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Old May 22, 2014, 09:20 AM
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Question
FrSky Taranis Antenna Upgrade and SWR Problem

Hi All,

I have a question about the FrSky Taranis. I've recently done a mod to mine where i took built in antenna off and soldered on a rp-sma connector so I can connect the FrSky 5db omidirectional antenna and the 7db patch antenna. The problem I've found is that with the original antenna on the SWR stayed on 0 but now it doesn't.

Here's what I've found.

If i screw on a little omni I took from a 2.4ghz module the SWR goes way up and the radio tells me there's a problem with it.

If i put on the 5db omni the SWR ranges from 17 to to about 40 depending on if i'm touching it or not. It usually goes back to 17 but some times only 30ish.

But here's the strange bit, for which I've attached photos.

The 7db patch goes to abut 32 when its just sitting there. If i grab the right side of it, its goes to 17, if i grab the right side it goes to 0. What's with that?

I assume that because grabbing the side of the antenna makes it goes to 0 i assume that there's no problem with the soldering or anything like that. Btw I mounted it by hot gluing the connector into the hole the old one that came out of .

Has anyone else come across this kind of thing and more importantly does any one know anything that I can do to get my SWR back to 0.

Thanks

Rob
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Old May 24, 2014, 08:24 AM
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I guess no one else has run across this. Surly I'm not the only one who's replaced the antenna on the Taranis.
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Old May 24, 2014, 08:45 AM
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I have put in a ufl connector to sma lead and have a 5db omni. I get the same results as you.
Some tests are getting done this weekend, weather permitting, to try a few combinations. We should get an update soon.
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Old May 25, 2014, 11:10 PM
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Thanks whimsical. I'll be very interested to see your results.
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Old Jun 04, 2014, 09:48 AM
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I did some reading on the OpenTx site about the SWR numbers and according to them, the actrually number isn't of much importance as long as its not above 51. So maybe this doesn't matter. I'd still rather mine be at zero.
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Old Jun 04, 2014, 12:39 PM
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I did the same upgrade, and worked fine, but is soldered the coax directly to the board. Did you tried to replace the patch?? and put a new patch?? Probably the ufl or the sma connector is not well crimped.

Before the upgrade I got 0 SWR, After, 17 SWR with 2dbi antenna.

With the FR-SKY patch antenna situation is better and I can get from 0 to 10 SWR.

One thing about the patch antenna is that points to my body instead to point the sky in front of me, and there is no way to point the antenna to the sky (where the plane is normally flying). Have you noticed that?? I had to disassemble the antenna to know exactly where is pointing and I confirm that is wrong mounted or wrong designed.
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Old Jun 04, 2014, 06:58 PM
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Hi pekote

I soldered my coax directly to my board as well. Maybe the connection where it joins the patch antenna is faulty. Anyway I might unsolder it and try another one.

As for pointing the antenna to the sky. I think the side with the sticker on it should be pointed at the plane. So you rotate your antenna 180 degrees and fold it down away from you and it will point up at the sky. If that makes sense.
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Old Jun 04, 2014, 10:50 PM
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ok, bad news, something has changed, now I tested again my patch antenna in gives me 50 SWR

2dbi antenna works pretty fine 17 SWR

As you can see from the picture, the antenna knee (not sure how to call it) is installed in such way that the small sqare is always pointing to me.

The "wifi sign" in in the back of the antenna, behind the shield.

Don't understand how this antenna works. Another thing is that there is a short circuit between the shield and the center pole of the coax. Never seen this before in other patch antennas.
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Old Jun 05, 2014, 06:48 AM
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Quote:
Originally Posted by pekote View Post
ok, bad news, something has changed, now I tested again my patch antenna in gives me 50 SWR

2dbi antenna works pretty fine 17 SWR

As you can see from the picture, the antenna knee (not sure how to call it) is installed in such way that the small sqare is always pointing to me.

The "wifi sign" in in the back of the antenna, behind the shield.

Don't understand how this antenna works. Another thing is that there is a short circuit between the shield and the center pole of the coax. Never seen this before in other patch antennas.
The small square is the Radiating part of the antenna. The big square in the back is the Reflector.

