Query for all you CB radio expert

Ok, so let's start off by saying I've not really got a clue about CB's - but I want one set up and working properly for laning, etc. so I bought a cheap used on from eBay and wired it in to my Disco 2.

As far as the wiring goes it seems fine, powers up and receives lots of static (and the occasional faint and static-filled sound of a far-distant CB user). So all seems to be basically set up.

Good so far!

After a little confusion over aerial installation, earthing, etc. I decided to go for a mini-springer aerial from my local shop (as the guy in the shop advised it was pre-tuned and therefore didn't need specially setting up). I do also have a base and middle loaded whip that came with the CB - it seems like a decent aerial but I understand this needs to be tuned in / length adjusted / or whatever with the aid of an SWR meter - a couple of members have already said they'll helpfully assist with this at LZ13, so should be good to go out in the lanes.

While testing the pre-tuned aerial I found it does seem to receive but very poorly. Wondering if this was a poor earth (gutter mount fixing not being the best earth position on Disco) I've added an earth cable to the mount and rub this into a the rear door jam area and fixed to one of the panel screws - so should all be nicely earthed (it's a proper earth cable - actually its the 5mm earth cable for a moped - so should be fine for this job). So i'm hoping all is now earthed and correct.

So then comes the problem - and I've actually got no idea what's causing this or why - I seem to get quite bad static interference and this gets significantly worse when I accelerate / noticeably improved if I take my foot off the throttle. Which obviously doesn't make for a very good "mobile" solution!!

Any suggestions as to why might be causing this and how to overcome it? I don't get any issues with car radio or mobile phone so i'm assuming it's something wrong with CB installation but can't think what.

Hi Paul.


No expert here either, but from what I understand and take this with a pinch of salt...But have you checked the following?

With a meter verified the antennae cable earth is good to the chassis/ battery negative? Use a multimeter to verify, I also used a jumper cable to verify I had a good earth when I was doubting it.
The antennae is connected properly to the mount? the isolation washer is in place?
Can you transmit to another user? do they receive you clearly?

Also, just in case, do not transmit if the CB is NOT connected to the antennae.

Cheers

There are a number of different kinds of interference.
Can you describe the interference you're experiencing a little better. Is it a loud hiss, a crackle or a whine which changes with the engine speed?

brian47 said:

There are a number of different kinds of interference.
Can you describe the interference you're experiencing a little better. Is it a loud hiss, a crackle or a whine which changes with the engine speed?

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it's like a slightly more course / gritty version of normal static white noise and it seems to cut in and out as throttle is depressed rather than slowly fade in (hope that makes sense?) but once it's cut in then it does seem to increase slightly more as the throttle is pressed harder. This is in addition to / over the top of the normal "nothing is being received" type white noise.

Not had chance to test it with someone locally as don't know anyone who's actually got one near me. Have turned it on a few times on the motorway but only to listen and see what reception is like - didn't want to transmit until I knew it was set up right.

OK, it sounds like it's just vehicle noise. I take it you have a squelch control on the set, does the noise/interference override the squelch?
It's going to be difficult to ascertain whether the interference is degrading a received signal .... until you receive a signal.

Incidentally, some of that noise is the leftover heat from the big bang 13.7 billion years ago, called the "Cosmic Microwave Background". The rest is vehicle noise and thermal noise in the first stage amplifier. As I said, checking exactly how much it detracts from a good signal will require a signal.

brian47 said:

OK, it sounds like it's just vehicle noise. I take it you have a squelch control on the set, does the noise/interference override the squelch?
It's going to be difficult to ascertain whether the interference is degrading a received signal .... until you receive a signal.

Incidentally, some of that noise is the leftover heat from the big bang 13.7 billion years ago, called the "Cosmic Microwave Background". The rest is vehicle noise and thermal noise in the first stage amplifier. As I said, checking exactly how much it detracts from a good signal will require a signal.

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The squelch adjustment can cut out the noise. I managed to get a fairly weak signal on the way home this evening (I could hear 1 person talking but not the other, the one I could here was heavily distorted by the static noise and I guess I could understand about 65-75% of what he was saying. Every time I depressed the throttle the static noise increase and the understanding of what was being said dropped to about 35-45%. I have no idea where the other guy was so don't know if the was so bad because at the end of the receiving range.

TBH, you can't expect BBC quality out of a CB receiver. The situation you've described says to me that both the stations you heard were either at the limit of range for the one you could hear and well out of range for the one you couldn't hear.
4 watts isn't that much in the way of RF power, I can't say exactly what sort of range to expect, but it probably won't be more than say 10 to 15 kms, on a good day with a following wind.
I'd wait until you can get a good solid signal from someone before you can say that the installation is good or faulty, but I'd say that you're probably on the right road. A good signal will be one that can open the squelch with no trouble, it is designed to blank out noise and the very weak signals which might be of no use to you.

Paul find the HIGHEST point were you live out of the way of all built up areas !
27mgs is LINE of SIGHT ! so if your in a built up area your going to struggle with signals !
Signals HATE buildings & DON'T go thru brick walls very good !
I have a sirio 4000 on the top of my truck & I still suffer with signals when in built up areas , were as in the open 20/30 miles aint a problem ! & if the skips running can talk state side no probs !
As for interference some's of your motor BUT i azade a guess and say that most of it's of solar panels because they chuck so much CRAP out !

Magicgrotto said:

As for interference some's of your motor BUT i azade a guess and say that most of it's of solar panels because they chuck so much CRAP out !

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Solar panels are purely passive devices, they don't emit any radiation, but their controllers do.

Peter

Get that Trailer finished Pete !
Instead of coming on here & nit pickin mi posts !
Hows it going Mate ??

Never used a CB but in the old days we had to put suppressors on the car electrics for this kind of interference. Just a thought.

backinblack said:

Never used a CB but in the old days we had to put suppressors on the car electrics for this kind of interference. Just a thought.

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I was wondering that myself - I remember the good old days of putting a suppression on my Audioline cassette player (with 3 band graphic equalizer - cos it was a posh one!!) to get rid of the interference when listening to good old Radio 1 on medium wave! Had a quick look on eBay and there seems to be a selection of noise suppressors available for CB gear.

I think i'm going to have a look at the earthing again at the weekend and make sure everything is 100% sound (maybe try the jumper cable test @neilly suggested) then i'll see what I can do about finding a decent signal to work with.

Paul Leinichen said:

I was wondering that myself - I remember the good old days of putting a suppression on my Audioline cassette player (with 3 band graphic equalizer - cos it was a posh one!!) to get rid of the interference when listening to good old Radio 1 on medium wave! Had a quick look on eBay and there seems to be a selection of noise suppressors available for CB gear.

I think i'm going to have a look at the earthing again at the weekend and make sure everything is 100% sound (maybe try the jumper cable test @neilly suggested) then i'll see what I can do about finding a decent signal to work with.

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I've put together a few notes on interference which might be of help, Paul

brian47 said:

I've put together a few notes on interference which might be of help, Paul

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That's brilliant, thank you. We'll I guess that's my weekend planned then - systematic check of the whole install until I've found the source and eliminated it (good thing the missus is away this weekend or she'd only find things to distract me!!)