Testing for a Defective SWR Meter
A defective SWR meter is rarely the cause of high SWR readings, but when it is, it can wreak havoc on your troubleshooting efforts. The easiest way to test for a defective meter is to take readings from a second meter and compare the results to those from the first meter. If it's convenient to borrow a meter from a friend, or you have a second one on hand, great. However, for those of you without access to a trove of back-up meters, please refer to our notes below:
If using an external SWR meter
A defective external SWR meter will often do one of two things. It will either:
- Be dead as a doorbell. No movement. Ever. This is definitely a defective meter.
- Always peg to the far right when the mic is keyed, with adjustment of the CAL dial failing to move it leftward.
In either case, you likely have a faulty meter that needs to be replaced. In some instances, the SWR meter CAL/REF switch may be wired backward, which we've seen on rare occasions. To test for this, you'll want to measure SWR in the following manner, which simply reverses the standard REF and FWD switch positions:
- With the meter correctly hooked up to radio and antenna, set the switch to the "REF" postition
- Turn the SWR calibration knob fully counter-clockwise
- Key the microphone and, while continuing to depress the talk button, adjust the calibration knob so that the needle touches the "SET" mark on the meter
- When the needle reaches the "SET" mark, flip the switch to "FWD"
If this procedure produces what looks like a reasonable SWR reading, it is a good indication that the SWR meter was wired backward. This faulty wiring won't affect the accuracy of the SWR reading, and a good reading achieved with this method can be trusted. Despite the accuracy, you may still want to replace the meter, as the reversed switch may cause confusion down the road.
If using an internal SWR meter
Unfortunately, SWR meters built in to radios have a reputation for being somewaht finicky. While they more often than not are good enough to perform a basic antenna tune, they tend to be much more unreliable than even the most basic external meter. If you have gone through all the previous troubleshooting steps, found no problems, and your built-in SWR meter is STILL alerting you to SWR above 3.0, you should try to get your hands on an external meter to double-check the readings. Frequently in these circumstances, it's the on-board meter that is to blame.The same rule applies for an on-board antenna warning light that refuses to turn off despite what you believe to be a correct installation. Test the SWR with an external meter. If the SWR is within an acceptable range, you likely have a malfunctioning on-board meter and warning light.