On Mon, 23 Feb 2004 16:01:50 +0100, "Jan-Martin Noeding, LA8AK"
wrote:

here is the first mention of IP3 in the thread, I've asked whether it
is important or not, but have not received any confirmation and will
therefore not comment. If IP3 was said to be important I am aware of
other mixers, and have used some douzens SBL1, SBL-1X, CM-1, SRA1 and
other since 1977. A very easy mixer to use is TBA120=SN76660N.

If you have a very high-Q tunable front end filter, you usually get
away with a mediocre IP3. However, if wide open (1 octave) front end
filters are used, you would benefit from a high IP3 if you are using a
decent antenna.

If you try to receive the 7000 .. 7100 kHz amateur band in Europe,
with 100-500 kW broadcast transmitters every 5 kHz starting at 7105
kHz, the input IP3 number would have to be at least 20 dB higher than
the strongest broadcast signals or even 30 dB higher if you try to
receive QRP stations.

Attenuating the whole antenna signal with a passive attenuator will
also rapidly drop the IP3 products, but sooner or later the weak
desired signal will be lost in attenuator thermal noise.

Paul OH3LWR