Helicopters and more

Silly Scope RF Sampler

Well I did threaten getting the oscilloscope working. I have borrowed the club scope to assist in the calibration, which incidentally seems to have worked a treat.

Not content with seeing volts I wanted to see some modulation. But how to get it into the scope? A google got me to a site that Bob Heil, he of the microphones, had put up a design for a box that takes a sample of the RF from the TX output without blowing up the scope.

So fearing I might be replacing the club one as it went up in smoke I pressed on regardless and using the component tester managed to track down the right capacitors. or in fact two that add up to the right value in parallel. And a trio or resistors that added up to the right sort of numbers.

I got a cast box for RF screening and went about copying the hell plans.

Screen Shot 2015-07-24 at 18.54.45

This looks something like this when put together
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Then for the big test….or bang.
I got the KX3 out and plugged the tx out into th boxm the other lead into a dummy load and took the scope tap off to one of the scope inputs. chrono - 2

Put the radio onto AM and .1W (just in case) and this is what you get

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Pretty eh.. Then SSB

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You can’t photograph the slopes that we learnt about well on CW
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But they are definitely there.

All in all a great 1 hour project and now I can’t wait to get myself a scope and have someone tell me what I need to be looking for re over modulation etc.

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