Duplex and simplex modes for UHF

G'day Marcel, simplex is the signal going from one radio to any other radios on the SAME channel. eg ch 13 recieves and sends. Duplex sends the signal out on one channel, which goes thru a repeater antenna and the signal is bounced out and recieved on another channel. Both radios need to be in duplex mode. The channels are 1 - 9 and 31 - 39, so if you are in an area where the repeater antenna is ch 3/33 you send out on 3 and the recieving radio recieves it on 33 even though they may be on ch3 & 33. Thats probably as clear as mud and I'm only confusing you more:~) So 1 and 31 go together and 5 & 35, and so on. To find out what the nearest or what repeaters are available in the area you are in, set your radio on duplex and put it on ch 1 or 31 and press the mike switch for a second or so, and if there is a repeater in range on that channel then you will get a beep-diddy-beep-beep-deep etc signal back. Work your way through to ch 9 and you will know what repeaters are in your area. Increases your range to at least 100km, line of sight, maybe better. A good aerial on your vehicle will help with range. 6db and above. But I am no expert on this and someone more technically minded may be able to make it easier to understand or correct me if I have made a mistake, please do if I have then I can learn something too. Good luck and good travels. Grant

To put its simply if duplex is on and your in range of a repeater then your signel will be boosted. This however only happens on channels
1-8 (not 9). There are very few times you would put any of the channels in simplex mode. So i would suggest keeping all your channels in duplex mode (1-8).

Repeaters are simply a special radio which recieves a singnal and retransmits it, extending the range of your signal.

Heres the list of repeaters in Oz.
www.exploroz.com/Interact/UHFRepeatersIndex.asp

Any more questions just email me.

Another fact worth mentioning is that if you are using a channel between 31-38 in simplex within range of a repeater then all your simplex conversations will be repeated to a much larger area on the corresponding output channel (1-8).

So unless you know exactly what repeaters are around it's best to never use channels 31-38.