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RE: "Dyson" Spiral antennas - AO40



Greg asked

> Has anyone tried these RHCP antennas for AO-40 or S-band receiving ?
>
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1374379117

I've used some very similar antennas at GPS (1.57 GHz). If you look at the
picture, you will see that the spiral appears to be LEFT-handed, but these
are back-fire antennas, fed backwards from the tip to produce RHCP. The
spiral is actually a log periodic structure and there are a pair of spirals
running down the cone.

These are simple broadband test antennas. They are quite lossy and have a
pattern that is equally poor in all directions. They work fine as a dummy
load, or as a wideband interference sniffer, but I can't think of a
practical way to make them into a low-noise, high-gain device.

The Ebay price looks like $6o. The last ones I got a few years back were
like $10-$20 each at some flea market.

73 de Tom, W3IWI

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