New design driver amplifier for QO100

Latest News and Discussion about the use of the DATV transponder on Es'hail-2
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G3VZV
Posts: 26
Joined: Mon Feb 25, 2008 12:38 am

New design driver amplifier for QO100

Post by G3VZV » Sun May 10, 2020 12:27 pm

Filtered 2400 MHz Driver Amplifier Kit designed by David Bowman G0MRF now available.

Contains all the parts required to drive a PA on 2.4 GHz for QO-100. The completed board will have a gain of about 25 – 26 dB and for best linearity, should be kept to 200 mW output

https://amsat-uk.org/2020/05/10/filtere ... fier-kits/

g8vpg
Posts: 358
Joined: Fri Oct 11, 2013 9:35 am

Re: New design driver amplifier for QO100

Post by g8vpg » Thu Jul 02, 2020 9:29 am

AMSAT also produce a 5W amplifier kit for 2.4GHz. I've recently been testing mine and have found that linearity is much improved if the recommended quiescent current is increased from 100mA to about 220mA. On ATV duty, this improved the shoulders by around 10dB. Going beyond 220mA didn't seem to produce any further improvement.
73 Shaun.

G8YTZ
Posts: 34
Joined: Sun Feb 10, 2019 7:43 pm

Re: New design driver amplifier for QO100

Post by G8YTZ » Fri Jan 29, 2021 11:46 am

What is the consensus for an acceptable shoulder attenuation for a DVB-S2 repeater or OSCAR-100 up-link? (0.35 roll-off)

g0mjw
Posts: 1612
Joined: Sat Sep 20, 2014 9:15 am

Re: New design driver amplifier for QO100

Post by g0mjw » Fri Jan 29, 2021 12:00 pm

Ideally we should aim for as low as possible, typically -50dB on 2m and 4m but with the satellite it's not quite so critical. I would say as a rule of thumb 10 dB below the noise floor is not likely to bother anyone too much.

That means if you have C/N or 10 dB you should be at least 20 dB down on QO-100. Ideally more.

Mike

Edit - for an S2 repeater, as low as possible, it depends on the other band users. At least 50 dB and probably more as they tend to be on all the time.

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