Saturday, June 30, 2012

What is a MW0JZE - G3TXQ Hexbeam?

What is a MW0JZE - G3TXQ Hexbeam?

A G3TXQ Hexbeam is a full size 2 element Yagi beam with bent wire elements. From above the driven element resembles the shape of a letter M and the reflector resembles the shape of a letter  U. The Hexbeam can come in mono band or multi band versions with little or no loss of performance in any configuration. Each band acts as a monoband 2 element yagi with no coils or traps, so no loss. The whole antenna is fed with one 50ohm feedline and will require some sort of 1:1 balun/choke as close to the feedpoint as physically possible, this is normally 20m and is close to the top of the centrepost.

If you have a small area and want a monoband performance antenna then the Hexbeam will suit your needs.  At only 6.5 meters across it will fit inside most gardens. The turning radius is only 3.25 meters. Compare this to a 20m yagi with a span of 10.75 meters and a turning radius of 5.75 meters.

From the base of the antenna to the tip of the centre post the whole antenna is 107cm tall, this accommodates all 6 bands from 6M to 20M. As shown in the image below, 6m is the lowest band and all other bands are stacked above it.


How does the G3TXQ Hexbeam compare with other 2 element multi-band non trapped antennas? There are not many popular multi-band antennas available that are not trapped or that include the WARC bands. The first two that came to mind were the 2 element StepIR, this is a pure yagi antenna with straight elements and no traps mounted on a single boom. The second is the Optibeam OBW 10-5-10 which is more of a Moxon configuration with 2 elements for each band, wire elements and no traps. It does however use 2+ elements for 12m and 10m, not sure what this means but I guess it uses more than 2 elements on these bands in a parasitic format. I think the two comparison antennas are fair comparisons as the StepIR is a pure 2 Element Yagi, the Optibeam OBW10-5-10 is a wire antenna and the Hexbeam is a good mix of both.
Forward Gain Comparison Chart in DBd + 2.15 for DBi
Band2 Element StepIROptiBeam OBW10 5 106 Band G3TXQ HexBeam
Front To Back Comparison Chart in DB
Band2 Element StepIROptiBeam OBW10 5 106 Band G3TXQ HexBeam
 Cost £1000+ £1000+ £500
Size and Weight Comparison Chart 
 Antenna Weight Turning Radius
 2 Element StepIR13.6KG 5.53M
 OptiBeam OBW10 5 1014KG  4.3M
 6 Band G3TXQ HexBeam12KG 3.25M
MW0JZE - G3TXQ Hexbeam CentrePost
The MW0JZE - G3TXQ CentrePost is 107cm in height and material used is GRP tubing of 48.3mm OD with a 35mm ID (6mm wall)

Top of post is plugged with PVC rod and sealed with Epoxy Putty, a plastic cap is placed on top to give a finished appearance. A stainless steel eyelet is fitted to the top where all the support cords are to be attached.

RG-213 coax harness is fitted inside the post and M6 stainless steel machine screws are used to attach the wire elements to.

Stubmast is fitted to the base of the post and is 28cm long with 35mm OD. Wall thickness is 3.5mm and a plastic plug fitted is fitted to the end to stop any objects entering the inside of the post and damaging the coax harness.

Whole post is sprayed with spray paint and sealed from the elements.

Please note: This MW0JZE Centrepost is ONLY for the G3TXQ Hexbeam not the classic version

Hexbeam Hub
The MW0JZE - G3TXQ Baseplate is fitted to the bottom of the MW0JZE - G3TXQ Hexbeam centrepost, this is where the fiberglass spreaders are fitted.
Plate is formed from high strength and lightweight T6 aluminium plate, Plate is 6mm thick and professionally cut on a CNC machine for 100% accurately cut MW0JZE - G3TXQ Hexbeam baseplates every time. 
G3TXQ Hexbeam Hub by MW0JZE

All U-Bolts are M6 zinc and come with stainless steel washers, spring washers and nylock nuts. A maximum spreader diameter of 35mm can be fitted to the baseplate.
Top and bottom flanges are large diameter and will take a maximum of 48.3mm tube (not 2 inch). Flanges are formed from Magnesium Alloy, very light and very strong.
The MW0JZE - G3TXQ centrepost is fitted into the top flange, you can fit the bottom flange directly into a 48.3mm tube OR using the supplied collar it can be fitted directly into a rotator. 
Note: This MW0JZE - G3TXQ Hexbeam Baseplate will also work with the Classic version from Mike Traffie.

