The Electronics Universe
The CB Forum => How CB radio works => Topic started by: Lazarus on June 01, 2012, 01:34:56 AM
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test
ok i think i've got this figured out now
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Cool
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Here is a 1Khz amplitude modulator that i built tonight, i think you'll find that it will solve a few problems, just power the TX buffer in whatever radio you choose to make the Signal gen from with this circuit, it has the 1Khz sine wave generator on board, solving both the modulation point problem and the audio gen in one swoop, and it works absolutely perfect :), the VR controls carrier amplitude, adjust it to to obtain a 100% modulation envelope,
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Got my proto type built now. Did not get time to test yet. Will try tomorrow night.
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Got my proto type built now. Did not get time to test yet. Will try tomorrow night.
good deal bro,
this thing has given me an idea for a new controlled carrier project, :)
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oh sweet. Cant wait
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ok, this seems to work quite well, the modulation envelope will now stay at 100% at any amplitude level, and you should be able to turn it down to virtually nothing,
but in my case though it seems that my radio (29LTD) doesn't have a very clean signal to work with to begin with, it seems that a phantom 16.xxMhz VCO signal is seeping through at 50mv, even if i turn it all the way down, or even if i completely disconnect the TX buffer from all power its still there at the output of L17, so at first i had to turn the amplitude up to 500mv in order cover up the phantom VCO signal, then i detuned L17 as low as i could get it, now i'm able to get a clean signal down to 100mv, i could go lower if it wasn't for that phantom 16.xxMhz signal bleeding through,
also i had to add 2 100μf caps to the virtual ground divider network, because after removing the DC bias from the circuit my output waveform was distorted, so when i looked at the virtual ground at the mid point of the voltage divider it was swinging above and below mid point, in fact it looked much like the output, i should have included those two caps to begin with, it wasn't an oversight though, i intentionally left them out to make it smaller, and i thought it would work ok without them, and as it was originally it did, but not after the revision,