I'm quite comfy with any VSWR that's below 3.
ASTATIC PDC1 SWR METER INSTRUCTIONS FULL
Shorting out a feeder running full legal limit on a peaked and tuned high performance home brew design is going to kill it, because when you build stuff yourself, you don't build in idiot features to these designs, but it is VERY rare for commercial products to suffer bad effects.Ĭlick to expand.1:3.5 is a BAD VSWR? Ratio wise it's small in terms of actual power being reflected. In fact, if a transmitter had objected, I'd take this as bad design - and no manufacturer wants piles of stock arriving back under guarantee for repair because their products couldn't manage high VSWRs. The mismatches just mean nobody answers and eventually truth dawns. In all the years I've had transmitters I have never blown anything up - no Vesuvius moments. 5W portables can cope with the same ratio amounts coming back as normal everyday operation. Squirting 100 Watts down the cable and getting 10W back is quite a bit for the output stage to live with - and most high powered devices monitor VSWR and automatically throttle back to prevent damage. They don't then spend ages getting a radio fixed, they just have terrible performance.
ASTATIC PDC1 SWR METER INSTRUCTIONS PORTABLE
The fact is that portable radios NEVER have anything like a 1:1 VSWR, because the antennas are always rubbish matches, and mobiles frequently get their antennas banged flat by trees or car park barriers and often you see taxis drive past with their vertical antenna virtually flat. We get people panicking that they accidentally left off the antenna from their portable and press the PTT, we get people worried they accidentally connected the VHF antenna to their UHF radio and stuff like that. VSWR is about efficiency in the main - reflected power is wasted power, and it doesn't mean that the first time something comes back as reflected power things are terminal. All this doom and gloom about VSWR, damaging radios and warnings. We need to inject a little common sense here. As far as I'm concerned I want it as low as I can get, but once it's in the 1's, I stop worrying - it's such a small difference I cannot hear it on receive, and the transmitter doesn't care! My vehicle for work has a marine band antenna on it, and if I use this antenna on 2m, the VSWR is about 1.9:1. People get really obsessed with getting a 1:1 reading but 1.2:1 is as good as my system gets, and that's a tiny amount of reflected power, and it doesn't bother me. You often see it change when you change frequencies, as the perfect area can be quite narrow. Realistically - a 1:1 perfect reading is a kind of gold standard, and it's normal to have less than this. Some meters have a single meter, and on forward you adjust a knob to read 'max', then flip the switch and read off the reverse reading showing the VSWR (V for voltage) as a ratio - 1:1 (perfect), 2:1 (just about liveable with) and 3:1 or worse (indicating lots of wasted power which means something seriously adrift with your system. VSWR is the ratio of going out, vs coming back. So you set it to forward and take a reading, then switch it to reverse and take another. So most meters have a switch which reverses the diode. Swapping these connections around every time you want to take a reading is a pain. If you disconnect the meter and reverse the connections, then the diode is now facing the other direction and it reads the power going back towards the transmitter. So if you stick the meter on the output from the diode it reads forward going power. The meter uses a diode which allows current flow only in one direction. If the antenna is not resonant, then if you squirt 10W out of your radio, then not all goes out - some is reflected back where it's wasted, and could of course damage the radio, which doesn't appreciate power coming back up the cable. The point of a VSWR meter is to find out how much of your transmitter power gets out into the ether. VHF and UHF VSWR meters have much more precise internal construction as frequencies are much higher. The technical reason is to do with the diodes they use inside that have a frequency limit. CB VSWR meters probably won't work at UHF.