Planar Disk Antenna

Having seen some curious pictures of pizza pan antennas and a nice write up by Kent Britain, I decided to build one myself.  These antennas claim to be wideband (similar to a discone) but they are a lot easier to build!

I found some 23cm diameter cake tins for $5 a piece, which limits the low end of the antenna to around 200MHz but it is perfect for UHF all the way up to WiFi.

Soldering to carbon steel is a little tricky – you can’t just use hobby electronics solder because it won’t wet the metal.  Carbon steel requires an acid flux, so I used silver solder and some brush-on acid flux from the hardware store.  Electronics solder will mix with the silver solder so attaching the coax using a soldering iron was easy.

The main difference between the one I made and Kent’s is that I saw a recommendation to solder the coax shield to the antenna in a few spots.  This helps decouple the shield from being an antenna in its own right, and the return loss plot of my antenna is a little more consistent.  This extra step would have a minor impact on cleaning up the antenna pattern but probably not something you’d notice.  On the plus side it is great mechanical support for the coax.

Paired with an official rtl-sdr.com dongle I am all set for wideband listening!

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