The Radio Shop                                       Sales & Service

 

   cb radio 10 meter radio repair

          


 Setting or Measuring the SWR and How to Tune your CB Radio Antenna




On How to Use an External SWR Meter - Click Here





* For Radio's That Have a Built In SWR Meter *



 

             Understanding the S/RF, SWR, CAL switches on your CB Radio:


1.  S/  switch position is the Signal strength that you are Receiving.

 

       ( 1 to +30dB )


2.  /RF  switch position is the Frequency strength Transmitting out of your Antenna.


3.  SWR  switch position shows what the SWR is reading on your Current Channel of your CB Radio. Note : you must first use CAL per channel to get accurate SWR readings.


4.   CAL  switch position lets you Calibrate your CB Radio for an SWR measurement.

 

Exe: Channel-1, move switch to CAL position, key the Mic and adjust the SWR CAL knob on your Radio so the needle on the SWR Meter lines up with the red arrow in the top right corner of the SWR meter. Un-key Mic, move switch to SWR and key up Mic again for an accurate SWR reading.

 



Before we go any further, Below is some Important Info, and some Rules to use when adjusting a fiberglass Antenna, or cutting an Antenna steel whip.

 

Tuning the Antenna SWR for Wilson whip type , or adjustable Fiberglass

 

( Fiberglass Antennas you only adjust, Do Not Cut )

( Not All Fiberglass Antenna’s are Adjustable )

 

Please Note:

When you set up an Antenna to get good SWR on your vehicle, you are matching the Antenna to your Vehicle body (Cab). Once you get good SWR, you can change and use any Radio that you want, and the SWR from that Vehicle will not change.

 

RULES:

1.  If channel – 1  SWR  is higher than channel – 40  SWR,

     Raise the whip, or Raise the adjustment screw (Fiberglass antenna)

2.  If channel – 40  SWR  is higher than channel – 1  SWR,

     Lower the whip, or Lower the adjustment screw (Fiberglass antenna)

 

Important :  The main Idea when setting up your SWR is to have channels 1 & 40 the same and both typically have an SWR  under 1.5.  Channel 20 is in the center of the CB-radio range, so it will always have a lower SWR than channels 1 & 40.

 


 

Adjusting Your Antenna to set the SWR

 

1.   Wilson 1000 magnetic type, or T2000 Ball type etc, insert the antenna whip into the chrome antenna mast (has set screws) at the top of the coil and bottom out. (steel-whip Only)

 

2.   Adjustable Fiberglass antenna; temporarily take off the rubber cap at top of antenna, loosen the lock nut, and set the up and down adjustment screw in the center, then slightly tighten lock nut, and put rubber cap back on.

 

3.  Using the meter built into the radio, do a (CAL) on channel -1. Then switch back to (SWR) and record the reading on Chan-1. Do the same on channel- 40 and record the reading. You must compare Both Chan-1 and Chan-40 readings.

 

4.   If chan-40 SWR is higher than channel-1 SWR, the antenna whip must be shortened. Using a Fiberglass-antenna, the screw must be lowered. If the whip is already bottomed out in the mast, (per step # 1) (go to step # 5) (If chan-1 SWR is higher than channel-40 SWR, (go to step # 6)

 

5.   If the whip is fully lowered into mast and the SWR is still high, loosen mast set-screws, and remove the whip from mast. Using a hacksaw, grinder, or bolt cutters, cut 1/4" from the bottom part of the whip. Re-insert the whip into the mast, tighten the set screws, (steel-whip only).  For a Fiberglass antenna, remove rubber cap, loosen lock nut, and lower the adjustment screw 1-1/2-turns at a time. Tighten lock nut and replace rubber cap. For Both types of antenna's,  Repeat steps 3 & 5 until the SWR is typically below 1.5 on channels 1 & 40.

 

6.   If chan-1 SWR is higher than channel-40 SWR, the antenna whip is to short and must be raised. Loosen the mast set screws and raise the whip 1/4", re-tighten set screws, (steel-whip only).  For a Fiberglass antenna, remove rubber cap, loosen lock nut, and raise the adjustment screw 1-1/2-turns at a time. Tighten lock nut and replace rubber cap. For Both types of antenna's,  Repeat steps 3 & 6 until the SWR is typically below 1.5 on channels 1 & 40.

 

7. When you are done, make sure all set-screws on a whip antenna are tight, and on the fiberglass antenna, make sure the locking nut is tight, and also don't forget to put the rubber cap back on the top of the fiberglass antenna.

 

8.   If your SWR is 2.5 or higher, then you may have a bad antenna, antenna mount, antenna coax, or lack of ground-plane caused by many reasons


9. If you have any Questions, Please Click Here To Contact me.

 

 

 




                                    The Radio Shop


                                                         Copyright ©  TheRadioShop.net    All rights reserved