Re: SG-Labs,


militaryoperator
 

I was of course thinking about front end gain, before the rx mixer, not in the o/p gain of the trvrt to the transceiver. 

Even my poor old FT817's have enough life in them to be usable as an IF.

On 9Cm I have a DDK preamp with 26db of gain followed by about 13db of attenuation going into the SGL trvrt with the SGL rx gain turned down as well. 

Anyway, ETTO. 

Ben 

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-----Original Message-----
From: Robin Szemeti - G1YFG <robin@...>
To: UKMicrowaves@groups.io
Sent: Thu, 5 Nov 2020 11:39
Subject: Re: [UKMicrowaves] SG-Labs,

I had to put attenuators between my DDK preamp and the SSB electronics transvertor, as even with the cable loss and the preselector filter, there was still far too much gain.   The excess gain was OK when the band was quiet, but a real problem during a contest.

On Thu, 5 Nov 2020 at 09:34, Martin Phillips G4CIO <martin@...> wrote:
Yes and no re the preamps.

If you're using the preamp with a low NF transverter or receiver (like the SG labs tvtr) you can get away with quite a lot of cable loss after the preamp. With a mediocre nf receiver you'll still need low loss coax to avoid degrading the nf by much.

10 dB should be enough gain in the SG labs tvrt with its low quoted nf unless the following rx is very poor indeed.

Martin/

On 4/11/20 10:19 PM, militaryoperator via groups.io wrote:

The only trouble with SG Lab tranverters is the low rx gain, 10db. The Kuhne ones have 20db.

The SGL amp for 23 and 13 has an LNA but again, only 10db.

I think Mr H really needs to improve that on his next designs.

There's also a problem with timing on the rf v ptt switching, if you run the pa off the ptt there's a double kick in the pa dropping and going back to rx. 

I have the 23, 13 and 9 units and they are very good save for the above caveat. 

Ben G4BXD 


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Robin Szemeti - G1YFG

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