[hfsig] 20m WSPR shield for Raspberry Pi
bruce at raymondtech.net
Mon Apr 15 19:34:36 EDT 2019
You're very thorough - quite a virtue in its own right.
I have to admit to being lazy. I connect the transmitter to a 50 ohm
dummy load and measure the voltage across the load with my scope. I just
use (Vp-p^2)/400 as the power output and figure it's close enough.
Keith Wilson wrote on 4/15/2019 4:20 PM:
> Gentlemen - an update to my power output measurements on the 20m
> Raspberry Pi board:
> The (impedance unknown, alligator clips to BNC) cable between the
> board and the dummy load was affecting the dummy load impedance. The
> SWR was showing about 1.55 with a RigExpert!
> I tried an alternate method using the Flex panadapter and sampling
> with an Alpha Delta coax switch, attenuation about 90 dB. The WSPR
> board signal was down about 15 dB vs a 5 W signal. So that gives an
> output of 22 dBm which looks pretty good. I also tried a 0.5 Watt
> signal and the Flex panadapter looked pretty accurate i.e. down 9-10
> dB from the 5 W signal. I think this is a better test!
> Keith - KE4TH
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the hfsig