[hpsdr] Pennywhistle completed at last

[Chris Smith]

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