Quote Originally Posted by skimask View Post
Everything you said makes perfect sense to me. And it might also explain a few issues I've always had with a couple of my RF projects and lengthy/continuous packet transmissions getting dropped after a few seconds of transmitting. I'm going to try your 'pause between packets'/'making the packets smaller' idea and see what happens.
Almost all of my experience is with these specific superregenerative ASK receivers (at various frequencies) or with very similar superregenerative receivers. My suggestions may not apply if you're using more sophisticated receivers (e.g. superheterodyne) or FSK. Most of my applications send/receive 2-3 payload bytes. I think a wireless RS232 link and manchester encoding is overly complicated for such simple needs. If there's a need to send lengthy text or data streams, a superheterodyne or FSK receiver and a wireless RS232 link may make more sense.

I cited the following web page earlier in the thread.You can see the effects of AGC on the initial pulse in the top trace of the first 'scope screenshot. The slope is from the AGC reacting to the wide pulse. You can see the slope starting in the other direction after the pulse ends. If you look a a lot of 'scope screenshots you'll see the same (less pronounced) effect even between the data pulses and see more pronounced differences between a closely spaced series of 0-bit (narrow space) versus 1-bit (wider space). Of course, it's affected by the absolute pulse space widths as well.

The bottom picture is of a signal captured as a .WAV file with a soundcard. You can see that it's more difficult to discern a signal when it has no pronounced initial pulse to set the AGC. In this case, it's the signal sent by a Pronto touchscreen to a Philips RF extender. The three copies of the preamble contain information to address a specific RF extender and set its carrier frequency, etc. which must precede the actual IR code the extender is meant to relay. Philips doesn't use a superregenerative reveiver and they take other steps to improve reception (double modulation) but the picture illustrates the weaknesses of using no preamble or a narrow lead-in pulse with a superregenerative receiver.