Sunday, November 25, 2012

DXpedition Video

DX Expedition Aitutaki


DX Expedition with Norm at Ginas Garden Lodges Aitutaki Cook Islands. Christmas 2012. Sorry about the audio drop outs, must have been a faulty tape.

 VP6T Pitcairn Island 2012 DXpedition



VP6T Pitcairn Island 2012 DXpedition by F6BEE Jacques, F4BKV Vincent, FM5CD Michel, G3TXF Nigel, VE2TZT Gilles.


ZL9HR

Team Leader Tommy vk2ir working the 20mtr pile up www.zl9hr.com www.haraoa.com www.vk2ir.com


T30PY&T30SIX - 2012 Western Kiribati DXpedition official video (IOTA OC-017)

Official video of the 2012 Western Kiribati DXpedition on Tarawa Atoll (IOTA OC-017) Oct. 16th to 25th


IOTA DXpedition EU044 Mageroya isl. 1080p HD


Waldi SP7IDX and Mek SP7VC will be active as LA/SP7IDX and LA/SP7VC from Mageroya isl. EU-044,QTH locator KQ21VC ,area Nordkapp -Barents Sea -- between 20.07-29.07.2012.
Activity will holiday style (we also big fishing).We plans to use 2 stations.One HF band second for the 50Mhz.Operation will be 80-6m using ssb,rtty also in IOTA Contest 2012.
Our equipment consist of IC746,TS480sat+Heil headsetHC6,antenna farm-HEX-BEAM by SP7IDX TECHNOLOGY 20-10m,R-7 vertical 20-10m,6el. yagi for 6m,2x inv L 80-40m,PA for HF and 6m.Software Win-Test sending qsos to Clublog in real time and Mixw.
During the travel to Mageroya isl. possible activity with Seskaro isl EU-139 in the evening or at night 19.07 and the next day 20.07 in the morning.QTH locator KP15VR. as SM/SP7VC and SM/SP7IDX. QSL also OK via home call,the log will be uploaded in LoTW.


GB2BLE Lundy Island DXpedition 2010

September 2010 South Bristol Amateur Radio Club mounted its annual DXpedition to Lundy Island operating as GB2BLE.
This years team consisted of Julia, Matt G0ECM, Mike G0MEM, Steve G0UQT, Peter G0DRX, Norman G4NFS and Andy G7KNA.
We operated a FT847 on SSB and a FT857 on PSK31 from Government House. Quite a good week radio wise we managed to work into the United Arab Emirates with just 100W into a long wire.
We spread our time on Lundy between operating, playing computer, long walks and meals in the Marisco Tavern. The weather was good for the time of year, improving as our week went on but fog and high winds stopped the MS Oldenburg supply ship from making its scheduled Tuesday voyage leaving those guests due to depart on Tuesday stranded until the helicopter came in on Wednesday once the fog had lifted.

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Sunday, November 18, 2012

Contest Station OM8A


Our HF Antennas

1,8 MHz

INVERTED L 3/4 lambda long /abt 40m vertical and 80m sloping to the near trees/ with about 60 pcs radials 40 m long .

Wire right from tower





3,5 MHz

2 element yagi 50m up in the air.

Bobtail curtain (3 element vertical array) USA / VK

Bobtail curtain (3 element vertical array) JA / PY




7 MHz

Stack 3 over 3 element full size yagi 46 and 24m m high.



Another full size 3 element yagi 30 m high.




14 MHz

Stack 6 over 6 over 6 element yagi (OWA design) 38m, 25 and 12m high. Upper two rotatable, lower fix to North America.



Another 5 element yagi 30m high.




21 MHz

Stack 6 over 6 over 6 over 6 element yagi (OWA design) 34, 25, 16 and 7 m high. Upper two rotatable, lower two fixed to North America.



Another 6 element yagi 24m high.




28 MHz

Stack 6 over 6 over 6 element Yagi (OWA design) 30m, 23 and 17m high They waiting for their chance



6 element yagi 18m high.




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Saturday, November 17, 2012

Station Contest K5MR


K5MR
Click on any image to see a larger picture:

Looking up at the 15m 6 over 6 over 6 stack
That's the middle yagi in the center of the picture, the top 15m yagi above it, and a 5 el 10m yagi at the top of the tower
15 meter stack
10 meter stack in background

100' 20 meter monobander tower
and three stack towers

The three monobander towers
and wiring shed
The stacks

 
Read below for the many wire...
...  antennas hidden among the towers
Wire Antennas:
  • 80m 3 element bobtail curtain array broadside NorthEast/SouthWest
  • 80m 3 element bobtail curtain array broadside NorthWest/SouthEast
  • 80m horizontal dipole at 100', broadside East/West
  • 80m 1/4 wave sloper, feedpoint at 65' (off top of 70' 10m tower)
  • 160m 2 each 130' 1/4 wave wire verticals, phased and steerable, 5/8 wave spacing, broadside NorthEast/SouthWest
  • See also the beverage page.
Driving away from K5MR
K5MR towers from a distance

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Comparison Between Different Antenna Systems "in Free Space"


Table 1: Comparison Between Different Antenna Systems "in Free Space"
ANTENNA
FORWARD
GAIN
FRONT / SIDE
REJECTION
RADIATION
 RESISTANCE
1/4 Vertical
1.45 dBi
0 dBi
21 ohm
Vertical Dipole
2.13 dBi
0 dBi
72 ohm
Delta Loop (Equilateral)
2.96 dBi
2.4 dBi
115 ohm
Quad Loop (Square)
3.30 dBi
3.8 dBi
126 ohm
Delta Loop (Compressed)
3.55 dBi
5.2 dBi
31 ohm
Rectangular Loop
4.55 dBi
8.3 dBi
32 ohm
Half Square
4.83 dBi
8.3 dBi
32 ohm
ADR Loop
5.25 dBi
26.1 dBi
63 ohm
Bobtail Curtain
6.46 dBi
99.9 dBi
34 ohm
SDR Loop
6.57 dBi
19.3 dBi
50 ohm


1/4 VERTICAL

Quarter wavelength vertical antennas are widely used in phased arrays, expecially in those which cover more than two directions. The famous "four square" array is a good example of it. The down side of the ground plane is that it can be a very inefficient antenna. Unless one uses "elevated radials" with sufficient height, the antenna return current will travel through the ground, and back to the feed point. This will cause RI2 losses. Unless special cares are taken, there is a heavy price to pay in terms of losses when the radial system is located "in the ground" or "on the ground".

It is not uncommon to see the efficiency of a 1/4 wavelength antenna to be well below 50%. There is a number of experiments and publications which demonstrate how the efficiency of a ground plane is sensitive to its radial system. One experiment which can be easily conducted is to measure the feed point impedance of the antenna while adding more radials to the ground system. The difference of impedance observed represents the "loss resistance" which in practice translates into loss of power into the ground itself. Knowing the feedpoint impedance of the antenna and the theoritical radiation resistance also allows calculating the efficiency of the antenna.

