John's antenna page
Antennas (my Latin education squirms a bit, but no one uses antennae) are fun to make and very satisfying when somehing really simple and cheap works really well!
This page has been reorganised, with most recent stuff first:
23cm quad loop
With the 23cm transverter approaching completion I needed something quick and easy to test out the receive section. This design by DL5NEG appears in the International Microwave Handbook which is where I came across it. My version is hardly modified at all from that on the web. It uses wire from some old "flat twin and earth" mains wiring (hence the old UK mains colours - it wasn't worth stripping all that plastic). There's a BNC connector for the feeder which is fastened into a loop made in the copper reflector wires. The ends of the quad are supported on bits of wire sleeving glued onto the radiator and reflector.
In its first outing this antenna was just the job to pick up a local beacon.
2m lambda loop loft antenna
My home QTH is not a good location for amateur radio; it's a flat, it's in the city, it has a very small garden surrounded by high buildings, it's in a conservation zone where "unsightly" additions are frowned on, and it's on a north facing slope with hills to the south. Not very promising, for either HF or VHF. To allow me to chat to the locals on 2m SSB I decided to do something about it - and about the best I can do is an antenna mounted in the loft, as high as possible. This is also described in more detail as a small project.
It seems to work well for chat across central Scotland with the bare FT-817.
70cm DK7ZB 12 element homebrew beam
These DK7ZB designs seem to work, so I decided to try one for 70cm. It uses exactly the same construction as the 2m designs below; the result is shown here and described more fully as a small project.
It was quite tricky to set up the feeder to get a good SWR but I think it's OK now, though it needs some more testing in the field.
2m DK7ZB 7 element homebrew beam
Being pleased with the success of the 5 element design described below, I decided to try for a bit more gain with a 7 element design that could also be taken to the top of a hill. The result is shown here and described more fully as a small project.
It certainly is considerably more directional than the 5 element beam, and will get more outings in contests.
80m inverted V
A long time ago I used to help Guy G3ZHL set up his portable station consisting of a homebrew 80m transceiver powered by a very heavy car battery, and an 80m inverted V set up on a very heavy collapsible pole. We now have some excellent modern materials and the pole is certainly a lot lighter - I have the SOTAbeams fishing pole described below, and also now a Spiderbeam 12m pole which is a lot stronger. Here's the Spiderbeam pole with an 80m inverted V; click on the photo and you should be able to see the choke coil at the top of the feeder.
2m DK7ZB homebrew beam
The B and Q components used for the 6m beam (below) are pretty good, and I found some (cheaper and) better aluminium tube - not anodised - on another outing there, so some was bought to make a 2m beam.
I used the design tool on the DK7ZB web site; I went for a 5 element 50 ohm design. Reflector and directors are 6mm tube, lengths as specified; the reflector needed an extension to get the full length (over 1m, and the tube is sold in 1m lengths) which I did by using an internal screw to hold the extra few cm on one end.
The radiating element is 8mm tube, mounted in a plastic 10mm tube - a good push fit, but with screws to locate the inner end and act as electrical connections. I'll add a diagram when I have time.
The boom is plastic plumbing pipe 22mm diameter; it's over 1.5m long so I may make a two piece version which would be marginally easier to pack.
This antenna had its first outing on 18 October 2008 from Billinge Hill - a little hill near my birthplace in Lancashire, but a SOTA summit nontheless which was duly activated.
The activity was great fun - 13 contacts in an hour including a Jamboree on the air station GB2JAM and a new distance record for me on 2m - Don, G0RQL, in North Devon - about 320km. I'm looking forward to getting this antenna going when the band conditions are better.
6m beam
The 2m beam worked so well I was enthused to try a 6m equivalent. This is made from components from B and Q, and I will write it up more fully in due course. It had its first outing on 13 September 2008.
It's a pretty spectacular beast considering that it all collapses into a 1m long package. However its frst outing resulted in no QSOs. It does work though - I could hear a beacon really well and proved its directionality with that. However my Morse is very rusty - never really listened to a beacon before - so didn't note down enough to identify it (on about 50.050 MHz). Ho hum - nothing like experience. Didn't realise beacons say a lot more than their callsigns!
I was on Scald Law to activate a SOTA summit (21 September 2008) and carted the 6m beam up there. No QSOs on 6m unfortunately; I picked up a broadband interfering signal from the south, which was pretty well nulled out off the side of the beam (pointing E or W) and even quiet off the back of the beam - so at least I know it's got some decent directivity! I also used this antenna in October 2008 - the 50MHz contest day - but unfortunately at low altitude (near sea level in the south west of Scotland), so with my 5W didn't manage to work anyone, though heard quite a few stations (GD0EMG a big signal, and I must have been off the back of his large beam) and was able to test the antenna nicely. I decided that I needed to make a linear amp for 6m to improve my chances.
Latest update: with the 6m linear working, this antenna worked OK in the same contest in 2009, even though it was very windy and I had to keep the antenna low. I discovered when dismantling that in my haste I'd assembled the elements incorrectly, so it's still not had a proper test under contest conditions!
2m SOTA Beams antenna
With the idea of getting up the hills to do some operating, and the discovery of SOTA, this seemed to be the ideal companion to my FT-817. I first used it getting towards the top of Cairnharrow (SOTA GM/SS-191); I didn't get to the top - the mist came down and prudence comes first. It's a SOTA Beams SB270. It seems to work very well, and gave me a couple of solid contacts on SSB from Cairnharrow; it's shown here vertically polarised, used from the Mull of Galloway.
The fishing pole that comes with the complete kit is great, and I've used it for an 80m inverted V as well - unfortunately forgot to take a photo so that will appear later.