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Old May 27, 2011, 03:54 PM
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Canada,Quebec
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I use a 12t helical (2.4ghz) and an open biquad on the RMRC tracker work amazing.
I put an elastic band on the tilt to counter the weight of the helical.

-Hugo
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Old May 29, 2011, 09:15 AM
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United States, TX, Tomball
Joined Jan 2011
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Well I took the advice of cutting away the dead weight and cut away most of the PVC on the helical as well as removing the wooden base. Really lightened it up without sacrificing structural strength. May even be light enough for the tracker now. I think it looks kind of cool too .
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Old May 29, 2011, 09:10 PM
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Amherst, VA
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Originally Posted by imagebuff View Post
Why shouldn't I use a 5 turn helical on a tracker? Are you saying this based on the weight?

I already have the EagleEyes diversity and was planning on using the helical on the tracker, and another cloverleaf (need to order) on stationary RX #2. Cloverleaf on the TX/plane.

Thanks
Chris
Yes. The weight is the limiting factor. Helicals are large antennas. They are great for diversity, but not good for trackers.

In the near future I will be making 5.8GHz helicals that are high gain and tracker friendly

-Alex
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Old May 29, 2011, 10:49 PM
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Louisiana
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Alex, any idea what range to expect with a helical and clover leaf setup. . . .as compared to vertically polarized yagi and Vee on 1.28ghz?
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Old May 30, 2011, 07:03 PM
SpliceMILK, BeverlyHills,CA
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sawman

any idea what range to expect with a helical and clover leaf setup. . . .as compared to vertically polarized yagi and Vee on 1.28ghz?


If you are using the same Freq. (1.2ghz) and flying in the same location.

(CP) VidTx- CloverLeaf and VidRx- Helical versus

(LP) VidTx- Vee and VidRx- Yagi....

the 2nd setup will go a lot further, but keep in mind that the beam is a lot narrower,
you have to fly almost in a straight line, but you will go a lot, I mean a lot further!

:-)
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Old May 30, 2011, 07:18 PM
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I would have to say it really depends on the gain of the helical and the gain of the yagi. Between an 8dBi yagi vs a 13 dBi helical the helical should "win" rangewise on the same frequency for example.
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Old May 30, 2011, 11:54 PM
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Thanks guys. I feel a hi-gain yagi is easier to make, as Alex said the efficiency of the helical starts to diminish after 5 turns or so.
Beam width shouldn't be much of a problem seeing how it's a long-range set up anyway. Even if it were only a 11 degree beam (assuming 3db lobes), that's 1.2 miles at 6 miles out, 1/2 mile wide at 3 miles, and anything closer can get by with a bi-quad or omni.
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Old May 31, 2011, 02:02 AM
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Switzerland, LU, Buchrain
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Quote:
Originally Posted by sawman View Post
Thanks guys. I feel a hi-gain yagi is easier to make, as Alex said the efficiency of the helical starts to diminish after 5 turns or so.
Beam width shouldn't be much of a problem seeing how it's a long-range set up anyway. Even if it were only a 11 degree beam (assuming 3db lobes), that's 1.2 miles at 6 miles out, 1/2 mile wide at 3 miles, and anything closer can get by with a bi-quad or omni.
You may misundrestood this a bit. It's just that you need to make overproportionally more turns to get more gain the longer it gets. But high gain helicals are a reality and used in i.e. satelite comunication.

You can go for a yagi, but it will not be circular polarized. You can build what's called a cross yagi though but you have to be very carefull with the feed of the 90 degree crossed elements to end up with a truly cirular polarized one. I'm lacking experience but thougth to try this out one day but my gut feeling tells me that a helical is better due to the better adaption of the reciveing elements to the circular nature of the waves. I'm eventually really wrong here.

Markus
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Old May 31, 2011, 02:17 AM
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Quote:
Originally Posted by LexusFPV View Post
sawman

any idea what range to expect with a helical and clover leaf setup. . . .as compared to vertically polarized yagi and Vee on 1.28ghz?


If you are using the same Freq. (1.2ghz) and flying in the same location.

(CP) VidTx- CloverLeaf and VidRx- Helical versus

(LP) VidTx- Vee and VidRx- Yagi....

the 2nd setup will go a lot further, but keep in mind that the beam is a lot narrower,
you have to fly almost in a straight line, but you will go a lot, I mean a lot further!

