you to monitor seasonal change as the ground dries out in summer. Since the termination resistor is usually adjusted to minimise reception from the "back" or unwanted direction of the antenna, a significant change in earth resistance could influence its behaviour and could make readjustment of the termination resistor necessary.

Technical TIp 2: - How to avoid signal pick up on coax lead-in.
The length of the coax cable from the transformer to the receiver should be kept short to avoid it acting as an antenna in its own right. Sometimes there is no choice but to use a considerable length of coax and even good coax cable will pick up signals primarily on the outside of the screen. This can still be a problem since these signals may degrade the directional pattern of the main Beverage.

The way to eliminate pickup on the coax is to effectively break its length up with "braid breakers" that will attenuate any signal currents on the outside of the screen of coax but leave the desired signals inside the coax unaffected. There are two practical ways of building a braid breaker. One uses a ferrite tube designed specially designed for this purpose. This tube is slid over the coax cable and one placed every 5 metres or so and then taped in place. If you do locate such a source of tubes take care with them as they are both rare and fragile! Alternatively the coax cable can be wound several times through large a high-permeability ferrite ring of the sort recommended for interference suppression. Examples include Amidon or Micrornetals toroids with a -26 or -40 suffix (eg T68-40).

There are several more sophisticated versions of Beverages but the basic version is so simple and cheap to build and tolerant of design variations that I'd recommend one to anyone with the available space. Browse through any DXpedition report to see what is heard using Beverage antennas (and a good location of course).

Beverage Antenna Construction

Beverage Antenna Construction

such a simple, inexpensive antenna. Over the years I've continued to use, compare, and refine my Beverage antennas. Despite having very large vertical arrays, arrays of Beverages remain my primary DX receiving antennas. There isn't any other receiving antenna that is as simple, as easy to construct and maintain, and as foolproof as a Beverage! The only disadvantage is the physical length required, and the physical headaches associated with having a very long antenna.

I constantly refine my antenna systems by comparing systems against each other for extended periods of time, usually more than a year. My station has a convenient switching system allowing instant comparison of antenna systems. When an antenna system is almost never used, I abandon that system and try something else. Even though I use engineering tools (books and models), I always compare and measure actual working systems.  I presently have over thirty Beverages in three different clusters of arrays, the end result filtered through years of measurements and A-B testing of systems.

This control panel selects antennas for each receiver in the K3. The far left switch is for the main receiver which goes to the left ear, and the next switch left goes to the sub receiver which is the right ear.

The K3 is the only standard transceiver system offering true diversity. Other receivers advertise it, but the claims are false!

To have true stereo diversity each channel must have an identical phase-locked receiver. The filters and everything else must be identical, and all adjustments must track.

The small push button panel changes directions.

A great much has been written about Beverages. Unfortunately much or most information is a repeat of previously published information (and misinformation), from verbal discussions, or from other articles or handbooks! It is time to set aside some of the myths that have been handed down and repeated so much they have become "fact".

Types of Beverage Wire

The most commonly used wire types are single conductor hook-up or electrical wire, electric fence wire, and special antenna wire such as copperweld. The only significant and easily noticed difference between these commonly used wires is in physical properties, such as ease of soldering, strength, and life.

Insulated Wire  

We will occasionally hear or read claims that insulation prevents charged droplets of water from making an antenna "noisy". I've never been able to verify that rumor either in A-B tests of actual antennas or through planned experiments. Other reports, many from reliable sources, also seem to discredit this rumor.

One of my experiments was to charge a stream of water (against earth) with an extremely high voltage supply, and spray the water on a wire. Other than corona noise from sharp points, the type of wire (bare or insulated) made no difference at all in "noise". The charged water droplets were not discharging into the wire like hundreds of random charged capacitors, they generated no detectable noise at all. This is really what we would expect, if we consider that each drop contains only a very miniscule amount of change and also has nearly perfect insulation (distilled water is a very good insulator).

Controlled observations support the idea that corona, and not charges in individual droplets, actually cause precipitation static.

In Ohio, my long Beverages stretched across open farm fields. Snow would whip across the fields, rain would pelt the wires, yet insulated and bare wire Beverages running in the same direction always had the same noise level. Beverages that picked-up corona (or "p-static") noise were always near or aimed at tall towers. With corona sizzling at 40-over-nine on my tall towers, Beverages (and even small "magnetic" loop antennas) aimed at the towers would "hear" the same precipitation noise.

The same was true for tower-mounted antennas. The largest noise problems came from antennas mounted high on towers, and generally were with antennas that had "sharp" ends jutting out in the air. Lower antennas, even those of identical construction, were either significantly quieter or totally free of precipitation static. This effect was reported many times by contest operators and DX'ers with stacked antennas. They universally switch to low antennas to eliminate or reduce p-static, even though the same moisture is hitting the lower and upper antennas. This strongly indicates precipitation static is from corona discharge, and not from charges in each individual drop of moisture hitting the antenna.

After my move to Barnesville, Georgia my first antennas were all insulated wire. Hook-up wire was pressed into service in my first group of temporary Beverages. As non-insulated conductors in more permanent antennas were added, there wasn't any observable change in inclement weather noise. As before, only the antennas nearest or aimed at my tall towers picked up p-static noise. Antennas located away from the towers remained free of precipitation static, whether bare or insulated wire was used.

There is also some chance, if the antenna wire is not under significant tension, that insulation may sometimes hide a broken conductor.

Insulated wire may reduce leakage currents if a substantial part of the conductor is in contact with resistive paths, such as wet brush or tree branches, but you may be better off trimming back any substantial foliage in contact with the wire.

While insulated wire has no major performance disadvantage, it also has no advantage. Use it if it is readily available, but don't go out of your way to buy insulated wire.

Type of Conductor

Copper wire is a good choice if supports are close. Pure copper wire lacks the mechanical strength of steel-core wires, but is very easy to work with. It is softer, making it easier to bend. Copper wire can be repeatedly scraped, cleaned, and re-soldered without worries about piercing a thin copper coating and exposing a rust-sensitive steel core. Copper wire is readily available and relatively inexpensive in large quantities.

Copperweld wire is much stronger and has about the same RF resistance as 100% copper. Like copper, it is easy to clean and solder after it has been exposed to the weather as long as you are very careful to not scrape through the outer layer of copper. It is considerably more difficult to work with than normal pure copper wire, any small kink or sharp bend will substantially weaken the wire.

Most fence wire I've found is cadmium plated, rather than zinc galvanized. Using RF current meters, I have measured increased losses when using zinc or cadmium plated steel wire. Beverages already have substantial current loss due to the close proximity with lossy earth. I've measured about 60% of feed point current remaining (~4.4dB loss) after passing over around 700-feet of electric fence wire, and about 10% more current (~3.1dB loss) using copper-clad steel wire. Steel fence wire would aggravate losses that already limit the benefits of using long Beverage antennas.  In a very long antenna, the small additional loss of steel fence wire might slightly reduce performance.

In my Beverages, the important consideration is antenna maintenance. I use copperweld wire or electric fence wire, because strength is a primary concern. With spans exceeding 200 feet, my antennas need a large strength-to-weight ratio.

Don't use welding wire! It is a very poor material choice. It rusts (and as with aluminum) you'll have connection problems in no time.

Beverage Supports

Some would have us believe we need non-metallic supports for our Beverages, but there is not the slightest technical justification for using non-metallic support posts.

