CB Radio Guide
SWR is something that even very experienced CB'ers have trouble understanding, however this doesn't mean that you can ignore it and carry on regardless. SWR is very important to every CB set-up and should be checked every time a new antenna is purchased or an antenna is moved. Click here to view our SWR Meter range.
What is SWR?
SWR stands for 'Standing Wave Ratio' and basically speaking it is "the ratio of power that is reflected back down the antenna lead from the antenna."
In conclusion, the higher the ratio (SWR reading), the less power being radiated by the antenna, and the more power coming back down the antenna lead.
Why is SWR Important?
SWR is very important because if you have a high SWR reading then your antenna will not be performing as well as it was designed to, and will not be transmitting all the power you have put into it, therefore you will not achieve the best transmit range.
How can I check my SWR?
To check the SWR reading you must use an SWR meter. We sell a range of SWR meters and they are relatively inexpensive (£13.99 for a basic one), click here to view our range. (note: to connect the meter you will also need a patch lead).
1) Connect the SWR meter between the antenna and the radio, as per the diagram above.
What does the reading mean?
Check the table below to find how well your antenna is tuned in.
Which is the best channel to check the SWR on?
Your SWR is over 2 on channel 40…
Most mobile antennas have a grub screw, which you can unscrew slightly to alter the length of the antenna whip. Simply undo this screw and adjust the length, one small bit at a time then re-check your SWR. Remember, don’t adjust it too much, a small adjustment of only 5mm can make a big difference.
If it doesn’t have a grub screw, then it may be a top loaded antenna with a screw on the top that you can adjust to bring the SWR down. Some antennas have rings around the bottom to adjust the SWR, again though, a small adjustment can make a big difference so don’t get carried away.
If it is a homebase antenna, then there is probably a way of altering the length somehow, maybe with jubilee clips. If you are unsure on how to adjust your antenna please refer to the instructions that came with the antenna.
There was a time when every new CB antenna had to be fine tuned when it was put on a vehicle, luckily there now are antennas that are Pre-tuned. Most of the THUNDERPOLE antennas are now pre-tuned making the hours of fine-tuning a thing of the past (thankfully!).
Please Note:"When you purchase a new antenna or move your existing one you should always check the SWR reading(even if the antenna is pre-swr'ed) to make sure you have no other problems with your mount/groundplane etc. and that your antenna is tuned for optimal performance".