Post
by VK5YYY » Wed Jul 13, 2016 1:59 pm
We connected the I/Q output from the GPIO bus of RPi to an old school I/Q modulator from the junk box
2 1K pots were applied from the I and Q outputs to ground and a 1uf capacitor to isolate the wiper from the modulator
Hey presto we got a MER of 15, much simpler than half a digilite, but a bit crude
One of the quadrants has a high level , now to figure out how to bias these things
A bit of filtering wouldn't go astray
Can anybody supply any info on how these older style modulators were biased, an application note or a circuit
It's done with constant current from what I can gather
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Attachments
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- couldn't be simpler
- WP_000784.jpg (139.89 KiB) Viewed 13241 times
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- I/Q modulator circa 2000
- WP_000781.jpg (135.45 KiB) Viewed 13241 times