I just thought of something new to me. The Galaxy DX-959 has an auto swr checker. Is there such a thing as a high swr protection circuit that would prevent transmitting when a preset swr reading is detected?
Really? I assumed that nested dipoles work on the same principle. The rf goes the path of lowest swr. And don't say that the impedance of the dummy load and the antenna are too close because I have heard of hams using nested dipoles all cut for the same band to make their station more broadbanded. And the non resonant dipoles don't damage the transmitter either. Can you explain why it won't work?
Something like 30 years ago there was an antenna matching device, solid-state (potted so you couldn't open it), that was guaranteed to provide a good SWR match to almost any antenna you could connect to it. It'd work on almost any frequency, didn't much matter what band the antenna was tuned for. It 'worked', not well, but it 'worked'. Wish I could remember the name of that thing! The manufacturer wouldn't say how it was made, trade secret you know. So, someone X-rayed the thing. Turns out it was a 50 ohm resistor across the feed point terminals. Ooo, the outrage over that was really, really big and it dropped off the market amazingly fast.
Think about it.
That thingy had the characteristics of an SWR protection circuit, it would always indicate a nice SWR. It was a 50 ohm resistor in parallel with an antenna. Use an old 'Cantenna' as that 50 ohm resistor and you'd have a no-tune 50 ohm antenna that'd work almost anywhere. Your trnasmitter wouldn't ever 'cut-back', always provide full power out. It'd have a REAL 1000 watt continuous duty power rating!
- 'Doc
Does the 959 have a l.e.d that lights when the swr is high? You could use that to drive a transistor that opens a relay in the tx line from the microphone.
Yes it does. That's exactly what I was thinking. The swr warning led circuit is adjustable so that it could be set up to turn on and a predetermined level.