Question about Uniden PC78ELITE 40-Channels Base CB Radio

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Uniden pc 78 elite cb

Get no reception or transmission on cb.even the weather channels are silent.swr is at 3 bought new fiberglass antenna and coax but have not tried an external speaker.do not get any movement on meter while on 19 so am assuming im not receiving at all. the squelch does not static even all the way down.keying mic does make a sound in internal speaker . problems started after switching to cal to check swr but not sure if just coincidental.not sure if im calibrating correctly what do u suggest.

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I have receive but will not transmitt

Posted on Apr 18, 2008

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Hi, This is a link to your old post re SWR 3....http://www.fixya.com/support/t180697-pc78_elite_cb As stated SWR 3 is too high, it should be 1.5 or lower. Fiberglass antenna are kinda notorious in setup and experience wise have not performed well or at all. Maybe you should try a different antenna (metal rod). Some good brands/models I have tried with very good results are K40, Hokushin, Comet, Oscar, Maldol, Daiwa. To check if you can receive, stick an ordinay length of wire ('bout 9' long) at the center of your radio's connector. RX should work (pls don't key the mic or TX).

Posted on Aug 12, 2007

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1 Answer

Uniden PC76XL and a 4' Firestik fiberglass weak respetion


above the rear window should be a tubular hold down handletry mounting it there.does this truck have a fiberglass body as others do? If it does try grounding the antenna to the chassis with some heavy duty wire maybe like 12 or 14 guage. I drive a ch650 and to switch trucks I have to check my SWR constantly and ground the antenna. you could turn the volume up a little too. SQuelch all the to the left and RF gain all the way to the right.

Feb 17, 2013 | Uniden Pc76xlw 40 Channel Cb

1 Answer

I have tried 3 different antennas 2 magnetic and a k-40 solid mount now no matter what i do the swr is way to high and wont adjust and with 2 of them including the k-40 the antenna light comes on when i...


  • You need an external meter or at least replace the meter in your radio with another one. Even if it appears that meter is working right you need to put another one on there that will respond better. I repaired a Cobra 29 just two days ago with the same issue. The meter responded what looked to be great. Only the SWR was "8" so it said. I knew better. I had just tuned the radio and new better. I put in a new meter and the problem was resolved.
  • I always recommend an inline meter but the one on that CB should work good enough for a simple SWR check provided it is working right.
  • One more thing, not sure if the antennas you are using require you to provide a coax or weather the coax comes on the antenna already but I would suggest trying a new coax if your using the same coax for any of those antennas.
  • You may pop open the CB and make sure all legs of the P0239 antenna connector is solid.


  • Hope this helps and thank you for using FixYa.
  • If you have any questions feel free to ask.

Regards, Tony

Jul 05, 2011 | Cobra 29 LTD CB Radio

1 Answer

I have a Uniden PRO510XL radio and a 48" single


then the antenna needs to be moved. antennas have to have a ground plane to get correct swr below 3... or there may be a bad ground. try moving antenna @ different angles to see if it changes swr's or even opening the door away or closer to the body will make it change. also check the insulator it should be on top. call if you need help

Dec 22, 2010 | Uniden PRO510XL 40-Channels Base CB Radio

2 Answers

Got it peaked and tuned and hooked up a new coax and mirror bracket and my swr is at 4. Before I did all this I had the stock coax and swr was under 2. What do I need to do to get the swr down?


The antenna needs to be tuned. The reason all of a sudden your SWR is a 4 when it used to be a 2 is, after a peak and tune, the radio is putting out more power, there for more RF energy is being reflected back into the radio. That is why the antenna has to be tuned.

It is important to tune your CB radio antenna to the proper length. The length must exactly match the wavelength of the frequency you transmit on. Or be really really close.

All Cb antenna's have a way to adjust the length of the antenna. If it's a mag mount, the metal whip can be slid in and out of a metal collar. Usually a set screw. If its a fiberglass whip, the way to tune it is on top. It either has a small metal rod with a set screw to adjust the length, or it threads in and out to adjust length.

Either type you have it will need to be adjusted for proper length. Here is how to tune the antenna to lowest SWR.

Some radios have a built in SWR meter. Some do not. If yours doesn't have an SWR meter, then you have to use an external SWR meter. Radio shack carries one, and you can find them cheap on ebay.

If you have a built in SWR meter or external, the procedure is the same:

1. Turn the radio to CH 20.(This is the center of the band.)
2. Switch the meter switch to CAL. (CAL stand for calibrate.
3. Key the radio. (Important. Do not talk while keying the radio.)
4. turn the CAL knob up until the meter hits the CAL mark.
5. Now while still keying the radio flip the meter switch to SWR.

Where the meter falls after that point is you SWR reading. If its above 3, that is real bad. 2 is not gonna kill your radio but its not the greatest. 1.5 and under is a good place to be, but the lower the better.

