Interference RFI on CB Radio 11m Band

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Jim444444
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Interference RFI on CB Radio 11m Band

Post by Jim444444 »

This happens anytime of the day. Tried finding out what could be causing it by turning off the power to the house and running on battery power but it's still there. I can also hear it with the SDR off and just running my TS-590SG or CB radio. Any suggestions or ideas on what the source of the interference could be ?

Video of the RFI


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Seems to be city wide too as quite a few other CB users in the local radius report the same interference.
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NUBSTER
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Re: Interference RFI on CB Radio 11m Band

Post by NUBSTER »

I live in a very built up area in North London and I get that noise all the time plus other interference so ATM I can't be bothered to much in switching on my radio but even when I do cos of this noise it seems alot of others have the same feeling as me be its totally dead on the air it seems .
ChubbyChops
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Re: Interference RFI on CB Radio 11m Band

Post by ChubbyChops »

I get it on some channels and I'm sure it's power line propagation from broadband or some badly screened electrical devices.
LondonCbRadio
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Re: Interference RFI on CB Radio 11m Band

Post by LondonCbRadio »

Switch to PMR446 you won't hear any noise. I was on there the other day and someone was giving me no signal what so ever and i could hear him clear as day. Now if that was the CB he would have to give me s9. CB Radio with a big 18 foot antenna up vs PMR446 with a little 1 foot antenna up ? Because of noise issues on cb you will work better distance on PMR446 vs cb radio. I know it's hard to believe but it's true. As for the noise don't waste your time as you won't solve it.
paulears
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Re: Interference RFI on CB Radio 11m Band

Post by paulears »

HF is completely a mess nowadays. I gave up trying to cure it at the office - every wall wart power supply - my own broadband, by two neighbours close in with theirs, and the fact 5 broadband cables pass within a few metres of my antenna - I don;t get a chance to cause any interference as I never transmit because I can't hear anyone! Killing the office power reduces it - but leaves the neighbours. As for PMR446? It's another band and quiet - but has it's own problems, and you're never going to talk to somebody in America? At least with CB you could drive somewhere miles from anywhere and do it that way? It's the same argument the star gazer folk have - you can't see bugger all in cities and towns any longer because of light pollution. You need to get away from people.
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MotorhomeMatt
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Re: Interference RFI on CB Radio 11m Band

Post by MotorhomeMatt »

It's a sign of the times, unfortunately...
I have a CB in my campervan which I use to keep in contact with other vans whilst travelling. For the likes of the North Coast 500, Scottish Highlands, North Yorkshire moors et.al it still works great, but as soon I enter anywhere urban, I just end up switching it off altogether due to the qrm. The annoying thing is busy urban areas are where we usually need the comms the most!
Passing under power-lines, that's another issue....
Home is where you park it!!!
Rusty_Cockroach
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Re: Interference RFI on CB Radio 11m Band

Post by Rusty_Cockroach »

You can reduce noise in most cases and in my case by a far bit.

I live in a built up area, close to a row of shops... 10am to 10pm my receive noise is S7/S8. Outside these hours it can go down to S3/S4 on a good day.

With a little persistence I've got the noise down to S2/S3 during the day.

1. Properly grounding radio equipment and antenna.
2. Choke/filter AC supply to radio shack/shed/room or use batteries to power equipment.
3. Choke/filter coax, both radio end and antenna end.
4. Use a good X-Phase QRM eliminator with TX/RX sensing/relay.
5. Turn off your stuff thats causing noise.
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NUBSTER
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Re: Interference RFI on CB Radio 11m Band

Post by NUBSTER »

@ RustyCockroach I remember when CB was classed as a cheap form of communication buying all that stuff is not exactly cheap plus turning stuff off that might maybe causing may not be a option to some .
Jim444444
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Re: Interference RFI on CB Radio 11m Band

Post by Jim444444 »

Rusty_Cockroach wrote: 12 Sep 2021, 23:45 You can reduce noise in most cases and in my case by a far bit.

I live in a built up area, close to a row of shops... 10am to 10pm my receive noise is S7/S8. Outside these hours it can go down to S3/S4 on a good day.

With a little persistence I've got the noise down to S2/S3 during the day.