Here is an example of data obtained after having performed the experiment described above. I started the experiment with 21 radials, the antenna was tuned for 14.200 Mhz. The vertical section of the antenna was only 1 foot above the ground and the 1/4 wavelength long radials were laying on the ground. The feed point impedance was measured using an antenna analyzer model MFJ-259B. Here are the actual results obtained:

Table 2: Antenna Efficiency versus # Radials Used
# Radials
Feed Point Impedance
Antenna Efficiency
Power Lost
into Ground
(1 kw output)
Loss

(ohm)
(%)
(watts)
(dB)
0
94
27%
734
-5.8
1
84
30%
702
-5.3
2
69
36%
638
-4.4
3
61
41%
590
-3.9
4
55
45%
545
-3.4
5
49
51%
490
-2.9
6
46
54%
457
-2.6
7
42
60%
405
-2.3
8
39
64%
359
-1.9
9
39
64%
359
-1.9
10
38
66%
342
-1.8
11
36
69%
306
-1.6
12
36
69%
306
-1.6
13
32
78%
219
-1.1
14
31
81%
194
-0.9
15
31
81%
194
-0.9
16
31
81%
194
-0.9
17
30
83%
167
-0.8
18
30
83%
167
-0.8
19
30
83%
167
-0.8
20
30
83%
167
-0.8
21
30
83%
167
-0.8

These results are quite stunning; going from 3 to 14 radials decreases the feed point impedance by a factor 2, which in turn translates into a 3 dB improvement! In other words, the efficiency of the antenna would be doubled simply by using 14 radials instead of only 3. As mentioned previously, knowing the radiation resistance of the antenna allows calculating the efficiency of the antenna. The simple formula is shown below:

% Efficiency = Radiation Resistance (ohm)

Feed Point Impedance(ohm)

The theoritical radiation resistance of a 1/4 wavelength ground plane is 36 ohms over average ground. However, as the diameter of the radiator increases, the radiation resistance may decrease substantially. It is not uncommon to observe an actual radiation resistance closer to 25-30 ohms. Also, the proximity of certain metallic structures will interract with the antenna and will also contribute to decrease the radiation resistance. Based on the diameter of the radiator employed in the experiment described in table 2, the radiation resistance is estimated to be around 25 ohms. The calculation of the efficiency and power loss is based upon that number. We can also clearly see that even with 21 radials, the system is far from being 100% efficient. An in-ground or on-the-ground radial system would require about 120 of such radials to get closer to the 100% efficiency.

The experiment shown in table 2 has been conducted by many ham operators, often times measuring the field strength as opposed to the feed point impedance. The trend observed is always consistent with the results shown above.

The conductivity of the ground is also a key factor here. Poorer the ground conductivity, more dramatic the losses will be. Over a very good ground, a smaller number of radials will suffice to obtain a good antenna efficiency. Over salt water, only 2 radials will yield satisfactory results!

FULL WAVE LOOPS

(Quad Loop, Equilateral Delta Loop, ADR Loop, SDR Loop,

Rectangular Loop, Compressed Delta Loop)

Full Wave Loops are very simple antennas which can be extremely efficient if a minimum of precautions are taken in their design. For some reasons, only a few variations of these loops have been thoroughly documented; mainly the Quad and the Delta Loops. Interestingly, from a performance and “ease to feed” standpoints, these models are clearly not the most appealing ones. It is still a mystery to me why the other variations have not been better explored and documented.

One of the appealing characteristics of the Full Wave Loops is that they can actually exhibit a very interesting GAIN and even offer some directivity. The Table above shows the gain and directivity of different loop designs and other common antennas. Another interesting aspect of the Full Wave Loops is that they do not require radials for the return current. In a sense, they are “self contained”. In fact, a vertically polarized loop could be represented as being a pair of phased verticals, each with its own elevated radial.

Just like it is the case for all vertically polarized antennas, the quality of the ground is an important factor and will have a determining effect on many characteristics such as take off angle, gain, near field losses, etc. It is also important to note that the horizontal wire of the loop will tend to couple with the ground itself so one has interest to elevate the loop as high as possible and/or improve the quality of the ground underneath the antenna itself.

SHAPE OF THE LOOP

The shape of the loop itself will greatly influence its gain, radiation resistance and bandwidth. For example, the quad and the equilateral delta loop have both relatively high radiation resistance and similar gain. By compressing the vertical sides of these loops and widening the horizontal component, the gain will increase significantly and the radiation resistance will decrease to a level that can be optimized to perfectly match a 50 ohms coax line. The price to pay for these advantages will be some bandwidth. Following this logic, going from a quad to a rectangle or going from an equilateral delta loop to a compressed delta loop would provide the advantages mentioned above. Once again, the comparison table shown above testifies of these very facts.

EFFECT OF THE GROUND

Just like it is the case for all vertically polarized antennas, the quality of the ground is an important factor and will have a determining effect on many characteristics such as take off angle, gain, near field losses, etc. It is also important to note that the horizontal wire of the loop will tend to couple with the ground itself so one has interest to elevate the loop as high as possible and/or improve the quality of the ground underneath the antenna itself.

PERFORMANCE

Even though it is almost difficult to believe, going from a ¼ wavelength vertical to a simple rectangular loop can lead to 3-4 S-units improvement! The video clip below shows an example of this fact…. (copy email explanation here).
 
VERTICAL DIPOLE

The Vertical dipole...

DELTA LOOP (EQUILATERAL)

QUAD LOOP (SQUARE)


The Square Loop, often refered as "Cubical Quad",...

DELTA LOOP (COMPRESSED)

RECTANGULAR LOOP

The Rectangular Loop is the most performant antenna I have tried so far, not mentioning other interesting advantages like:

- No BALUN required (can be fed directly with coax).

- Radiation Resistance can be adjusted by changing the ratio of the height / width

- It is by design a dualband antenna where a 20m loop for instance will resonate as a 2 wavelength loop on 10m. Using a 75 ohm 1/4 wl. section cut for 10m will give a perfect match for both band.

-
HALF SQUARE

(The example shown in the picture is an "inverted" Half Square)

This is one of the best antenna I have tried. Compared to the 4BTV, signals were either equal or had an advantage of 1-3 S-Units. The inverted version does not seem to work as well as the standard version. However, this conclusion is questionable since tests made were not extensive enough.

It is obvious that in the case of the inverted version, the horizontal wire is closer to the ground which implies more ground losses.

In all case, the there was a significant effect of the feed line on the SWR which indicates a strong issue with RF feedback. A BULUN is clearly a MUST.

