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PostPosted: Mon Jan 30, 2017 4:12 pm 
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Joined: Sun Mar 16, 2014 3:18 pm
Posts: 2
Hi,

I wonder if anyone has tried using the HR50 with a Red Pitaya (Hermes compatible SDR)?

Since the RP has a maximum output of 10mw it doesn't have enough drive for the
HR50 even with the pre-driver board installed.

What type of circuit (pre-driver -> Pre-Driver) or changes to the Pre-Driver would you
recommend?

Tnx,

Rick / N1GP


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PostPosted: Mon Jan 30, 2017 9:30 pm 
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Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
Hi Rick,

The driver amp is capable of about 20 dB gain. We use a very similar circuit in the RS-HFIQ which takes the output of the driver stage at +15 to +20 dBm up to +37 dBm. On most bands 2-3 watts is all the HR50 needs for full output so the driver modified for maximum gain might get you there. If the output of the Red Pitaya really is +10 dBm max you'll might need another stage to get up near +20 dBm for the driver.

Send me an email (wa2euj at arrl dot net) and I can get you some more info. You'll need a small MMIC amp like the MMG3H21NT1 from Freescale, it has a P1DB of +20.5 dBm, a gain of 20 dB, SOT-89 package and it's active bias so it runs on a 5V supply. I have a small PCB that can mount the amp and the biasing components then it will be easy to use the driver amp to push the HR50 to full output.

73,
Jim WA2EUJ


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PostPosted: Tue Jan 31, 2017 8:02 pm 
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Joined: Sun Mar 16, 2014 3:18 pm
Posts: 2
Tnx Jim, email sent.


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