The AM Forum

As I am wrapping up a home carpentry project I am left with a quantity of scrap pieces of white cellular PVC trim board material.  Was wondering if this stuff might be useable for use as stand off insulators for mounting things like large pi-network coils and spacer bars for winding such coils, mounting large power resistors, etc.  The stuff I most recently have been working with is the Veranda product line sold by Home Depot.  I also have some leftover Azek trim.

Better not use it, PVC has very large RF losses and melt when high RF voltages are present. Use the plastic cutting boards used in the kitchen. That is normally PP or HD PE and has no losses at RF

Take a sample for a ride in the microwave oven......It will tell you a lot about how it reacts to RF.....

I was going to say the same thing.  Sample material in the nuke.

If it gets any kind of noticeably warm, toss it.

Learned that trick testing big forms for LOWfer ops in high school.

--Shane
KD6VXI

Will try the microwave oven test...IIRC I should also put a mug if water in there so as not to let it run “unloaded” in case the test item does not absorb any RF.

With a mug of water, the RF voltage may be quite low and the foam seems ok. I rather test putting a sheet between two plates and put a few kV over it at e.g 10 meters.  But whatever, PVC is very lossy. For that reason we solder it using RF.  Almost all bags for liquids in hospitals and plastic folders for papers etc. are PVC and soldered with RF at 27 MHz. If it shows ok, it defenitely is NOT pvc or your test isn't good.

Maybe a shot glass of water.

But, I never used any.  Just throw the nuke in for 10 to 15 seconds, feel the pvc with your hand as soon as it chimes its done.

Warm, toss it. Not warm, try it for a longer period.  Still not warm after 30 seconds, you should be fine.

--Shane
KD6VXI

"are PVC and soldered with RF at 27 MHz."
I hope it's not done inside a Faraday cage and there are CB antennas all up and down the block.  ;D I'd test any plastic in a microwave oven accompanied by a 6oz GLASS of water for 30-40 seconds. Don't worry about that much water absorbing too much RF, that maggie spitting a kilowatt into a resonant cavity is plenty of juice... make mine fresh squeezed OJ (not Simpson).

Modern European systems are well shielded. Many others are not. And we use powers up to 50 kW at 27.12 MHz. Nice CB xmtr.....
A 1/4 wave wire connected to the press will lit all fluorescent tubes around the system.