On advantage of the Half Square is that it can easily be made multiband by adding relays on the vertical sections. By choosing a compromise dimension of the horizontal wire (like 29 feet to cover 17-20m), good performance can be obtained. The model I tried was:

Horizontal wire: 29 feet  Vertical wires: 19 feet

The litterature recommends to connect the ground of the coax to the vertical section and the positive to the horizontal wire. Apparently, that should help minimizing the RF feedback issue.

I tries it and did not noticed any significant improvement. Reversing the polarity also had the effect to increase a bit the resonant frequence from 14.200 MHZ to 14.600 MHZ.

ADR LOOP

BOBTAIL CURTAIN

SDR LOOP



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"Hang & Play" Classic Zepp Antenna


"Hang & Play" Classic Zepp Antenna

These days many Hams are seeking ways to improve their reception and up their signal strength, and are resorting to wire antennas from the past fed with ladder-line, used in conjunction with tuners and/or baluns to accomplish matching to 50-Ohm coaxial line. G5RV's and various flat-top configurations fed at the center, or off-center as in the Windom antenna, are very popular as well.
These are generally used as multi-band antennas, but usually require tuning of some sort on each band as previously mentioned. Routing the ladder-line into the operating environment sometimes results in RF voltage nodes appearing in the operating area (shack), and may cause interference/adverse affects to telephones, computers, and other electronic/ electrical devices used in the home.
When an end-fed antenna is desirable or when a center-fed antenna is not possible or convenient, Hang & Play™ end-fed Zepp antennas provide excellent no-compromise performance. The name "Zepp" harkens to the days of dirigibles, or Zeppelins, which used trailing wire antennas that, by definition, had to be fed at one end.
The MFJ version of the classic Zepp consisting of a ½ wave radiator certainly fits the bill in all these circumstances. And, as a bonus, you can virtually "hang & play" this antenna as we construct them. No tuning, trimming, etc. required. Once connected, you'll find the antenna presents a low SWR across the entire band. However, it is a "one-band antenna" depending on which band you chose.
Figure 1 is a generic illustration of the antenna with its shorted stub and coaxial connection.

Figure 1
Classic Zepp Antenna ("Hang & Play" Version)
Dimension "L" represents a ½ wave, and "F" represents a ¼ wave, which, in this case is a ¼ wave stub, used for matching and phase-shifting. The antenna is a "broadside radiator," bi-directional perpendicular to the run of the wire. A pair of these antennas at right angles (NE/SW; NW/SE for example) can provide world-wide coverage. And, when used with a suitable antenna switching system (Ameritron RCS-10), switching is convenient and fast, with only a single-line feed into the shack. Or, you can run both coaxial lines into the shack, and effect switching with a wall-mounted unit (MFJ-1700C).
If height is a constraint, this antenna functions better than average at even a bit less than a ½ wavelength above ground/structure. However, it really performs best if "hung" at a ½ wave; up to ¾ wave. Higher than that provides diminishing return.
Especially important is keeping the symmetry of the antenna in reference to its ½ wave radiator. It must not sag more than a foot or so, with pulled-tight being the best installation. The feedline/stub can be "bent" at the bottom, or pulled away at an angle, and some twisting is OK. Practically, it is best to let the stub/feeder hang straight down and tie it off with rope to avoid lashing about in windy conditions.
To summarize, these antennas are intended for single-band use (your favorite):
  • 17 meters (27 feet long; 13.5 feet high)
  • 20 meters (32 feet long; 16 feet high)
  • 30 meters (45 feet long; 22.5 feet high)
  • 40 meters (65 feet long; 32.5 feet high)
They require two tie-off points spaced far enough to accomodate their width/length, and a height at least close to ¼ wavelength. When using two antennas, try to locate the antennas in an "L" or "T" ("X") configuration (at right angles) as illustrated in Figure 2.

Figure 2
Two Antennas at Right Angles (Suggested Optimum)
We hope you will benefit from their ease of installation, efficiency, and quality construction.

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1/2 Wavelength "L" Antenna


1/2 Wavelength "L" Antenna

The ½ wave Inverted "L" antenna, with Hi-Z feed point requires only a minimum ground to be an effective radiator. Accommodate coax lines with an L-Network match.
Use the formula: 492/fMHz (259.4 @ 1.9MHz for example) to find the overall length of the aerial, which is composed of H (Horizontal) + V (Vertical) components. Try to get the vertical section as tall as possible, since the current distribution is maximum at the midpoint of the aerial (129.7 Ft @ 1.9 MHz). That being true, it can provide good radiation from both H and V components. The H component can slope down (or up), but this tends to skew the max radiation towards the direction of slope, which is sometimes desirable. For instance: working VK/ZL, JA, Africa, or Europe.
The overall best advantage of the aerial is that only a minimum ground is needed unlike the 1/4 wave version. Make for 160, 80, 40, or 20 meters with the appropriate single-band L-network. Patterns vary per band if actually cut for 160, then used also on 40 or 80. 40 is good off the ends; 80 is good broadsides and vertical at the same time (more so than on 160). Use a tunable L-Network or any antenna tuner capable of matching high impedance loads, and it's a good multiband system. Discrete parts (wire, insulators, pre-cut coils, and capacitors) are available from MFJ.

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Ultimate Portable HF Vertical Antenna


