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Monitoring Repeater Inputs

posted Jun 11, 2017, 7:16 PM by Charles Boling   [ updated Jun 11, 2017, 9:53 PM ]
It's sometimes very handy to be able to monitor the input frequency for a repeater.  (Less frequent, but also handy on occasion, is the ability to transmit on the repeater's output frequency.)  It's something that hams operating on VHF/UHF ought to be able to do -- particularly those who desire to be of service during an emergency when the need to communicate iis greater and the ability sometimes lesser.

Why would you want to listen to the input frequency:
  • If the person is relatively close to you, you may be able to hear them better than the repeater can.  If someone isn't hitting the repeater well enough to be understood, having an army of people listening for their simplex signal is invaluable.
  • Extreme example of the above: Repeater can't hear them at all because they're not transmitting the [correct] PL tone.
  • Their approximate location can be determined by how well various people can receive them
  • You can determine whether noise/distortion is being generated by their transmitter, or if it's being added by the trip through the repeater.
  • You can learn what simplex radio paths are/aren't effective -- planning for times when the repeater's not available.
  • If you're listening to a repeater and don't know what PL tone it requires, you can scan someone else's transmission to determine what PL they're using.  (Some radios have the ability to scan CTCSS tones).  Note that some repeaters are kind enough to repeat the PL tone (i.e. they output the same tone used to work them) so you don't have to listen to the input.

Why you'd want to talk on the repeater's output frequency:

  • If the repeater is down, most people will still be listening to its normal output frequency, wondering what's happening and when the repeater's going to be back up.  If you are able to reverse your Tx/Rx frequencies, you can talk to them (at least those who are in simplex range). Note that other people may live in areas with high RF noise and keep their squelch set high, so even if you can hear a weak signal clearly, they may not hear you.
  • If you can't hit the repeater but are near someone (and either they don't know you're there at all, or they're not smart enough to listen to the input freq) you can talk to them and they can relay for you to the repeater.   Note that talking on an active repeater's output frequency is not normally considered to be good practice, and it can be confusing for other repeater users, but if the situation calls for it, then you do what you need to do.  You may find it helpful to quickly inform you user that they're hearing you simplex -- not through the repeater (hopefully they get what you're saying) -- and warn them that most other people can't hear you, so they need to say what's going on and relay for you.

How do you listen to the input freqency?

There are several ways to do it. Many radios have a dedicated function to make it easier.  Let's discuss the ways:

  • VFO - This is the obvious way.  Switch from memory to VFO mode and tune to the input frequency.  Don't know it? You should! Example: W7DG Longview is 147.260 output, w/ + shift. Standard 2m offset is 600 kHz; therefore, the input frequency is 147.860 MHz. Some radios will display this frequency when you talk on the repeater channel.
  • Memory - This one takes preparation ahead of time.  I find it convenient to program a memory adjacent to the "normal" repeater channel w/ the Tx/Rx frequencies reversed. Then it's only one click of the knob or press of a button to switch back and forth between them.
  • REV button - Some radios (e.g. Yeasu) have a button that temporarily reverses the input/output, making it effortless.  Caveat: Often this will activate tone squelch (using the frequency of the tone you're sending to the repeater) so if someone is failing to transmit the PL tone, you won't hear them any more than the repeater does!
  • MONI button Other brands have a monitor button that temporarily opens the squelch, and, if in duplex (repeater) mode, switches to your transmit frequency to listen.  Unlike the REV button, this doesn't allow you to transmit, only listen.  On some radios (e.g. Icom) this button is a toggle; on others (e.g. Baofeng) it's a momentary -- only active as long as you keep the button down.