1. Properly grounding radio equipment and antenna.
2. Choke/filter AC supply to radio shack/shed/room or use batteries to power equipment.
3. Choke/filter coax, both radio end and antenna end.
4. Use a good X-Phase QRM eliminator with TX/RX sensing/relay.
5. Turn off your stuff thats causing noise.
Hello Rusty, thanks for the pointers appreciate it. I have done 3 and 5 and the next project will be to build a filter taken from here https://gm3sek.com/2019/10/11/clean-up-your-shack-2019/ I have a QRM eliminator works great for FM mode but for SSB the relay goes crazy not sure how to hook up the PTT to my rig. As for grounding my radio equipment currently on a second floor so probably not an option.
Rusty_Cockroach
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Re: Interference RFI on CB Radio 11m Band

Post by Rusty_Cockroach »

Jim444444 wrote: 15 Sep 2021, 19:22 Hello Rusty, thanks for the pointers appreciate it. I have done 3 and 5 and the next project will be to build a filter taken from here https://gm3sek.com/2019/10/11/clean-up-your-shack-2019/ I have a QRM eliminator works great for FM mode but for SSB the relay goes crazy not sure how to hook up the PTT to my rig. As for grounding my radio equipment currently on a second floor so probably not an option.
Hi Jim, that link is perfect, just what I did. In my case the mains filter didn't help much, but my noise level was so bad, any little bit helps. Depends whether you have excessive levels on mains AC.

In my case the filters on each end of the coax was more useful, although I have a particularly noisy 5/8 wave antenna.

As for PTT to your rig/X-Phase! Most CBs don't support this, unlike good amateur transceivers. A socket could be fitted and wired to the CB board in some way! But I've got no idea how this could be done. An expert with this sort of stuff would be needed.

Have a look at this...

Not saying its the right way to go about such things, but I thought it was interesting.

As for grounding... Run a thickish copper wire from the second floor to a grounding rod, if you have grass/soil at the base of the wall (nobody will notice!) Grounding rods are usually around 1m long, best practice is to use two at least 1m apart. This is the best vid I've found, that explains how to ground stuff properly...
LondonCbRadio
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Re: Interference RFI on CB Radio 11m Band

Post by LondonCbRadio »

QRM eliminators only work with one source of noise. If you get noise from many places then i wouldn't even bother with one unless one source is very strong then it might be worth it. Personally i've given up with CB as i can't listen to crackle with everyone. That's when you even hear someone on air. Where i am there is no one local so it's a waste of time.
Rusty_Cockroach
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Re: Interference RFI on CB Radio 11m Band

Post by Rusty_Cockroach »

LondonCbRadio wrote: 18 Sep 2021, 17:36 QRM eliminators only work with one source of noise.
Not strictly! They can encompass more than one source.

In my case I tune my QRM eliminator for external noise S2/3. Then I turn on my 24v PSU for my amp (which is quite noisy). This brings my noise level up to S4/5, with a little minor re-tune of the eliminator it comes down to S2/3 again.
LondonCbRadio
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Re: Interference RFI on CB Radio 11m Band

Post by LondonCbRadio »

Rusty_Cockroach wrote: 19 Sep 2021, 21:40
LondonCbRadio wrote: 18 Sep 2021, 17:36 QRM eliminators only work with one source of noise.
Not strictly! They can encompass more than one source.

In my case I tune my QRM eliminator for external noise S2/3. Then I turn on my 24v PSU for my amp (which is quite noisy). This brings my noise level up to S4/5, with a little minor re-tune of the eliminator it comes down to S2/3 again.

Playing with the gain control don't mean it's lowering the qrm.You might as well turn down the rf gain and claim you have lowered the qrm.

A video showing us you doing what you said while someone is talking would be great.
Rusty_Cockroach
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Re: Interference RFI on CB Radio 11m Band

Post by Rusty_Cockroach »

I don't play with the gain control of the main antenna much! Yes I agree turning down gain will reduce all RX, that's not what said nor what I meant.

In my case... I can make minor changes when I turn on my 24v PSU. Just saying my PSU's interference can be encompassed, which reduces both sources. If it didn't I'd just use my two 12v batteries instead.

And I'm not saying these QRM eliminators are designed to eliminate more than one source, just happens in my case it does. Just means both sources are similar!
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