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Old Nov 27, 2012, 07:44 PM
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Thought this was a very interesting read:


Cheap biquad antenna extends LAN between apartments

http://hackaday.com/2012/11/27/cheap...en-apartments/
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Old Nov 27, 2012, 09:28 PM
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Alex, what do you think about these extensions from HK to build my antennas ?
i am kind of tired of crimping those damn connectors !!
lol

http://www.ebay.com/itm/12in-RP-SMA-...item25752897f4
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Old Nov 28, 2012, 08:50 AM
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^Those work fine. It's the easiest way to make your own. Do you really think I crimp all my own leads

-Alex
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Old Nov 28, 2012, 09:16 AM
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Quote:
Originally Posted by bakchos View Post
Alex, what do you think about these extensions from HK to build my antennas ?
i am kind of tired of crimping those damn connectors !!
lol

http://www.ebay.com/itm/12in-RP-SMA-...item25752897f4
Be carefull, except for FoxTech products, which use RP-SMA, all other systems need SMA.

HTH

Markus
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Old Nov 28, 2012, 09:18 AM
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Quote:
Originally Posted by markus123456 View Post
Be carefull, except for FoxTech products, which use RP-SMA, all other systems need SMA.

HTH

Markus
Thanks for the heads up, all my gear is RP-SMA, i got these extensions and also right angle ones.
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Old Nov 28, 2012, 02:15 PM
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Thanks to IBCrazy!
Im getting good FRSky range tests with home made biquad
How efficient is the biquad compared to say a helix antenna?
Gain does not tell..... or does it??
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Old Nov 28, 2012, 02:40 PM
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Quote:
Originally Posted by sweflyer View Post
Thanks to IBCrazy!
Im getting good FRSky range tests with home made biquad
How efficient is the biquad compared to say a helix antenna?
Gain does not tell..... or does it??
It somehow would tell. However, a helical antenna is circular polarized, and unless you replace your receiver antennas with circular polarized antennas too, using a CP antenna on the transmitter side of things would mean you would loose about 3dB because of the partial polarisation mismatch. Other than this, a low turn helical (3 or 4 turns) would do about the same as your biquad. The biquad is however the better aproach for the FrSky as you can continue to use the standard cat wisker antennas on the receivers.

Markus
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Old Nov 29, 2012, 09:01 AM
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Quote:
Originally Posted by bakchos View Post
Alex, what do you think about these extensions from HK to build my antennas ?
i am kind of tired of crimping those damn connectors !!
lol

http://www.ebay.com/itm/12in-RP-SMA-...item25752897f4
I bought those exact ones from that seller and built two antennas - a BiQuad 1280MHz and a DragonLink RX antenna 433MHz. Works great!
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Old Nov 30, 2012, 04:32 AM
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Quote:
Originally Posted by IBCrazy View Post
MXM000 - Your return loss looks a bit unstable. You might have a defect in the cable (or the feed) causing some resonance effect. This could be skin effect tracking down the tube. Your second major trough in your plot is most certainly skin effect of the signal tracking down the tube.

-Alex
Thanks. I've rebuilt it using a copper plated PCB as a reflector and without the copper tube, but the return loss is largely the same. In any case, the range improvement is still massive!
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Old Dec 01, 2012, 09:39 AM
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Guys I built a 2.4ghz biquad antenna. I tried it on my Wifi Router. With a default antenna it gives signal strength as excellent, but when replaced with antenna it gives signal strength as low. I dont think i did anything wrong while building.
Now I am reluctant to use this on my radio.
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Old Dec 03, 2012, 12:42 PM
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I recently built mine for 1280

Galvanized steel reflector
12ga solid copper wire with jacket left on it
Popsicle stick stand-offs
1/4" copper tube
1/4" particle board backing
Lots of hot glue

No images right now but here's a vid out to just 1100ft on my hexacopter (battery limited). VTX has a standard omni whip. The BiQuad is on a tripod inside a screen patio, 12in above ground.

DJI F550 + Naza + Skylark Trace OSD (4 min 45 sec)
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Old Dec 03, 2012, 05:45 PM
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Alex,
I'm thinking about a project and would be really grateful for your advice.

At both the last 2 big FPV meets I've been to over in here in the UK we have lost a plane. One was a flyaway; It just stopped responding to controls and off it went, the second was a loss of spacial orientation by the pilot, he lost sense of direction and with no OSD his video faded to nothing before he could work out which direction was home.

In both cases there was a little bit of video intereference remaining on the channel as seen from the flying field, suggesting that the VTx on the plane was still transmitting, but nothing strong enough to get a feel for where the plane was or even to get a decent direction from using a directional antenna from the ground.

In the UK because of the legal issues most of use 5.8Ghz (I know you're not a fan of it) and virtually all use RHCP due to the popularity of your designs.

All of which made me wonder, could I build a plane finding pod that would fit on the bottom of something like a skywalker 1900. My concept was 3 or 4 5.8ghz receiver modules, linked to directional antennas with slightly overlapping beam patterns and then using a simple board to compare the RSSI outputs of each to give a rough direction finder. Maybe even a downward looking camera on the pod to confirm location visually and of course GPS to give a lat and long display. If I'm feeling clever the direction output from the RSSI comparison could be displayed on the OSD for the pilot, or a simpler option just to drive a set of LEDs positioned in front of the FPV flight camera to give steering cues.

My main questions what sort of antennas would you advise for this? They would have to be compact and have low side lobes, be directional, but not too narrow in azimuth and while CP may be best, I guess the other factors may mean its better to accept the 3db loss and go for linear? They would also need to be pretty easy to build so that I can make 4 fairly well matched ones, although I would expect to put a bit of calibration tweakability into the RSSI circuit.

It started off as something practical, but it's now getting to the point that I'm thinking of building it even just as a fun project.

Grateful for your thoughts, especially on antenna selection, but on any other bits of the idea too.

Thanks,

Dave

P.S. Obviously the plan would be for the carrying plane to use 2.4GHz video to avoid you flying round in circles finding yourself.
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Old Dec 03, 2012, 09:31 PM
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Why not just one receiver and one antenna pointing down with a video repeater? The plane in the sky picks up the signal and retransmits it on another band. From there, since the antenna on the aircraft is directional, you have some idea where it is located.

-Alex
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Old Dec 04, 2012, 11:42 AM
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Could do. I wasn't sure how easy that would be to find the direction initially before you had a stable video picture. Would you just suggest a single helical then?
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Old Dec 04, 2012, 12:05 PM
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Yes. A single helical would do fine.

-Alex
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