Transmission1

Hope that grabbed your attention.

I've been observing some recent failures in 2m FM band,THIS COULD BE A REGIONAL ISSUE?

1.QRM pollution of simplex channels while mobile of HT portable.

2.Repeaters with short hang delay times or pratically zero delay,no pip tone courtesy tones.
Needs 5-6seconds for mobiles and HTs

3.OPS Confusion of 12.5khz nfm simplex channels.
Mixed up equipment specs in use etsi ham,etsi LMR,FCC

4.lack of use FM,far too many fm channels.

So few of us have got together,discussed some of the issues suggested the following to try out.


1.QRM pollution-very difficult to solve
Solution: S19-23 renumbered ,change bandwidth wider,add a National CTCSS tone 151 4hz
It won't solve the QRM issues but does help resolve hearing it due to "FM capture effect"

We suggesting not to use 12.5khz nfm 8k5 11k5 2.5khz bandwidth/deviation
Movement back to 16ko 5k 25khz FM 151.4hz with a added ctcss tone.
Due to improved audio quality and compatibility with 99.5% of old and new FCC and ETSI ham and commercial Land Mobile Radios.
NFM 12.5k we noted there seems to be a lot of mixed specifications with kit ,this causing lots problems in the field.

We suggested than digital voice move to 6.25/12.5khz only ,drop the use of nfm 12.5k spacing fm analogue.

Keeping FM 16ko 5k dev more International compatibility for overseas visitors and older equipment users.
Most old kit can retro fit pic based ctcss boards from various places,enabling old kit to continue to be used in 2026
A national ctcss tone 151.4hz won't remove QRM but help block it from being heard,giving ease of the ears.

Reducing FM simplex Channels-
By reducing FM channels more commonality ,less spread out finding stations to talk too,seems to be general moan hams are saying Inc older kit not technically capable of 12.5k channels spacing system.
Idea is Keep it Simple FM Comms.

So ideal is
S simplex
T tone
V or U band type

ST(V)-18 25k 16ko bandwidth 5k dev 151.4hz
ST(V)-19 25k 16ko bandwidth 5k dev 151.4hz
ST(V)-20 25k 16ko bandwidth 5k dev 151.4hz
ST-(V)-21 25k 16ko bandwidth 5k dev 151.4hz
ST-(V)-22 25k 16ko bandwidth 5k dev 151.4hz
ST(V)-23 25k 16ko bandwidth 5k dev 151.4hz

Question I asked is do we actually need more than 6 Simplex general FM channels when most are pretty much dead activity ?
Less is more effect ?
Density maybe better on limited amount of channels?

Ctcss will give less squelch fatigue on ears while driving in QRM high polluted areas,won't solved it but just add some relief to ears and make scanning a little less annoying stopping on carriers and other QRM issues,plus you can scan 6 channels lot quicker than all these 12.5k and 25k channels.
So bunch of us going to try this rethink ,hopefully other hams,clubs give it a go and Nationalised ctcss tone number across UK on 2m.
wont fix QRM,just means wont hear it coming through your radio!
some of these observations maybe a regional problem?

73's Rob.P
RPC Systems.

Must all be very local to you, as no issues with interference on VHF here or on any of my travels. UHF, now that is a different story, especially on the analogue simplex channels around 433 MHz, with competing LPD transmissions.

On that, CTCSS is already in operation on 100 Hz, as described here;

https://www.eham.net/article/36268

OK, so that originated over the other side of the pond, but has been adopted here (as in these parts...) for UHF simplex to eliminate pulses of noise. But otherwise, no issues with VHF. And we have more UHF simplex going on in this locality than we have on VHF.

2. Repeaters - Don't need delays and the majority of them are used in commercial applications, where there are no delays or other complexities. CTCSS access and thats it - Job done. even commercially, analogue repeaters are phasing out quickly to be replaced with digital, mostly DMR.

3. I have no idea who could get confused with something as simple and standard as 12.5 kHz channel spacing. Compare with marine VHF - Many moons ago, that had 28 channels with 50 kHz spacing - some simplex, some duplex. Then, still many, but a bit less, moons ago, channels 60 - 88 were added in with 25 kHz spacing, interspersed between the original channels. Then as if that wasn't enough, some of the older duplex channels originally used for telephone linking have been split into simplex channels with numbering like 1020, 1024 etc. But yet, I have never heard anyone on marine VHF be confused over channel numbers.

4. I very much doubt that lack of use is caused by too many channels. Its not like people are sitting around on a specific channel wondering why there is no-one else on it. Lack of use is due to folk not picking up the mic and pressing the PTT. Even here, local amateurs insist on using social media or email as their main form of communication, and rarely, if at all pick up the mic. You can blame things like FT8 for people who just hitch up a radio to a computer and let it get on with it. That's why your channels are dead.