The only requirement for the support is it must hold the antenna up, and it can not connect the antenna to ground. A metal pole with a small PVC stub for an insulator is every bit as good as a full non-metallic pole. Trees make good supports, especially if you use nail-type electric-fence insulators for use with wooden posts.

A typical cross-over point in my installation of over 30 beverage antennas.

PVC is wedged over the end of standard metal conduit. The PVC is notched and sanded smooth so the beverage wire can slip freely through the PVC. String may be required to hold the lower wire in the notch.

Physical separation is six inches to one foot.

I've never seen a problem allowing a wire to contact a branch, although  I do trim out the branches and avoid any contact with trees.

Notice the wire floats freely through the insulator. This allows a single tensioning point, and easy checking at one point to see if the antenna has lost tension from a break.

I never anchor or wrap the Beverage wire around insulators, except at the ends. I always allow the wire to "float" through the insulators.

Where the wire need support from overhead, I use a strain or compression insulator:

The standard strain insulator hangs from a branch. The beverage wire lays across the insulator webbing, fully floating. Only the hanging wire wraps the web.

 A wooden cross-over support post

For end supports, I use trees, pressure treated lumber, or landscaping timbers. With a lot of tension, I backstay the poles to a dead-man (generally an old brick) buried in the ground. When I set end-posts with my power auger, I line the hole with copper flashing. That becomes part or all of the feed point (and termination) ground connection.

When the wire floats along the length between ends, you can tension the entire antenna from either end. If anything breaks the wire, you can see it at any point! A "floating" wire is much easier to repair if it is damaged, because you only need release tension on one end to splice the wire. Re-tension that same end, and everything is restored.

It takes no more tension to support a 1000-foot Beverage with supports every 100-feet than it does to support a 100-foot wire between two rigid supports, but it is a much more difficult to break the longer floating wire. A longer "floating" wire will often take-up enough slack to remain up after deflecting a large tree branch, where a shorter rigidly-anchored span will almost certainly break either the insulators or wire.

 Beverage Insulators

If you expect a long-lasting antenna and have a long antenna, be careful when choosing  insulators! Some types of electric fence insulators will not last long. The unreliable types of post insulators have two square folds to hold the wire, a square shaped base, and nail through a small molded plastic angle. The weak points of this insulator are the square retaining tabs, and the molded nail tube at the insulator base. When this type of insulator is mounted horizontally, the wire's weight will stress both the molded nail tube and a single tab. I typically find about 10% of the insulators fail within a few months. After three years, the few dozen installed here have virtually all failed.

Avoid these types!

Round yellow or back plastic insulators with the nail going through the center, like the examples below, are much more reliable post insulators

Ceramic post insulators may look great, but they do not allow floating the wire across the insulator. Even if you do manage to find a ceramic insulator that allows floating the wire, the ceramic will quickly wear away at the constantly moving wire. Avoid ceramic insulators, unless you are prepared to "buffer" the wire through a UV resistant soft plastic bushing!

Good end-insulators are becoming difficult to find. I always use compression types, but the material has to be either ceramic or very thick plastic. Some very thin plastic compression insulators will actually cold-flow and allow the wire to pass through the insulation. This is particularly true with thin steel wires that are tensioned over 25 pounds. Heavy-walled egg insulators are much more reliable, and not subject to wire migration through the thin insulation.

 My favorite insulators are large these rather thick Fi-Shock yellow plastic insulators. They are slippery enough to allow the dead-end wire or rope to loop over the insulator, and create a 2:1 mechanical advantage when tensioning.


I've found very little performance difference with height, unless the Beverage is more than .05WL high. As the height exceeds .05wl, performance seems to be reduced. Small rolling hills or ravines also seem to make any difference.  Follow the contour of gradual slopes, and go straight across ditches or narrow ravines without following the contour.

Sloping Ends 

There really isn't a logical reason to slope the ends of a Beverage. After all, six-feet of vertical drop is six feet, no matter if the drop is over 50 feet or straight vertical.

Consider, for example, the K9AY or Pennant antennas. Both have sloped wires, yet virtually all of the response is from the vertical slope of the wire in the antennas. As a matter of fact, the actual shape makes very little difference in the way each antenna works. Why would anyone, knowing how a Pennant or K9AY works, think that a Beverage somehow magically breaks tradition and stops responding to vertical signals in the wires when we slope them a bit? What difference would it make in noise anyway, since the entire antenna responds to vertically polarized signals?

There isn't any possible way, including use of shielding or additional conductors, to prevent the end-wires from having the very small effect they have. Save yourself time and worry, and avoid a needless hazard. Just drop the end-wires vertically right down to earth.

Multiple Antennas Crossing

Crossing of Beverages has little effect if they are not parallel or nearly parallel. Try to cross at an angle of 90 degrees if possible. Even a few inches of spacing is enough for right angle crossing. With shallow angles, assuming they can not be avoided, increase wire spacing to a few feet.


Always use isolated transformers for feeding Beverages. It is cheap, simple, easy insurance against unwanted common-mode ingress of noise and signals into the antenna from the feedline shield. See the Common Mode Noise page for an analysis.

I use 73-mix FairRite Products 2873000202 cores (about 1/2 inch square and 1/3 inch thick 73 material) in my transformers. These cores require a two-turn 50-75 ohm winding. The high-impedance winding is 5 turns for 75-ohm cables (6.25:1 Z ratio) or 6 turns for 50-ohm cables (9:1 Z ratio). Small insulated hookup wire is actually better than enameled wire. The thicker insulation is much less susceptible to developing shorted turns in rough service.

While my early transformers were waterproofed with Krylon and coated with insulation foam, I have finally laid out enclosed transformers and terminations with internal lightning protection. The transformer sections have F-fittings, and all use stainless steel hardware.  

For a Reversible Beverage, I use the following:  

Multiple Antennas at One Feedpoint

Never bring multiple antennas to one feedpoint, especially when they share one common ground.  I've noticed a definite deterioration in pattern with multiple feedpoints arranged with only ten feet of spacing, even when they had separate ground  systems. One set of Beverages installed with 5-10 foot of feedpoint separation has noticeably poorer patterns than other identical length antennas with wide separation at the feedpoint.

Multiple antennas actually may be the only case where a sloped feeder can make a difference, the slope will actually move the effective feedpoints further apart. The best idea, however, is to separate the feedpoints by several times the antenna height.

Termination Value

Having precise termination values isn't necessary, but get as close as you reasonably can. There are some impedance measurement suggestions circulating that absolutely do not work. One is to just use a tuner to match the terminated (or unterminated) antenna, and work backwards with loads to measure tuner impedance ratio after matching. This won't tell you a thing about proper termination, unless you repeat the measurements on dozens of frequencies spread over a wide range!

