Interference? 'Jammed'? Equipment degradation??

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Interference? 'Jammed'? Equipment degradation??

Postby angelyork » Sat Aug 13, 2016 11:55 pm

I have previously posted about my adventures with Intaride radios - here: viewtopic.php?f=5&t=3970 if anyone is interested... thanks for all your thoughts there, by the way.

I am going slightly crazy here... I have less than 100m range, with my licensed radios and midland pmrs. But not always. Sometimes it's maybe 200 metres, sometimes there is nothing AT ALL getting through. It seems totally random, I can have no problems in a very specific place one minute, then half an hour later in the very same spot - useless. Sometimes my recipients can hear me fine, sometimes they just get interference or broken transmission, occasionally it's completely dead. There is no rhyme or reason to it and it's turning me into a paranoid wreck!

The setup - intaride wiring harness with PTT mounted to bike handlebar, with my radio in a tank bag on the bike. My trainees carry their radios in their jacket pockets, with listen only earpieces. Just a basic system that has been working for bike training schools for years... I don't know if the radios are just useless (intaride own brand (as mentioned in my other post, they are probably chinese rebranded) and midland licence-free both having the same problems)? The fact that it's happening with both radio systems suggests it must be the wiring harness/mic, I know, but... a fellow instructor is also having interference/complete loss of transmission problems. Is there any kind of device or method of 'jamming' or otherwise interfering with UHF signal? I ask because we have been having some rather uncomfortable problems with another training school in the area (see, paranoid wreck).

I really know next to nothing about all this stuff, which is obvious from reading this! I thought I had done enough research before settling on a complete intaride system, as in every instructor I spoke to uses it without issue... So, yeah, I guess I'm most concerned at the possibility of 'sabotage'?

Please tell me that I am, in fact, a paranoid wreck who needs to spend a great deal more money on DECENT equipment, and that there is no way anyone could be intentionally 'interfering' with my radio signal!

Thank you for your patience :-)
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Re: Interference? 'Jammed'? Equipment degradation??

Postby G4RMT » Sun Aug 14, 2016 7:38 am

I've got the PMR446 channels in one of the radios in my van, and amuse myself from time to time when some poor instructor is having troubles with his charges - and it would be a simple matter to pick up the mic, hold down the button and wreck what they're doing with 25W and an aerial on my roof. They'd not hear me because the CTCSS tone would be missing = but you can bet I would be stronger than the low power radio inside the leathers of the instructor. It would be a very simple process to wreck what you are doing.

What could you do?

It's unlikely that if it is jamming it's being done from any distance, so probably a small radio, low powered and close, suggesting a deliberate act. First thing I would do is change the channel you use between each session. Not sure how many other similar firms or other users you have locally, but it's important to change frequency, not CTCSS tone - so that gives you six channels to pick from once you work out what they are. I don't know your radios, so can't help.

Changing frequencies introduces an extra element of work in 'finding' you, if it's a deliberate act, and I suppose that a court would consider somebody following your channel changes to interfere deliberately would be an important element if your students suffered any damage as a result of the interference? Probably never get to court unless something truly horrible happened.

It could be something totally different. It is not beyond imagination for the system to be faulty. Modern bikes, like cars (I've been told) have on board computers to manage the engine and this could be faulty, producing emissions. Same on the students bikes if they are yours, rather than theirs. The harness used to attach to the helmet mic and PTT could be faulty, allowing the interference in. If the system works and is stable, does it fail ONLY at certain locations - so the system is being affected by something faulty at that place? Roadside cabinets and road loops are a potential culprit here.

You need to be systematic. Tie it down. Common denominators. Repeated identical problems, and could I suggest you attach a spare radio to a recorder of some kind so you can record a journey from the students end so you and perhaps us can hear the problem. Co-channel interference is quite distinctive and if we could hear it, we may be able to say pretty accurately what it is from what we hear? Jamming is pretty obvious once you know the characteristics.
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Re: Interference? 'Jammed'? Equipment degradation??

Postby m0lsx » Sun Aug 14, 2016 8:06 am

angelyork wrote:I have previously posted about my adventures with Intaride radios - here: viewtopic.php?f=5&t=3970 if anyone is interested... thanks for all your thoughts there, by the way.

I am going slightly crazy here... I have less than 100m range, with my licensed radios and midland pmrs. But not always. Sometimes it's maybe 200 metres, sometimes there is nothing AT ALL getting through.


I guess the first question to ask is
What antennas are you using & are they in the clear or against the bodies of the riders?

If you have a small antenna inside a jacket & with a human body between you & that radio. I would say 100 yards is not bad at all for UHF.
There is a good reason why dispatch riders & the old police radios are worn the shoulders with the antennas in the clear.
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Re: Interference? 'Jammed'? Equipment degradation??

