I need a crash course in tuning my stock Cobra 29

Discussion in 'CB Radio Forum' started by LDH26, Nov 23, 2008.

  1. LDH26

    LDH26 Light Load Member

    Sep 7, 2008
    How do you calibrate the SWR. I don't want to send it to a shop or anything like that. I just want to mess with it myself and get it working as good as I can and call it good.
  2. Sixx Burning Sky

    Sixx Burning Sky Light Load Member

    Aug 23, 2008
    Using either the meter built into the radio or a good external SWR meter, calibrate on channel 20. Switch back to SWR and record the readings on three channels; 1, 20, and 40. External meter is the better option here.

    If the lowest SWR reading occurs on channel 1, the antenna whip is too long and must be shortened. Loosen the mast set screws and lower the whip 1/4'' into the mast. Tighten mast set screw and again read SWR. Repeat until lowest SWR is obtained. If the lowest SWR reading occurs on channel 40, the antenna whip is to short and must be raised.
    rabbiporkchop Thanks this.
  3. brinkj23

    brinkj23 "Asphalt Cowboy"

    Dec 26, 2005
    So I got a cobra antenna with a metal tip that will slide up and down. If its all the way down can I trim the metal piece so I can get it shorter??

    BOOTYMONSTER Light Load Member

    Oct 3, 2008
    yes you can cut the stinger if it is too long .
    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.
    the stinger doesnt have to be bottomed out but you dont want to cut more than a 1/2 inch at a time off . if you go a lil past the lowest reading just raise the stinger up a 1/4 inch and secure the set screw to hold it in place .

    Equipment needed: SWR meter, short jumper coax 3 foot.
    Procedure: 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.
  5. Smokeonebooda

    Smokeonebooda Bobtail Member

    Aug 21, 2017
    Keep getting two red lights when i try to cal need some help
  6. johnnytech

    johnnytech Light Load Member

    Jul 26, 2017
    You have a bad match in your antenna system, also maybe some grounding issues.
  7. Meteorgray

    Meteorgray Medium Load Member

    Jan 1, 2016
    Smokeone, you haven't described your setup. But, if you have just installed your antenna, maybe it's not configured correctly. One common problem is to put an insulating o-ring in the wrong position on the antenna shaft, thus creating a dead short to ground which the radio would see as a red-light fault.
  8. craig_sez

    craig_sez Road Train Member

    Sep 5, 2013
    Youtube covers most if not all questions in this thread
    rabbiporkchop Thanks this.
  9. Sgonza101

    Sgonza101 Light Load Member

    Mar 10, 2018
    How do I tune my 23 channel cb radio?
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