[hpsdr] PowerSDR Gain settings

[Chris Smith]

Hi Paul

I recently replaced Penny with Pennylane. I hadn't rotated T2 on Penny and I could only get about 350mW so the 6dB pad restricted the o/p of Pennywhistle to around 5 or 6W.

When I was using Penny I did just what you suggested and set up separate gain settings for each band.

I rather assumed that Alex would supply the necessary ALC to limit the o/p of my PA via Pennylane/Pennywhistle to 100W but that doesn't seem to have been the case.

I'm not completely sure that the PA transistors are damaged but the indications are such that I believe they are damaged. For instance driving the PA with about 1W causes the PA to draw roughly 15A and produce only 1W o/p. Seems fairly likely they're ex-transistors!

I'll go round the band gain loop again and see what transpires. Then replace the MRF454s.

Thanks

Chris

On 8 Sep 2011, at 21:58, Paul Fletcher wrote:

> Hi Chris,
> 
> I'm not sure it's that simple. Penny and Pennylane have different output stages for a start. I would do this the simple way and begin by taking your 100W PA out of circuit and measure the output of Pennywhistle, while adjusting the gain figures to get 5W out at 100% drive on each band - this will give you some idea of a starting point when setting up your 100W PA. Also if you are using Penny you want to adjust your input pad for Pennywhistle so that Penny is near 500mW for 5W out from Pennywhistle to keep the signal as clean as possible (Pennylane shouldn't be affected by this as much if at all)
> 
> HTH
> 
> 73 Paul M1PAF
> 
> ----- Original Message ----- From: "Chris Smith" <chris at vspl.co.uk>
> To: "HPSDR list" <hpsdr at lists.openhpsdr.org>
> Sent: Thursday, September 08, 2011 7:34 PM
> Subject: [hpsdr] PowerSDR Gain settings
> 
> 
>> ***** High Performance Software Defined Radio Discussion List *****
>> 
>> Hi
>> 
>> Am I right in thinking that the Gain by Band (dB) settings in PA Settings on PowerSDR should reflect the total gain after Penny(lane)?
>> 
>> If I'm interpreting this correctly then assuming a mean gain for Pennywhistle of around 40dB LESS the 6dB pad I have on Pennywhistle's input PLUS the 14dB mean gain of my PA the TOTAL gain = 40 - 6 + 14 = 48dB.
>> 
>> Should I set the Default gain to 48 or all band gains to 48 before doing a Calibrate with a Cal. Target of 100(W?)? What is the Advanced Calibration Routine?
>> 
>> I'm asking because I think I've destroyed the pair of MRF454s in my PA by over driving them. :-(  I believe I should have had a 12dB pad on the input of Pennywhistle to limit the input to my PA to 5W.
>> 
>> 73
>> 
>> Chris G4NUX
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