Radiation pattern, the major lobe, beams outward from the Radiation part. So if I understand you correctly, you had it beamed AT You instead of the craft.
But no worries. It's only tens of milliWatts of power. Much higher, you'd be golden brown by now.

If you touch the antenna somehow, like described in earlier posts, you've a changed its characteristics by becoming part of the antenna, thus its beam pattern and its efficiency which may cause some energy to be reflected back into the radio.
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Old Jun 05, 2014, 06:58 AM
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Here's my mod.

Make this IBCrazy inspired BiQuad and no noise !

RSSI with original dipole: 74 at 100yrds and 200' up.

RSSI with BiQuad: 92 at 120yrd and 200' up.
And 82 at 532m away (0.5km).
It's very directional, garner available energy and beams it to the direction I pointed it to (the craft), thus not wasting energy by spreading it all over places where the craft is not, like a dipole.
It's also doesn't bathe you with microwave energy if you stay behind the reflector.

Amplifying it to 1 watt, you can get RSSI at 99 about 2km away !!!
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Old Jun 05, 2014, 07:19 AM
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Awesome!! please! share the antenna plans !!!

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Old Jun 05, 2014, 07:41 AM
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Quote:
Originally Posted by pekote View Post
Awesome!! please! share the antenna plans !!!

It won't take you long... to build.

http://www.rcgroups.com/forums/showt...ghlight=Biquad

This is 11dB which means narrower beam and longer reach than a patch of 7 dB. But a patch is better if you've got a fast plane.

I'm flying a Quad, on 22-30mph speed, so I tend to know exactly where it is and I have FPV.
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Old Jun 05, 2014, 05:30 PM
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The FrSky 7db patch I obtained had a paper sticker on the back! There is an arrow on the top pointing in the direction of radiation. I had to modify it to allow suficient rodtation to allow it to point toward my glider when mounted on a DFT module. It increased reported RSSI and seemed to work fine after this mod. No SWR numbers (thankfully).

I read on another thread that the "short" is at a node at the oprating frequency of the antenna and that means the voltage there is always zero, no functional short.
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Old Jun 06, 2014, 05:49 AM
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Quote:
Originally Posted by Modglock20 View Post
It won't take you long... to build.

http://www.rcgroups.com/forums/showt...ghlight=Biquad

This is 11dB which means narrower beam and longer reach than a patch of 7 dB. But a patch is better if you've got a fast plane.

I'm flying a Quad, on 22-30mph speed, so I tend to know exactly where it is and I have FPV.
Thanks for sharing. I'm am going to build one of those asap for my Taranis. I'm also going to take apart by Taranis and try and see if I can find any problems with the coax or joints. I'll post my findings here.
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Old Jun 06, 2014, 02:49 PM
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I was about to do the external antenna mod too - I have even ordered the u.fl. socket and u.fl. to SMA bulkhead pigtails - then I started reading about all these random SWR problems and decided not to.

Watch this:
Taranis Antenna Mod Issue. (26 min 49 sec)

for a possible fix!

Also, the 7dB Frsky patch's radiating side is falsely marked with a sticker and of terrible build quality (read relevant threads on fpvlab forum).
Get this one instead:
http://www.dx.com/p/wifly-city-2-4gh...5#.U5IZcvnV9cQ

Check out how well built is on the inside!
Unfortunately sold out right now in dx.com since it's extremely well performing and popular but you can find it elsewhere if you "google wifly city 10dbi".

I decided that the mod does not worth it so I had another approach to the problem. Since I am flying FPV and have a tracker too, I though why not put that directional antenna on the tracker and untangle myself from unnecessary cables with a ground based R/C relay.

Here is what I did:
http://www.rcgroups.com/forums/showthread.php?t=2173690

and the system works wonderfully:
https://plus.google.com/photos/10610...Kb75Mbbi-Hc6QE

Now I have all the range in the world with my stock Taranis in hand. No wires hanging - no bulky patches to aim on the plane.

Next: I am building a 2.4Ghz cross-hair antenna for the tracker and change the Rx dipoles to cloverleaves!!!



/Dimitrios
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