--- In digitalradio@yahoogroups.com, "jgorman01" <[EMAIL PROTECTED]> wrote: > > I'm not sure what HF Packet BBS's you're talking about but all my > packet tnc's had a carrier detect feature and would not transmit if > one was detected. Was it perfect, heck no! But it was available AND > it was turned on. > > Jim > WA0LYK
Well Jim, The DCD mechanism of an HF TNC does not transmit when there is another PACKET signal on the frequency. When there is a voice or other signal it does not understand it and continues transmitting on top of them. Some times it might stop because it confuses the voice or other noise with DATA, but this is not how it was designed to work. Really the DCD only works with the same waveform as the TNC transmits. So in the PACKET RADIO case it should only stop at the presence of another PACKET RADIO signal, but not at the presence of a voice or CW signal. What you are referring to can only work either with the squelch turned on if your HF Radio supports it, and if anyone does it on HF they will get no chance of transmitting at all due to the constant noise. That was common on VHF before the DCD software state machine of the TNCs became more sophisticated, so people had to rely on the squelch and many LIDS started whistling on the frequency, so the PACKET station never got a chance to transmit. Now the carrier detect that you are referring to is an option in the old TNCs and nobody ever user since all the LIDS could stop their DATA transmissionwhenevr they pleased, just like some people proposed in this list using Anti-PACTOR missiles. Hi Hi Hi!!! 73 de Demetre SV1UY
