[NLRS] How much receiver gain is the "right" amount for a transverter?

[Jon Platt]

Too much gain eats into your dynamic range ..... this is more of an issue on the "low" bands, and also dependent on how close you are to other operators (or say there is a big 6m E's opening with lots of very strong signals).    Here in the city, dynamic range is important because of several high power stations that are close by.  The gain question also depends on the band (6m vs 10 GHz) and if your are aiming terrestrially or up (like EME or satellite).    I think those numbers you quoted sound reasonable for what I know.  More important may be what is the noise figure of the front end ..... a less than stellar front end with a poor noise figure cannot be compensated for with more gain (after the front end) .... in those situations more gain just makes the noise louder.    For low band terrestrial work, something under a 2 db NF is fine, then adjust the following gain just so the back ground noise starts to come up.  That would tend to set your best dynamic range for the given system.   EME is different because your aiming up and away from the "noisey" earth so you can take advantage of a lower NF and more gain.   YMMV 73, JonW0ZQ  -----Original Message-----
From: David Palm <thepalmhq at gmail.com>
To: NLRS List <nlrs at mailman.qth.net>
Sent: Fri, May 3, 2019 10:45 am
Subject: [NLRS] How much receiver gain is the "right" amount for a transverter?


 I've been back to working on the various projects I have here and, with
the acquisition of a Pluto SDR (awesome!) and using the spectrum analyzer
at work, have been able to measure the receiver path gain on a couple of
commercial transverters.

As I mentioned in an earlier email, I have an old KK7B-style 1296
transverter built by DEM that has 16.5 dB of receiver gain.  Just today I
measured my Elecraft 222 MHz transverter's Rx gain and measured 18 dB at
222 and 19 dB at 223 MHz.

In on-line sources I find these various references to receiver path gain:

Kuhne 222 MHz transverter: "The overall gain in the receiver path was
deliberately set to only 15 dB, as even high-performance HF transceivers
have still large signal problems at 28 MHz."

Kuhne 70/144/432 MHz transverters: 25 dB gain

SSB electronics, 50 - 432 transverters: 20 dB gain

SG Lab 1296 transverter:  -5 to +10 dB, adjustable

Q5 Signal transverter: 20 dB

So my questions are: what is the "right" amount of Rx gain in a transverter
and why?  And what happens when you have too much?

Thanks and 73,

David  W9HQ
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