Ultimate Portable HF Vertical Antenna

Introduction

Due to the tremendous response to my portable vertical antenna (July 2002 QST), I've continued to evolve the design. Now, I've come up with a longer, lighter and more compact (when disassembled) antenna that is easier to build, and easier to find parts for. And band coverage is now 60 through 10 meters.
As before, this new antenna breaks down into multiple mast sections, a whip, an air-wound center loading coil, and a base support. No piece is longer than about 20-inches so it will fit into most suitcases, yet the fully assembled antenna has a length of almost 16-feet! Photo "Author & Package" shows the disassembled antenna with guys and radials. See photos "Author & Vertical", and "Front Yard" for pictures of the fully assembled vertical. As most of you know, the key to antenna efficiency is length. The longer the antenna, the greater the radiation resistance and therefore the less impact on efficiency from ground and coil losses. This antenna is a full quarter-wavelength on 20-10 meters, and minimizes the coil necessary for 60-, 40- and 30-meters.
Gathering the parts
Most parts can be found at your local hardware store and McMaster-Carr (www.mcmaster.com). McMaster prices are 25-50% of hardware store prices. The loading coil, coil taps, 10-foot telescoping whip, and SO-239 are available from MFJ. The Radio Shack 72 inch telescoping whip I originally used is no longer available, so I've moved to the MFJ 10-foot telescoping whip. Other options are the 66 inch Buddipole telescoping whip, or the MFJ 12-foot telescoping whip. Gather up the following parts:
  • One 5" long x 2.5" diameter x 10 TPI air wound coil (MFJ-404-008 @ $14.95 each)
  • One 10-foot telescoping whip (MFJ-1954 @ $19.95 each)
  • One SO-239 chassis mount connector (MFJ-610-2005 $ $2.95 each)
  • Five coil clips (MFJ-605-4001 @ $2.95 each) -- Optional, see text.
  • One 3/8" diameter wood dowel (Home Depot -- only 5-1/2" needed)
  • Two 3-foot pieces of 1/2" OD - 3/8:ID AL tubing (Home Depot, ACE)
    Or 6-foot ½ inch OD-3/8:ID AL tubing (McMaster 89965K54 or Texas Towers)
  • One 3/4" PVC-T (Home Depot, ACE, McMaster 4880K42)
  • Two 3/4"-to-1/2" PVC adapter (Home Depot, ACE, McMaster 4880K201)
  • One 3/4" PVC slip plug (Home Depot or ACE Hardware)
  • One 1/2x1/8 NPT brass adapter (ACE, McMaster 50785K64)
  • Five 1/8 NPT brass couplings (Home Depot, ACE, McMaster 50785K91)
  • Four 1/8 NPT CLOSE nipples (Home Depot, ACE, McMaster 50785K151)
  • Three 1/8 NPT hex nipples (Home Depot, ACE, McMaster 5485K21)
  • Two #8 brass wing-nuts (ACE)
  • Two #8 x 3/4" brass screws (Home Depot or ACE)
  • Two #8 brass nuts (Home Depot or ACE)
  • Two #8 copper-plated steel split lock washers (ACE)
  • One 36" long-1/8" dia. brass rod (ACE, Home Depot, McMaster 8953K41 $1.77/6')
  • One 3/8x16 x 1-1/4" hex head carriage bolt, zinc plated (Home Depot, ACE Hardware)
  • One 3/8x16 x 12" hex head carriage bolt, zinc plated (Home Depot)
  • One 3/8x16 coupler, zinc plated (Home Depot or ACE Hardware)
  • Two 3/8x16 nuts, zinc plated Home Depot or ACE Hardware)
  • One 3/8 lockwasher, zinc plated (Home Depot or ACE Hardware)
  • Four #6 stainless steel 3/8" sheet metal screws (ACE Hardware)
  • Two #4 stainless steel 3/8" sheet metal screws (ACE Hardware)
  • Three #8 spade lugs (Home Depot)
  • 90 ft wire (Any gauge, insulated or not, for six 15-foot ground radials)
  • Six #8 x 1-1/2" brass wood screws (Home Depot or ACE Hardware)
Note: Recommended Tool - Harbor Freight 39391-5VGA Tap & Die Kit @ $12.99 is inexpensive and provides all the thread sizes you'll probably ever need.
You can order the parts as the MFJ-1964K kit through the MFJ website.
Aluminum Rod Preparation and Assembly
Referring to Figure 1, cut the 1/2" OD tubes to 18" lengths with a hacksaw or tubing cutter and de-burr the tubing. Thread the inside of both ends of three of the 18" long aluminum tubes with a 1/8NPT tap. See photo "Tapping". Once you've tapped these tubes, screw a 1/8NPT hex nipple into one end of each tube finger tight. Slide two 1" pieces of ½" heat shrink tubing over the rods. Then, on the opposite end of each tube, screw a 1/8NPT CLOSE nipple and a 1/8NPT coupling, again finger tight. See photos "Female & Male parts". Now grasp each hex end with pliers and tighten everything as tight as you can. Don’t strip out the threads, however! Refer to "Male & Female with & without heat-shrink" to see photos of the completed tube ends with and without the heat-shrink in place.
Loading Coil Assembly
Screw a 1/8-NPT coupling on each end of a 0.7" 1/8-NPT CLOSE nipple as tight as possible, using pliers or wrenches. Now unscrew the couplings. One end of the nipple will brake loose from one coupling, and the other end will stay tight in the remaining coupling. You’ll now have a female and male end that will fit over each end of the 3/8" diameter wooden dowel used for the coil support. See "Nipple & couplings". Referring to Figure 2, thread a 3-1/2" long piece of the 3/8" diameter wood dowel using the 1/8NPT die. Now you can screw the male and female brass pairs directly onto the wood dowel (screw the couplings snugly on, but do not strip the wood threads). Drill a 1/8" diameter hole completely through each of the 1/8-NPT brass couplings and dowel as shown. Next cut two 3" lengths of the 1/8" diameter brass rod. Insert one of these 3" sections through the holes on one brass coupling. Center the rod so that equal lengths are available on both sides of the coupling, and solder the rod to the coupling with a large soldering iron or torch (be careful not to burn the wood dowel with the torch!).
Now cut a 3" length of the MFJ-404-008 coil and position this coil such that the 1/8" diameter 3" brass rod just installed pokes through the last two turns on the coil (Note: You can use the full 5" length of coil if you wish, which will give you more options for shortening the antenna on given bands. Change the wood dowel length to 5-1/2" if you elect to do this.). See "Coil before soldering". Solder the coil turns to the rod. On the opposite end of the coil assembly, insert the remaining 3" brass rod through two adjacent turns on this end of the coil, through the brass coupling, and through the coil turns. Solder the coil turns to the brass rod, and then solder the brass rod to the coupling. See "Coil after soldering". If you wish, you can use a 1-1/2" piece of 1/8" brass rod and support each side of the coil at a single point. This will make assembly easier, but the coil support won't be as robust.
Now indent every other turn on the coil with a small flat-head screwdriver. You will need to do this on opposite sides of the coil to give you plenty of adjustment capability. Finally, on the end of the coil with the brass nipple (male end), solder a 6" piece of insulated wire terminated with an alligator clip. For extended outdoor use, you may wish to treat the wood dowel with varnish.
Base Assembly
Note: Check the alternative matching bases in another article on this web page.
I used a 3/8x16 x 12” zinc plated hex head carriage bolt for the base spike. Only 1-1/2" of the carriage bolt is threaded, so I used the long smooth end of the bolt to go into the ground after cutting off the hex head. I also used a 3/8x16 x 1-1/4" zinc plated hex head carriage bolt at the base of the PVC assembly, and a 3/8x16 zinc plated coupler to attach the 1-1/4" bolt to the 12" bolt as shown in Figure 3. This way you can leave the long bolt off if you want to bolt the base assembly directly to a metal plate or trailer mount. Or you can screw on the long bolt for ground mounting.
Referring to Figure 3, drill a 3/8" diameter hole into the 3/4" PVC plug used for the base support 1-1/4" carriage bolt. Cut off about half of the length of the 3/4" PVC plug to leave plenty of room inside the "T" for wiring. Solder a ground wire to the head of the 3/8x16 x 1-1/4" carriage bolt as shown, insert the carriage bolt threaded end into the plug, and secure with a 3/8x16 nut and a lockwasher as shown.
