Tuesday 22 June 2010

Mea maxima culpa

OK guys (that's a gender inclusive "guys", if I'm fortunate enough to have attracted any readers from the fairer side) - I goofed.

I left you with news that the new beacon receiver hadn't enough audio gain. After a few moments poking about with a 'scope probe and an audio oscillator I was forced to admit the truth. I'd made a mistake (at the schematic capture stage in Eagle) which had inadvertently swapped the inverting and non-inverting inputs of one of the op-amp stages. It was a miracle the system "worked" before at all - but work it did - I showed you the spots to prove it!

Having tracked down the error, I was able to pull off the changes on the PCB (requiring surprisingly little "butchery") and so we're back in action.

I came into the shack this evening and heard a lot of activity on the 30m WSPR segment - but was getting no spots.

Ironically (given my earlier comments) I had now set the AF gain TOO HIGH (!!) - so I needed to back off the gain setting trim pot just a little.

Now the spots are coming in nicely...

I can't leave the receiver running all night (some guests have the temerity to interpret the shack as "the guest bedroom" and won't be happy with the PC fan noise) but I'll post an update of catches during the evening if there's anything to be pleased about.

...-.- de m0xpd

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