CB problems maybe...

Hello everyone, OK here is what happened...

For the past couple of months I have had my Bearcat PC68XL hooked up in the truck but not mounted (I just stufed it between the seat and console) last week I mounted it and noticed after mounting it that the "swing" on the needle it not nearly what it used to be... before It would peg the thing now it is maybe moving 1/4 of the way up and to 1/2 way up with good modulation. I have talked on it once and it seemed to work OK but am worried about doing damage if something is wrong... COAX problems maybe?

 

[Rick]

Could be coax problems or an antenna problem. Best way to check is with an SWR meter.

 

[pickupman]

what is the meter measuring? is it set for SWR, and your SWR wnt down? is it measuring your modulation? are you watching it as you talk to other people?

more info.... though Rick is deffinitely right.... check your SWR. if it's good, you probably don't have any real problems.

 

[User675438756]

I don't have SWR ont he radio so it was just the RF or whatever...

I checked SWR and it was way off for some reason I try a little to get it back in with no luck (I am going to be ounting a whip on the bumper next week so why bother for now) but when I had the SWR hooked up the "swing" was back to the way it used to be. I guess I will wait till next week mount the whip and figure it all out.

thanks
Jim

 

[Sandy]

How about the RF Gain Knob or the Mic Gain Knob, if you have them.
Maybe one or both moved when you moved the radio.

Turning down either will reduce the swing of the meter.

Ltr,

 

[jimbo74]

try not to use it until you mount it with your new antenna mount if possible, if swr is all jacked it can fry the internals of the cb... most people think it wont do any harm, but from all the stuff i have read, says its bad... http://www.firestik.com/FAQ.htm covers that issue of frying the internals

 

[pickupman]

yes - the final transistors will be working outside their normal operating ranges if the SWR is high. they'll take it fo a short time, but they will eventually blow.

don't let the smoke out of the radio!

 

[User675438756]

both RF and MIC gain are all the way up... I think that it is strange that the swing is normal with the SWR hooked up but half that whithout...

 

[K-9Search]

Hi,
When you say it has full swing with the SWR hooked up, I take it, you mean that with a meter in line you get a good reading? if so maybe the meter on the rig has gone bad, just a thought.
Sandy ( KG2MM)

 

[User675438756]

with the SWR in line I get a good reading (RF/MOD) on the radio. without the SWR in line I get half the reading I get with the SWR in line...

 

[pickupman]

i would thinhk your SWR meter is somehow affecting your readins...if this is the case, you need a new SWR meter.

The other thing to keep in mind (assuming you'rearmiliar with the operation of your meter) is that you want a LOW SWR. I would also venture to turn your mic gain down a bit. your RF gain should only be affecting your receive signal strength, and should not affect your actual transmitted power.

good luck!

 

[User675438756]

if I blew up my radio due to bad SWR how would I be able to tell?

 

[Rick]

You would need a dummy load and an RF power meter. Your SWR meter may be dual function. If it is all you need is a dummy load. With that equipment you can see exactly what the output of the radio is under ideal conditions. If there is no output or if it is greatly diminished you blew the radio's power transistors.

Many radios have built in limiting circuits which will reduce the radios output if it is transmitting into an unbalanced load. If that's the case the radios output will go back to normal once the antenna/coax problem is solved.

 

[pickupman]

SOMETIMES when you blow the finals, the radio will power off (basically, the finals short out, thus shorting out other parts of the radio).

beyond that, you may notice a lack of power output (on a power meter), or people even very close to you may not be able to hear you when you key up.

 

[User675438756]

UPDATE: I finally got around to mounting the whip (pics soon) I had an old 102" SS whip that I was planing on using. when I mounted it all up I could not get the SWR under 2 (it was like 2.8 at the highest). bummer its short. I had a huge 8 foot firestick that I got for free at some yard sale in the shed I figured it was junk but gave it a shot anyway. Well, with no trimming got 1.1 across all. so I guess it is on the up and up... however I don't want to keep running this firestick so on to my next question...

my whip is 102" I have a 4" spring everything that I have read says that 1/4 of the CB wave is 108" if I get a 6" spring to make my overall size 108" should that work? (if that makes any sence)

 

[User675438756]

(picture)

 

[pickupman]

102" is the regular whip length. if a spring doesn't help, you may want to try a quick connect as well....

The difference between the 102" and 108" is actually a free-space/ real-life difference. 102" is the real life calc, given a perfect ground plane, which is only "approximated" if you mount the antenna on the center of the roof. by mounting it where you did (and this is not a problem, that is a good mounting location as it picks the antenna up off the bumper, and it keeps you from whacking overhead obstacles), you are adding capacitance between the antenna and ground..... in laymans terms, your antenna is a little shorter electrically than physically.

sorry if this is too in depth.... I would, however, recooment sticking with the 8 footer if it works....

 

[Sandy]

AND why not keep the Firestik ?

It is a good antenna, if not visably worn or you are getting a bad SWR reading, which you are not, then keep using it.

The Firestik is proably a 5/8 Wave antenna, the 102" SS Whip is only a 1/4 Wave, you will get better performance with the Firestik.

The 102" Whip will not be allowed on some Trail Runs, they whip around (the name implies it all "Whip") and are dangerous.

Luck,

 

[CobraXP]

Probably too late because you have already drilled and mounted the antenna, but I found the back and side of my Explorer was making my SWR high. Don't know if it has something to do with the electronics in the back for the wiper motor or just feedback from the side of the steel. But when I moved my antenna to the top with a standard mark mount, my SWR dropped to below 1...

 

[pickupman]

the location of the groundplane affects your SWR. since, on the side of your vehicle, your groundplane is right next to your antenna, and with the groundplane UNDER your antenna (the roof), your antenna approaches an "ideal" 1/4 wave antenna..... this might be partially because of the "preset" antenna you said you were using...it's "pre-tuned" for an installation like the roof, where the groundplane is a large flat metal sheet mounted under the antenna.