To prepare the 12" carriage bolt, cut off the hex head and round this end with a file. Screw the 3/8x16 coupler over the threaded end, and screw the 3/8x16 nut against the coupler (lockwasher should be between the nut and coupler). This 12” carriage bolt assembly can now be easily screwed on to the 1-1/4” bolt on the base assembly for ground mounting.
Now place the SO-239 temporarily over one of the 1/2"x3/4" PVC adapters and mark the location for two #4 x 3/8" stainless steel machine screws that will hold it in place. Carefully drill two 1/16" holes at these points. Place the 3/4" PVC plug/spike assembly in the "T" and drill two 1/16" diameter holes through the "T" and plug. Remove this assembly from the "T" and drill out these 1/16" holes in the "T" to 1/8". Also drill out two holes in the SO-239 connector to 1/8" since the holes to give plenty of space to pass the #4 x 3/8" sheet metal screws.
Next we'll prepare the antenna interface at the top of the base. First, cut off part of the 3/4 x 1/2" PVC adapter so as to leave additional room in the "T" for wiring. Solder a piece of #14 copper house wire directly to the inside lip of the 1/2 x 1/8NPT brass adapter. You'll need a large soldering iron or a Solder-It torch since the brass adapter mass is pretty large. Screw this adapter tightly into the 3/4 x 1/2" PVC adapter.
Now solder a wire to the center conductor of the SO-239 connector as shown. This wire should be soldered to the wire stub on the 1/2 x 1/8NPT brass adapter at the antenna interface, and then to the upper wing-nut assembly. Solder a short piece of copper braid (from a piece of RG-58 cable) from the SO-239 ground (solder directly to the SO-239 body) to the brass ground screw, and finally to the wire soldered to the head of the 1-1/4" carriage bolt. You can now complete the assembly of the base by inserting the PVC plug/1-1/4" carriage bolt assembly into the "T" and installing the stainless steel sheet metal screws as shown in Figure 3. Alternately, you can PVC-glue everything in place, but you'll never be able to get the assembly apart again if you do this. Incidentally, the upper wing-nut assembly shown is used to add capacitive or inductive base matching should you want to improve your VSWR on the lower bands. See photos "Base with Spike" and "Base and Spike".
Ground Radial Network
The radial network consists of six 15-foot radials using any gauge wire, insulated or not (I use #22 insulated wire). I've found it best to make up three pairs of two wires each attached to a #8 spade lug on one end of each pair. This minimizes the hassle of deploying, and later rolling up, the radials. The three #8 lugs attach to the ground screw on the base assembly. When the wires are rolled up, hold them together with twist-wraps. On the outer end of each radial, solder on a 1-1/2" brass wood screw. These screws are pushed into the ground to hold the radials in place. Put a blob of hot glue on each wire/screw soldered interface to give it a little strain relief.
Guying
While this antenna is self-supporting in a low-breeze environment, in many cases it will be necessary to guy the antenna due to its 16-foot length. For effective guying, I attached nine-foot lengths of nylon cord (3 pieces) just above the base of the 10-foot MFJ telescoping whip. This is easily done by taking a tie-wrap and closing it just enough so that it won't slide over the base of the MFJ whip. Cut the 9-foot sections of nylon cord and heat the ends with a match to fuse the nylon so it won’t unravel. Tie one end of a 9-foot section of nylon cord around each tie-wrap and secure with hot glue or epoxy. For the ground stakes, you can use the extra piece of aluminum tubing (you only used 4-1/2 feet of the 6-feet purchased). Cut the remaining 18" piece of tubing into three six-inch tubing sections. Attach the non-tie wrap end of the nylon cord to one end of each tube with hot glue. Also plug the open ends of the three tubes with hot glue. For storage, wrap the nylon cord around each brass stake and hold in place with masking tape. See photos "Guy Closeup", and "Nylon wrapped". See "Coil & Guy" for a photo of the guys attached to the telescoping MFJ whip. When bolted to a trailer mount or plate, the antenna should really not need guying unless the wind is very strong.
Antenna Assembly
To assemble the antenna, first screw the three 20-inch rods together, and then screw these into the top of the base assembly. Push this base/rod assembly firmly into the ground, keeping it as vertical as possible. Next screw the loading coil and telescoping whip assemblies together. Slip the three guy tie-wrap/nylon cord assemblies over the whip and extend the telescoping whip. Screw this entire top assembly into the female end of the aluminum tube assembly currently pushed into the ground. Finger tight is all that is necessary for all brass fitting interconnections. Finally, push the guy rods in the ground and extend the six radials. Attach the common ends to the ground screw on the base assembly.
Antenna Set-up
To begin, use an antenna analyzer set to 5340 KHz to locate the coil tap point that gives the best VSWR. Mark this tap point. Repeat at 5380 KHz. Move to 40 meters and repeat, again selecting two taps on 40 meters so as to give you enough band coverage. Repeat again for 30 meters -- only a single tap is required for this band. For 20-meters, you will find that only the top turn of the coil is necessary for resonance. The antenna is almost a quarter-wave long on 20 meters.
For 17, 15, 12 and 10 meters, you will need to short out the entire loading coil and then adjust the whip for resonance. On these bands, the antenna will be a quarter-wave long. Alternately, you can remove two tubing sections for 17 and 15 meters, and all three sections for 12 and 10 meters, but you’ll still need to adjust the telescoping whip length. Use a permanent black marker pen to indicate the correct band positions on the telescoping whip.
You can either clip the alligator clip-lead directly to the coil turns, or use the MFJ-605-4001 coil clips. From this point forward, just go back to these tap points, or re-adjust the top whip as necessary. The VSWR should be fine.
If your rig cannot tolerate a 2:1 VSWR, you will need to add a 330 pf 300V silver mica capacitor across the two wing-nut assemblies for 60 meters, and a 220 pf capacitor for 40- and 30-meters. See "Base & capacitor". No capacitors are needed for 20-10 meters. I find that neither my IC-706MKIIG nor my IC-703 is bothered by a 2:1 VSWR.
Mounting Options
You can easily make a 3/8x24 interface so that the antenna can be mounted on a standard 3/8 x 24 ham mount. This would be useful for those with a standard ball mount on their car who want to use this extended length antenna when stopped. As discussed earlier, the 1/8-NPT thread is just a slightly tapered 3/8x24 thread. And, while the 3/8x24 standard stud will screw into a 1/8NPT thread, the 1/8NPT nipple will not screw into a 3/8x24 threaded hole. Therefore, an adapter is necessary.
Referring to Figure 4, screw a 3/8x24 bolt (your local hardware store again) tightly into a 1/8-NPT coupling. Cut off the head of the 3/8x24 bolt with a hack saw and file carefully so that the threads are OK for screwing into a 3/8x24 socket. You can now screw this assembly onto the 1/8-NPT nipple on the bottom aluminum rod section.
Conclusion
This antenna is longer, lighter, more compact, easier to fabricate, and gives you more mounting options than the original unit published in QST. Experiment with the antenna length -- i.e. remove a section or two, use more or fewer sections, decrease or increase sections lengths, or place the loading coil in different positions. For best efficiency, try to keep the antenna as long as possible and the coil as high as possible.
And don't hesitate to make changes based on hardware availability. Try brass or copper tubing, or even wire wrapped 3/8" fiberglass or wood dowel. Use different PVC assemblies. Its fun to design antennas "on the fly" while standing in the plumbing section of your hardware store, which can lead to interesting discussions with the clerks!



