At 05:02 AM 6/3/2009, Martin wrote:
Hi Jim and others.
For ordinary Repeaters the Rx/Tx in the same band is mandatory. But just think of the filtering needed for TX'ing lots og watts just 600kHz away from your Rx-frq. This is also the reason why most repeaters (at least that I know of) uses really big cavity-filters.
Either that or _very_ widely spaces antennas. For example, to avoid the need of rather large cavities, 10m repeaters often use two sites, linked by UHF, to separate Rx and Tx.
But for Rx/Tx on the same frequency - Forget it. What would be the purpose anyway?
Nice way to create a feedback loop. :D You can create an appearance of full duplex by using a high speed switching scheme on a digital transmission. In fact, this is exactly what happens if you run Echolink over a wifi connection. The radio itself is half duplex, single frequency, but the high data rate and fast T/R switching allow full duplex for any VoIP on top of it, at the price of a tiny amount of latency.
In my terms, a full-duplex radio is a radio that listens on one band, whilst transmitting on another.
Nope, full duplex refers to any communication channel capable of transmitting and receiving information simultaneously. While I know of no radio capable of running full duplex on the same frequency, as someone pointed out, the humble analog (landline) telephone does exactly that.
73 de VK3JED / VK3IRL http://vkradio.com