CB Radio Information and Installation

No, problem! Also, if anyone is in the Northern VA area, I can help with the tuning.

 

sub'd

 

To bad your closer to the right coast than the left. I would definitely take you and yours out for dinner and drinks for a bit of help.

 

Thanks Frogsauce for putting together this thread, good job man..

 

The problem I have is that my SWR is at 1 on 40 and 1 on 1. It cant be that good.

Not trusting the built in SWR system on the radio, I bought a stand alone SWR meter, it had the same problems.... no scale movement and in this case, no deflection to calibrate...most the time. Its like something is broken in the radio, when it does seem to work, I get SWR in the ranges of 6.2 etc. Ground seems ok, jumps around from less than an ohm up to 1.4 ohms.

 

Where are you drawing your power from?

 

The cigarette lighter slot, or the power plug, both are in decent shape, no flickering, good voltage. I'm using a 3 pin to lighter socket connector.

 

I would try a direct shot to the battery and see if that helps. It may be the radio though, these things crap out all the time.

 

Retried some stuff, it passes "antenna check" and "tx check" on the radio's diagnostics... (pass) w/o the stand alone SWR meter. The internal SWR read 1.1 (finally some actual movement) and a 1 on other channel still

Add the external meter and its all out the window.

I'm going to try a radio test with someone at work tomorrow, it worked fine in the yard, but that was 80' apart. Maybe I'm just fine.

 

What kind of radio and antenna do you have?

Also, your antenna cable is not spooled up into a coil (circular shape) anywhere is it? I have seen some funky SWR readings from that.

And like LUSETACO says, try a direct connect from the battery. With Radios, a direct connect to the battery is the best route.

 

Grounding the antenna alone will not lower the SWR in all applications. It also depends on how much of a ground plane it creates. On my 07 Tacoma, I mounted a 102" whip in the center of the bed behind the cab. I used a custom mount that put the antenna just over 6" away from the cab to keep the whip from hitting it. Since the bed is made of composite material, there's no metal for a ground plane. So, I used the braid from left over coax and made a connection to the frame on each side of the truck. SWR was well over 3:1. I was able to resolve this issue by creating a better ground plane. You know those metal tracks that run along the top of the bed used for the adjustable tie downs? I connected them all together using some more braid. Then I connected the one behind the cab to the antenna mount. This essentially created two ground plane radials that went towards the back of the truck. SWR dropped to 1:1 over all 40 channels and then some.

 

When I first got started, I was told that 18' or more should be used for SWR issues - but if the length of coax affects your SWR then you have a problem.

I don't like Firestick antennas because, IMO, they mislead people. For instance, if you look at their website under products, they advertise all their antennas as being 5/8 wave with their 7 ft model listed as a 3/4 wave....which can lead the uninformed to believe they're getting something they aren't. Where radio is concerned, the closer to a full physical wavelength, the better the performance. So, it stands to reason that a 5/8 wave antenna will perform better than a 1/4 wave and a 3/4 wave will perform better than a 5/8 wave. Here's the thing - Firestick uses either a 5/8 or 3/4 wave length of wire and then helically winds it around fiberglass shafts ranging from 2 ft to 7 ft. While the electrical length of the antenna is, indeed, 5/8 or 3/4 wave, the physical length is not and the antenna will perform accordingly. The electrical length simply provides the proper impedance (50 ohms) to the transmitter. The two foot model would perform very poorly because, while electrically 5/8 wave, the physical length is less than 1/4 wave. Each model above that will perform a bit better than the model below it with the 7 ft model giving the best performance overall because of its length being very close to a full 1/4 wave length physically.

The only reason I bring this up is because a few years ago I and several other radio enthusiasts got into a heated discussion with someone who SWORE that his 7 ft Firestick was indeed a 3/4 wavelength antenna and performed just like one. Nothing anyone told him would convince him otherwise so we finally let him continue believing that he was driving around with a 3/4 wave antenna mounted on his vehicle.

 

RG8X is fine for HF use. The losses for the amount of coax a typical person will use for mobile applications is negligible. On VHF/UHF I would suggest something better but that isn't practical in mobile applications.

 

I left out the bit about ground planes because of the many different antenna placements out there. I agree it can make or break your SWR with some antennas.

It seems more important on those long whips though. All the 3-5 footers with high or mid coils don't seem as affected by their ground plane.

Hence mine mount on the tailgate, with almost no ground plane, but still SWR under 1.5 and pretty good range. Could be better with a nice big flat metal surface, but for wheelers, we don't need that much range.

If I was going for maximum range, I would mount it on the center of the cab roof. Or another flat metal surface. And I would probably use a 102, instead of a 4' whip.

 

Yeah, it's for this reason I left the cable length part at a short statement. Plus, most cable you buy from stores comes in either 9' or 18' segments. I think most people on here are just going to go with one of those.

I recently read an article covering the 18' cable myth and actual physical wavelengths. The research they did showed the only way you would benefit is if your cable was stretched out to length, and your antenna wasn't coiled.

The places I go hunting would destroy anything longer than 4'. But for highway and long distance, a full 102 would be what I used.

 

A bigger problem might be that the antenna is too close to the cab considering the rather short length of the antenna.

 

This probably the WORST place to draw power from for a CB. These ports aren't designed to provide the current that some radios can pull...especially if the radio is modified to put out more power in any way. The best place is always the battery.

 

Coiling coax shouldn't impact SWR. All it does is form a common mode choke...which helps eliminate RF on the shield of the coax. If coiling coax causes a change in SWR - you have a problem somewhere else.

 

I thought the choke would also affect your reflection. Or is that only high power satellites?

I'm was working with a guy who was having issues with SWR and noise; his readings would fluctuate badly until we uncoiled the cable. He still had bad SWR due to a poor (partially painted) ground. But the fluctuations stopped.

EDIT:
Ah, the tight coiling was causing inductance, which affects the SWR. It's for AR but I think its the same concept at a lower power application for CB (last part): http://www.karinya.net/g3txq/chokes/

Basically, a large diameter coil would cause a choke on the outside of the cable (which would reduce interference). But a small diameter coil (like what would typically happen in our small space trucks), would distort the cable and change it's impedance. That would cause the SWR fluctuations.

 

The frame is a ground plane all ready if you feel that is not enough then run a counterpoise under the bed, bottom line a vehicle is a very poor ground plane no matter what you do but that is all you have. The metal bed rails are all ready grounded. The term "grounding the antenna" is misleading if you did it would be absolutely worthless basically you are creating the other half of the antenna with the ground. A half wave antenna requires no ground plane but a 16+ foot antenna on the back of your truck is not real practical.