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Author Topic: CTCSS tones on repeaters..Can you decode?  (Read 14894 times)

Posts: 6

« on: June 01, 2010, 03:57:37 PM »

Okay I hae a 2m rig that can decode CTCSS tones..but if one is travelling around the's not as easy to scan for nearby repeaters to talk with som e least not as easy as it used to be.  Repeaters that use CTCSS seem closed.  Do they not want me to check in and say howdy?  Is there a setting on a radio that would recieve the tone, then TRANSMIT it back in order to use the repeater?  OR do I have to carry a repeater guide with me everywhere?

If there is such a rig..can you let me know what it would be, and how to program it?  OR do they all do that, but must be programmed to do so?

Posts: 397

« Reply #1 on: June 01, 2010, 04:08:08 PM »

No there is no radio that will set the PL tone for you. Most will scan for it if you set them up but you have to program it in once you find it. And having a repeater directory is a good thing. Spend the $15 and have a good reference. And no most repeaters that have PL are not closed to the public. PL is use most of the time to STOP interference and intermod not keep folks out. Oh yeah, the repeater directory shows closed/members only/stay off repeaters. Another reason to spend the $15. Do the research and BUY a repeater directory. I own 4 repeaters and all of them have PL on the input AND the output to stop intermod and interference. None of them are "CLOSED" and get used all the time. LEARN LEARN LEARN....

Posts: 393

« Reply #2 on: June 01, 2010, 07:04:35 PM »

Hi Jeff,

As CTCSS tones are below the 300 hZ to 3 kHz. audio band pass of the repeater's transmitter, you will not, or I should say, should not, detect the tones on the output.

If you had a rig that would decode and display the CTCSS tone being used you would have to listen to the input frequency to get it.

It has been suggested many times that all 'open' repeaters in a given area use the same tone but apparently that made too much sense.


Posts: 393

« Reply #3 on: June 01, 2010, 07:13:18 PM »

I forgot to mention that on commercial repeaters and perhaps a few amateur repeaters that want to transmit a CTCSS tone, it is reintroduced past the transmitter's band pass stage.

I have run into setups where the input and output tones are different.  That's more of a commercial thing though.

Posts: 6642

« Reply #4 on: June 02, 2010, 01:13:27 PM »

Some repeaters don't use tones.
Some repeaters sometimes use tones.
Some repeaters use tones on their INPUT only.
Some repeaters will pass the tone AND re-transmit it.

So the single answer is... it varies with the repeater!  And even if your eqpt will scan and determine the code, it might be changed later.  So your eqpt would only determine what is being used... NOW.
The best answer is to check with your local repeater group and find how they are using it.


Posts: 14491

« Reply #5 on: June 02, 2010, 01:30:02 PM »

Many open repeaters use CTCSS tones to prevent interference and not to keep people from using it. The frequencies are often available on the club web page.

Some put CTCSS tones on the repeater output so that users have the option of using CTCSS squelch on their receivers so that they don't have to listen to noise from cable leakage and other sources.


Bob  AA4PB
Garrisonville, VA

Posts: 532

« Reply #6 on: June 02, 2010, 01:42:39 PM »

Wow, what a lot of mis-information!

There ARE rigs that will decode and set it for you, I have one.

I know of NO repeaters that retransmit the PL.  They may transmit PL, but it is REGENERATED as a NEW PL.  It may be the same frequecy, but they just don't pass it through.  But even there, don't rely on the output PL being the same as the input PL.  In fact, I know of one repeater that has multiple inputs, with different PLs, but the output is a single transmitter with the PL of the 'main' input.  That could really mess you up trying to figure that one out!

You CAN hear the PL on the output, it's just usually very very low.  Higher in the table PL tones can be heard by ear from your radio, but that's really a function of the filters in your radio, but even the lower ones that you can't hear can usually be detected by a program like Spectogram.  I've fed scanner and 2M radio audio to my laptop and looked for PL with Spectogram.  It's not good enough to tell you if it's spot-on, but between the display and a table of valid PL values, you can usually see what's there.

There's a lot of equipment out there that can decode PL.

WinRadio SDRs for example, can decode.  If you have the optional software package, it's pretty extensive what it can do.  But even without it, you can still do it in some cases.  On my G305e I just set any PL tone and turn squelch on PL on.  When a signal is detected that doesn't match, a little window pops up in the display telling me what it really is while it won't let the audio through.

And my Alinco DR-590 dual band radio in the car has a function called A.R.M.  Stands for automatic repeater memory.  You hit that button, and it puts into memory not only the frequency, but the offset AND the PL, assuming of course that the output PL of the repeater is the same as the input.  I've been told some of the newer Alinco radios have an even MORE advanced capability.

The Alinco is 20 years old.  But I've been told a lot of modern rigs have this feature or something similar, it's just a matter of digging into the manual to find it and how to use it.

Heck, my Alinco will even record touchtones and decode them for me, so I can see what someone is using as 'contol codes' if I'm close enough to hear them on direct!  But that feature I couldn't find in the main manual, I only found that in the supplimental special features manual that wasn't normally distrubuted with the radio.

« Last Edit: June 02, 2010, 01:53:51 PM by Mike Yetsko » Logged

Posts: 884

« Reply #7 on: June 02, 2010, 02:20:09 PM »

My Motorola R2600 can decode tones (not scan, but actually decode), but it's a tad heavy to lug around.

I think ComSpec makes a tone decoder box with a display, but, depending on your radio, it may not be able to decode.  Some radios only give "deemphasized" audio out the speaker.  Deemphasized audio means that the RX audio is first run through a high pass filter of 300-3kHz.  You'll need to tap onto the discriminator or find a "flat" audio output (no filtering done) in order to get necessary audio for the decoder to work properly.

Then again, your radio might actually give you flat audio out the speaker.  Only way to tell is to use an audio generator and set it to something below 300 Hz.

I think Radio Shack makes a scanner (maybe PRO-164?) that displays the CTCSS code instantly, as well.  Might be worth looking into.
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