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Talk about CP Antenna construction

bbmagic

Junior Member
#1
I'm just getting into FPV for my tricopter and I thought that I would start with the difficult stuff first, constructing my Tx and Rx CP antennas. David's site rcexplorer.se is the best instructions that I could come up with so I followed his guide using 1280 Mhz as the frequency I wanted. I started with the Tx antenna (clover leaf) because I thought with one less lobe than the skew planar (the Rx antenna) it would be easier to construct. I didn't know of a local source for the RG316 coax called for, so I purchased a SMA male jumper that was 18" long from IBCrazy's web site videoaerialsystems.com. This will give me the SMA ends and coax needed for both of my antennas already assembled. I wanted to also mention that there was no shipping charges on my order from IBCrazy!
RG316 Coax M to M.jpg
I located the .030" copper coated MIG welding wire at Home Depot. That is about all the essentials needed to construct these antennas.
I cut the 3 wires as described in the guide and sanded the ends square and to length with a dremel and drum sanding attachment. Straightening these wires is just a matter of patience and a good pair of pliers so that the wire doesn't want to twist while your coaxing it straight. Following David's guide I bent the wires into a U shape using the measurements that his calculator spits out for you. The next step is forming the arcs. I just had to stumble through this because I never did find a reliable way that would make a smooth arc and make the ends meet. It isn't hard but it is a bit slow going and a little frustrating. The next step is getting the coax prepared. I cut the lead I had purchased about 3 inches from one end hoping if I screwed up I had enough that I could start over with the length I would have left after cutting the mess off. I stripped the outer plastic off about a half inch and started straightening the woven shielding.
Teasing shielding wire.jpg
and then I twisted the strands into 3 equally spaced wires. I also stripped back the center insulator as close as I dared to the shield (not as close as David's). I didn't want to tempt fate and have something touch that isn't supposed to! I was surprised to find the center conductor is stranded!
coax shield twisted.jpg
I thought I was really going great when the first mess appeared. I had the 3 lobes on my jig and one of the lobes fell out of the already wrapped shielding wire. I couldn't get it inserted through the spiral of wire that used to surround it and it made a mess. It is really a cosmetic thing but I hate it when that happens! It was here that bmsweb mentioned that these antennas are a bit fiddly in construction so I thought I needed to firm up everything before I attempted to solder the signal wire to the lobes. I made 3 foam wedges that I hot glued to the template and also to the lobes to firm everything up.
wedges affixed.jpg
This pic shows the mess on one lobe and it is ready to solder the signal wire.
ready to solder center.jpg
This shows it soldered. I came back and added a bit more solder but didn't take another pic.
center soldered.jpg
This shows the completed antenna with hot melt glue reinforcing the connections.
completed.jpg
I thought I'd also show the jig as it ended up.
jig.jpg

If you have ANY thoughts on a nice way to form the loops or any other bits of wisdom I'm all ears!! Remember I still have another one to tackle that might even be a bit harder!
 

ananas1301

Crazy flyer/crasher :D
#3
I'd really like to know how it affects your video quality. I think I'll have to wait for that!
I think I can answer this:
What he want to get with those antennas is some more range.

The rubber ducky once are simply linear, so when the plane goes into a bank, you´ll loose signal.
But this has a effect of a circularly polarized antenna so it gives you A more range and B also better video quality, throughout the flight.

Correct if I am wrong thought