There are three fast, simple ways to test for proper termination:

With an Antenna SWR Analyzer

Connect the antenna analyzer at the Beverage feedpoint through a good matching transformer
Sweep the analyzer frequency from 1.8 to 7 MHz (or over a ~4:1 frequency range near the frequency intended for antenna) while watching SWR
 Adjust termination for minimum SWR variation (not minimum SWR, minimum SWR variation!)
When installation (including grounds) and termination is proper, SWR VALUE will remain nearly the same regardless of frequency

With an Antenna Impedance Meter

Measure the feedpoint impedance (right at the feedpoint) of a roughly terminated antenna at the frequencies of highest and lowest resistive impedance. You can do this through a known good transformer by correcting impedance for use of the transformer
Multiply the lowest measured impedance by the highest, and then find the square root of that number. This will be the correct termination  impedance of the antenna
With a Clamp-on RF Current Meter

(This does not work well with voltage, because of measurement method error problems)    

Apply a small amount of power from a transmitter, do not exceed antenna system component ratings!
Measure current at the termination, and several points up to a distance of at least 1/2 wl from the termination
Adjust termination resistance so current shows a smooth current decline as you move the meter towards the termination

In about 500-800 feet of distance, power loss in a Beverage is around 3dB. This corresponds to a 1/3 reduction in current. If you attempt to adjust for equal currents (or voltages) over any distance, the antenna will be MIS-terminated!

Termination Components

Identifying a Composition Resistor

We commonly assume any brown phenolic resistor is a carbon composition resistor, but that isn't true. Most of the smooth brown-colored phenolic cased resistors manufactured after 1960-1970 have actually been carbon film resistors. There are only a limited number of manufacturers supplying carbon composition resistors. One is Allen-Bradley. They are expensive special-order parts, and the buyer must specify composition types.

As we see from the photo, it is impossible to identify a composition resistor by external appearance.

The only sure way to identify a resistor, short of ordering it from a reputable source, is through a destructive test. We can, for example, apply a large momentary overload and look for a resistance change. A resistance change indicates a film-type element. We could also cut the resistor open, and look for a non-conductive core. A non-conductive core indicates the resistor is a film style component.

Why Composition Types?

We need composition resistors in any application where the resistor is subjected to very-large very-short overloads, or where the system demands a nearly pure resistance at a very high frequency  (F>100MHz).

Obviously, in the case of a Beverage at a few MHz or lower, we could get away with using many styles of wire-wound resistors or spiral-film resistors. A small amount of inductance would not be a major problem, and virtually ALL carbon or metal film resistors (constructed with resistance elements deposited or cut in a spiral on an insulated core) would not have excessive inductance. The thing we can not tolerate is the sensitivity of non-surge rated components to damage from lightning storms, even distant storms.

The life of a carbon or metal film resistor, when used as an antenna termination, is relatively short in most locations. Just a few coulombs of energy, when applied in a few milliseconds, will cause a carbon or metal film resistor to change value. Worse yet, the resistor will not be altered in appearance. (Carbon also has a strong tendency to change value with heat. Even modest operating temperatures, over a period of time, will cause a carbon resistor to change value. Metal resistors are more stable.)

Unless you want to make a full-time career out of testing your antennas and replacing resistors, use a energy absorbing composition type resistor!

I install a small lightning gap of about 1/8th inch across my antenna's ends, both at the feedpoint and the termination. This helps immensely with very close strikes. I use either Ohmite OY-series metal compositions or A-B carbon composition resistors.  You can buy metal composition resistors at DX Engineering.

Ground Systems

The ground system mainly provides an RF and lightning ground. Having a very low ground-resistance is not especially important, unless an Autotransformer or Un-un is used! Autotransformers and Un-un's don't isolate the feedline for common-mode. The antenna needs a stable ground, not necessarily a low-resistance ground.

In my tests over the years, a 3/4-inch copper pipe driven five feet or deeper into the soil typically measures between 50-150 ohms of RF resistance on 160-meters. (DC or low frequency AC measurements will NEVER give the correct earth resistance for RF, and they certainly can not tell us ground conductivity.) Unless you have exceptionally poor soil, going deeper than five feet will not reduce RF resistance on frequencies above 1.8 MHz. Skin effect limits the depth of RF current in the soil, so the extra rod depth does nothing. Lower resistance values (about 55 ohms) were obtained in a wet marshy area of NW Ohio, with a very rich black acidic sandy loam soil. The higher resistance were obtained in rocky clay soil typical of the Atlanta, Georgia area.

My present location has rolling pastures and wet clay soils, providing under 100-ohms of RF resistance at 1.8MHz with a five-foot rod.

The general guideline I follow is to use at least two five-foot copper rods (I use 3/4" copper spaced 5 feet apart). If I can not get full depth, or if the soil is particularly poor, I add a few 30-60 foot buried radials. The idea is to obtain a reasonably stable ground, so termination does not change.

If you are unsure if you Beverage's ground is adequate, measure the impedance of the beverage with an antenna analyzer with your operating ground systems. Note the reading. Add two temporary radials 1/4 wl long suspended above earth at right angles to the Beverage, and re-measure the impedance. (It is OK to have them there at right angles to the antenna and not have them connected, and them connect them while taking readings.)

You can measure the impedance on the low-Z side of a good transformer. Under almost any condition, the wires would have 100 ohms or less impedance. If you see a very noticeable change in impedance, you probably should consider improving the ground system. Impedance changes of 15% (or larger) indicate a potential ground stability problem, because the ground resistance would be nearly 100 ohms. This test should be done when the ground is dry, or any time you think you might be having a ground problem.

Always remember to keep the shield of the cable isolated from the Beverage ground! Never use un-un or autotransformers.    


For length considerations, see the directivity factor text. It is not necessary, nor does it do any good, to go beyond 1-1/2 or 2 WL. By the time the antenna is that long, current is so low any addition length makes the pattern worse. I limit my 160-meter antennas to 800-feet, and use multiple antennas when a sharper pattern is required.

Directivity can actually decrease if a longwire-type array is made too long. This is true with Rhombics and Vee Beams, and it is also true with Beverages.

Zigzagging Wire

While a nice clear straight wire looks great, it does more to make us feel better than hear better! Minor ups and downs in height or dips or valleys don't really seem to have any noticeable impact.

Although it probably is a good idea to keep the wire as straight as possible, it is the overall direction and length that is most important because each small area contributes on a similar small portion to the overall directivity and signal reception.

Introduction to the EH Antenna

Introduction to the EH Antenna

Welcome to and the wonderful world of EH Antennas. Those of you who have visited this site previously will find major changes, primarily deletions. Diversified Technology Inc. (DTI), based in Ridgeland, Mississippi, has obtained a license to develop, manufacture, and sell EH Antennas for all applications, excluding AM broadcast and ham radio. In conjunction with selling the license for three of his EH Antenna patents to DTI, Ted Hart has agreed to work with the company as a consultant to develop the EH Antenna for specific applications.
Military tests have proven that the EH Antenna, which is much smaller than standard antennas, significantly enhances the communications range of radios. The military is now funding DTI to develop EH Antennas for various military radios. The significance of this new antenna cannot be overstated; the Director of Research for the Department of Defense has even declared it to be a “quantum leap in technology.”
The EH Antenna has very broad applications. For example, a small loop antenna modified to be an EH Antenna provides a significant enhancement to RF Identification (RFID) systems. In addition to increasing the range to the transponder (tag), it allows a large number of tags to be read simultaneously. The modification of the loop antenna produces a radiation pattern which is orthogonal to the loop. As there is no reactive field, the tags are immersed in a true radiated field. This allows more freedom in the positioning of the transponders. In contrast to older systems which required tags to be parallel to the axis of the conventional loop antenna, practically any orientation of the EH Antenna and the tags will provide maximum magnetic coupling.
The first commercial EH Antenna for AM broadcast is now operational in El Salvador. There, as in so many places, land acquisition presents a significant problem. In many areas the amount of land needed for conventional antennas requiring large ground radial systems is cost prohibitive. Other areas lack sufficient land that is flat enough to position radials. Of course, the economic factor is paramount; thus the unique characteristics of the EH Antenna make it the antenna of choice.
An additional advantage of the EH Antenna is that it provides signal power equal to that of a conventional tower while requiring only half the conventional tower’s height. This website includes a document entitled “El Salvador,” which reports on the installation and test of the first 700 KHz EH Antenna. Many more EH Antennas will follow.
A process has been initiated that will allow the FCC to grant broadcasters a license to use the EH Antenna in the United States. Current regulations require AM broadcast antenna vertical radiation patterns to conform to a specific equation that was originally devised for a conventional tower with radials. The EH Antenna is especially well suited for night-time operation because it requires a smaller vertical radiation pattern.

