14-11-2017, 12:29 PM
When I checked on coupling tuned circuits I determined that I had probably got nearabouts optimum coupling for RF output. Somewhat lucky as I was only putting a small value in to avoid loading issues. I have now done further tests and found the radio to be stable. Range seems to be as required, covering the house fairly well and dying away at boundaries. Further tests will be required to verify.
I have found, as previously mentioned, that modulation depth may be the tricky part. Reproduction seems good, but with high modulation (overmodulated) audio is harsh. It is possible to see reasonable modulation on the scope, even with music output, but such monitoring is really impractical for portable operation. At present I have used a preamplifier fed by my Sony disc player, this pre-amplifier being a speech processing circuit for Tx use which I constructed from an article in ham book many years ago (when I mostly just constructed rather than designed things). A suitable amplifier with output monitoring may well be a useful addition. I will think and research. In fact now is the time to reflect!
I have now managed to write things up a bit - shown here. The notes are really as a reminder to me.
Anyone looking in should note that this, although looking complete, is really a bit experimental, and a prototype rather than something to be copied as a working item (although it does work and seems very stable). Mainly a colletion of ideas!
I have found, as previously mentioned, that modulation depth may be the tricky part. Reproduction seems good, but with high modulation (overmodulated) audio is harsh. It is possible to see reasonable modulation on the scope, even with music output, but such monitoring is really impractical for portable operation. At present I have used a preamplifier fed by my Sony disc player, this pre-amplifier being a speech processing circuit for Tx use which I constructed from an article in ham book many years ago (when I mostly just constructed rather than designed things). A suitable amplifier with output monitoring may well be a useful addition. I will think and research. In fact now is the time to reflect!
I have now managed to write things up a bit - shown here. The notes are really as a reminder to me.
Anyone looking in should note that this, although looking complete, is really a bit experimental, and a prototype rather than something to be copied as a working item (although it does work and seems very stable). Mainly a colletion of ideas!
