Saturday, May 9, 2009

Triangle Diversity

I decided that 2 antennas for diversity reception was not adequate. I have 2 verticals in the back of my property with good ground planes. In the front there is a pine with an eyebolt at about 45 ft. and a rope that goes through the bolt. I decided to cobble together a third vertical for RX. I made a little feed point bracket so I could attach a wire for the vertical element and added two radials at 180 degrees. At 45 ft the wire is a little long on 40 and a little short on 80 but should give pretty good output on either band.

The triangle is not a perfect equilateral triangle. It is 100ft on the base and about 180ft on each remaining side. With the F5K I didn't even need to make any kind of switching arrangement. I merely plugged one vert into ant 1, one vert into ant 3 and one vert into RX2. With this arrangement I can choose 1-rx2, 3-rx2, and 1,3 from the antenna control panel in the F5K

It happens there is some kind of contest happening in EU so the low end of 80M is quite active and its just a few minutes past the terminator flying over my head as I write.

Here is a clip of a HA8 station on 3503,


The effect is somewhat subtle but there is definite improvement is readability using the diversity set up.

I rotated around between the 3 antenna pairs and there was a definate advantage with ant 1.3 vs the other 2 pairs, both in signal to noise and in fading. I switched to 160 and there was only one domestic station calling CQ in 4 land and I was not able to get much diversity on him no matter what combo I chose. I switched to 40 and listend to some Russians in the contest and a completely different set of antennas gave the best response. This time RX2, 1 was best with RX2, 3 close behind. I have a lot more evaluation to do, but I think a triangle is a good first start for actually honing this receiving technique. At some point I may phase 2 of the antennas by making a phasing box, or possibly using my MFJ 1026 and feed that box's output against a single antemma

So much playing to do, such little time, and all it took was flipping another wire up in a tree.