Figure 3 -- Base Assembly

Figure 4 -- Adapt to Standard 3/8x24 Base

Author & Disassembled Antenna

Author & Vertical

Front Yard

Tapping The ½" Aluminum Tube

Parts For Female End

Parts For Male End

Female End: With & Without Heat-Shrink

Male End: With & Without Heat-Shrink

Nipple & Couplings

Coil Before Soldering

Coil After Soldering

Base With Spike

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Some Thoughts on What to "Hang", and Where


Some Thoughts on What to "Hang", and Where

You've just arrived at your potentially "new" QTH for the first time, and decide to do what most hams do; look around for possible antenna sites! Let's see... Would a tower and beam install here? Well, you'd better see how far away it is to potential electrical hazards like overhead power lines and their associated drop-lines to the house, garage, or out-building. The height of the tower, and width of the beam elements come to bear when distancing from those hazards. Should it/they fall over, or the elements come into contact, it's BIG trouble, or even injury, and/or death!
Now it's time to investigate possible sites for other/alternative antennas. Suppose your mindset is on a nice ¼ wavelength vertical with radial system (Groundplane). Is the roof of the dwelling an option? Sometimes your XYL will permit such an installation, but will your subdivision or housing association? If they're not issues, then the roof might be a great place for a ground plane... The radials can droop most times, and even a multi-band vertical rests well "up there..." Cut a few radials for each band ("snake" them if you have to), or use an AV-14RMQ Roof-Mounting Kit when possible, and you'll probably be happy with the performance. Be sure and create a good path for lightning to terminate! Remember, the XYL...
Another place for the ¼ wavelength vertical, or an inverted L with radial system, is ground-mounted... First, it's time to check the soil condition(s). If it's high-resistance, consisting of a lot of silicates (sandy) and mica-shist (insulators), then I would think twice unless I could go to a ½ wavelength installation (voltage-fed or MFJ-1796,98 series). With poor ground conditions, you'll never have an efficient Marconi (current-fed) system, even though your "match" may be 1:1; losses are too great. So, the voltage-fed ½ wavelength vertical or inverted L may be the solution; sure would be efficient in these soil conditions compared to the current-fed "Marconi"... Use an L-Network at the base of the vertical (or vertical section) and you'll get the match you want, and some nice bandwidth to tune as well.
If good soil ground conditions exist, then go for your home-built or commercial antennas (MFJ-1792; 1795 series; or Hy-Gain series) using a good ground plate as well (MFJ-1904). Install the ground radials for best performance, and you're on the air!
If you find that a tower or pole in the yard isn't an option, and an inverted V hasn't a place to hang, or the coax can't come down in the center of the yard, then try an end-fed antenna. The End-Fed Zepp (MFJ-61xx series) is a great radiator, and doesn't demand a lot of height. Now, it's time to look for places to erect "poles/masts".
If you have a privacy fence (or any fence for that matter), and it follows the property boundaries to an extent, then try a couple of masts at ~30 feet high or so; even ~20 feet will do in most cases... Guying may not be an issue if you can affix to a sturdy privacy fence, and don't try to hang heavy gauge wire and traps. Use #18 copperweld for your antenna radiator; light-weight and strong. Sturdy masting helps eliminate the guying requirement as well. Once you establish the maximum distance between "poles" or other tie-off points such as structures (ends of the house) or trees, you can determine what antenna you can "hang".
The End-Fed Zepp is available in a single-band configuration (MFJ-61xx series), so you only need to attach the coax, and operate! For multi-band use, run the ladder-line into the shack or to a 4:1 balun, with coax to the shack, and you'll tune most bands. The inverted L has already been discussed, but finds a home close to structures just fine. So, using one next to a pole is quite acceptable.
Even antennas with some degree of gain can be erected using the schemes already mentioned. The 2-element collinear array (MFJ-62xx series) can find a nice place to hang, and give a bit of gain too (See Antenna Talk #1).
How about dropping that 17 or 20 meter, or even 30 or 40 meter ¼ wavelength vertical down from a run of horizontal line between two supports? Or, even from a horizontal section of an existing antenna? Place an insulator on the wire or line, and "hang" the vertical antenna (up to 30 feet or so) from that point! Then, install your ground system and/or matching device right there (at the hang-down point). It may even help your radiation from the horizontal antenna!
Look for a basement window retaining wall as a good ground connection as well if it is indeed metal. The deeper the wall, the better the ground. It's a good location for a feedpoint of a ¼ wavelength Inverted L. You'll find this in Townhome/Condo situations most often. Shortened wire antennas (MFJ-17754; 17758) can be located where not much horizontal distance is available. Use an external antenna coax switch (Ameritron RCS series) to select your antenna of choice.

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3-Element Bob-Tail Curtain Array


3-Element Bob-Tail Curtain Array

Bob-Tail Curtain Vertical arrays do not require a radial ground/earth system, nor do they need any "steering". The antenna is "broadside" array, bi-directional, and perpendicular to the run of the wire. The center ¼ wavelength wave is fed with coax using a simple "L-Network" installed at the base of the center vertical if the pole is at, or near minimum height (35 ft). A hi-voltage variable capacitor of ~ 100 -150Pf, and ~20 turns of an 8 TPI, 2 1/2" diameter Airdux coil will do. Another option is using a remotely-located, weather-protected auto-tuner (MFJ-993), which can also provide operation on other bands.
The end verticals act to "binomial-cancel" signals off the ends, and vector add to the center vertical resulting in gain (~10-15dB over a single vertical at ~2000+ miles). The real benefit comes from the deep nulls off the ends, which can effectively null-out such stations such as "JA's/Caribbean" when the interest is Europe/Oceana. The downside: noise levels are typical of verticals when compared to horizontal arrays (2-3 units higher in most cases).
Orientation is best broadsides NE/SW and/or NW/SE; however, super results are achieved with right-angle installation pairs for world coverage. Great signal reports result; while cutting through the pile-ups to DX stations of great distance. Long path results are very good, and one usually can work Europe "round the clock" in winter from higher latitudes.
The Bobtail Curtain Array is enhanced when a ½ wavelength vertical element is placed between 0.2 and 0.25 wavelengths behind the center element to afford some unidirectivity as a parasitic reflector. Similarly, a parasitic director vertical element placed in front of the center vertical at about 0.12 to 0.15 wavelengths enhances unidirectivity even more. These elements can be "loaded" to achieve their 1/2 wavelength electrical length. However, when going unidirectional, you lose the world coverage aspect of a pair of arrays in right-angle configuration.
Another configuration is adding another array aligned in parallel, spaced 1/8th wavelength, and connected by a 3/8th wavelength coaxial delay line. This provides maximum forward gain and good unidirectivity.

