[hpsdr] Pennywhistle completed at last

[John Petrich]

Chris,

You might be over thinking this a bit.  Given the same situation  with my 
AN762 amplifier, I just set the Power SDR PA settings at some arbitrary high 
number such as "56" and then gradually decremented the setting to get the 
desired output per band.  Simple.  No calculations.  And, like you I'm 
running my PA about 3 dB down from maximum, 90 watts, to provide head room 
on SSB to keep the IMD reasonable.

Hope this helps,
John Petrich, W7FU


Hi

Despite taking delivery of PW before Christmas, I've only just completed the 
kit. My excuse is that I have a (virtually) unheated shack in the back 
garden and the weather in this part of south-east England has been dreadful 
since Christmas. The day-time temps have only recently risen above 0C or 32F 
in old money.

Now, bearing in mind that I haven't taken the action with regard to the O/P 
transformer on Penelope mentioned in the errata, I was wondering what the 
gains in the PowerSDR PA Settings should be?

I have Pennywhistle followed by the 140W version of the Motorola AN762 PA. 
I'm assuming that the dB figures in the box for each band is the combined 
gain of PW plus any additional PA required to produce a fixed o/p, perhaps 
100W, at the antenna socket. Is this correct?

The gain figure quoted for the 140W version of the AN762 amp is 13-15 dB and 
Pennywhistle has a gain of approx 19 dB - a combined gain of 32-34 dB. Let's 
say 32 dB.

In light of the reduced o/p from Penelope (320mW instead of 500mW), which in 
my simple mind represents  a power loss of just under 1 dB, if I'm aiming 
for an o/p of 100W i reckon the boxes should be set to around 33-34dB. 
However 38dB seems to be the minimum setting. However, I'm sure this would 
result in a dreadful over-driving of the final.

If I set the Tune Power to 20W in the Transmit window, I get 100W out into a 
dummy load on Tune.

So, I'm confused. Can anyone put me right please? I'd prefer to under-run 
the PA at 100W with a little in reserve than push it to max o/p.

Cheers & 73

Chris
G4NUX


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