:-)
This statement is plain and simply not true. You can make a high gain helical, and the gain of a vee is not really (significantly) higher than the gain of a cloverleaf (not even one dB). There are reasons why helical antennas are so widespread used in satelite comunications.

You may loose a little by going cicular polarized in a pure dB kind of comparison, but in reality you gain, cause the link is of better quality. The way the tx and rx antennas are lined up against each other does not matter by the nature of cirular polarisation.

One should compare apples to apples meaning if you look at what i.e. Trappy used on his record flights, I'm absolutely positive he would have been able to do the very same if he were to use circular polarized antennas with the same (or even slightly less) gain than the setup he was using.

These days it becomes aparent that the video link and rc link alone are no longer the limitting factor when it comes to range. Flight batteries (and patience of the pilote) are where the limits are.

The biggest advantage of CP antennas over LP antennas is that you never have trouble with banking etc. You also have much better chances to fly behind trees and still have a good signal than by doing so using LP antennas. Apropriate tests were made already many years ago as CP waves etc is not something that was invented for FPV but exists for long. Penetrating a forest using CP antennas usually means loosing 3dB. Doing the same with LP (upright) antennas means loosing 42dB. Doing the same with LP (horizontaly alligned) means loosing 12dB. You can look this up in the "Rothammel" antenna book if you like.

Markus
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Old May 31, 2011, 03:36 AM
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Alex,
what cable would you suggest to use?
RG174/RG58/RG316??

Which is the best for CL/SPW/Helical

Thanks
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Old May 31, 2011, 06:53 AM
SpliceMILK, BeverlyHills,CA
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Joined Feb 2011
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Markus,
thats for the explaination....

I'm trying to go out far this time around in a couple weeks.

I have 2.8m powered Glider, and I'm using 1.2ghz LawMate VidTx and VidRx.

My VidTx has a "V" and my VidRx (diversity-2x BiQuad).....
all Linear Polarization..... we will see how far I can glide out....

I want to keep it simple and I just want to go out in a straight Line,
(boring :-) )
but we will see and I will let you know.... Im not going through trees' or hills,
so I don't need Circular Polarization....I'm very high up in the air and I'm going
in a straight line out ..... no banking, just turning around to come back.
I hope to get 15-25 miles out ! :-)
I will let you know in a couple weeks when I do it for fun :-)
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Old May 31, 2011, 07:43 AM
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Switzerland, LU, Buchrain
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Quote:
Originally Posted by LexusFPV View Post
Markus,
thats for the explaination....

I'm trying to go out far this time around in a couple weeks.

I have 2.8m powered Glider, and I'm using 1.2ghz LawMate VidTx and VidRx.

My VidTx has a "V" and my VidRx (diversity-2x BiQuad).....
all Linear Polarization..... we will see how far I can glide out....

I want to keep it simple and I just want to go out in a straight Line,
(boring :-) )
but we will see and I will let you know.... Im not going through trees' or hills,
so I don't need Circular Polarization....I'm very high up in the air and I'm going
in a straight line out ..... no banking, just turning around to come back.
I hope to get 15-25 miles out ! :-)
I will let you know in a couple weeks when I do it for fun :-)
There is nothing wrong with linear polarisation. Especially not on the somewhat lower frequencies bands like the one you use. CP is just safer, more stable. It does not mean that you could not fly this way. Last not least we all flew this way up until not so long ago.

I wish you good luck for your long range attempt!

Markus
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Old May 31, 2011, 10:43 AM
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Amherst, VA
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Quote:
Originally Posted by aSa2 View Post
Alex,
what cable would you suggest to use?
RG174/RG58/RG316??

Which is the best for CL/SPW/Helical

Thanks
I use rg316 for cloverleafs and Skew-wheels. I use RG58/U for helicals.

-Alex
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Old May 31, 2011, 11:07 AM
RC pilot by soul
Israel
Joined Apr 2005
2,472 Posts
Alex,

Where do you get the stiff thin wire you use for all of your antennas? i would like to get some on Ebay since i wasnt able to find it locally.
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Old May 31, 2011, 12:46 PM
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Amherst, VA
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I use Mig welding wire from thae hardware store. It's cheap and it works.

-Alex
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