Duplex and simplex modes for UHF

Submitted: Thursday, Feb 14, 2002 at 01:00
ThreadID: 758 Views:20227 Replies:3 FollowUps:4
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Could anyone tell me what the difference between simplex and duplex modes for UHF radios are and how do I use the to there full potential, especially duplex mode.thanks.
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Reply By: Grant Taylor - Thursday, Feb 14, 2002 at 01:00

Thursday, Feb 14, 2002 at 01:00
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
AnswerID: 2103

Follow Up By: Dion - Friday, Feb 15, 2002 at 01:00

Friday, Feb 15, 2002 at 01:00
Whoa there Grant. Let's provide accurate info to Marcel. UHF repeaters use channels 1 to 8 (31 to 38), not 9 and 39. The transceiver transmitting on duplex sends out on the upper of the duplex pairs, ie channel 3 duplex is transmiited on 33, and received by all other radio's on channel 3 from the repeater. Another comment about repeaters is, know where repeater stations are located, so that if when travelling in convoy, don't use a channel between 31 and 38 where it could be in range of a repeater station, and bogs down the repeater. Repeaters are not needed for close convoy work. Cheers, Dion.
FollowupID: 733

Follow Up By: Grant Taylor - Friday, Feb 15, 2002 at 01:00

Friday, Feb 15, 2002 at 01:00
Sorry. Thanks for correcting me. Don't know if I would like my radio on a repeater channel though. A new repeater was setup near us, on the channel we had been using for years, we soon shifted, nearly drove us mad, as the traffic increased 100 fold.
FollowupID: 734

Follow Up By: Marcel - Saturday, Feb 16, 2002 at 01:00

Saturday, Feb 16, 2002 at 01:00
Thanks for your reply Grant I understand it better now with yours and others avice, Cheers.
FollowupID: 740

Reply By: Andrew - Thursday, Feb 14, 2002 at 01:00

Thursday, Feb 14, 2002 at 01:00
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.

Any more questions just email me.
AnswerID: 2106

Follow Up By: Marcel - Saturday, Feb 16, 2002 at 01:00

Saturday, Feb 16, 2002 at 01:00
Thanks Andrew for your reply on repeaters with the others its helped alot. Cheers
FollowupID: 741

Reply By: Nigel - Sunday, Feb 24, 2002 at 01:00

Sunday, Feb 24, 2002 at 01:00
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.
AnswerID: 2179

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