On Sat, Sep 12, 2009 at 12:32 AM, John Geiger aa5jg@yahoo.com wrote:
What is the minimal antenna you can use on 10m to hear the AO7 downlink in Mode A? I have a homebrew G5RV type antenna up and can't hear AO7 on it at all. What kind of antennas are others using on 10m for mode A?
73s John AA5JG
John --
I have had verticals of heights between 23' and 45' that could hear the 10m downlink, even when connected to 100' of RG-8 and no preamp.
My guess is that your G5RV is highly directional at 10m. Such long doublets develop flower petal lobes of high gain in the horizontal dimension with very deep nulls between them. On HF this isn't such a big issue, since the RF is going *somewhere*: you probably don't care if you work NZ or Australia. (Ok, with the sunspots these days you'd be overjoyed with either.) However, with satellite reception such patterns make reception very difficult. Moreover, your G5RV is likely to be up a good height at 10m, pushing its vertical pattern down to the horizon. So now, to hear this bird, it has to be between, say 5 deg up and 15 deg. up and within the 'petals' of the horizonal pattern.
Here's a situation where less truly might be more. A lowish dipole will reduce the lobes, and crummy vertical will too, though in the other dimension.
Let us know how things work!
73, Bruce VE9QRP