Crosshair - 10 dbic Circularly polarized antenna tutorial!

**Jack2010** · 13th July 2012 06:01 AM

I am just wondering - in terms of pure performance only - is this antenna any better then the one mady by OMM: http://www.rcgroups.com/forums/showp...&postcount=406

**IBCrazy** · 13th July 2012 10:46 AM

@elang - Aluminum foil won't work. You can't bond the balun properly.

@Jack2010 - Yes it is certainly better the the open BiQuad. The open BiQuad is actually an older design. I forget who designed it initially.

-Alex

**Jack2010** · 13th July 2012 04:02 PM

I have already some home-made CL and SPW and did 2km on 1.2GHz 600mW AV with my MWC quadrocopter. I am about to bild a hexa and would like to go for 5km... probably I would need to change my AV RX antenna in order to do so, so sounds like I will follow your project...again

**adamchicago** · 13th July 2012 11:17 PM

For you radio frequency guru's, if I place a TSLR Tx (433mhz x 2W) directly above a VRx (1280mhz) on the ground station is the VRx reception safe due to the Tx's null being directly above and below?

I currently have the TSLR Tx on a separate tripod because my Aurora 9 radio has interference issues with the Tx being attached directly to the radio and you get better range being off-radio up on a tripod, but I'm getting sick of packing an additional tripod with cables etc when I can attach it to my current VRx tripod setup.

Thanks...kindly

**Guilherme** · 14th July 2012 05:54 PM

I was thinking about making a box filled with expanding foam to protect the antenna.

Would this affect its performance?

I would use expanding insulation foam.

**IBCrazy** · 14th July 2012 07:35 PM

Insulation foam is a VERY bad idea. it would seriously harm performance. This antenna is very fickle as it uses phase shift vectoring to obtain its characteristics. I would advise making a large enclosure over the entire antenna instead. The further away from the elements, the better.

-Alex

**airtruksrus** · 17th July 2012 06:28 AM

I found some old, thin plastic food containers sitting in my cupboard that haven't been used in a very long time, and fit perfectly over the elements. Rtv'd the corners, and painted the galvenized steel plate with a clear coat after brushing it up a bit. The copper tube balun soldered up easy to the plate with enough heat. The video was dam good at 2 miles along the ground, looking to extend it next trip out.

Still very thankful for sharing the designs of this antenna or i'd be stuck at the 1 mile range mark for a long time.

**durangoflyer** · 17th July 2012 09:35 AM

Good stuff...

I did more testing with mine and I must be fairly close without knowing the SWR yet I was able to go out a Km over water right down on the deck between two trees and my video was good. My tuned SPW in the same location was fuzzy.

Update: I retuned my elements stack and am getting even better results on a 8x8 panel. I love this antenna for my quadcopter!

**martyester** · 24th July 2012 10:19 PM

I am using a 300mW 1.258Ghz tx with a CP antenna on the plane and a Rx from RMRC with his receiver. I tested my homebuit crosshair with a 9x9" reflector. Found a stretch of road that was 3 mile flat and no trees. Video got marginal at 2.5 miles. Don't know if that is good or bad. I know it has better range than the CL with the SPW.

Alex, I was 0.6 miles away with the crosshair and had perfect video but when I pointed the antenna 180 degrees from the tx I still had good video. Only in a finite direction did the video get bad. I was expecting to loose the video if it was behind the antenna. Does this seem normal? It was mostly good no matter what direction I pointed it.