The EH Antenna boasts several features which make it the antenna of choice for most broadcasting needs. First is its small size and its ability to be mounted on a tower about half the height of a standard broadcast tower. The EH Antenna is also a complete dipole antenna and requires no ground radials other than a lightning ground connected to the tower. The EH Antenna also features very high efficiency and a wide bandwidth.
Compare these characteristics to those of a conventional antenna which requires a greater tower height, several acres of ground for its 120 buried ground radials, and a complex matching network and is less efficient than the EH Antenna. The documents provided in this website explain these differences in greater detail, but even without reading them you can see that the unique features of the EH Antenna translate to a better system at a lower cost than the traditional antenna.
Obviously, economics dictate the use of an EH Antenna unless the cost of land is insignificant. However, another major factor in favor of the EH Antenna is its reliability. The antenna has two cylinders, a tuning coil, and a single capacitor. A high quality capacitor has virtually infinite life, as do the other parts of the EH antenna. Compare that to a standard tower that requires a complex matching network that uses numerous components, any of which could become faulty at any time, adversely affecting broadcast quality.
The prototype AM broadcast EH Antenna was located in Eatonton, Georgia, and tested in accordance with conventional FCC procedures in 2003 by Stu Graham, a broadcast consultant. For convenience it was located at a low height (one-tenth wavelength), yet it offered great performance.
As with all prototype systems, its purpose was to identify any issues before beginning production. The only issue was that the instantaneous bandwidth was much lower than expected. Later it was discovered that the lowered bandwidth was caused by magnetic coupling of the cylinders to the steel tower sections inside which were used as supports. This reduced efficiency. However, the measured performance showed the antenna radiation was only 0.84 dB (18%) below a standard quarter-wave tower with 120 buried radials. The tower sections are now made of aluminum, and this problem no longer exists.
In 2007 a radio station in El Salvador, Central America, went on the air using an EH Antenna on 700 KHz. This station has excellent coverage of the country even though the height of the antenna is only 0.14 wavelengths, or 200 feet. A detailed performance report is included in this section of the website.
The El Salvador antenna is a “large” EH Antenna with a diameter of three feet and a total length of thirty-nine feet. The antenna can operate on any frequency between 540 and 1200 Hz with a simple change of its tuning coil. The antenna is rated at 10,000 watts. For radio stations running 1000 watts or less and on any frequency between 1200 and 1700 KHz, a smaller antenna is available. It is designed to sit on top of either a guyed or unguyed tower, uses cylinders that are eight inches in diameter, and has a total height of less than twelve feet.
When mounted on a standard 100-foot-tall self-supporting tower, this antenna will provide coverage equal to or greater than a conventional quarter-wavelength broadcast tower with 120 buried radials. In contrast, the conventional tower would be 205 feet tall at 1200 KHz.

Because of the EH Antenna’s small size, it is now possible for the first time to locate a radio station in a densely populated area. The EH Antenna can even be mounted atop a large building because it does not require ground radials. Because the smaller EH Antenna has much greater bandwidth than a conventional tower, the fidelity of the broadcast audio is limited only by the transmitter, not the antenna.
For detailed performance data on the prototype antenna, please contact Graham Brock, Inc. at As stated earlier, a full report on the radio station in El Salvador is included on this website.

Welcome to the Amateur Radio section of the EH Antenna website. The EH Antenna has useful applications in all areas of communications and offers many advantages to ham radio operators. It is a very small yet very high performance antenna. Its smaller size increases communications opportunities for many hams who have been restricted by a lack of space to grow antennas. How can an antenna be so small and have such high performance? The answer is that the EH Antenna is a new concept in antenna theory, and therefore does not need to follow the rules of older antenna theory.
The Hertz antenna has been around since the 1880s, and today there are an unlimited number of variations on that early concept. However, each variation is limited within the constraints of a resonant antenna. The wires may be straight or bent into various shapes, but they must be resonant, or resonated with an antenna tuner. Resonance is necessary for maximum current flow. Hertz antennas are based on the concept that current flow on a wire causes the development of a magnetic (H) field and that a changing magnetic field creates an electric (E) field. Because one field creates the other, they have a time phase difference of 90 degrees. The two fields do not become in phase and develop radiation until they have traveled a distance of about one-third of a wavelength from the wire. This is called the “far field.” When the fields have the proper phase, amplitude, and physical relationship, radiation is created.
Compare the older antennas to the EH Antenna, where the E and H fields are actually in time phase at the antenna itself. Because the two fields are very efficiently integrated, the radiation resistance is higher than that of a wire antenna. A major factor is that the elements of an EH Antenna are cylinders and have a much larger diameter than a wire. The two elements, therefore, have high capacity between the elements, which, in turn, allows the antenna to be small. This large capacity and high radiation resistance combine to provide very wide bandwidth and high efficiency. All of this comes from an antenna that may be less than 1% of a wav elength, compared to wire antennas that are 50% of a wav elength, or ¼ wav elength with radials. On this website you will find technical information that will allow you to roll your own. We hope you enjoy this information and the use of the antennas you build. There are an untold number of EH Antennas already on the air, and many more are added every day. If you choose to buy rather than build, we have provided a link to the only company that currently manufactures and sells the EH Antennas under a license agreement.
For those hams without antenna and RF experience, buying is most likely the better option. However, we have also provided some helpful hints to those hams who feel competent enough to build their own antennas or who enjoy a challenge. First, choose a diameter that is equal to or greater than those indicated in the list below. “Meters” refers to the Ham band.
80 meters: 4 inches
40 meters: 2 inches
20 meters: 1.5 inches
10 meters: 1 inch
You may use a smaller or larger diameter to achieve less or greater bandwidth, respectively. Make each of the two cylinders equal to six times the diameter, and space the cylinders the same as the diameter. This is relatively easy, but it gets harder from here. The next step is to wind a tuning coil and locate it about three diameters below the lower cylinder. This coil resonates the capacity of the cylinders. Like a Hertz antenna it is resonant. However the difference is that the antenna is a miniature dipole that is voltage fed, which allows the E and H fields to develop simultaneously. For the first try, use small wire with an enamel coating. Later you should replace it with heavier #14-gauge wire. Connect the top of the coil to the bottom of the top cylinder, and connect the bottom of the coil to the top of the bottom cylinder. Use a grid dip meter to find the resonant frequency, and then change the coil to bring it near the desired frequency. Next, connect a capacitor having a reactance of about 100 to 200 ohms to a tap on the coil about one-tenth the number of total turns above the bottom of the coil. Then connect a short piece of coax (less than five feet) to the antenna, connecting the shield to the bottom of the coil and the center conductor to the capacitor. Also connect a ground wire to the low side of the coil and to a good ground such as the power outlet safety ground in the shack.
Now it really gets interesting, so be sure you have the proper test equipment. You must adjust the tap on the coil to provide a 50-ohm match and adjust the coil by changing the top wires on the coil to bring the antenna close to the desired frequency. The desired frequency is best found by using a field strength meter and low transmitter power. It is preferable to use a signal generator for this test. A good impedance match is readily found by use of a VSWR bridge. Once this is accomplished, you must mount the antenna to simulate the final location. Connect a wire from the bottom of the coil to ground. This stabilizes the capacity of the antenna and allows final tuning and matching.
When the antenna is mounted vertically, it is a great general-coverage rag chew antenna on the low bands and a great DX antenna if the height is between one-eighth and three-eighth wavelengths above the ground. The antenna is a miniature dipole and can be mounted horizontally for high-angle radiation on the low bands.
There is a great discussion forum on Yahoo ( if you need help in building or tuning your antenna.
Click here for a list of EH antennas available for amateur use. They are manufactured by FR Radio Lab in Japan, the only manufacturer that is currently licensed to manufacture EH Antennas for ham radio operators.




