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| Rev B 28MHz WSPR receiver |
Adding more audio decoupling around the oscillator and adding a common base FET RF preamp has totally fixed the common mode hum issues with my Polyakov mixer based DC receiver (
WISPY) for 28MHz WSPR. Even running from a mains PSU I am getting good sensitivity and no hum. The board is working on the bench with no attempt at screening and appears totally fine. The oscillator buffer appears redundant, so has been removed.
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| Wispy Rev B (built using MeSquares) |
One possible further mod is to make the input to the RF amp a series tuned circuit. This would be needed when the full transceiver version is made (back-to-back diodes would short the cap to ground on TX). For now, I will leave the little RX running to see what I spot.
5 comments:
Seems like a very nice circuit for a low cost 40 meters band receiver...
Do you have at hand a circuit diagram that can be seen better than the one
published , because it is blurred .
TNX
Arnie Coro
CO2KK
From Arnie Coro CO2KK
request for more info on your
direct conversion receiver
Congrats, a job well done.
Can you show a picture of the rig with higher resolution ?
73 Ron
PA2RF
Arnaldo - was that little girl in the picture on the key(cw) when you took that pic?!!
Hi, good work, really enjoying reading your blog. Polyakov is so ingenious in his designs. This mixer is LO drive sensitive. The optimum is drive that achieves 50% duty cycle for the mixer diodes. Best wishes, Will
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