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Author Topic: why simplex?  (Read 509 times)
BVSCIGUY
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Posts: 11




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« on: April 22, 2007, 03:37:58 PM »

Hello again,
What is simplex used for? I understand that it is one way communication, but if your not supposed broadcast, what is it used for?
Thanks,
bvsciguy
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AA4PB
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Posts: 12685




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« Reply #1 on: April 22, 2007, 03:48:51 PM »

Simplex is not one-way communication as in broadcasting, it is one-way at a time. In other words, I transmit to you on a frequency and you reply back to me on the same frequency after I have finished transmitting. We can't both talk at the same time.

Duplex means that both people can talk at the same time, similar to a telephone. This requires the use of two separated frequencies.

In amateur radio we generally use the term simplex to indicate that we are not using a repeater. A repeater picks up our transmission on one frequency and simultaneously retransmits it on another frequency. If the repeater is located at a high location, it can extend the range between two user stations considerably.
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BVSCIGUY
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« Reply #2 on: April 22, 2007, 04:12:34 PM »

Okay, that makes alot of sense. Thanks.
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KB5DPE
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Posts: 298




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« Reply #3 on: April 23, 2007, 09:48:40 PM »

I might add, most ham repeaters are "half-duplex".  That is, while the repeater is transmitting (the signal you hear) and receiving (your transmitter) at the same time, most stations talking through the repeater still alternate between transmit and receive even though they do use two different frequencies, ie. they don't operate telephone style.  While full duplex is possible and is frequently done at a base station (usually using two radios) it gets a lot more complicated when using a single mobile to do so.  Some of the older commercial two way gear was capable of doing this mobile but conversion to ham use is very difficult and just about impossible on 2 meters.
Tom
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KE4SKY
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« Reply #4 on: April 24, 2007, 06:01:34 AM »

You might want to check out the files on this link for more information on how simplex operating is used in emergency communications.

http://www.usraces.org/training/simplex.htm
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N6AJR
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« Reply #5 on: May 13, 2007, 10:00:06 PM »

I often use simplex to talk to my local ham friends  and not be tying up one of the repeaters, and also if I am driving with a nother ham in seperate cars we will pick a freq (147.555 is common) and use it simplex to talk on while traveling . Remember you still have to id every 10 even on simplex.

on HF most communication is done simplex unless it is done "split"
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