If your SWR is high, Here is how to find out if your antenna is too long or too short.

1. Turn to CH 1
2. Repeat SWR procedure. You must calibrate every time you do it.
3. Remember the SWR reading.
4. Turn to CH 40.
5. Again repeat SWR procedure.
6. Compare the reading between CH 1 and CH 40.

Now if the SWR is higher on channel 1 then channel 40 your antenna is too short. You must make it longer.

If the SWR is longer on channel 40 then on channel 1, then the antenna is too long, you need to make it shorter.

Make height adjustments about an eight inch at a time, and take reading each time.

once the SWR is significantly lower and the reading on channel 1 and 40 are about the same, you a about matched. At this point turn the radio to the center of the band, channel 20 and take an SWR reading.

You should now have a low SWR reading, 1.5 or under. If you are 1.5 or under, you are good to go.

If you cannot get the SWR to an appropriate level, there may be an antenna problem.

Nov 17, 2010 | Cobra 29 LTD CB Radio

1 Answer

I've got a Cobra 29 with WX and BT, the antenna light comes on, the swr meter barely moves and it doesn't seem to send or receive, still gets weather. May have been run with a bad antenna, got a new...


Please make sure you are tuning the antenna correctly.



It is important to tune your CB radio antenna to the proper length. The length must exactly match the wavelength of the frequency you transmit on. Or be really really close.

All Cb antenna's have a way to adjust the length of the antenna. If it's a mag mount, the metal whip can be slid in and out of a metal collar. Usually a set screw. If its a fiberglass whip, the way to tune it is on top. It either has a small metal rod with a set screw to adjust the length, or it threads in and out to adjust length.

Either type you have it will need to be adjusted for proper length. Here is how to tune the antenna to lowest SWR.

Some radios have a built in SWR meter. Some do not. If yours doesn't have an SWR meter, then you have to use an external SWR meter. Radio shack carries one, and you can find them cheap on ebay.

If you have a built in SWR meter or external, the procedure is the same:

1. Turn the radio to CH 20.(This is the center of the band.)
2. Switch the meter switch to CAL. (CAL stand for calibrate.
3. Key the radio. (Important. Do not talk while keying the radio.)
4. turn the CAL knob up until the meter hits the CAL mark.
5. Now while still keying the radio flip the meter switch to SWR.

Where the meter falls after that point is you SWR reading. If its above 3, that is real bad. 2 is not gonna kill your radio but its not the greatest. 1.5 and under is a good place to be, but the lower the better.

If your SWR is high, Here is how to find out if your antenna is too long or too short.

1. Turn to CH 1
2. Repeat SWR procedure. You must calibrate every time you do it.
3. Remember the SWR reading.
4. Turn to CH 40.
5. Again repeat SWR procedure.
6. Compare the reading between CH 1 and CH 40.

Now if the SWR is higher on channel 1 then channel 40 your antenna is too short. You must make it longer.

If the SWR is longer on channel 40 then on channel 1, then the antenna is too long, you need to make it shorter.

Make height adjustments about an eight inch at a time, and take reading each time.

once the SWR is significantly lower and the reading on channel 1 and 40 are about the same, you a about matched. At this point turn the radio to the center of the band, channel 20 and take an SWR reading.

You should now have a low SWR reading, 1.5 or under. If you are 1.5 or under, you are good to go.

If you cannot get the SWR to an appropriate level, there may be an antenna problem.






Now: If you have adjusted the antenna properly and you still get the antenna warning light, then the antenna warning circuit may be out of whack. Use an external SWR meter.

You may also be getting common mode current. Its when RF comes down the outside of the coax. If the swr goes up with modulation then it's common mode.

Here is how to stop common mode.

As close to the antenna as you can while still inside the vehicle, take about 6 to 8 inches of the coax, and coil it up into tight even coils and secure into shape with electrical tape.

This is an RF choke, and will stop the common mode current.

If all other radio's are fine and no ant light come one, and are all showing low swr, then turn VR6 back to disable the ant warning light. "only do this if the ant light comes on when SWR is lower then 1.5 and does not swing up with modulation showing that the ant warning light is miss aligned.

Nov 07, 2010 | Cobra 29 LTD CB Radio

1 Answer

Having trouble setting swr .moved anttena up and down 1/4 inch at a time and there is no change


There are several things that can cause you not to be able to get an acceptable SWR.

The first is the most obvious. Poor antenna, or bad coax. Make sure your coax is good. Make sure the antenna is mounted in a good location.

Some things I have seen that cause this problem.

