Thanks Gian. At this QTH, which is in the first hop zone of 40m BC signals
on their way to N.America, the receiver's IMD3DR needs to be > 110 db approx
at 2 kHz spacing if used for weak signal SSB DXing above 7130 kHz. Of course
the LO must be very quiet. The big problem I have here is BC transmitter
phase noise and the enthusiastic levels of modulation some use especially
when broadcasting music.
The old mixers might be fighting back but I don't think that they will win
:-)
73,
Geoff
GM4ESD
Giancarlo Moda <[EMAIL PROTECTED]> wrote:
To: <elecraft@mailman.qth.net>
Dear friends,
A Front-End with an IP3 over +50dBm?
Some of you may think …”it’s a joke ! Gian ‘s brain
got heated-up by the South Italian sunshine” ….
Maybe….
Our friend Martein, PA3AKE, as you know, has done
quite an important work on looking and measuring
performances associated to the H-Mode Mixer with
different kind of switches starting from the FST3125
and ending with the FSA3157, resulting with IP3 around
+50dBm. But what can we do with a mixer like that when
front-end Band pass filters may have problems to reach
an IP3 of +40dBm (see the CDG2000 input coils and
transformers IMD limitation) without talking about the
post mixer roofing filter that may not even reach an
IP3 of +30dBm.
<snip>
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