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"Balanced Line" Franklin Collinear Arrays


"Balanced Line" Franklin Collinear Arrays

The Franklin Array exhibits good gain (~4.5 Db), and delivers better than average signals, even when hung at only a quarter wavelength (low). This is possible since the array has no vertical component or vertical directivity, while capture area, and horizontal directivity and gain increase substantially with the 4-element collinear configuration. The MFJ-64xx arrays use fully balanced tuners (MFJ-974H, MFJ-974, and MFJ-971 series) to apply power to the array, and match the system to coax input. Figure 1 illustrates a Franklin Array.
Dimension "L1" represents a ½ wave, "L2" represents slightly less than ½ wave, and "F" a ¼ wave, which, in this case is a ¼ wave stub, used for phase-shifting. The antenna is a "broadside array," and is bi-directional perpendicular to the run of the wire.
A pair of these antennas at right angles (NE/SW; NW/SE for example) can provide world-wide coverage when used with a suitable antenna switching system. The added gain means your array presents an effective power gain of "3". This means 100 watts applied results in the effective radiated power of ~300 watts! What if you apply 1500 watts out? Pretty good results for "hanging wire!"
If height is a constraint, this antenna functions better than average at even a bit less than a ¼ wavelength above ground/structure. However, it really performs best if "hung" at a ¼ to ½ wave; up to ¾ wave. Higher than that provides diminishing return. Once fully balanced tuned, you'll find the antenna presents a low SWR across the entire band. However, it is a "one-band antenna" functioning as a Franklin Array; other bands provide varying patterns when tuned and matched.
Especially important is keeping the symmetry of the antenna in reference to its ½ wave radiators. They must not sag more than a foot or so, with pulled-tight being the best installation. The feedline/stub can be "bent" at the bottom, or pulled away at an angle, and some twisting is OK. Practically, it is best to let the stubs/feeder hang straight down and tie them off with rope to avoid lashing about in windy conditions.
Figure 1
Franklin Array (Four Half-Waves Collinear/In-Phase)
To summarize, these antennas are intended for single-band use (your favorite):
  • 15 meters (92 feet long; 12 feet high)
  • 17 meters (108 feet long; 13.5 feet high)
  • 20 meters (136 feet long; 16 feet high)
They require two tie-off points spaced far enough to accomodate their width and length, and a height at least close to ¼ wavelength. Note that these arrays "hang and play" in about same distance taken by an 80 meter doublet. When using two antennas, try to locate the antennas in an "L" or "T" ("X") configuration (at right angles) as illustrated in Figure 2.
(Looking Down From Above)
Figure 2
Two Antennas @ Right Angles (Suggested Optimum)
We hope you will benefit from their ease of installation, efficiency, and quality construction.

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"Hang & Play" Basic Collinear Arrays


"Hang & Play" Basic Collinear Arrays

These days many Hams are seeking ways to improve their reception and up their signal strength, and are resorting to wire antennas from the past fed with ladder-line, used in conjunction with tuners and/or baluns to accomplish matching to 50-Ohm coaxial line. G5RV's and various flat-top configurations fed at the center, or off-center as in the Windom antenna, are very popular as well.
These are generally used as multi-band antennas, but usually require tuning of some sort on each band as previously mentioned. Routing the ladder-line into the operating environment sometimes results in RF voltage nodes appearing in the operating area (shack), and may cause interference/adverse affects to telephones, computers, and other electronic/ electrical devices used in the home.
What if we used an antenna that in the first place is quiet when compared to inverted "Vee's" (and verticals, especially)? A reduction of two to three "S" units of noise may make the difference in that DX contact you can now hear above the noise! And, the modest gain this antenna exhibits (1.6 - 1.8db) might also make the difference in whether that station also hears you. For example, only 1.5 db of gain increases your effective radiated power by half-again as much; from 100 watts to 150 watts. Increased receive capture area is another factor in the good performance of this antenna; twice the capture area of a doublet, or inverted vee-type "droopy doublet."
The MFJ version of the classic Collinear Array consisting of two ½ wave radiators in phase certainly fits the bill in all these circumstances. And, as a bonus, you can virtually "hang & play" this antenna as we construct them. No tuning, trimming, etc. required.
Once connected, you'll find the antenna presents a low SWR across the entire band. However, it is a "one-band antenna" depending which band you chose. Figure 1 is a generic illustration of the antenna with its shorted stub and coaxial connection.
Figure 1
Two-Element Collinear Array
Dimension "L" represents a ½ wave, and "F" represents a ¼ wave, which, in this case is a ¼ wave stub, used for matching and phase-shifting. The antenna is a "broadside array," and is bidirectional perpendicular to the run of the wire. A pair of these antennas at right angles (NE/SW; NW/SE for example) can provide world-wide coverage. And, when used with a suitable antenna switching system (Ameritron RCS-10), switching is convenient and fast, with only a single-line feed into the shack. Or, you can run both coaxial lines into the shack, and effect switching with a wall-mounted unit (MFJ-1700C).
If height is a constraint, this antenna functions better than average at even a bit less than a ¼ wavelength above ground/structure. However, it really performs best if "hung" at a ½ wave; up to ¾ wave. Higher than that provides diminishing return.
Especially important is keeping the symmetry of the antenna in reference to its ½ wave radiators. They must not sag more than a foot or so, with pulled-tight being the best installation. The feedline/stub can be "bent" at the bottom, or pulled away at an angle, and some twisting is OK. Practically, it is best to let the stub/feeder hang straight down and tie it off with rope to avoid lashing about in windy conditions.
To summarize, these antennas are intended for single-band use (your favorite):
  • 17 meters (54 feet long; 13.5 feet high)
  • 20 meters (64 feet long; 16 feet high)
  • 30 meters (90 feet long; 22.5 feet high)
  • 40 meters (130 feet long; 32.5 feet high)
They require two tie-off points spaced far enough to accomdate their width/length, and a height at least close to ¼ wavelength. When using two antennas, try to locate the antennas in an "L" or "T" ("X") configuration (at right angles) as illustrated in Figure 2.
(Looking Down From Above)
Figure 2
Two Antennas @ Right Angles (Suggested Optimum)
We hope you will benefit from their ease of installation, efficiency, and quality construction.

