Tuesday, 12 April 2011

Homebrew 2m Moxon.

Thoughts have turned (no pun intended) to directional antenna's, having looked at the Yagi and Quad antenna designs, I then stumbled across the Moxon Rectangle, this 2 element antenna offers similar gain figures to a 3 element Yagi, with better F/B ratio's.

I am quite active on the 2m band, but mostly on FM, you know chatting with your radio club pals etc, however in the vehicle I have the Icom 706, which has 2m SSB, I have made a few calls, but with little success, knowing that most use horizontal polarisation, myself using a dual band Watson 2m/70cm vertical.

For the Moxon I used two  3/4" 'tee' piece's and some scrap plastic pipe, along with some bare wire found at work, an SO239 socket and some cable ties, the most useful item ever.

Following dimensions found in the internet (link at the bottom) with use of a hacksaw, side cutters and tape measure, knocked it up in about 1/2 an hour.

I am unable to check the SWR properly, as I don't possess a VHF meter, and for some reason the 706's meter shows 1.2 even with no antenna connected, I did try it with an old cb twin meter, swr meter, checking on the cars vertical first for a 'sanity check' reading, against that it showed an SWR of around 2.5:1, so some adjustment required.

Initial test's showed it has directional properties, it opened a repeater 11 miles away, then did not when I turned the antenna around, I also found a continuous signal around 145.000 which I could alter the level of signal with the moxon, managed to find the direction and the signal was also better with the antenna in the horizontal.

The signal was an S9+ 10dB on Moxon horizontal, in the vertical position it was S9 with little noise, the Watson 5/8 vertical was then tried, S9 again, but slightly noisier.

Further tests to follow..

Typical radiation pattern.

No comments:

Post a Comment