The rest of it probably comes under the banner of "trying to keep the past alive". You mention S19 - S23. Sorry, but that form of channel numbering went out in the 90's, to be replaced with V16 - V47. There are no known issues with using 12.5 kHz channel spacing, apart from those that wish things could go back to what it was like when they were a lad in the 1950s. That's not going to make your channels busier. Most folk that have found renewed activity have done so on digital, on things like DMR. Not by turning the clock back 4 decades. CTCSS on analogue is the only thing that should be implemented universally, just like commercial analogue radio did decades ago. But striking off in a different direction, with a different tone will just make your channels even quieter. even CTCSS is outdated, with DCS on analogue being a superior squelching system. When the GB3NG repeater was still operational, it was plagued with a (simple to fix, but never done) issue of insufficient deviation on the output CTCSS tone. It was OK when there was no voice modulation, but as soon as someone spoke, the voice modulation overwhelmed the CTCSS and a radio with CTCSS RX would intermittently mute. A simple fix on the Tait repeater, involving slightly raising the CTCSS deviation and/or lowering the modulation deviation, which was suggested to the keeper, but never implemented, as the old guard preferred to have no CTCSS on receive so they could listen to the ident every 10 minutes.... Now, due to lack of use, there is nothing to listen to, not even an ident..... All is not lost however as Aberdeenshire now has a healthy crop of digital repeaters.

Oh my god.

Amateurs now have little or absolutely no understanding of the difference between mic gain and FM deviation. No understanding at all of channel spacing and deviation. Little to no understanding of CTCSS endode, decode or dencode. Evidenced by many people encoding random tones on straight simplex conversations, sometimes with a 1750Hz burst too. No harm done but it illustrates the point. No understanding that just because a fine old piece of gear can tune 12·5kHz steps, that it's not a good idea to use said piece of kit on 145·4875MHz. That produced some good entertainment and language worse than CB a few days ago...

There are a lot of brainless thin-skinned prima-donnas on the airwaves...

There is diddly-squat chance of anyone understanding or caring about a new sensible use of the bands. This is particularly true of the newcomers but true of many old hands too.

Yes there is no hope.

The idea was keep it simple stupid really.
I come from a business radio background see this far to often more so now over complicated communications.
Yes I know about those RV channels but have failed to see them in use,think that was then point.
Inyetnationally 25k FM 16k0 5k dev on 2m and 70cm still is defato standard in many countries for ham bands.
Is this a case of following a trend?
Nothing wrong with "old",it was more a case of simplying FM operations and condensing the fm channel plan,everyone on same hym sheet.
Digital while correct is pushing forward its not B all,it has certain disavantages too.most wont discuss those facts.
What i have observed is mixed up fm and narrow in operations,reason why we going back to basics thing,try it out.

Hang delay on repeaters think miss quoted me,when your a mobile station moving ,terrain is constantly changing,if there zero hang delay you end up keep dropping out of repeater,if hang tx delay not there this can cause operation problems.
All my business kit uses 5-6second hang hold delay on tx to prevent this from happening,main point is really hT and Mobile users Ive observed this issue on 2m repeaters that this parameter seems far too short a time.
Problem does not happen with fixed base sites as your not moving about talking to the repeater ,so signals are steady.

as for qrm 70cm Its QRM alley here in my locations on 433mhz full of it.
Business 446,449,458mhz no issues.

Maybe this as said is regional problem In wales?

We giving a go see what feedback get from ops,nothing ventured nothing gained so to speak.
As you put it FM is in decline so does it really matter now?

kind regards

rob.P

RPC Systems

rpcomms wrote: 26 Jun 2026, 13:46 The idea was keep it simple stupid really.
I come from a business radio background see this far to often more so now over complicated communications.
Yes I know about those RV channels but have failed to see them in use,think that was then point.
Inyetnationally 25k FM 16k0 5k dev on 2m and 70cm still is defato standard in many countries for ham bands.

Looking at the IARU bandplans, only region 3 have anything wider than 12 KHz bandwidth for FM telephony. Meanwhile, regions 1 and 2 are pretty well aligned. So going back to wider channel widths will only align with a smallish part of the world, and will deviate (pun intended....) from the rest of region 1 which we are in. RSGB bandplan has adopted the same 12 kHz bandwidth, and have an annotation;

- Note 3: 12.5kHz simplex channels numbered V16-V45. V16=145.200 MHz.

So deviating (pun intended again....) from that is making it less simple. A visitor to the UK from region 1 or 2 is baffled why 12.5 kHz channel steps are not being used and why bandwidth is 20 kHz, when the bandplan says it should be 12.

At a time when the ITU are driving towards ever narrower bandwidths, hence FDMA and TDMA, asking to officially go back to wider bandwidth is unlikely to be well received (yet another pun intended....)

There's a case t say that if you cannot find an interference free channel between V16 and V47, then something is fundamentally wrong. Possibly extremely locally. OFCOM / ITU may well suggest the solution to your interference issue is to follow the trend and go digital, thereby actually decreasing your band occupancy, which is what they like.

And yes, from a commercial and marine radio background myself, I am aware that there are issues with digital - Just maybe not as many as there can be with analogue these days. DCS largely obliterates the need for hang timers, as a DCS encoding can cut through a high noise floor better than a CTCSS tone, especially as mentioned before, if the CTCSS deviation is not optimal. But there will always be a point when even the best optimised CTCSS cannot match the performance of DCS, and that's a fact of life. You will likely end up at a point where the DCS encoding is able to be deciphered in the receiver, but the modulated audio isn't. So maybe what you should be doing, if not advocating full digital, is moving to DCS rather than CTCSS.

As you say, analogue FM is in decline, with repeaters shutting down through lack of use. Looking at UK Repeaters, more and more are going multimode to try and stay in operation, with analogue only ones shutting down. Just a month or 2 ago, both GB3NG and GB3GN shutdown permanently in Aberdeenshire. But conversely, quite a number of digital repeaters and gateways have sprung up in the same area.