You'll not find in these pages the "bible" of EH, but just a simple description of my tests regarding this antenna;
I just want to share my test and result with other hams: nothing more.

EH inventor say that this antenna is based on a "new theory" which is very different from "Hertz theory": nothing to say about that, I can not say it' true or not;
You can read more directly on Ted's page (the inventor)  (Ted Hart, w5qjr) or on Arno Elettronica (the italian promoter);
Here follow same words from the EH home page:

The Hart EH Antenna consists of two (2) elements having a natural capacity between them. (Think of a fat dipole) When a voltage is applied to a capacitor an E field will be developed. Also, the current through the capacitor (called displacement current) will develop an H field at right angles to (encircle) the electric field. However, when current flows through a capacitor, the phase of the current leads the phase of the applied voltage. Therefore, the phase of the H field leads the phase of the E field and the difference in phase (time) prevents satisfaction of the Poynting Theorem for this configuration.

If the external power applied to the EH antenna is first applied to an inductor between the source and the antenna, the inductor will retard the phase of the current relative to the applied voltage. Therefore, within the antenna the phase of the voltage (E Field) and the phase of the current (which causes the H Field) can be made to be the same. In other words, they occur simultaneously, thus, the name of the EH Antenna. This allows satisfaction of the Poynting Theorem and radiation occurs at the frequency where the reactance of the external inductance causes the phase of the current thru the capacitor to be the same as the applied voltage. This is at a frequency approximately equal to the resonant frequency of the external L and the internal C of the antenna. More complex phasing/matching networks and/or feedback techniques may be used to enhance bandwidth by maintaining the desired phase relationship over a range of frequencies. Greater amounts of radiation also result from more complex networks.

Due to the high efficiency of the integration of the E and H fields within the physical sphere of the antenna, where they are created simultaneously, the antenna need only be a very small fraction (less than 1%) of a wavelength. This is due to the very strong fields. The Poynting Theorem says Radiation = E x H. Since the space between the capacitor plates is only a fraction of a meter, the E field, measured in volts/meter, is large even for small applied voltages. The H field, measured in amp turns/meter, is large but relatively low, since the H field is less than the E field by a ratio of 377, the impedance of free space.

The EH Antenna can be physically configured to allow antenna pattern gain in the E plane in two different ways. One enhancement method is similar to that of a microwave horn, even though the operating frequency is such that the physical size of the antenna is very small compared to the operating wavelength. This is most evident in the Bi-cone version of the EH Antenna, where radiation occurs between and in a very small area at the apex of the cones, and the remaining cone area enhances the gain by shaping the antenna radiation pattern. The other method is to have long cylinders relative to the diameter of the antenna for the dipole configuration.

Due to the necessity of the H field being a closed loop (circle), the bi-cone must be non-directional in the H plane. In fact, all basic EH Antennas are non-directional in the plane orthagonal to the E field. Directive gain in the H plane may be achieved with phased arrays made of active EH Antennas, or special shapes.

Due to the E and H fields being primarily within the physical sphere of the antenna, Electro Magnetic Interference (EMI) is virtually eliminated. Since the E and H fields are contained, the EH Antenna can not be used as a parasitic element in an array.

Since the antenna is not a resonant structure, the frequency of operation is totally dependent on the external-phasing network. Since the typical phasing network only covers a small range of frequencies, the EH Antenna virtually eliminates harmonic radiation.

Since antennas are reciprocal, the EH Antenna offers full performance for both transmitting and receiving. In addition, since the E and H fields are primarily contained within the physical sphere of the antenna, the antenna rejects external E or H fields and receives only radiation. Thus, the EH Antenna is exceptionally quiet, thus producing very high signal to noise ratios in the presence of man made and atmospheric E field or H field noise.

Well, after this short introduction, i must say that I've built a EH antenna after I've  heard:
"EH antenna, wich is just hundred time smaller then dipole, have the same gain and same performance of standard dipole".
That make me very curious so that I decided to build a 160 meter EH antenna, with the following measure (caming directly from Stefano, IK5IIR, the italian promoter).

Diameter of cylinders =25 cm
Height of cylinder= 37,5 cm
Distance between cylinder= 25 cm
Total Height (Cylinder + Network) 1,5 mt
Needed Capacitance 128 Pf
Number of turns for L1=19
Number of turns for L2=16

So, if what people say about EH antenna is true, this very small antenna will perform as good as a full size dipole (80 mt in 160 mt band)...
The following pages are just a short technical describtion of EH I've built; at the end you'll find my test and results.

Now the first cylinder is ready;
Insert the first cylinder in the 250mm PVC pipe (10 cm) and lock with rivet; now make the second cylinder and cut the 250 mm PVC pipe at 45 cm: you will have a 37,5 cm cylinder + 25 cm space (PVC) and a second 37,5 cylinder
Lock the second cylinder with rivet;
Make 1 turn of wire on each cylinder as in picture;
Cut the wire longer (you will connect there the network,later); the upper "coil" wire will pass in the center while the bottom one on the side, near the cylinder.

At this point the antenna is ready, we need to made the network; in the first prototype I've used a 160mm PVC pipe (3 mt lenght) used also as support; on the upper side turn L2
then L1 using a 4mm wire; fix it with hot glue.
Let's make capacitor; in the first prototype I've used commercial variable capacitor as you can see in the picture.

Now we must add the two cylinder to the network obtaining a single "pipe"; in the first prototype I've used a threaded bar trought the two cylinder and the 160mm PVC pipe;
Make a hole for the SO239 connector.
The Eh is finished, let's tune it.

For a easy tune, I've mounted the antenna on a 3 mt PC pipe situated on my roof (the antenna is at 2 mt from the roof, 6 mt from the ground).
This prototype was wery hard to tune and instable;
When transmiting, S.W.R. changed quickly I suppose due to the small variable capacitor I've used;
With this antenna performance were very bad, but I went on with same modifications;


80M - 6 Foot EH Antenna

80M - 6 Foot EH Antenna

This is a picture of my EH 'STAR' antenna for 80 meters. It has two cylinders made from aluminum flashing 30 1/2" long, wrapped around 2" (2.375") PVC pipe. Below the cylinders are two coils for matching and developing the EH fields. There is a phasing coil between the cylinder. This antenna is described in Demonstration # 5 on the EH Antenna Web Site.

