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Old Oct 17, 2011, 01:18 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
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Quote:
Originally Posted by Carlos230023 View Post
So ibcrazy dude. Is there a thread on the method you mentioned of tuning 5.8 stuff without a $10,000 swr meter. I've brought it up a few times. There was minor discussion but no circuit layouts or component lists. I'm despitate to make some vaguely accurate way of tuning my 5.8 cloverleaf and helical antennas and I know your the man to ask. Not being an engineer of any credable notoriety :P. If you could help out that would be great!

Cheers dude.

CJ
You could rectify the output of a directional coupler and test both directions. Hooked up normally you'd get full voltage. Hooked up reverse you should get zero. I am working on a DIY SWR meter as well. Progress is slow these days. Too busy flying

-Alex
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Old Oct 17, 2011, 01:21 PM
um.. yeah, I can make that fly
Carlos230023's Avatar
United Kingdom, Milton Keynes
Joined Jun 2007
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Would rapid or farnell stock any of that stuff? It's a bit of a forign language :P.

Better flying than designing. Much less stressful, unless you crash that is :P. Will be following closely when you figure out the 5.8 swr meter .

CJ
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Old Oct 17, 2011, 01:27 PM
Alicante, Espaņa
Joined Jun 2010
379 Posts
Thank you very much Alex, but I suspect that sending my 15,5 turns (1 meter long) Helical from Spain to USA and Back is a lot more expensive than just buying an helical from you. (eventually, if I can't obtaing good results from my helicals, I will buy one from you, but a little bigger than the one you use to sell).
But, by now, I will go on "playing" with my new toys, and making some other.

The next one I make, will be just 10 turns, like you propose, and with 4 mm cooper tube, instead of 2,5 mm wire.

Like I said, sooner or later I will be going to 30 km with this antennas, helical, your CP Biquad, CloverLeaf and Skew Planar Wheel.

By the way, I remembered I asked you some time ago, how to make an staked CP biquad. You answer me, but I didn't understood very well what you meaned. If you find some time, I would like to make a CP Stacked Biquad with your measures, if you give them to me (the measures)



Quote:
Originally Posted by IBCrazy View Post
Helicals really require tuning. Most people building a helical are reaping the benefits of the incredible axial ratio and directivity of the helix, but few are getting anywhere near top notch performance. The good news is, if you pay for shipping, I will happily tune your antenna for free.

Every time I build a helical the matching stub needs adjusted. This is why no 2 helicals are alike and all of them have adhesive built up at the wavetrap to keep it from moving.

The tapered microstrip and wavetrap usually hit the closest on a blind shot. However I usually find myself moving the wavetrap a bit closer to the feed point and find myself lowering the feed at the tapered microstrip as low as possible. This inconsistency is the very thing that will keep the knock-offs (and yes HobbyKing is in the middle of ripping me off) from ever being comparable.

-Alex
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Old Oct 18, 2011, 06:47 AM
2^p - 1
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United States, MO, Springfield
Joined Feb 2003
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I have a question about mounting the Tx antenna. My current plane has a CF spar in the wing so I have two options: on the bottom of the wing but very close to the CF spar, or on top of the plane about 6" in front of the spar. I'm thinking below the wing would block the signal less, is this correct?
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Old Oct 18, 2011, 07:44 AM
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United States, MI
Joined Dec 2002
1,068 Posts
Where can you get extension cable for these? Is this something Radio Shack would carry? The extension the antenna came with is pretty short. I want to run the antenna out to the wing. The other option is to just extend the vtx I guess.
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Old Oct 18, 2011, 08:41 AM
um.. yeah, I can make that fly
Carlos230023's Avatar
United Kingdom, Milton Keynes
Joined Jun 2007
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eBay is a good cheap source I use. Slot comes from china so there's a bit of a wait but the prices are good.

