The AM Forum

Building a directional microphone and looking for a parabolic reflector, 12-18”. Need not be metal or glass, in fact I’d prefer plastic or PVC. Edmund Scientific has one, but they are ridiculously expensive. I’m thinking that a CCTV dome would probably work.

Snow sled:
https://www.google.com/search?client=firefox-b-1-e&sca_esv=0aa168a204f4e042&q=circular+sled&tbm=isch&source=lnms&sa=X&ved=2ahUKEwihsPfckpOEAxXCF1kFHTaPBw4Q0pQJegQICxAB&biw=1174&bih=723&dpr=1.36

OR
Large serving platter or bowl.

Ya just have to figure out the focal point for best performance.

Back in the "good old days" we used round aluminum sleds as part of a parabolic dish antenna.

There is a reason that cake pans and large bowls resemble satellite antennas.

Any guidance on how to figure out the focal point.

Any thoughts about using a plastic umbrella? The mic could be mounted on the handle shaft.

Google is always your friend - mouse over:

calculating focal point for parabolic dish (https://www.google.com/search?client=firefox-b-1-e&q=calculating+focal+point+for+parabolic+dish)

The "party goods" stores that sell all sorts of inexpensive decor, plastic champagne drinkware etc also sell some good sized cheap plastic punch bowls.  \They are cheap enough to experiment with for ham projects.  I used one to build an ultrasonic receiver setup with an SDR-IQ to track down arcing power line hardware.  It worked, kinda, but I think I needed a pit more amplification in front of the SDR.
In the Portland Maine area the store is "Paper Party House".  I think it may be a chain but certainly there are similar places in your locality.
73 de Norm W1ITT

Thanks to all, I’m going shopping!