Building the aantenna is very easy and inexpensive. It has outperformed my other antenna (dipole made from two mobile whip antenna up 20 feet and a vertical w/o radials). The first test was when I checked into the weekly ARES Net (Stateswide ARES Net for South Texas). usually have to check in from an alternate net control station due to a weak signal. The first night net control heard me the first time without any repeats. I next checked into the Southwest Traffic Net with the net control in Hot Springs Arkansas without any trouble. For a limited space antenna it appears to be doing a good job.

Bill of Materials:
2" PVC Sch. 40 Pipe 10'
$ 4.25
Home Depot / Lowe's
2" PVC Cap
Home Depot / Lowe's
Aluminum Flashing 10" X 10'
$ 4.57
Home Depot / Lowe's
2" PVC Short Couplings (2)
$ .88 (ea)
Home Depot / Lowe's
# 14 Enamel Wire (~ 40')
$ 0.23/ft
The Wireman (Internet)

I drilled a small hole to start winding the Phasing Coil on one of the 2" PVC Couplings. The hole will also be used to place the wire down the middle of the cylinder, making sure the wire will reach the bottom of the turning Coil (5 feet). Secure the winding using hot glue. I made each item (cylinder, coils) and then assembled them. It is easier to handle the smaller pieces that the large piece.

                                                       Componet parts before assembly

I cut a 24 inch piece of 2" PVC pipe to be used for winding the Tuning and Source Coils. I would the Tuning Coil about 2 1/2" below the top of the pipe (when assembling the antenna this will be cut to maintain the dimensions of the antenna). Wind 34 turns on this PVC pipe (the source coil will be installed later). Antra two turns are used to fine tune resonance of the antenna (it is easier to remove "turns than to add them).

                                                                           Phasing Coil

                                                              Tuning & Source Coils

I cut two pieces aluminum flashing 8 1/2" X 30 1/2". This is used to make the cylinders. Cut 2 peces of PVC pipe 36 inches. On one of the pieces mark the pipe 3/4" from the end (top of the top cylinder). Bend the flashing around the pipe starting at the mark. This will be the top cylinder. Secure the flashing with sheet metal screws every 1 - 2". Drill a hole on the bottom of the cylinder (long protion) and mount a 8 X 32 brass bolt 1/4" above the end of the cylinder.
Mark the other PVC pipe 1 3/8" from the end. This will be the top of the bottom cylinder. Secure the fashing to the PVC pipe using sheet metal screws. Mount a 8 X 32 bolt 1/4" below the top of the bottom cylinder. Drill a small hole just above the bolt (this will be used to route the # 14 enamel wire to the inside of the tube). Run the # 14 enamel wire down the inside of the bottom tube. This wire should be as close to PVC pipe as possible. Route the wire through the hole and mount to the bolt (remember to scrape the enamel off the wire before connecting to the bolt).
Install the top cylinder to the 2" PVC coupling with the Phasing coil using PVC cement. The aluminum flashing should be against the coupling (we will cut the bottom cylinder PVC to get the correct spacing). Ensure that the end of the coil is lined up with the bolt. Scrape the enamel off the wire and install on the bolt. Put the bottom cylinder ito the coupling for measurement. The two cylinders should be 1 diameter spacing (2 3/8"). After cutting the bottom cylinder to the correct imensions it is time to glue it into the coupline. The tap on the bottom should be mounted 180 degrees fromthe tap on the top cylinder. Measure the bottom end of the bottom cylinder and cit it off so the flashing is flush with the bottom coupling. Glue the couplin in place. Measure the pipe containing the tuning coil to all for 1 diameter spacing between the cylinder and the tuning coil. Glue in place. Now we are ready to tune it.
Using the instruction in the Demostration documents, tune the antenna. After the antenna is tuned, the source coil should be wound on the pip and tuned per instructions.


Ground vs. Radials

Ground vs. Radials

The need for radials with a ground mounted vertical has invoked lots of discussion among amateurs over the years. The literature contains many references to how many radials are needed, how long they should be and what affect they will have on the performance of a vertical antenna. And yet lots of confusion still exists. In this section we will take a look at ground mounted and above ground mounted vertical antennas, especially with respect to the radials and try to make some sense out of the subject.
Ground Mounted Vertical. First, let's look at a ground mounted vertical antenna. As shown in the sketch, it consists of a vertical radiator that is mounted directly on the ground and fed at the base. As should be apparent, in the case of a perfect ground, the potential (voltage) with respect to ground is precisely zero on the side of the feed point attached to ground. That means that the entire voltage of the source is applied to the vertical radiator. This is different than a dipole, where the voltage swing is applied to both sides of a dipole.
In a dipole, the voltage with respect to ground is equal and opposite on both sides of the feed point. In a ground mounted vertical with a perfect ground, the voltage on the ground side of the feed point is always zero with respect to ground. This is inherently an unbalanced antenna and there's not much that can be done to change that. It will also have a take off angle of zero degrees and an impedance of 36 ohms at resonance.
Note that a perfect ground has zero resistance and reactance. Therefore there can be no voltage differences, no matter how much current is flowing in the ground, and therefore no losses. So far so good.
But what happens in the "real world"? In reality, there is no such thing as a perfect ground with zero resistance and reactance. Real ground conditions do indeed induce losses and there are voltage gradients caused by ground currents around an antenna. So what can be done?
One approach is to make the ground as close to perfect as we can. That means putting a metal plate or mesh or a large number of radials at the surface of the ground to decrease the ground resistance and impedance. Obviously, the more metal we can put down, the better it will approach a perfect ground and the more efficient the antenna will perform. That's why we often hear the guidelines that "the more radials, the better." An alternative is to mount the antenna over salt water, which has a very low resistivity and makes an excellent ground. We are simply trying to turn our real ground into something as close to a perfect ground as possible.
Above Ground Verticals. In a vertical antenna mounted above ground, the situation is a little different. As shown in the figure, the antenna is usually fed at the base of the vertical element, however, the radials are not directly connected to the ground and there is nothing to keep them at ground potential. In this situation, the radials will have current flowing on them and at the feed point the current on the vertical element will be balanced by the current flowing on all of the radials. This is still not a balanced antenna, though, since the currents are not symmetrical around the feed point. In fact they flow vertically on the vertical element and horizontally (or at some other angle) on the radials.
Now, since there is current flowing on the radials, there will also be radiation from the radials, but we want to minimize the radiation in order to maintain the desireable properties of the vertical antenna, including low angle of radiation. One way to do that is to arrange the radials symmetrically about the base of the vertical. In the case of symmetric radials, the current in each radial is flowing in an opposite direction (away from the center) to the current on the radial directly opposite to it and the total radiation in the horizontal plane will cancel. Therefore, in that respect, the radials will have little effect on the low angle radiation.
But not all is perfect. There will also be radiation vertically from the radials and some of that will interact with the ground. Of the part that interacts with the ground, some radiation will be reflected and some ground currents will be induced, leading to ground losses. But that's not what we wanted!
So what can be done? One obvious possibility is to mount the antenna as high as possible, thereby minimizing the interaction with the ground and avoiding ground losses as much as possible. Hence the guideline "The higher the better". The other possibility is to add as many radials as possible in order to minimize the current on each radial. The current on each radial will be equal to the total current on the vertical element divided by the number of radials, so "the more the better".
Another way to look at the effect of radials in a vertical mounted above ground is that the radials are shielding the antenna from ground. In effect we are trying to create an "artificial ground" that is better than the real ground that mother nature gave us to work with. From that viewpoint we would like to have as many radials as possible, as long as possible. Again, consistent with the guidelines commonly quoted by amateurs. However, in my opinion, that viewpoint is too simplistic, since it ignores the fact that we can never completely shield the antenna from the ground in practice. No matter what, there will always be a potential difference between the radials and the ground, so there will be some interaction. It seems much better to forget about the analogy of shielding and just treat the antenna and radials as a complete antenna system that will interact with the ground to some extent. The important point is that, whether we want to think about them separately or not, the radials are part of the antenna.
Radial Angle. It has been stated many times that angling the radials downward at a 45o angle will improve an antenna. Let's see what happens when the radials are not horizontal, as in the ideal case above.
The above graph shows the impedance, the take off angle and the gain of a ground plane vertical as a function of the radial angle. In all cases, the lowest part of the radials was 10 ft above an average ground, which would represent mounting the antenna so the radials don't cause problems for people walking nearby. As can be seen, the gain doesn't vary much at all and neither does the take off angle. Certainly we probably could not detect the small differences in gain and take off angle shown. However, the impedance does vary from some 70 ohms for a vertical dipole to about 25 ohms when the radials are horizontal.
The implication of this graph is that the angle of the radials will have a minimal effect on the antenna perfomance, but it will change the feed point impedance. The minimal effect on the radiation can be understood by noting that the radials are symmetrical and their radiation in the horizontal plane cancels, as previously noted. However, somewhere around 45o the feed point impedance is very close to 50 ohms at resonance. So from an impedance matching standpoint, there is a reason to make the radials slope downward at an angle of about 45o. Changing the angle on the radials may make the antenna perform a little better, but it will also be somewhat easier to match.
Bent Radials. Since we're interested in limited space antennas, one common problem is what to do when you don't have room for the radials. After all, the radials for a 40m groundplane vertical require about 33 ft of space around the antenna.
Fortunately, the exact position of the radials isn't all that important. Just as we noted that we can bend a dipole all around and it will still work, so we can bend the radials around, too. In fact, as long as we keep the radials symmetric, there will be little effect on the antenna performance, since radiation from the radials will still cancel. Although the computed performance isn't shown here, it is even possible to arrange the radials in a spiral pattern around the base of the vertical and still maintain performance and impedance characteristics.
So, just as for the dipole, the ground plane vertical can be modified within reason and still be made to work under less than ideal circumstances.


