On Thursday (06/13/2024 at 10:46AM -0500), Jon Elson via cctalk wrote: > On 6/12/24 22:32, Gavin Scott via cctalk wrote: > > Is it possible they were thinking about really old FAX paper which > > might have been wet to support marking via an electric discharge > > through it (and to (slightly) reduce the frequency with which the > > receiving machine caught fire)? > > Yes, there was teledeltos paper, that had a silver top layer and a carbon > layer below that. > > A high voltage spark burned away the silver layer and left a black image.
The OP mentioned that the story may have originated at Varian, where they historically did a lot of work on high power _microwave_ stuff. I could imagine that a roll of paper might make an OK attentuator at the end of a piece of waveguide, into which you can dump a bunch of power. But it probably isn't going to be a very good impedance match. I don't see it working well at all at HF, VHF or UHF frequencies if the RF source (transmitter) is expecting any sort of normal impedance like a 50 ohm termination-- because how are you connecting the feedline to this roll of paper? What is the mechanical and electrical interface between the unbalanced (or balanced) feeder and the roll of paper? Maybe they put an actual dummy load resistor inside the roll of paper and were using it as a heatsink-- you know, before it lit on fire ;-) Seems like some important details of this story are missing... Chris N0JCF -- Chris Elmquist
