Resources list for DIY 1090 Mhz antennas and filters

Stacking with Coax Cables as Transformation Lines (DK7ZB)
http://www.qsl.net/d/dk7zb/Stacking/coax.htm
"The stacking cables are made of odd multiples of λ/4-coax-cables (3/4-, 5/4- or 7/4-λ).
They use the transformation attribute of an electrical quarterwave-line. This can be a coax-cable or power splitter.
"



I've been testing small antennas and found one that seems pretty good.
http://forum.planefinder.net/threads/very-small-collinear-antenna-300-mm.177/
A question came up about stacking these small antennas, one above the other, to increase gain by 3 dB.

I'm not sure what the vertical spacing between to of these little antennas would be,
but I think stacking with 75 ohm coax cable transformation lines would be the best way to stack two very-small-collinears.

I use 50 ohm coax cable on my Ham tower, so my Coax Stacking Harness would be a 'T' adapter fed with 50 ohms (from the radio room)
and the two 75 ohm matching sections would use low cost TV 'F' connectors on both ends.

I can build these antennas using a TV 'F' connector attached at the 50 ohm feed point. (see pic below).
Or solder the 75 ohm cable directly to the antenna. (Once the correct 75 ohm cable length is known).
upload_2014-7-17_14-36-36-jpeg.440


I can tune these antennas to a 50 ohm match using my SWR test set..
http://forum.planefinder.net/threads/adf4351-signal-generator.161/
breadboard_zps0d77ae93.jpg



This test rig can also be used to test/tweak the length of 75 ohm matching sections,
by terminating the antenna end (of both sections) with a standard 50 terminator.
When the 75 cables are cut correctly, the SWR will be at it's lowest.
 
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