CB Receiving without antenna?

Joined
Jan 30, 2018
Messages
4
#1
Hey guys,

I created an account just for this, I've been lurking through all my google searches but either I wasn't using the correct search terms, or I was using the wrong terminology.

So here's the short of it, I've been trying to troubleshoot some engine noise on my CB. I thought I got rid of most of it but I still have to turn the squelch up a lot to cut out a lot of noise, so I took my antenna off of the stud until I could work on it during the weekend. I decided to turn my CB on today to listen for any specific harmonics while I drove to work, and forgot it was on after 10 minutes; without the antenna on and with my NB/ANL filter toggled, all the noise was all but gone but a faint whisper, so I had the squelch turned basically off. So I'm at a red light and all of a sudden I start receiving and I could hear someone talking (I was on CH. 19). It lasted for a solid second or two and then it was gone. A second or two of silence (I guess someone responding) and then I heard the same person talking again.

All I have set up right now is the CB to the battery, and the coax (Firestik Fire Ring) to the antenna mount and connected to the antenna stud (FireStik K4A, also all the insulator washers are setup correctly). Do you think that the antenna stud is acting as a very tiny antenna? Or could it be something else?

Thanks,

Kel
 
Joined
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#3
The coax will act as an antenna, especially if the length of the coax is close to a wavelength (1/4, 1/2, 5/8, full) of the frequency being received. Add a strong signal to that and your radio will receive.
 
Joined
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#4
The coax will act as an antenna, especially if the length of the coax is close to a wavelength (1/4, 1/2, 5/8, full) of the frequency being received. Add a strong signal to that and your radio will receive.
Is there any way to test that the cable is acting as an antenna? Also if it is the coax, is it possible that it is also contributing to the engine noise or static I hear when I have the antenna attached?

I'm going to remove the stud and tuck the coax under the hood and see if I still receive signals. I might be barking up the wrong tree though because I'm really just looking for potential propagators of the static my CB is picking up. I'm wondering if the coax picking up signals is just a red herring distracting me from the real cause.
 
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#5
Disconnect the coax from the radio. If the static continues unchanged, it's coming in through the power leads, and you'll need to put a filter inline to filter power before it goes to the radio. If the static goes away, then you are hearing either background noise or RFI.
 
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#6
Is there any way to test that the cable is acting as an antenna?
Disconnect the coax at the radio

Also if it is the coax, is it possible that it is also contributing to the engine noise or static I hear when I have the antenna attached?
Maybe, maybe not. depends on the routing.

I'm going to remove the stud and tuck the coax under the hood and see if I still receive signals. I might be barking up the wrong tree though because I'm really just looking for potential propagators of the static my CB is picking up. I'm wondering if the coax picking up signals is just a red herring distracting me from the real cause.
I would start with this: https://www.amazon.com/12-Volt-Noise-Filter-Engine-Remover/dp/B00XKV114K
 
Joined
Mar 12, 2014
Messages
1,014
#8
Kel,

What type of noise are you hearing? Common causes are ignition (kind of a repetitive, clicking) whining (usually caused by the alternator) or even a more random crackling that could be caused by bad antenna connections. These are the only sources but are quite common.

Use decent quality coax and connectors. Some of the cheaper coax doesn't have a great shield. Also, keep the coax and power cables as short as possible while routing away from other cabling as best as you can. You'd be better served running power cables right from the battery rather than picking it up from inside the passenger cabin.

As far as hearing a signal with no antenna, as others have mentioned, it's very possible especially if the source is close to you.
 
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#10
Kel,

What type of noise are you hearing? Common causes are ignition (kind of a repetitive, clicking) whining (usually caused by the alternator) or even a more random crackling that could be caused by bad antenna connections. These are the only sources but are quite common.
Well when I first had everything set up it sounded like alternator noise, it increased in pitch and volume with engine rpm. When I grounded the chassis to the battery it went away now the noise seems to be purely static, kind of like old white noise static you'd hear on TVs. It's constant in its pitch and volume and there are no abnormalities to it i.e. crackling or popping. I have to keep the squelch at 50 to 60% to tune it out. I plan on adding ground straps to my antenna mount, might even bond my vehicles hood (Jeep 15 Wrangler JK) to the chassis.

I have isolated the noise as coming through the antenna, that's why I was surprised that when I removed it I was still receiving transmissions. I had initially thought that maybe that's why I was having issues but from the replies I've gotten it looks like its just someone transmitting close to me or has a really strong signal.

I have some ferrite chokes and grounding straps coming in as well as a portable AM radio I plan to use to sniff the source out.
 

N4GIX

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#11
Most likely since it isn't ignition or alternator noise is simply the ambient noise generated by the thousands of folks talking all at once on every available channel!

Back in the late sixties, I didn't even need my squelch control at all; there simply wasn't any such white noise... ;)
 

manlius

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#12
Maybe they were close enough to you to be heard even without the antenna.


A little off topic, but back in the day a buddy and I would have to shuttle vehicles from one dealer to another, so we would be in separate vehicles. We made dummy loads by soldering a small lightbulb directly into the back of a PL259 male connector (I don’t recall the size, but I believe 12v). We could talk to each other from vehicle to vehicle without hearing a lot of other traffic, without bothering other people and most importantly, without destroying our CB’s with a crazy SWR.


Sent from my iPhone using Tapatalk
 
Joined
Jan 30, 2018
Messages
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#13
I just wanted to write a quick reply, thanking everyone for their input. I'm going to try to figure out this static problem, since it is there with the cable removed I'm going to try some ferrite chokes, and move up to the filter if it doesn't help. I thought since the CB didn't measure the static on the dB scale as it does with the antenna attached (around 3dB) that it was isolated to the antenna side of things, so maybe things are looking up.

But it was very interesting to read all the replies and gain some insight into things, especially that a coax cable can act as a very weak antenna, and that you could use a light bulb for short range comms (lol!).
 
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Mar 12, 2014
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#15
Well when I first had everything set up it sounded like alternator noise, it increased in pitch and volume with engine rpm. When I grounded the chassis to the battery it went away now the noise seems to be purely static, kind of like old white noise static you'd hear on TVs. It's constant in its pitch and volume and there are no abnormalities to it i.e. crackling or popping. I have to keep the squelch at 50 to 60% to tune it out. I plan on adding ground straps to my antenna mount, might even bond my vehicles hood (Jeep 15 Wrangler JK) to the chassis.

I have isolated the noise as coming through the antenna, that's why I was surprised that when I removed it I was still receiving transmissions. I had initially thought that maybe that's why I was having issues but from the replies I've gotten it looks like its just someone transmitting close to me or has a really strong signal.

I have some ferrite chokes and grounding straps coming in as well as a portable AM radio I plan to use to sniff the source out.
I think N4GIX called it. It's probably just background noise and your description of it sounding like white noise points to that direction. Two other tests you could consider: Is the noise the same whether the engine is running or not? If so, that points to external sources. If you drive to a secluded area, away from buildings, electrical lines, etc. does the noise level go down? That would point to ambient RF as a culprit.
 
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