Is there a circuit diagram handy for hooking up that directional coupler. And where would I get one from?
cheers

CJ
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Old Oct 18, 2011, 11:02 AM
Engineer for Christ
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Amherst, VA
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Originally Posted by signflyer View Post
I have a question about mounting the Tx antenna. My current plane has a CF spar in the wing so I have two options: on the bottom of the wing but very close to the CF spar, or on top of the plane about 6" in front of the spar. I'm thinking below the wing would block the signal less, is this correct?
Yes, that is correct. However if your transmitter frequency is 1.3GHz or less, I wouldn't bother putting it underneat as the change will likely not be noticed.

-Alex
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Old Oct 18, 2011, 11:42 AM
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Hi all,

I really want to try these CP antennas out, I've got a few questions if anyone would be kind enough to answer them. I have had a read of a lot of posts in this thread but not all, so I apologise if they've been asked before.

Could I use 14awg enamelled copper wire for the antenna part, or would this have a detrimental effect on performance? Just been into my local electrical component store and this seemed the closest thing they had.

Is there any other downside to using a longer feed wire other than the slight increase in db loss through the cable? I only want it about 18" to go onto the horizontal stabilzer of my skywalker using RG316.

Does anyone still use a low-pass filter with these antennas, my vx system is on 900mhz, I recently ordered one from readymaderc.

any help appreciated, thanks
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Old Oct 18, 2011, 12:49 PM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
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You cannot use 14AWG wire. It is too soft. Go to your local hardware store (or machine shop) and get.035" Mig welding wire. You can also go to a craft store and get memory wire. You must use steel wire or the antenna will be too soft.

-Alex
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Old Oct 18, 2011, 03:13 PM
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United States, MO, Springfield
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Thanks again Alex.
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Old Oct 18, 2011, 07:44 PM
More Combat Please!
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Utah
Joined Dec 2003
7,852 Posts
A friend of mine just built me one of these antennas today. I tried finding the materials locally to build one myself, but the local stores didn't carry the RG316 coax cable, or the male SMA connectors.

Needless to say, this antenna has changed my FPV experience. I constantly got video noise during maneuvers with my stock antenna on the 500mw Lawmate 2.4ghz.

Stuck this cloverleaf on there and I couldn't get it to produce noise at any attitude. Flew three sorties today without a glitch in the video.

Simply awesome! Now I can have the confidence in my system to start pushing it... which we did today when I scaled a mountain and bombed down it in proximity for the first time. VISCERAL!

Thanks so much Alex for making this available to us. It's a night & day difference.
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Old Oct 18, 2011, 08:16 PM
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Japan
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Was able to get #18 (about 1.2mm/0.047") copper wire for my 2.4 antenna. I also have 2 spare whip antennas from my broken 2.4 VRX/VTX.
Is it OK to recyle the coaxial cable and use this wire guage to make the clover and wheel antenna?
Thanks
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Old Oct 19, 2011, 12:43 AM
um.. yeah, I can make that fly
Carlos230023's Avatar
United Kingdom, Milton Keynes
Joined Jun 2007
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This the sorta thing I'm after?

http://www.e-meca.com/rf-directional...128&SpecsID=11

CJ
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Old Oct 19, 2011, 07:23 AM
Engineer for Christ
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Amherst, VA
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^ No. You need a directional coupler between 10 and 20 db. Go to Ebay. Lots of used ones available for $70 or so. Just be sure to check the frequency range. Then li=ook for microwave diodes. They'll cost about $2 each. They are really small.

-Alex
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Old Oct 19, 2011, 07:24 AM
Engineer for Christ
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Amherst, VA
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Quote:
Originally Posted by TheNiceGuy View Post
Was able to get #18 (about 1.2mm/0.047") copper wire for my 2.4 antenna. I also have 2 spare whip antennas from my broken 2.4 VRX/VTX.
Is it OK to recyle the coaxial cable and use this wire guage to make the clover and wheel antenna?
Thanks
Yes, but the #18 wire is not. It is too soft. You need a plated steel wire.

-Alex
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