John Wells, M5AML.  QTH: Derby,  IO92GW. 

HOMEBREW AERIALS

 

I have successfully built the following aerials at my QTH:

 

1. 100' (30m) long wire at about 5' above ground (80m and 40m)
2. Indoor inverted vee dipole in the attic (20m to 10m)
3. Three element beam (2m band)
4. Four element beam (2m band)
5. Seven element beam (70cm band)
6. Short five element beam (2m band)

1. The longwire ran up one side of my garden (north east to south west) next to a wooden fence. Its height above ground was on average 5' (under 2m). At the house end of the wire there was a metal tube which I knocked into the ground to form some kind of earth. This was where I connected my ATU and ran co-ax through the conservatory window to my radio. I have successfully contacted stations in Wales, England, Scotland and Holland with this aerial on the 80m and 40m bands. This aerial was a real compromise but was invisible to neighbours! This aerial is really invisible now because I have taken it down so it isn't damaged during hedge cutting.

2. My inverted vee was my first amateur antenna and is the most used. It is situated in my attic and by using my ATU I can make contacts on any band between 40m and 10m. Performance is best on 17m and 15m and it really becomes poor at the lower end of 20m and on bands above 12m. Good contacts have been made at these extremes into Europe and during sporadic E openings on 10m. DX has been worked with just 5 or 10W PEP on 15m when conditions have been favourable.

3. For some 2m FM work I made a 3 element 2m band beam. I designed it using MMANA software and it has a theoretical front to back ratio of over 18dB. It is a real Heath Robinson affair at the moment - I used the ribs from an old golf umbrella, which were 2mm diameter for the elements and screwed these onto a piece of 1/2" timber from B&Q. I later replaced the director and reflector ribs with 2mm fence wire which I fixed onto the boom using hot-melt glue. The whole thing is fed using not-so-ideal RG58 coax with a BNC which is then adapted to an SMA connection for use with my VX5-R. This highly lossy method of feeding still gives me strong West Midlands stations at S9+ and also GB3DX (S4), GB3HH (S2), GB3VT (S3), GB3IN (S9) and of course GB3CF (S9).

The directivity of this aerial is quite impressive. At the moment I use it in my shack, balanced on top of a wardrobe. I have made contacts with a maximum of 5W PEP into North Nottinghamshire, West Midlands, Shropshire and under lift conditions Essex and I have even opened a French repeater! One summer I joined some clothes props together to form a 19' mast and put my Yagi on top. I could actually hear quite a few stations from the north including Barnsley and NW Manchester. Sadly this "mast" was too difficult to put up due to it tangling up in a couple of trees and a washing line, so now I am experimenting with an 8m long telescopic roach pole.

Since I acquired a Kenwood TR-751E I have been trying this aerial on 2m SSB with it mounted on a camera tripod in the shack.  At present most contacts have been made in the RSGB 2m UK Activity Contests with 5W PEP, best DX being Isle of Wight and almost making contact into France under tropospheric lift conditions.  Many contacts over a distance of 150km have been made using this set up and stations even further away have been heard including GM, GD, OK, and DL. 

I have now scrapped this aerial in favour of a short 5 element beam.  See 6.

4. I wanted to increase signal strength on 2m so I designed (using MMANA) a four element beam antenna with a greater F/B ratio than the 3-element aerial shown above. Initial tests showed that the directivity of the aerial was better than the 3-element but overall received signal strength was only marginally better than before.

This aerial was much larger than the 3-element which made it very difficult to handle especially indoors. The small improvement in performance over the 3-element beam didn't justify keeping the 4-element, so within hours of constructing the 4-element aerial, I dismantled it and then constructed a 70cm aerial (details below).

This 4-element aerial was constructed using 1/2" timber as the boom and the elements were made out of 2mm diameter steel fence wire. I didn't have any more umbrella ribs but I had acquired some of this wire which was much easier to cut than the umbrella. The elements were attached to the timber using hot-melt glue.


5. This 70cm yagi was constructed after I had decided that my 4-element 2m aerial was just too cumbersome. The 70cm aerial was designed using MMANA and was built using 2mm fence wire for elements, 1/2" timber for the boom and hot-melt glue for fixing the wires to the wood. I haven't had much opportunity to test this aerial but it shows very good directivity and a significant amount of gain over a telescopic whip. GB3GB and GB3CB come booming in! Low activity on 70cm FM means that I haven’t had any QSOs with it yet, but when there's that lift on I hope to be there.


6. This 2m beam is made from timber, M6 threaded rod (or sawn off bolts) and 8mm diameter aluminium tubing with a wall thickness of 1.5mm.  The inside diameter is 5mm which is ideal for tapping to accept an M6 thread.  Short threaded rods are pushed through holes in the wooded boom and secured with nuts either side of the boom to enable the tapped aluminium elements to be screwed on.  The length of the tubing is calculated by subtracting the boom thickness from the element length then cutting in half to create two tubes for each element.  A gap should be left between the two halves of the feedpoint.  I'll leave it up to you to work out how to achieve that.

Because of its screw-together construction all the elements can be unscrewed from the boom and packed away when not in use.  Much tidier than the other directional aerials I made.

I have tried this aerial mounted on a camera tripod indoors mainly on SSB in the RSGB UK Activity Contests and have worked as far as northern France without any difficulty using 5W.

Those are all the successful aerials I have made so far.  Time permitting I am also experimenting with other antenna systems the emphasis at the moment being on improving 2m performance.  Most aerials on this page have been designed using MMANA software.

 
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