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40m Carolina Windom


There are two versions of the CAROLINA WINDOM® 40 Compact™ Attic Antenna. Each utilizes all of the main features of the CAROLINA WINDOM® 40 Compact™. Beyond that, the antennas are optimized for installations that are close to the ground, like attic and similar installations. The difference in the two models is only in the length of the Vertical Radiator and the bands covered. All of the major HF bands are covered by both models. However, the CAROLINA WINDOM® 40 AV6 Compact™ has a slightly higher SWR on 30 meters, but can still be tuned with a manual tuner or a wide range automatic tuner. If, for some reason, the automatic tuner in your transceiver cannot tune the CAROLINA WINDOM® 40 AV Compact™, an automatic tuner range extender (MFJ-914) can be used.
CAROLINA WINDOM® 40 AV9 Compact™9 foot Vertical Radiator
CAROLINA WINDOM® 40 AV6 Compact™6 foot Vertical Radiator
The Vertical Radiator may be supported by the attic's rafters to gain the extra length needed. The antenna's radiation pattern will be skewed slightly, but there are many other factors which will affect the radiation pattern of an attic installation, so this is not a major issue.

SPECIFICATIONS

  • Freq. coverage: 40 - 6 meters**
  • Radiator length: Horiz. = 34'
  • Foldback element approximately 8.5'/8' drop
  • Polarization: Both vertical and horizontal components
  • Feed line: 50 ohm Coaxial cable
  • Tuner needed: Yes
  • Power Rating: >1000 Watts but this level is not recommended. For maximum safety, keep the power output of the transceiver at 200 watts or less.***
  • Radials? Not required
FEATURES
  • Most ham bands covered including the WARC bands and 6 meters.
  • It is an excellent receiving antenna.
  • Installation is easy. It's far less trouble than putting a lot of separate antennas in your attic.
  • Special Matching Transformer
  • High efficiency - no ground losses
  • Ground independent - radials not needed
  • The Vertical Radiator provides important vertically polarized components to the radiation pattern which improves signals on the higher bands.
  • The new Matching Unit enhances vertical radiation
  • Automatic tuners in most current rigs will tune this antenna.
* Based on user reports, field evaluations, and product reviews. Gain is due primarily to the low angle radiation pattern.
** The CAROLINA WINDOM® 40 AV6 Compact™ may require a manual tuner or wide range automatic tuner to cover 30 meters. An MFJ-914 automatic tuner range extender will extend the tuning range of your automatic tuner by a factor of about 10.
*** While the antenna is capable of handling more than the recommended 200 watts output on SSB or CW, the close proximity to people and electrical devices inside your house may result in excessive RF radiation levels. Interference with other electronic devices is possible when an antenna is in such close proximity. 
6 m: Limit the power to 100 watts and limit the use to CW/SSB duty-cycles.
Depending on the installation, this antenna may be able to handle AM, FM, RTTY and other high duty-cycle modes if the output power from the transmitter is kept below 100 watts. Under no circumstances, should you exceed 100 watts in these modes when utilizing the antenna inside your dwelling. Also, monitor your reflected power. It it drifts, reduce power.


Performance
An antenna support at a height of 15 feet above ground is not going to perform nearly as well as the same antenna supported at 50 feet. Fortunately, the Vertical Radiator in the CAROLINA WINDOM® 40 AV9 or AV6 Compact, will provide better performance than a simple dipole at the same height, but the low support height will reduce the effectiveness of any antenna. However, that doesn't mean that an attic antenna isn't effective. There is a member of a local DX club who uses only attic antennas and has worked hundreds of DX countries (entities). He does live in a two story house, so his antennas are between 25 and 30 feet in the air. Still, it's quite an accomplishment.
I will say that during the testing phase of the CAROLINA WINDOM® 40 AV Compact™, I was pleasantly surprised at how well it actually performed. Most of my testing was done at 20 feet above ground. My reference antennas are supported much higher, but there were times when there was little noticeable difference. The signal strength of incoming signals and signal reports received were only down an S-unit or so from the standard antennas. On other occasions, the difference was larger, as you would expect. The bottom line is this: The CAROLINA WINDOM® 40 AV Compact™ provides a way to put out an acceptable and certainly effective signal on most, if not all, important HF bands. The actual results will depend on your installation, circumstances, and the actual location and height of the antenna installation. Some attics are loaded with metal ducts and wiring. This does not lend itself well to good antenna performance. In some cases an attic installation may not be practical due to metal faced insulation, duct work, wiring and many other things that will interfere with an antenna operation.
Initial feedback from customers installing the CAROLINA WINDOM® 40 AV Compact™ in their attics report better than expected results. Certainly, installing a CAROLINA WINDOM® 40 AV Compact™ is going to give you better results than not having an antenna at all. The multiband coverage and coax feed are all pluses of this antenna system. Still, it can't defy the laws of physics. On the other hand, it just might be your ticket to years of continued enjoyment of Amateur Radio.
Outside Installation
The CAROLINA WINDOM® 40 AV Compact™ is fully weatherproofed (you have to install some Coax Seal which is provided to complete weatherproofing). The antenna could be installed on top of a roof and held in place with roofing cement or other appropriate product. It can be painted to camouflage the installation. It can even be installed as a normal antenna between two supports. If you have that option, support the antenna as high as possible.
With an attic installation, keep the power down. Insulate the wire from wood rafters, floors, etc. The wire is insulated, but you want to insure that the safety factor is high. Don't just nail the wire to the wooden structure. Just use good installation practices, keep safety foremost, use the proper antenna geometry and you'll enjoy many years of service from the antenna. 
VERT™ (Vertically Enhanced Radiation Technique)
The CAROLINA WINDOM® was the first antenna to take advantage of 'VERT™' (Vertically Enhanced Radiation Technique), and this feature continues with the CAROLINA WINDOM® Compact™.
VERT™ (Vertically Enhanced Radiation Technique) is a radiating feed line technique that produces a controlled, low angle vertical radiation pattern. The effect is absent from most ordinary antennas. Field tests, user reports and seven product reviews confirm that the CAROLINA WINDOM® will give you a remarkable performance advantage. The off-center fed CAROLINA WINDOM® provides unusually good performance on all bands covered, including the WARC bands. It's an ideal antenna for those of you who do not wish to use a tower and beam. The CAROLINA WINDOM® is also ideal for those who want a high performance antenna to cover the bands not covered by your beam antenna.

The Secret

It's the Vertical Radiator. Combined with the Dedicated Matching Unit and special Line Isolator, it is responsible for the improvement in the low-angle, vertical radiation pattern.

NRAI Snug Fit Insulator 
Nail-on Rafter Insulator for wood holds antenna wire about 3/4" from surface. Use with rope or insulated wire* up to 5/16". At least 10 insulators are recommended for rafter installations.Requires two (2) #8x3/4" screws supplied by the user.
 SRAI Standoff Insulator
Screw-in Rafter Insulator for wood holds wire about 6" from surface. Recommended for a deluxe installation. Use with rope or insulated wire* up to 5/16". At least 10 insulators are recommended for rafter installations.
Go to the antenna insulators page
*Use insulated wire in attic installations.

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