help with cb radio

[steve103]

help. i have just installed a cb in my rig and cant seem to get it to work. when i test the swr it is in the red 12 on the meter. i have a firestik11 with a uniden 520 radio. the antenna is mounted on a arb bumper which is powder coated so i added a ground back to the body and still no luck. can anyone give me a hint at other points to look at.
thanks for your time. steve

 

[corax]

Assuming you used a new antenna lead wire, are you sure you're calibrating the SWR meter correctly before you key up?

CALIBRATING THE METER/MEASURING SWR

1. Set CALIBRATION/FS/SWR on the front of the meter to CALIBRATION/FS.

2. Turn on your radio. Then select a channel or frequency on your
transmitter and hold down its transmit key. Do not speak into the
microphone.

Notes: An SWR reading will be different for different frequencies
(channels). If you transmit on one channel more often then
any other, select that channel. If you transmit on several
channels, choose a frequency in the middle of the range of
channels you use. (For example, if you transmit on all 40 CB
channels, choose Channel 20, because it is midway between
Channel 1 and Channel 40.)

If you use a CB that has sideboard modes (SSB), do not select
any of these modes. (Use only AM for SWR measurements).

If you have an amateur radio, select the continuous wave (CW)
or tuning mode to check the SWR.

3. While you hold down the transmit key, rotate the meter's knob until
the needle points to CAL.

4. Release the transmit key, then set CALIBRATION/FS/SWR to SWR.

5. Press the transmit key again, then read the SWR by noting the needle's
position on the upper SWR scale. A meter reading of 1 on the upper
scale is ideal.

The figure shown between the upper and lower scales on the meter
(% REF POWER) indicates the percentage of power that is wasted
through reflection of the signal from the antenna back into the
antenna cable. For example, an SWR reading of 1.5 also means that 4%
of your signal power is lost. However, 96% of the radio power is more
than enough for almost all applications.

6. Repeat Steps 1-5 for each channel or frequency you want to get an SWR
reading for.

a bit more on the results are here: http://4x4icon.com/offroad/antenna/cb_swr_instructions.htm

 

[steve103]

thanks for your reply. i have done all that your note said but still very high reading,12 on the swr meter that i have. any other hints i might try. steve.

 

[KA5IVR]

If you can't get it to tune, check for a short in your connector/coax/mount and your ground:
1. With the Radio and the Antenna removed & unhooked, use a VOM to check it. It should NOT be shorted between the center conductor and shield wire.
2. If that is good, use the VOM to see if your mount is grounded to the vehicle.
3. Also, double check your mount and make sure the insulator is in the right place.
3. If all of that is good, try a different antenna.
4. Still no luck, try to find someone with a Antenna Analyzer to check it.

 

[C-Fish]

You have a short somewhere. Coax is most likely the main culprit.

Did you build the coax yourself? Meaning, did you install the RF connector(s) [after passing through the truck]?

Do not use your radio if the reading is over a 3, as you will harm the radio.


edit...KA5IVR has good points above, check them as well.

 

[steve103]

thanks all. so this is what i have tried. second antanna and coax cable and still nothing. because it is on an arb insted of grinding the powder coat i added a ground back to the body. cant seem to see what the hang up. we have done so many mods and this is the first one to hang me up. i have done lots of electrical on cars so i figure that works. the radio comes on and set channel. when the mic is pressed the meter moves, just cant get the reading below 12. help!!!!!!!!!!!!!!

 

[DaveInDenver]

Sounds to me that you have a short or complete open. For an antenna that is anywhere close to resonant the SWR should be fairly close, 3:1, maybe 5:1, if all it needs is tuning.

If you're >10:1, there is probably only two reasons. There is functionally no antenna (open or short) or the antenna is not even close to right, like using a VHF ham antenna for 27MHz CB.

http://www.firestik.com/Tech_Docs/mkfr-instl_nohook.htm

Make sure the insulator ring and feed look like this.

Assuming you have the feedpoint ring on the bottom, then that is the side where you'd need to grind off powdercoat to allow the outer ring of the Firestik connector to touch vehicle ground. The center section and bolt should NEVER touch the vehicle.

The previous suggestion to use a DMM is very good. That tells you in no time if you're working or not. Open to DC = good, shorted to DC = bad. With a multimeter the resistance with no antenna should mega ohms. You'd be measuring between the center pin and shield of the connector.

 

[steve103]

plastic washer is in right way, and i have added a ground insted of grinding powder coat. all i can think of is my ground is still not right . but if that is the case im not sure what to do.

 

[DaveInDenver]

plastic washer is in right way, and i have added a ground insted of grinding powder coat. all i can think of is my ground is still not right . but if that is the case im not sure what to do.

Where is the ground? Photos would help.

 

[steve103]

ground is under mounting tab,where the contact to the bumper and washer would ground. then i ran #10 wire to a factory ground point in the engine bay, sanded the paint off and the put together.

 

[steve103]

ground is under the mounting tab where the washer would contact for ground. then i ran a #10 wire to the engine bay to a factory ground point and even sanded the paint off the put back together.

 

[steve103]

ground is under mounting tab,where the contact to the bumper and washer would ground. then i ran #10 wire to a factory ground point in the engine bay, sanded the paint off and the put together.

 

[DaveInDenver]

I'll have to admit, I'm confused. There is no washer on the ground side of the Firestik ring. If you look at the molded ring at the end of the cable, there are two rings. One is supposed to touch the vehicle or mounting surface and the other is supposed to touch the nut and bolt. The washer goes between the coupling nut and shoulder nylon piece. I'm still wondering if you are shorting the bolt to the body some place.

In this photo, the top (assuming the mount is from below) is shown. There is a slightly raised shoulder above the metal ring of the cable end. That is the insulation from the body to the bolt and the shoulder of the shouldered nylon washer will just touch that when mounted. On the bottom the bolt sit flush against the metal ring, which is conductive to the center of the coax.

This the single most common problem (I think) with Firestik installation, getting the molded ring upside down or shorted. With a /correct/ installation of the parts, even if you don't expose a little metal, the SWR will be sorta OK.

This is assuming that the coax itself is not shorted or pinched.

A DMM will go a long way here.

 

[steve103]

i had to add a washer on the underside because the hole in the tab on the bumper is 9/16. so after your last replyim thinking the yes it is not grounding to the post sides with the washer im using. coax is good i have checked it with new coax.

 

[KA5IVR]

The mount may look something like this one, same basic principle.

Did you disconnect the coax from the mount and radio to check the coax with the VOM by itself for a short?