The future is sub-audible tones

Submitted by admin on Wed, 2023/05/10 - 18:00

While many will dread the news, its time has come - the IRG will be phasing in the use of "PL" tones on our repeaters.  It's one change among many that will have the most impact on users.

With the explosion of new wireless electronics,  radio frequency interference is everywhere.  Keeping it out of a province-wide system with dozens of repeaters is nearly impossible.  The best way to reduce interfering signals is to move to implementing CTCSS tones on the repeaters.  It won't happen all at once, it will be phased in on a site-by-site basis.  But you can get ready now to avoid problems as our upgrade plan rolls out.

Sub-audible tones (also known as "PL" or "CTCSS" tones) are low frequency tones that ride along with your transmission.  They are inaudible to most human ears.  You will need to program your radio to send the correct CTCSS tone with your transmission, or the repeater will not work.  You'll still be able to hear the repeater, but you won't be  heard without the tone enabled on your radio.

In order to make it as simple as possible, we plan to use the same tones on all repeaters:  151.4 on VHF, and 141.3 on UHF repeaters. 

The CTCSS tones on repeaters will be phased in.  In some cases, advance notice may not be possible.   Because of that, we urge users to start programming their radios now to send the CTCSS tone on your transmit (151.4 on the IRG VHF repeaters, 141.3 on the IRG UHF repeaters.)  Don't set the CTCSS on your receive yet ("tone squelch"), as that might mean you won't hear repeaters that are not yet upgraded.

It won't hurt to set your radio to use the CTCSS tone starting now, even on repeaters that don't require it.  Do it now, and you'll not be stuck with trying to program it in a panic later.

So get out your manuals and start getting your radios ready for CTCSS tones before it's too late.  Don't be afraid to ask for help, there are other members out there who can lend a hand if you ask.

Questions and Answers on CTCSS tones:

Q:  What are CTCSS tones?

A:  CTCSS stands for "Continuous Tone-Coded Squelch System".   Sub-audible tones that are sent alongside a normal FM transmission.  They are often called "PL" tones (a Motorola trademark of "private line" tones).   They are used to let a radio or repeater recognize a signal that is intended for it.  For everything you wanted to ever know about CTCSS tones, visit here.

Q:  Are these tones the same as the linking tones I send with my microphone buttons?

A:  No -- don't confuse CTCSS tones with DTMF tones.  DTMF tones are the tones you hear when you press the number buttons on your keypad, or like you hear when you dial your phone.  CTCSS tones are very low frequency tones that ride along with your transmission, not audible to most human ears, but the repeater hears them and swings into action.

Q:  Why is the IRG implementing CTCSS tones?

A:  With the growth of new repeaters and other electronics, the only way we will be able to effectively reduce interfering signals is to move to implementing CTCSS tones on the repeaters.  Stray signals are keying up and causing noise on repeaters, which causes them to re-transmit to all other repeaters -- interfering with normal use and proper network operation.  More frequent tropospheric conditions makes the problem even worse.  The IRG is one of the last groups to not use CTCSS tones on its repeaters. 

Q:  Will I need to buy a new radio?

A:  Not likely.  Most VHF or UHF radios built in the last three decades (even the very cheapest ones) allow you to set CTCSS tones.  If you are still using a very old radio (like, VERY old!) you could add an encoder board, but it's probably easier to use a new modern radio.  Even cheap $25 Baofengs can be set to use CTCSS tones.  And if you just want to listen, you don't need to change anything.

Q:  How do I turn on the CTCSS tones on my radio?

A:  That varies with every brand, and some are very simple.  Your manual will guide you.  It often involves setting  "Tone"  to "on" and using the menu to set the correct "repeater tone".   Set it to use 151.4 on the VHF repeaters, and 141.3 on the UHF repeaters.   Don't forget to save your changes to memory along with the frequency, offset, or other things your radio will remember.  Get out your manual and look in the index for "CTCSS" or "repeater tone".  It's often covered in the basic use sections for setting up your radio.  There are also some video links at the end of this article for various models, and we'll be adding more.

