QRP EME on 432 MHz
If you have ever wondered what a single 14 foot yagi can do on 70cm, here is my experience.
I started experimenting with 432 EME in November 2000 using a single FO-22 yagi (no elevation). With 250W I was able to get QRZ? from a couple of stations on random. After increasing power to 550W, five stations were worked on skeds January through March 2001. Now I was hooked!
Everything came down off the tower in March (3 feet of snow on the ground) so I could add an elevation rotor. In addition, the preamp was relocated from the top of the tower to near the yagi feedpoint and cables were replaced. It's now fed with 55 feet of 1/2" LDF4-50A, then approximately 15 feet of Belden 9913F7 around rotors, up the H frame and to the relay mounted above the yagi boom (that's the transmit line). The result of this operation...
Far bottom -- 13 elements on 144 MHz; Near bottom -- 11 elements on 222 MHz;
Far top -- 5 elements vertical for 2m FM; Near top -- FO-22 and preamp for 432 MHz.
Next is a view of the preamp and relay mounted on the yagi.
Preamp and relay supported above the yagi boom
As you can see it's a little crude. By the way, there are three layers of plastic over the assembly, not just one! Although not easy to see here, there are seperate receive and transmit feeders plus a control cable running out of that assembly and along the boom. Finally a view looking down the boom...
Looking down the boom of the FO-22 yagi
Signal recordings...starting with an easy one and slowly moving toward weaker ones.
DL9KR, random during contest unfiltered or filtered.
KA0Y, random unfiltered or filtered.
K5JL on a sked unfiltered or filtered.
G3SEK on a sked unfiltered or filtered.
Several of the stations I have worked on random compare to this KA0Y sample. Many more fall somewhere in the range of the K5JL and G3SEK samples. I should mention that preamp is lucky if it manages 0.5 dB NF, so the receive is not as good as it could be. Unfortunately, the filtering used for the above samples doesn't do as well (at least for me!!) as what I use when I am operating. I don't have a proper setup for recording signals after my audio filter, so the samples were recorded with no filtering. Later, simple bandpass filtering was applied to each file to produce the "filtered" samples here. It's good but for me it's not as good as my trusty active audio filter can do.
I have worked 23 stations as of April 2002, several of them on random. I have heard many others and believe it is possible to work most stations having at least 26 dBi antenna gain. I have heard stations with 24 dBi, but so far they have not heard me.
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