Bad CB Range! (1 Viewer)

[CTiger]

I recently installed a cobra CB into my 62 with a 3 foot firestik fiberglass along the hood line. Works pretty good- when I'm at my house and I listen to 19 or 9 I can usually hear truckers etc talking , and I'm a few miles from the interstate.
The problem starts here-- my buddy just got a midland CB in his Tahoe, and he mounted a firestik just like I did. He gets almost NO reception. When I'm trying to talk to him, we start to not be able to hear eachother at less than half a mile.
Right now, I'm thinking it might be his coax because he's using a 18 ft cord and so the extra cord is coiled up under his hood. Doesn't he need to cut and re-strip etc. his cord just enough so that it will reach his CB? because the firestik coax (which he is using) ships dis-assembled. You have to screw on the pl-259 connector and solder the tip. What I did was just cut the coax to length and then re-strip the end, put on the connector, and solder it. I've always heard that loops in a coax will kill reception...
Any advice? Thanks!

Mike

 

[alvarorb]

I'm thinking it might be his coax because he's using a 18 ft cord and so the extra cord is coiled up under his hood. Doesn't he need to cut and re-strip etc. his cord just enough so that it will reach his CB?
Mike

Yes, that's the problem. I don't think that making the cable shorter is the solution. Ask him to see if he can do a longer run to get to his CB inside his vehicle.
Also, make sure that both your and his systems are properly tunned.

Regards

Alvaro

 

[CTiger]

thanks, alvaro...ya, I forgot to put that we tuned our antennas and got both of them to down to 1.1 easily.
He's got SO much extra coax that I'm thinking that it might just be easier and cleaner to cut it to length, but we'll mess around with it and see...

Mike

 

[alvarorb]

Maybe someone that knows more about radios can pitch in. But I was under the
impression that antenna cables needed to be a certain length (multiple of x feet).

What most likely is happening right now is that the cable is making a coil that makes interference.

Regards

Alvaro

 

[MrMoMo]

Uh, not with an SWR of 1.1. That is pretty damn good. Does he have a lo/hi power setting on the CB that is on low? Is TX good, but reception bad or both? I am surprised that you got an SWR of 1.1

I would also suspect the screw on connector, sometimes you can get a bit of the braid touching the RF conductor, I hate screw on connectors. Crimp or solder or both. The length of the excess cable should not make that much difference, and if you are getting an swr of 1.1 then it is saying that it is not the problem. are the wires supplying the power large enough, perhaps there is a significant voltage drop over the wires, causing the unit to not get full power and then not be able to amplify the signals enough? dunno, just a thought...

 

[riverliver]

As a 25 year veteran of the 18 wheel world , allow me to help:
No more than 8 - 10 ft. of coax cable- excess (if any) should be coiled large...

WE USE: UNIDEN , GRANT XL'S. 40 CHANNEL WITH UPPER AND LOWER SIDE BANDS. ( side bands travel large distances) . Most cb's come with only 5 watts. So we have a cb shop lower the wattage in the stock radio. and put in a 30 watt add-on amp inside. Some "large car" guys have 500 watt exterior amps that can reach russia while rolling...waste in my opinion.

Have you thought about "GWRS" Handheld radio's? Sold at k-mart's , radioshack...but those punks in there will ask you for your ham license. Those things, for no bigger than they are, friggin' rock! $80 bucks at k-mart.


one love,

RL

 

[CTiger]

From this site:http://www.bellscb.com/cb_radio_hobby/swr.html

If you have an antenna that's say, three feet or less, and the SWR tunes great (less than 1.5) across all the channels than maybe your antennas feedline coax or the antenna coil is "lossy". In "Lossy" I mean that maybe the design or construction material is inferior and is wasting some of your energy as ground losses or increased heat dissipation. This causes both the forward and reflected power to be partially absorbed, thus showing a lower SWR on the meter.

I'm wondering if there is something to this. When I set my SWR I had to mess with the screw a little bit to get to 1.1/1.2. But today when we set the SWR on my buddy's, it was 1.1 on 40 and 1.2 on 1 right off the bat. No tinkering whatsoever. I noticed that we had done the test with his tip off, so we put it on and re-tested but nothing changed.

MrMoMo-when our range starts to come to an end, I can hear him clearly but he says he can't hear me. He said that to hear me at about .5 mile he has to turn his squelch down and put up with the static in order to hear me.

As for how he has the CB powered, he said that he has the power ran to a relay so that the CB turns on when the key's in acc or on. I don't know if this is right or how that works because I don't know much about electrical.

Does this clear anything up? Sorry for the long post....