Q:  Should I set the CTCSS tones for both RX and TX?

A:  Maybe not both -- at least not yet.  Just set it to send the CTCSS tones on YOUR transmissions for now, even if your local repeaters are not yet set up for tones.  Repeaters which are upgraded in the future will be both sending and receiving CTCSS tones.  When that time comes, you WILL BE REQUIRED to have your CTCSS tone set to send if you want to make a transmission through the repeater. 

Q:  Will the repeater also send out a CTCSS tone when it operates?

A:  Repeaters which get upgraded will be set for CTCSS on BOTH the RX and TX sides.  This will allow you set set up your radio to only open squelch on signals  from that repeater - this might solve any local noise issues you might have (see more on this below).  But don't set that up on repeaters that have not be upgraded - it might mean you won't hear a non-upgraded repeater at all.

Q:  Why are we setting repeaters to also send out a CTCSS tone?

A:   Having the repeater send out a CTCSS tone along with its signal can help eliminate some interference that only plagues you locally.  In some cases, your radio might be picking up signals from other systems or devices, such as distant digital signals, and that's annoying.  Even things in your neighbourhood can spew out noise on the repeater frequency your radio is on.  If you set your radio to the same CTCSS the repeater is sending out, you'll be able to eliminate the unwanted interference - your radio squelch will only open when the repeater is transmitting - and maybe not when your kids turn on the big-screen TV.

Q:  Will my local repeater still be heard by people with a scanner?

A:  Yes, any signal from any repeater will still be heard on any radio or device without a CTCSS encoder or decoder.  The real difference is that an upgraded repeater will only re-transmit signals from a transceiver that includes the proper CTCSS tone in its transmission.

Q:  Do I have to wait before I set my TX signal to include a CTCSS tone?

A:  No, you can set your radio to send the repeater tone any time now (151.4 for VHF repeaters and 141.3 for UHF repeaters).  The repeater will still work fine, even if it has not been upgraded.  Just don't set your RX tone squelch up yet-- you won't hear the repeater if it has not been upgraded to send out the CTCSS tone with its signal.

Q:  If it's being phased in, how will I know when I'll need to use a tone with my local repeater?

A:  The best plan is to program all your radios now, in advance of any change.  The priority repeaters will be ones that have experienced the most interference, or repeaters which are replaced or serviced during a future site visit.  Sometimes this will not allow for much advance notice.  We will send a message out to all members when any change is planned or implemented.  In addition, there will be a page on the IRG web site which will list the repeaters which are upgraded and the CTCSS tones.  And a sure sign will be if you find out you can't trip the repeater any more - it may have been upgraded to require a CTCSS tone. 

Q:  How can I know what the CTCSS tone is, will I have to carry a chart with me all the time?

A:  When in doubt, you might be able to let your radio tell you what the new tone is.  Upgraded repeaters will be sending out a tone along with its transmission, and modern radios allow you to do a "tone scan" on the repeater signal to decode the repeater tone.  Once you discover the tone, you can program that into your radio.  We'll also include the CTCSS tones on the future network diagrams and web site.

Q:  OK, I programmed my radio.   It looks like I'm tripping the repeater, the meter shows a signal, but I hear no audio.  Why?

A:  You may have set the tone on both RX and TX, before the repeater has been upgraded.  Even if the repeater has not been upgraded, you can use a tone from your radio, no problem, it will work.  But don't set your radio to "tone squelch" (TSQL on some radios) on a repeater that has not been upgraded.  If you do, you may see a signal on your meter, but no audio.

Help with CTCSS tones:

Video:  Setting up a Yaesu VX-8DR radio

 Video:  Setting up tones on various radios using RT computer software, helps explain "TONE" vs "TSQL"