Postby angelyork » Sun Aug 14, 2016 9:35 am

G4RMT wrote:... it would be a simple matter to pick up the mic, hold down the button and wreck what they're doing with 25W and an aerial on my roof. They'd not hear me because the CTCSS tone would be missing = but you can bet I would be stronger than the low power radio inside the leathers of the instructor. It would be a very simple process to wreck what you are doing.


This is what I was worried it might be - There have been one or two occasions, when I've pulled in to park and have no wind or engine noise, when I've heard a little 'click' type noise in my ear pads. Very much like the sound you get when you press the ptt on the radio itself (when it's switched off - just the physical 'click', if you know what I mean?). ALMOST imperceptible.

I have tried a different channel each day, it would be easy to believe that I have no problems initially - like there is a 'pause' in the problem whilst the 'jammer' catches up... but truthfully I haven't systematically checked that theory. I am training in a completely different area tomorrow - a perfect opportunity I guess!

m0lsx wrote:I guess the first question to ask is
What antennas are you using & are they in the clear or against the bodies of the riders?

If you have a small antenna inside a jacket & with a human body between you & that radio. I would say 100 yards is not bad at all for UHF.
There is a good reason why dispatch riders & the old police radios are worn the shoulders with the antennas in the clear.


Hmmm... standard, stubby antenna inside the jacket... so yes, for the rider up front, there is a 'body' between us. I have been considering getting the extension kit for my antenna, to mount on the bike.

I really don't understand why sometimes, the signal just disappears completely - if I turn my radio off and on again, it will work again :dizzy: Even more confusingly - I have been using the Midland radios for 3 years with no problems, until the last few weeks. Incidentally, the manager of the previously mentioned school did mention (as if it was completely normal and ok) that he has heard me on the radio (I've never heard him!!). This person has made it his mission to 'catch out' other schools/instructors - whenever he deigns to talk to any of us direct (VERY rare) he opens his radio so that whoever is back at the base (or wherever) can listen to the exchange...

Anyway, enough with the paranoia... :biggrin: There are some things I can try, thank you for your input. I will try having the students wear the radios in belt-bags to remove the 'body-between' situation, and the bike mounted antenna for my own radio.

Thanks guys :thumbup:
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Re: Interference? 'Jammed'? Equipment degradation??

Postby G4RMT » Sun Aug 14, 2016 7:37 pm

At the distance I see you guys working, I would be very surprised if body absorption is the issue. I guess the extra pair of ears listening would be the best thing, because they would hear everything. I'd definitely record it and analyse it later.
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Re: Interference? 'Jammed'? Equipment degradation??

Postby m0lsx » Sun Aug 14, 2016 8:01 pm

angelyork wrote:..I really don't understand why sometimes, the signal just disappears completely - if I turn my radio off and on again, it will work again :dizzy: Even more confusingly - I have been using the Midland radios for 3 years with no problems, until the last few weeks. Incidentally, the manager of the previously mentioned school did mention (as if it was completely normal and ok) that he has heard me on the radio (I've never heard him!!). This person has made it his mission to 'catch out' other schools/instructors - whenever he deigns to talk to any of us direct (VERY rare) he opens his radio so that whoever is back at the base (or wherever) can listen to the exchange...

Anyway, enough with the paranoia... :biggrin: There are some things I can try, thank you for your input. I will try having the students wear the radios in belt-bags to remove the 'body-between' situation, and the bike mounted antenna for my own radio.

Thanks guys :thumbup:
[/quote]


It sounds like maybe it's more a radio issue, than a reception issue. What batteries does it have & have you checked them? Also if radios are going inside a jacket day after day over several years, it could be a connection issue with the antennas.
All you need to do is program your radio with no CTCSS code & you too can listen in to other instructors. And if he is keying his mike then you will know it & will you simply need to key your radio to jam his transmission of your conversation or better still make it clear he is bugging peoples conversations.
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Re: Interference? 'Jammed'? Equipment degradation??

Postby angelyork » Sun Aug 14, 2016 8:43 pm

m0lsx wrote: It sounds like maybe it's more a radio issue, than a reception issue. What batteries does it have & have you checked them? Also if radios are going inside a jacket day after day over several years, it could be a connection issue with the antennas.


The intaride radios have only had a couple of weeks use - one week when I first got them, but I returned to the midlands, then this past week. I guess the midlands have had about 18 months, I used company midlands before that. I'm thinking of replacing just my radio, maybe with a kenwood or motorola...

So I need to work out how to record my transmission... help? :biggrin:
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