Quote:
Originally Posted by G0HZU_JMR
This can expose the bias tee to a very high RF voltage and if this happens at a resonant frequency then the bias tee inductor can get very hot very quickly. I usually use a thermal camera and a special load I designed to let me explore various VSWR circles at the load whilst looking for hotspots in any bias tee components. Sometimes it's capacitors that can get hot if they have a resonance with a certain load at a certain frequency.
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This is very interesting work indeed, Jeremy. Thanks for sharing the specialised techniques that you use at these sorts of exacting frequencies.
For my part, I'm glad to have an insight into a way of looking at resonances that hadn't occurred to me, and that is within my capacities to replicate to some degree here (likely spectrally, if I hunt around for suitable tubes.) Of course, I am operating at rather low frequencies with a lot of headroom.
It did occur to me that at the frequencies you are describing, even
an open circuit track on a circuit board is now an unwanted resonator at some frequencies. Of course I already knew about parastic inductance on metal strips connected to something, but had no insight into the condition under which even a completely open circuit conductor could be a problem.