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More: Circular patch behaves linear


For whatever it is worth, I made the following mods to
my K3TZ-style patch to improve the mechanical

First, I drilled a 1/8" hole in the center of the
patch and put a metal 4-40 screw through it to
short the center to ground. This should have no effect
on the return loss or circularity but I wanted the
patch at DC ground and the screw helps the mechanical

Next, I drilled 4 holes in the patch, one in each corner.
Each hole was 3 cm from the center of the patch. I drilled
1/8 inch holes and used a nylon 4-40 screw to hold the
patch in place.

I initially used a nylon 4-40 nut and washer to space the
patch at 3 mm. The return loss measured a mere 6 dB this way
and the circularity was worse than 10dB in a quick bench test.

I noticed that the return loss improved if I put pressure
on the patch surface, so I lowered the patch to 2 mm by
using only a nylon 4-40 nut with no washer in each corner.

When re-assembled this way, the patch return loss dramatically
improved to about 16.5 dB and the circularity to within 2-3
db (I didn't measure it more accurately than that.)

This arrangement seems much more stable mechanically and the
patch return loss also seems very stable this way.

It would be interesting to hear if anyone else tries this
and if so, how well it works.

Tony AA2TX


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