G3TXQ Hexbeam fibreglass spreaders
The MW0JZE - G3TXQ Hexbeam Spreaders form the shape and the framework of the Hexbeam.
Each MW0JZE - G3TXQ Hexbeam spreader comes in three (3) sections of pullwound fibreglass tubing for high strength and durability. 
1 x 1.5M with 22mm OD
1 x 1.5M with 17mm OD
1 x 1M with 12.7mm OD
Total assembled length of 353cm, NO CUTTING OR MEASURING REQUIRED!
Element clips are fitted to the spreaders to hold the wire elements in place, there is one for each band. These are made from UV resistant non conductive materials. They are held in place with a stainless steel machine screw and nut.
The end of each spreader section is sleeved with aluminium ferrules to prevent them splitting when pressure is placed on them when they are bent to form the shape of the G3TXQ Hexbeam by MW0JZE. Two (2) cords are fitted to the ends of each spreader be means of an eyelet or similar non ferrous fixing. One (1) is to be attached to the top of the MW0JZE - G3TXQ Hexbeam centrepost to form the bend in the spreader, the second (2nd) cord is attached to the tip of the next spreader, this forms the radius support for each tip. The cords are UV resistant polyester and each have a stainless steel hook or loop attached to the ends.
Note: These G3TXQ Hexbeam Spreaders by MW0JZE are suitable for the classic version by Mike Traffie

MW0JZE - G3TXQ Hexbeam Wire Elements
The G3TXQ Hexbeam by MW0JZE can be monoband or multi band. Normally due to size the Hexbeam comes in five (5) or six (6) bands from 6m to 20m. Each element is a separate entity and in no way reliant to any other bands. Adding or removing any element has little or no effect on the other bands.

Element format is Driver - Spacer Cord - Reflector - Spacer Cord - Driver with polyester cords being used as the spacer cord.  
Each G3TXQ Hexbeam element from MW0JZE is made from seven (7) stand copper wire with a PVC coating with polyester spacer cords, all joints are sealed with heat shrink wrapping.
Note: All elements come complete, no measuring or cutting is required

I have recently bought a MiniVNA and am improving on the SWR charts and readings.
More info will follow soon.
SWR is under 2:1 on all bands 
Forward Gain and Front/Back Figures Modeled @ 6m above ground
BandForward Gain DBd + 2.15 for DBiFront to Back DBd
For more in-depth info you can visit Steve G3TXQ the broadband Hexbeam inventors website by clicking here

1:1 Balun Options
Steve G3TXQ has done a lot of research on the use of different types of cores and air cored ferrites, the results can be seen on the chart below. For a link direct to his page please click here
The two types I refer to within this site are the 8T RG58 on FT240-43 but substituting the RG58 for RG142. Also the 6 x FB-31-1020 on RG213. There are many other ways listed on Steve's list below and more info can be found on his site.
6 x FB31-1020 Beads

The bead method is by far the cheapest way of introducing a 1:1 choke the antenna. Simply place six of the beads over the coax as close to the feed-point as possible. These beads have a 10mm ID so will only except coax such as RG-213.

 I sell the beads at £2.50 each or can make up a feedline as below for £30

  • 1M RG-213
  • High quality PL-259
  • High quality SO-259
  • 6 x FB31-1020 beads
  • Split end of coax WX proofed to feed Hexbeam.
Note always feed Hexbeam at lowest band!

FT240-43 Torriod
This form of choke is refered to as an Inline-Isolation Balun. Design is quite simple. 70cm of RG-142 high power coax coiled six times round a FT240-43 Torroid housed in a waterproof box and potted with Polyester resin. Termination is a chassis-mount SO-239 on opposite ends of the box. 

Fully Assembled Balun £50
Parts to build your own
Torriod £9.00
1M of RG-142 £10.00

Complete In-line Isolation Balun consists of
  • 10cm x 10cm x 5cm UV resistant Box
  • 1 x FT240-43 Torriod core
  • 1M RG-142 high power Teflon Coax
  • 2 x SO-239 Chassis Mounted Sockets
  • All fixing hardware stainless steel
  • Whole unit potted for 100% WX proofing
 Customer supplies own pigtail to feed antenna, feed at lowest band

Mounting Suggestions for the MW0JZE - G3TXQ Hexbeam
There are three ways in which to mount your MW0JZE - G3TXQ Hexbeam
  1. Directly into the rotator, this is by far the easiest but I would recommend a fairly robust rotator.
  2. On top of a stubmast in a cage, this has the advantage of being able to use a slightly lighter weight rotator as you can support the stubmast in a bearing arrangement on top of the cage. The Hexbeam has a low wind load of approx 5 sq feet so not much force on the rotor when placed in a cage
  3. Clamped to the side of another vertical pole using vertical pole clamps. This is a fast way to mount the MW0JZE - G3TXQ Hexbeam while portable, fast and cheap!!! Click here to purchase the clamps in the UK or just Google Shelly clamps, they are fine for the job.

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