  • Wilson Little wil, almost impossible to get under a 1.6 SWR.
  • Fiberglass antenna's, a break in the wire near the top of the antenna. Will show the antenna as being too short, and adjusting the top will do nothing. This antenna is no good.
  • Common mode current. This is when the RF is traveling back down the outside of the coax, and or causes the coax to act like part of the antenna. SOLUTION. As close to the antenna as you can, take 6 to 8 inches of coax, and coil it into a tight coil, about the diameter of a spray paint can. In fact using a spray can to wrap the coax around works well. Use electrical tape to secure the coil so that it will stay tight and uniform. This will stop common mode.
  • missing foil/vinyl membrane on bottom of magmount antenna. This is essential for the antenna to see ground plane.
  • bad connections on coax connector.
  • Cracked isolator on stud mount.
  • incorrect procedure for taking SWR reading.
  • Poor location of antenna. E.g. antenna's load not above roof of vehicle.
  • Incorrect length whip being used.
  • corrosion of any part of the antenna system.
There are some cheap antenna's out there that you just can't get lower then say a 1.5 or worse, like the wilson little wil. Wilson makes great antenna's. The 500, 1000 and 5000, as well as their silver load antenna's are excellent. I have been able to get them all to at least a 1.1 SWR, and some like the 5000, and silver load fiberglass whip to 1.0 using an analyzer. The Little will is just a poor antenna. Anything under 2.0 SWR is okay of a barefoot radio, although I don't like going over 1.5 my self. A barefoot radio, will do a 2 swr all day. If the radio is stock, and not peaked and tuned, 2 swr is fine and won't hurt the radio.

You should always try to get the lowest SWR that you can in any case. The lower the SWR, the more RF energy is leaving the antenna. As well, receive will improve the closer you get to a perfect match. This is known as being "On Que".

Check everything I have listed that applies. And if nothing fixes it, you may want to try a different antenna. Some antenna's just don't work well on certain vehicles.

Oct 13, 2010 | Cobra 29 WX NW ST 40-Channels Base CB...

1 Answer

Cant get SWR below 3.5


A ground wire will not replace the lack of ground plane. Try a different antenna altogether (possibly one with a magnet mount) and mount it on some metal surface like even the front hood and retest.

I am sure the problem you will find is with the lack of a proper ground plane.

May 31, 2009 | Cobra 29 LTD CB Radio

1 Answer

Matching c b antenna with c b radio


here is some information that will help you test SWR with an inline watt meter. To get proper results you need to use an inline watt meter. Here is a really good site you can go to for help www.cbradiotalk.com

Equipment needed: SWR meter, short jumper coax 3 foot.
midland.jpgProcedure: The SWR meter needs to be placed in line between the antenna and the CB. Connect the antenna (normally connected to the back of the CB ) to the connector marked "Antenna" or "Ant" on your SWR Meter. Connect one end of the short jumper coax to the "transmit" or "Xmit" on the SWR meter. Connect the other end of your jumper coax to the CB.
Assuming you have a standard SWR meter the switches should read as follows: REF or SWR, FWD, and there should be a slide switch marked "set" or "Adjust". If different consult your meter's owners manual.
With the radio on the lowest channel (1 on CB) and the SWR meters switch in the Forward (FWD) position, depress the transmit switch (key up) located on the microphone. While holding the unit in this transmit mode, adjust the meter needle to the set position using the Set or Adjust knob on the meter. As soon as the needle is in alignment with the corresponding mark on the meter face, flip the switch to the Reference (REF) position. The meter is now showing your SWR on channel one. Note the value and quickly release the microphone switch. Record this reading.
Repeat the previous step on channels 19 and 40.
How to read your results: If SWR on channels 1, 19 & 40 is below 2.0, your radio can be operated safely.
If SWR on all channels is above 2.0 but not in the "red zone" (normally over 3.0), you may be experiencing coaxial cable reaction (bad quality, wrong length, etc.), insufficient ground plane, or have an ungrounded antenna mount.
If SWR is in the "red zone" on all channels, you probably have an electrical short in your coax connectors, or your mounting stud was installed incorrectly and is shorted. Do not operate your radio until the problem is found, serious damage can occur to your radio.
If SWR on the lowest channel is higher than it is on the highest channel, your antenna system appears to be electrically short. Your antenna length may need to be increased.
If the SWR on channel 40 is greater than that on channel 1, your antenna is considered to be "LONG" and reduction of physical height and/or conductor length will correct this situation.


Aug 01, 2008 | Cobra 29 WX NW ST 40-Channels Base CB...

2 Answers

Galaxy DX959 CB radio reception and broadcast


You Need to check and set you SWR on the antenna system. You may also have a bad coax or the ant studs ( mounting hardward ) for the antennas may be bad. It definally sounds like an ant/coax problem Good Luck
Ed
NC Electronic
Mills, Wyoming

Dec 08, 2007 | Cobra 18 WX ST II 40-Channels Base CB...

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