The RF Ground

The RF Ground

One often hears about the need for a ground or ground system. There are recommendations to run 1/4 wave counterpoise(s) and do other things to ensure a good RF ground is available for optimum performance. In this section, let's take a look at what a ground is and isn't and whether one is needed or not. In general, there are 3 separate uses for a ground system in the typical ham shack: safety ground, lightning ground and RF ground. We will evaluate in detail only the RF ground here, after briefly taking a look at the other types of grounds.
The Safety Ground. First, we'll take a look at the safety ground system. In most houses and buildings one of the wires in the normal electrical wiring is connected to ground for safety purposes. Certainly we do not want to risk anyone being electrocuted by touching the chassis of any of our radios or other appliances. The best way to ensure that doesn't happen is to connect the grounded electrical wire to the chassis. Then if someone touches the chassis, they are at ground potential and no harm is done. This ground system should be part of the electrical wiring of the building. If it isn't, that problem should be fixed before going any further! All electrical codes require a functioning ground system as a normal part of home and building electrical wiring.
But then we run an additional ground wire for our radio equipment. Normally this additional ground wire is connected, either directly or indirectly to the chassis of the radios, tuner, amplifiers, etc. So we now have the situation where the chassis of our equipment is connected to ground through 1) the house electrical system and 2) our additional ground wire. One could certainly ask the question: Why 2 separate connections for the same thing?
Under normal circumstances having 2 ground connections will be unnoticable. Problems can occur, however, if the house ground comes loose. In that case, the entire house would be grounded through the radio ground connection. While that might be better than having no safety ground at all, that probably is not the purpose most hams had in mind. Of course, the proper action is to fix the house ground! In that case, the additional ground is not needed for safety purposes.
In any case, the issues surrounding a safety ground are covered by the building electrical codes. For further information on safety grounding, consult the electrical codes and guidelines for house and building electrical wiring.
Lightning Ground. Another use for a ground connection is to divert lightning which may strike an antenna to the ground, thereby by-passing problems in the shack. However, if the antenna is connected to our rig and our rig is connected to the ground, then all of the current from lightning striking the antenna must pass through the antenna, feedline, radio and ground connection. Most likely it will burn up lots of things on its way there!
The subject of a lightning ground is an entirely different matter, since its purpose should be to bypass the current from a lightning strike away from our house and equipment. This subject is important, but beyond the scope of this dicussion. Additional information is available in various books on antennas and from companies that specialize in lightning arrestors and diverters.
RF Ground. So, now we have ensured that our equipment is grounded for safety and lightning purposes. What is the reason and utility of providing an RF ground? Let's take a look at 2 fairly common ham situations.
Balanced Transmission Line. In the first situation, we will consider that the transmitter is using a feedline to a remote antenna. If we look at the RF circuit of such a station setup, it would look similar to the following figure:

Using this figure as a guideline, it is apparent that the current from the transmitter, It, will be equal to the current from the antenna, Ia, plus the current going to the ground, Ig. If our transmission line is balanced, however, we know that the current on both feedline conductors is equal. So if It = Ia, then obviously Ig = 0. And if Ig = 0, then we can disconnect the ground wire and not observe any difference.
For this situation, the purpose of the RF ground is to make up for deficiencies in the balance of the antenna. Any excess (i.e. common mode current) will be bypassed to ground instead of going back to the rig and radiating from power cords, etc. But, it should also be apparent that whatever current goes to ground represents energy that is produced by the transmitter and is not radiated. That represents an inefficiency in the system. Although the ground may appear to solve some RF feedback problems, it does so at the expense of antenna system efficiency. It would be better to get rid of the common mode current by improving the feedline balance. In this case the presence of the ground should have no effect on a properly installed antenna system.
End Fed Random Wire. The second situation is where our antenna consists of an end fed wire. The RF circuit for this setup is shown in the following figure. As can be seen there is no direct return path for the antenna current, It, so therefore the return path is through the ground connection and thus Ig must be equal to It.

So, what happens if we disconnect the ground? According to the figure there would be no return path for current, we would have an open circuit and the system would not work. In practice, though, there would always be some sort of return path, through our house wiring, even through someone's fingers touching the case. Of course we probably don't want our house wiring or our bodies to be part of our antenna system! In this case, the RF ground is absolutely necessary to avoid problems. So what do you do when a good RF ground connection is not available?
The answer can be seen by comparing the preceeding two figures. We can see that the need for the RF ground is due to the lack of a return path and due to not having a balanced antenna/feedline system. So if we can't get a good RF ground, we can convert the antenna to a more balanced system by adding the missing antenna element. Some people choose to call it a counterpoise or artificial ground, but as can be seen, it is really just making up for the lack of a current return on an unbalanced antenna.
Conclusions? So what can we conclude from this evaluation? Basically it appears that if we have a balanced antenna feed line with no common mode currents, there is no benefit to having a good RF ground. It is only when the antenna transmission line is unbalanced that an additional return path for the current is needed and an RF ground can supply that. However, it is generally agreed that the ground is the most inefficient part of any antenna system, so whatever curents flow to ground represent inefficiencies in the antenna system.
My recommendation is that when possible a good RF ground is a nice backup, just in case something goes wrong. However, checking the current flowing on transmission lines and in the ground connection should be done periodically. If the currents are large enough to be noticeable, then something should be done to reduce them.
In the cases where one cannot install a good RF ground, such as in the upper floors of a multi-story building, don't dispair. It simply means that we're forced to take care of the common mode currents and make sure our system is balanced. In general, using a counterpoise or artificial ground wire can appear to help, but the best solution is to take care of the real problem, which are due to common mode currents caused by an unbalanced system.


