>From: Peter Chadwick <Peter.Chadwick@gpsemi.com>
To: <topband@contesting.com>
>Date: Mon, 6 Oct 1997 17:13:38 +0100
>
>The Anzac patent on noiseless feedback should have run out by now. I
>can't find my copy of it, but it's pretty old - back in the 70's. I
>guess one point to bear in mind is how the amp responds when the tx
>antenna is radiating. If you don't really need a noise figure in sub 3dB
>area (which I doubt on 160), you could consider using a tube!
>
>73
>
>Peter G3RZP
>
Peter,
It is true that on 160 or generally on the low bands for that
matter, the background noise level is moderate to high. And full
size beverage antennas although not very effecient, are effecient
enough that an extremely low noise figure in the preamp is
probably not necessary. However, physically small wideband
(untuned) loop based antennas are very much les effecient than
even a short beverage. So these types of antennas (including the
EWE if sized to preserve pattern up to 7 - 10 MHz) really do
require a very low noise figure for the preamp that they require.
The Anzac circuit (or a push pull version of it for balanced
designs) should be near ideal for use with small wideband loop
receiving antennas for topband. Generally, the preamp needs to
be quiet enough so that you can hear the band noise with the
antenna.
73, Eric
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