Mike

 

[Cruiserdrew]

Likely a combination of problems. Check the antenna grounds in both vehicles. The total length of cable is very important-13 feet is one of the magic intervals I think but I don't remember with certainty. Any coil in the feed line will wreck the quality of your signal because of inductance into the wire as it goes around-no coils!!!

CTiger-I remember your antenna was on the hood-It would help to get it on top of the vehicle.

Here is a test-get(borrow) a mag mount antenna with the coax attached and place in the center of your roof. Have the coax feed inside with no loops or coils-a nice smooth run to the radio is what you want. Do the same set of tests. You'll know in an instant if it's your antenna install or just the limitation of CB.

Check your power supply too. If it's attached to a small pre-existing circuit, you may be getting excessive voltage drop on transmit. You want a direct supply from the battery with 12 guage wires.


Just to make you think a bit-a mobile 2 meter (Ham) radio would solve all of these problems and many more. Something to consider if your buds will make the jump to real radio.

 

[Kofoed]

Coiling coax is bad. Run it radomly in cab if you don't want to cut

I vote that the center conductor connector was not soldered properly or is broken some where. Get out your multimeter and test continuity.

 

[cruiserdan]

. Most cb's come with only 5 watts. So we have a cb shop lower the wattage in the stock radio. and put in a 30 watt add-on amp inside. Some "large car" guys have 500 watt exterior amps that can reach russia while rolling...waste in my opinion.

Not to mention illegal but not enforced like it used to be.

 

[Pskhaat]

Maybe someone that knows more about radios can pitch in. But I was under the
impression that antenna cables needed to be a certain length (multiple of x feet).

Yes & No. You generally hear suggestions of keeping the coax in multiples/logarithmic divisions of the wavelength so that the coax can act as the counterpoise (ground plane/other 1/4 end of the 1/2 wavelength). You only want this if you are the average joe and have not found a proper ground plane for your antenna.

Obviously, coax should do nothing but transfer the RF signal to the antenna feed, introducing as little loss and thus as little length as possible.

 

[CDN_Cruiser]

I agree with Scott - the coax should be acting as a transmission line, not the counterpoise of the antenna, assuming it's grounded properly.

I don't think this is the case, but one question would be if either of you tried any transmissions by mistake without the antenna - this could have damaged the 'finals' of your transmitter. In this case, it would imply that you fried your transmitter and he can't receive because of this. Have you tried contacting others to see if the radios are working properly?

To me, it also sounds like an antenna problem. However, I also worry that if the antenna connection is shot in some way and he is still trying to transmit, it may have done some damage to the radio.

What do you think Scott?

Cheers, Hugh

 

[Pskhaat]

Yeah, I've even burned up way too many CBs unknowingly because of crimped/bad/cheap coax. Worst case, get a mag mount antenna, shove it on the top of the truck and try xmitting, you generally can't go too bad with a mag mount.

 

[CTiger]

I don't think this is the case, but one question would be if either of you tried any transmissions by mistake without the antenna - this could have damaged the 'finals' of your transmitter. In this case, it would imply that you fried your transmitter and he can't receive because of this. Have you tried contacting others to see if the radios are working properly?
Cheers, Hugh

I definitely didn't try to transmit w/o an antenna, and I would bet my friend didn't, but I'm not positive. When we are close to eachother, we can hear very well...It's when we start getting farther apart that it gets bad. For reference, I can hear tons of stuff on say channel 19.

We're going to look at his coax this weekend...

Mike

 

[Bob_Garrett]

Couple of things to check:

1. Seperate the vehicles to where your signal is noisy to him. Then have him shut off his motor while you're transmitting. If the noise level decreases, chances are he's picking up electrical interference from his vehicle (ignition, alternator, etc.)

2. If your antennas have the removable PL259 connector at the antenna, unscrew that and measure the SWR there. That will give you the SWR of the antenna alone, not the combination of the antenna and coax.

3. 3 ft antennas don't have very good range at cb frequencies, especially if they don't have a good ground plane. If its mounted in the middle of the roof, it will do ok, otherwise the range will be pretty limited. The other folks you're hearing at greater distances are probably running better antennas.

Specific lengths of coax are only needed if you are using a dual antennna setup (found on some 18 wheelers). Best bet is to keep the coax as short as possible to reduce losses in signal between the radio and antenna. Coiling the coax generally won't cause any problem (except for the signal loss) as long as you are using good quality coax and have the antenna grounded properly.

Hope that helps

 

[FJ40_owner]

Coax lenght affect is nil.

Meter the coax on Ohms for a short.

Disconnect the entire coax. I'll bet you fouled up the Pl259.

 

[mk1pickle]

check for kinks

do a resistance check on BOTH ends during a wiggle test

eliminate loops

check swr meter on other antennas