Antenna Scaling

Antenna Scaling

Electromagnetic waves have a characteristic length which is related to their frequency, as discussed in a previous section. Since antennas are made to radiate and receive electromagnetic energy, it can be shown that their perfomance depends not on their physical size, but on their dimensions relative to the wavelength.
One fundamental implication of this is that antennas can be scaled from one frequency to another by expressing their dimensions in terms of wavelengths. Thus if we have an antenna design for one frequency, it is easy to convert the design to any other frequency simply by making the antenna the same size in terms of wavelength.

It should be noted that for the procedure to work exactly, all dimensions must be scaled. That includes wire or conductor diameters and height above ground, as well as the lengths of any elements or wires. Normally the lengths are easily scaled, but scaling the height above ground and the wire diameters is difficult in practice. Fortunately the effect of the wire diameter on performance is normally not overly important, as we will see in later sections. The height above ground, however, can have an important effect on the radiation pattern. Generally speaking, scaling an antenna to a lower frequency (ie. longer wavelength) will make the antenna larger and higher above the ground. If we cannot actually raise the antenna, the lower height will probably decrease performance. Conversely, scaling to a higher frequency generally means smaller antennas and we can lower the antenna and still maintain the same performance.
Since we can scale any antenna design to any frequency, it may be much easier to experiment and prototype antennas at very high frequencies, which correspond to short wavelengths and smaller antenna structures. It is much easier to try an antenna designed for the 2 meter band, where a wavelength is less than 7 feet, rather than the 80 meter band, where the wavelength is more like 270 feet.
Scaling Procedure. There often seems to be a lot of confusion over how to actually go about scaling an antenna to a different frequency. Actually the procedure is very straight forward and can be summarized in the following steps:

  • Calculate the wavelength WLold of the design frequency.

  • Calculate the wavelength WLnew of the new frequency.

  • Calculate the length scale factor by dividing WLnew by WLoldSF = WLnew / WLold

  • Note: Since wavelength is inversely proportional to frequency, the scale factor can also be calculated directly from SF = Fold / Fnew

  • Multiply every dimension in the original design by the scale factor SF to determine the actual antenna dimensions at the new frequency. Xnew = Xold * SF

    Let's try a simple example to illustrate the procedure. Assume we have a quarter wave ground plane antenna that works great for the 2 meter band (146 MHz), so we want to try the same antenna on 80 meters (3.6 MHz). The 2 meter ground plane antenna has the following dimensions:

    Antenna Design for 2 meters
    Vertical Element19.5 inchesLength
    Vertical Element0.5 inchesDiameter
    Radials20.5 inchesLength
    Radials0.25 inchesDiameter
    Height10 feetAbove ground

    We proceed by first calculating the wavelength of the original antenna at 146 MHz and determine that WLold = 984 / 146 = 6.7397 feet. Similarly we can calculate the wavelength at the new frequency WLnew = 984 / 3.6 = 273.3333 feet. The scale factor is therefore SF = 273.3333 / 6.7397 = 40.56. Multiplying all of the dimensions by the scale factor gives the following antenna dimensions for our 80 meter version:

    Antenna Scaled for 80 meters
    Vertical Element790.84 inches = 65.9 feetLength
    Vertical Element20.28 inches = 1.7 feetDiameter
    Radials831.39 inches = 69.3 feetLength
    Radials10.42 inches = 0.65 feetDiameter
    Height405.5 feetAbove ground

    As can be seen the 80 meter version of the antenna is enormous! If we could actually build an antenna like that, you can rest assured that it would perform amazingly well!

  •




    The Oceania DX Contest, formerly the VK/ZL Contest, started in 1935 and is one of the longest running amateur radio DX contests. The aim of the contest is to promote HF contacts with stations in the Oceania region. Oceania stations can work other Oceania and non-Oceania stations. Non-Oceania stations can only work Oceania stations.
    The contest provides a unique opportunity to make QSOs with a large number of Oceania stations using SSB and CW modes and on all of the non-WARC bands between 160 and 10 meters. As well as many VK, ZL and YB stations there is also a good turnout from some of the rarer South Pacific entities. This year the Oceania Amateur Radio DX Group is undertaking a major DXpedition to Vanuatu and will be active in the contest using the callsign YJ0VK.
    Prize for the Oceania DX ContestThe contest was originally established by the Wireless Institute of Australia and the New Zealand Association of Radio Transmitters. The management of the contest was delegated to a joint VK and ZL committee in 2001. This committee has grown the participation in the contest from around 300 logs in 2000 to 1100 logs in 2010. The contest is now one of the larger ones on the international calendar and is also recognized as a qualifying event for Oceania amateurs who are interested in being considered for the 2014 World Radio Team Championship (WRTC).
    A range of trophies, including attractive plaques for the leading CW and PHONE stations in Europe, will be awarded as listed on the web site at Certificates will be awarded to the winning stations in each of the entry categories – for each continent and country. A participation certificate will also be awarded to every station that makes at least one valid QSO.

    Rules of Oceania DX Contest

    Here is brief summary of the rules for the 2011 contest:
    PHONE: 08:00 UTC Saturday 1 October to 08:00 UTC Sunday 2 October
    CW: 08:00 UTC Saturday 8 October to 08:00 UTC Sunday 9 October
    Bands: 160M to 10M (excluding WARC bands).
    Exchange: RS(T) + serial number.
    QSO points: 20 points per QSO on 160M; 10 points on 80M; 5 points on 40M; 1 point on 20M; 2 points on 15M; and 3 points on 10M.
    Final Score: The sum of the QSO points multiplied by the number of prefixes worked (the same prefix can be counted once on each band).

    Categories of the Oceania Dx Contest

    Oceania Dx FoundationEntry Categories:
    Single Operator All Band Low Power (max 100W)
    Single Operator All Band High Power
    Single Operator Single Band Low Power (max 100W)
    Single Operator Single Band High Power
    Multiple Operators and Single Transmitter (only one transmitted signal at any time)
    Multiple Operators and Two Transmitters (no more than two transmitted signals at any time and on different bands)
    Multiple Operators and Multiple Transmitters (no more than one transmitted signal at any time on each band)
    Shortwave Listener (receive only) All Band
    A range of trophies and plaques will be awarded as listed on the web site at Certificates will be awarded to the winning stations in each of the categories above – for each continent and country. A participation certificate will also be awarded to every station that makes at least one valid QSO.
    Deadline: All logs must be emailed or postmarked NO LATER than 7 November, 2011.
    More information about the contest, including the detailed rules, is available from the Oceania DX Contest web site at .. You can also forward any questions to