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Channel redundancy


WRPF281
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Being new to GMRS, my question is. Why do we have two same frequency channels? If I set tones on channel 24 (repeater), I lose all receiving non tone transmissions on GMRS 16. 

Second question is about the Emergency channel repeater 20. Is the tone 141.3 used for both rx and tx?

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1) A "Repeater channel" is a combination of two channels - a sending channel, in the 467Mhz range and a receiving channel in the 462Mhz range.  The receiving channels are shared with some of the 'regular' channels, so you can hear someone talking on Repeater 24 on CH16, but if you transmit back on 16, they (likely) wont hear you.  When you put both a TX and RX tone on Ch24, you are setting the radio to only listen to Ch24 repeater traffic.  If you want to listen to ch16, put the radio on Ch16 OR, dont enter a RX tone on Ch24

2) Depends on what "emergency channel repeater 20" you are referring to - But in general, you must enter the correct TX tone to use the repeater.  As eluded to in #1, adding the RX blocks out all other traffic except for traffic using that tone - so if the repeater is transmitting with a tone, if you DONT enter that tone you would still hear the repeater, and you would also hear anyone else talking on that shared channel.  If the repeater does not transmit a TX tone, and you enter a tone (or enter the wrong tone) you wont hear the repeater - you will only hear transmissions that are sending the tone you've entered.

Since you're new to GMRS, it is my job to make sure that you also know about Channel 19 (no tone) which many people use as the "unofficial official" road and travel channel, and Channel 16 (no tone), which many people use as the "official" off-roading/hiking/adventuring channel.   Also be aware that "some people" will prefer to argue over the use of those channels rather than actually do/say anything helpful or constructive - just remember that nobody cares what the complainers have to say so you can ignore them - dont worry, they'll be easy to spot.

Welcome to the forum and welcome to the exciting world of GMRS!

 

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3 hours ago, WRPF281 said:

Being new to GMRS, my question is. Why do we have two same frequency channels? If I set tones on channel 24 (repeater), I lose all receiving non tone transmissions on GMRS 16. 

Second question is about the Emergency channel repeater 20. Is the tone 141.3 used for both rx and tx?

As @OffRoaderX mentioned, the GMRS repeater channels share the same output frequency as the "simplex" channels 15-22. Here's a long-winded explanation:

Just to clarify, a repeater is a system that takes the output from your radio and re-transmits it, generally with more power and from a better location. This allows you, through the repeater, to get a signal out to a wider area, and potentially, to a wider audience. The repeater channels (numbered 23-30 on many radios) receive the signal from your radio in the 467 MHz range, and re-transmits the signal in the 462 MHz range. The exact frequency depends on the channel you select, but if you use, for example, Channel 26 (Often called "Repeater 18" or "Repeater 4" or something similar), the repeater receives at 467.625 and transmits on 462.625. Some radios call this "Repeater 18" because it uses the same transmit frequency as Channel 18. Others call it "Repeater 4" because it's the fourth "frequency pair" of the designated pairs. There are 8 in all.

Your radio, on the other hand, when tuned to that channel receives on 462.625 and transmits on 467.625 (opposite of the repeater). This allows your radio to hear the repeater and vice-versa.

Simplex communication uses the same frequency for both transmit and receive. On most radios, Channels 1-22 are simplex channels, and use the same frequencies as Channels 1-22 on FRS radios. This mode is for direct radio to radio communication without using a repeater.

Now, regarding your question about the "Emergency" channel repeater 20...

GMRS does not have a designated "Emergency" channel for the most part. There may be some communities where a channel is monitored in the event of an emergency, and there may be repeaters that are designated for use by emergency services, but that would be established within a small area, and is not common to the GMRS community as a whole.

It seems as though in your area, you may have a repeater designated for use in emergencies, that is tuned to the "Repeater 20" channel (The repeater is tuned to receive on 467.675 and transmit on 462.675). You mention a "tone" of 141.3. This is what is referred to as "continuous tone coded squelch system" or "CTCSS." This is a sub-audible tone that is generated by the transmitter, which "opens" the squelch of the receiver, allowing the message to be heard. Without the proper tone, the receiver ignores incoming transmissions, and only listens to those using the proper tone. If no receive tone is designated, the receiver will listen to all incoming signals.

If you set your radio to use tone 141.3 on transmit only, it will generate the tone needed to open the squelch of the repeater, but will receive all incoming signals regardless of the tone associated with those signals. In general, this is the configuration I use for repeater channels as it allows me to hear all incoming traffic on the frequency regardless of tone. That means I may be hearing simplex transmissions in addition to those coming from a repeater.

If you set your radio to use tone 141.3 on receive only, it will not generate the tone needed to open the squelch on the repeater, so the repeater will ignore your transmission. You will also only receive incoming signals that are encoded with that tone, and you radio will ignore all other incoming signals.

If you set your radio to use tone 141.3 on transmit and receive, it will generate the tone needed to open the squelch on the repeater, but will only receive incoming signals that are also encoded with the same tone. If you have a lot of incoming signals that are not from the repeater, this is a way to "filter" those signals out so you only hear the repeater.

There are also some repeaters that use "split tones." This is where the transmit and receive do not use the same tone. This is helpful to reduce unauthorized use of a repeater as it makes scanning for tones a bit more difficult (but not impossible). This also only affects you if you enable CTCSS on receive on your radio. I just wanted to mention it so you're aware that some repeaters use this configuration.

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23 hours ago, WRPF281 said:

Being new to GMRS, my question is. Why do we have two same frequency channels? If I set tones on channel 24 (repeater), I lose all receiving non tone transmissions on GMRS 16. 

A wise man once said:

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A Picture is worth a couple a dozen words... at least! 

 

KG-XS20G.jpg

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