434MHz Patch Antenna

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OverTheTop
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434MHz Patch Antenna

Postby OverTheTop » Fri Jan 02, 2015 8:40 pm

PATCH ANTENNAS
I needed an antenna for my new TeleMega. I thought I'd make up a patch antenna. That would give me a patch and a yagi to use for tracking at 434MHz.

There is a great article on creating patch antennas. Search for "goof proof patch antenna" and you go for:
http://www.rc-cam.com/gp_patch.htm
As it stands it is sized for 2400MHz. It is easily scaled to whatever frequency you want. Note that I did deviate somewhat from the original plans.

Once dimensions were worked out, some 1.25mm steel sheet was cut to size on a guillotine. Holes were drilled for the connector (SMA), tripod mount bracket and some spacers. It is 594.6mm square for the required frequency.

Spacers were turned out of Ertalyte which I had lying around. They were tapped to take M4 screws.

Spacers were glued (epoxy) and screwed to the large backplane. SMA connector was fitted.

Spacers and connector were masked and the backplane spray painted.
Spacers.JPG


Central wire was made and the top patch glued and screwed in place. Don't forget to kink the middle wire a little to allow for when the antenna flexes. We don't want to pull the wire from the antenna!

Wire is soldered in place using a propane torch. Remember that solder has no mechanical strength, so bend the wire over the plate before soldering.
Patch.JPG


Mask and paint top element.

Into the EMC chamber for testing. Frequency turned out to be 435.5MHZ instead of 434MHz as targed. It is only down by around 1dB so I will live with that.
EMCChamber.JPG


Now I just need to add some finesse items to it before it is complete for Thunda:
Mounting hole for hanging
Carrying handle
Protection for SMA connector
Deburr all edges (forgot the front element)
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Re: 434MHz Patch Antenna

Postby cryoscum » Fri Jan 02, 2015 10:02 pm

Gain & directional beam width?
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Re: 434MHz Patch Antenna

Postby OverTheTop » Sat Jan 03, 2015 8:11 am

Can't remember beam width but gain looked to be within about 2dB of the Yagi I have built on another thread. I will look into patch antenna theory when I have time, after Thunda.

I didn't have time for extensive testing in the chamber. I had too much other work to get done. I was happy just to get functional verification as it was the first patch antenna I have built.
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Re: 434MHz Patch Antenna

Postby OverTheTop » Sat Jan 03, 2015 3:05 pm

FYI, Courtesy of Wikipedia:
PatchWikiresize.png
PatchWikiresize.png (238.63 KiB) Viewed 2732 times
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Re: 434MHz Patch Antenna

Postby OverTheTop » Sat Mar 21, 2015 7:26 pm

This antenna happily tracked my Orange Revolution to 21512' and 4.5km downrange, so I guess it works!

If I get time I might even mechanise the antenna with an altazimuth mount and get it tracking directly from the TeleMega data. I think that would be cool 8)
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"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)


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