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

[Dr. Gerald N. Johnson]

Jon, you explained it perfectly and exactly. I can't add any more.

73, Jerry, K0CQ

On 5/3/2019 2:10 PM, Jon Platt via NLRS wrote:
>
> 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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