Rik, tnx very much. I will test it and am curious about that!
That would of course be even the easiest solution for the RX.
In 08/2001, Rudi/DJ2EY has published a bandpass filter (4 LC Filters, loose
capacitive coupled) in the CQDL. I already thought about building such one. If
one is choosing an attenuation so that the Ls will not be overdriven, that
could give a fine SNR, better than with a attenuator that even filters the
wanted spectrum?
73, Stefan
-----Ursprüngliche Nachricht-----
Von: [email protected]
[mailto:[email protected]] Im Auftrag von Rik Strobbe
Gesendet: Montag, 28. Dezember 2009 17:50
An: [email protected]
Betreff: Re: AW: AW: LF: Influence of a TX antenna to a small rx antenna
Hello Stefan,
the problem with "big" antennas for RX is that they overload the
receiver and cause IMD effects. Most harmfull is 3rd order IMD and the
good thing with an attenuator between antenna and RX is that for every
dB attenuation the 3rd order IMD is reduced by 3dB. Therfor you may
want to increase attenuation as long as the external noise level is a
bit stronger (let's say 3 to 6dB) than the internal (RX) noise level.
As long as this is the case the attenuator will not affect the overal
RX sensivitity (although you will get little or no s-meter reading),
but IMD behaviour will improve by 100dB or more.
73, Rik ON7YD - OR7T
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