When using a radio, it is very useful to know exactly what your transmitting power output is, and how much of the power is being reflected back to your radio. SWR (Standing Wave Ratio) is an expression of the measurement of how much of a radio transmitters’ power is being transferred to the antenna (and thus radiated out as a signal) compared to how much is being returned to the radio. This number is expressed in ratios like 1:1 (pronounced 1 to 1) which is a perfect match. In a 1:1 SWR, all of the power is being transferred to the antenna, and none is being reflected back. A 2:1 SWR means 11.1% of your signal is being returned to the radio. A 3:1 SWR means 25% of your power is being returned, which is very bad. The formula to find out how much power you are losing at a certain SWR ratio isn’t a simple one (Power in Watts x ((SWR-1) x (SWR-1)) / ((SWR+1) x (SWR+1)) = Loss of Power in Watts), but there are charts that can show you the percentages for each ratio online. Basically, the higher the first number, the more of your signal that is being returned to the radio and being dissipated as heat. Anything above a 2:1 is considered bad, and above a 3:1 can burn up the finals (power outputs) on a radio.
The best way to know this information, is to use an SWR/Watt meter inline with your radio to be able to constantly monitor your power and SWR. Even if that antenna is a perfect 1:1 when you install it, things can go wrong at any time and make that number change. A squirrel could chew your wire, the antenna could fall or get damaged, water can get in the coax, and so forth. By having an SWR / Watt meter, you can keep an eye on things and know instantly if something is wrong (or starting to go wrong).
A single-needle meter will only show Power or SWR, but not both at the same time. All of the meters I list below are either dual-needle, or digital, and will show you both readings at the same time.
Let’s take a look below as some of my favorite meters.
DAIWA CN-501V 140-525 MHz Cross-Needle SWR/Power Meter
Frequency Range: 140-525 MHz
Power Range (Forward): 20/200 w
Power Rating: 200 W (140-525 MHz)
Dimensions: 5″ wide by 3″ high by 4″ deep
I was lucky enough to get a great deal on the higher powered version (which goes up to 1,500 watts) of this meter a while back, and use it on my Yaesu FTM-200DR base station. 1,500 watts is gross overkill for most VHF/UHF rigs, so I really recommend the 200w version listed above, unless you just really need the extra power handling. It works great, is very accurate, and has an easily read adjustable cross-needle display. I like the size, and it has some nice removable rubber end caps that make it anti-slip when used. It has a backlit display, and I have never had any issues with it. I did a lot of research before I chose this meter, and I always came back to this one as the best buy for my needs.
Daiwa CN-901HP Professional Series Bench Meter
Frequency: 1.8-200 MHz
Power Range (Forward): 20/200/2kW
Dimensions: 6.25″ wide by x 4.3” high by x 4.8” deep
This is the HF/VHF version of the meter above. It is a little larger, so the display is a little easier to read. It handles up to 2 kW of power. Just like the CN-501, it works great, is accurate, and has an easily read adjustable cross-needle display. It has the same nice rubber end caps that make it anti-slip when used, and it has a backlit display.
PICTURE PLACEHOLDER
Intellitron WM-1020A HF/VHF 3in Cross-Needle Mobile SWR/Wattmeter
Frequency: 1.8-200 MHz
Power Range (Forward): 30/300W
Dimensions: 3.25″ wide x 3.25″ high x 3.25″ deep
Display Size: 3″ Lighten Cross-needle meter
This meter is great for home or portable use. This meter is great for a “go box” due to its smaller footprint and easily read backlit cross-needle meter. With the low price point, you can dedicate one to HF, and one to VHF for only slightly more than you would pay for a single meter of the other models that require you to switch between HF and VHF. This meter fits just about anywhere, and is lightweight, which keeps the overall weight of your gear down for portable use. This meter does not cover UHF, so if you need that, you need to look at another meter.
NISSEI DG-503 200W Digital SWR and Power Meter
Frequency: 1.6-60MHz & 125-525MHz
Power Range (Forward): 200W
Dimensions: 5.51″ wide x 3.30″ high x 4.80″ deep
The DG-503 model is FM ONLY. If you need one that handles AM, SSB, or DMR (TDMA), you need the DG-503MAX model.
This SWR/Power meter is planned for one of my next amateur radio purchases once I have enough saved. I love the digital readout and accuracy. No more having to read two cross-needles, or switching switches to change power ranges. This ha a nice large 3.5″ lighted display. These meters are extremely popular throughout the Amateur Radio community, and have great reviews all-around. You can calibrate this meter using screw style trimmer potentiometers inside the unit. It’s not that hard if you know the actual ohms of your dummy load, and do a simple SWR calculation. I still like the idea of having some analog meters, but I want at least one digital, and this is the one I chose. I have seen a few reports on the longevity of this meter, specifically that the HF side goes out. I believe this is being caused by people who do not understand that this is an FM only model.
There are a lot of different options on the market for SWR and Power meters. You will need to do your research before you buy one. Ask your fellow Hams and get some opinions on what they like or don’t, decide what features you need or just want, and what your budget will allow. Hamfests are a great place to find gear, and usually at a good discount. This not only helps you save money, but puts some back directly into another Hams pockets so they can buy more gear.
Have fun, and 73!
N4MCP