What is a SWR Meter ??
The SWR meter measures the standing wave ratio in a transmission line.
This is an item of radio equipment used to check the quality of the match between the antenna and the transmission line.

How to use it.
" Web Williams from 11meteramps@yahoogroups.com write's this ::


1. This meter is inserted between your radio and antenna, or, if you're using an amp, between your amp and antenna.

2. Most SWR meters have a SET or CALIBRATE function. You cannot accurately set SWR in SSB mode, you have to send a continuous carrier to accurately check SWR with an SWR meter. So first, set your meter to the SET or CALIBRATE function.

3. Put the meter into CALIBRATE, and key your radio on a channel near channel 20 (this is assuming everything is hooked up and ready to operate). For most SWR meters, you want to line the needle up on the hash mark at the far right side of the scale. Once calibrated, unkey the radio.

3a. If you use mostly the high channels or mostly the low channels, you might want to set your SWR on the channels you use "mostly" or find a higher or lower channel to use for SWR setting purposes. SWR can also affect receive to some minor degree as well as transmit, so choose based on this.

4. Move the switch on the SWR meter to SWR, and key the radio. At this point, the less the needle moves, the better.

5. In an ideal world, you'd want the needle to just sit still and not move, but there are many variables. In some cases, it would be normal for the needle to move up scale to about 1.5. A 102" mobile whip, when installed to the best of anyone's ability, presents a roughly 36 ohm load to your radio, not the "perfect" 50 ohm load, and this roughly calculates out to about a 1.5:1 SWR. If you're not seeing a 1.5:1 SWR on a 102" whip (in other words, your SWR is lower than 1.5:1), you're seeing ground loss effects. (A bad thing, but certainly nothing to worry over. You probably have your antenna mounted low on the body of your car). If you're seeing much higher than a 1.5:1 SWR, either trimming or lengthening of your antenna is dictated.

6. If it's a base antenna, follow the manufacturer' s recommendation on how to tune the antenna. Some have rings that move up and down, some have slide bars, etc. etc., and there's no way for me to explain all the various types of matching networks here.

7. SWR will go up based on predictable curves when your antennna is too long OR too short. If an antenna doesn't give you ANY means to tune it, then the tuning method is probably cutting the antenna tip off, and the manufacturer has most likely allowed some extra length for this purpose.

8. If you want to read the "scientific" version, here it is: http://en.wikipedia .org/wiki/ Standing_ wave_ratio

and here are some other websites to help explain:
http://www.wenzel. com/documents/ swr.html

http://www.firestik .com/Tech_ Docs/Setting_ SWR.htm

9. Basically, setting an antenna for best SWR means tuning the antenna so that it presents a 50 ohm impedance AT RESONANCE to your 50 ohm radio. Keep in mind that it is possible to have antennas that are at resonance but NOT 50 ohms (you need a balun or unun to make it work with your 50 ohm radio). I'm unaware of any radio that is designed for other than a 50 ohm antenna system, but I'm sure there is one out there somewhere. One exception is tube radios which have the ability to match a wide range of impedances because they normally have an internal pi-network (usually) which allows you to tune the radio to the antenna to some extent on their output.

10. If you get your radio working well enough to talk on, usually you can find someone on the air who is willing to help you check your SWR who knows a little bit about what they're doing. You'll also find jokesters who will tell you to do stupid stuff and think they're funny. Be careful that you can tell the difference! When I first got into electronics (CB) back in 1973 at age 15, they had me put my antenna mast in a bucket of water and buy a half-dozen different antennas thinking everything I was buying was defective! There are jackasses in every bunch. I hope you never have to meet them.

11. 11. Lastly, if your antenna checks satisfactorily, and you're running an amp, sometimes there may be a problem with the input impedance of the amp that will cause problems with your radio, but make you think it's the antenna. Take the amp off-line until you get your antenna tuned, then hook it back up. The SWR of the antenna should not change just because you installed an amp (unless the antenna has a load coil that is going into meltdown because your amp is more than the antenna can take!).

Good luck, -Web