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Old Jan 29, 2013, 04:57 AM
Foam Snow
South Africa, WC, Cape Town
Joined Aug 2011
1,334 Posts
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Understanding diffent 433mhz rx antennas

I'm currently flying a small wing using RangeLink with this antenna from TBS:




Apparently it's far from perfect because it's made for a diversity receiver setup.

Would I be better off with this antenna from ReadyMadeRC:



Or could I get away with using this little thing from Goodluckbuy:



Or should I just build a turnstile antenna - I don't know if it's going to fit on the wing.

I'm confused as to the pro's and cons and would like to save a few $ not ordering the wrong one.

Can someone explain the difference?
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Old Jan 29, 2013, 06:14 AM
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http://fpvlab.com/forums/showthread....about-antennas
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Old Jan 29, 2013, 08:17 AM
Foam Snow
South Africa, WC, Cape Town
Joined Aug 2011
1,334 Posts
Quote:
Originally Posted by Mictronics View Post
Appreciated!
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Old Jan 29, 2013, 08:32 AM
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If you decide to go for half wave dipoles then here is how to make one:
http://www.mictronics.de/2012/01/433...ipole-for-lrs/

A better TX antenna might extend you range as well. A simple and cheap solution:
http://fpvlab.com/forums/showthread....-for-433MHz-TX
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Old Jan 30, 2013, 01:09 AM
Foam Snow
South Africa, WC, Cape Town
Joined Aug 2011
1,334 Posts
Thanks again, though I don't think I'll be able to fit a half wave dipole on my Swift 2. Love the beercantenna But 13km is not really far, considering that RangeLink should get 30km on stock antennas.
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Old Jan 30, 2013, 02:16 AM
Crashomatic
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United States, CA, SF
Joined May 2010
2,071 Posts
I just have the ground part of the dipole hanging down when i don't need to have the "maximum range" (and in fact, i barely ever need it :P)

that makes mounting a lot easier on many planes/helis.. well specially helis/multis.
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Old Jan 30, 2013, 11:28 AM
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Powder Springs, GA
Joined Sep 2010
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^ You don't always buy range w/ extending the ground plane - you also get reliability. If you put your plane in places where "it desn't belong" in order to pull off the trick HD shots then iyou definitely want to extend the ground plane.

For the EzUHF crowd (sorry Sander) I am not a fan of any monopole that I've tested - maybe that's bc I started on dipoles and they are unbeatable. Also, as I said here ( a few posts down) I've taken the GoodLuckBuy common mode antennas out 14 miles with non issue. The other added benefit to these is reducing yaw wobble on flying wings - and of course tidiying up the install on my multirotors.
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Old Jan 30, 2013, 02:35 PM
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Lakewood, Colorado
Joined Aug 2002
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I've done a tremendous amount of ground range testing of various UHF systems
using monopole and dipole antennas on the Rx and found the performance of
the latter to far exceed the former. I also found that monopoles seem to have
more pronounced nulls when they're near the limit, meaning if you bank the plane
at long range it's more likely to lose the signal. A diversity system like ezUHF may
help mitigate that, but it's undesirable on most other systems. I've also found that
simply having the ground plane attached was a lot more important than its orientation.
It doesn't need to point exactly opposite the active element. In fact, sometimes having
it off angle or a bit curved seems to fill in the nulls a bit giving better all around coverage
with no significant reduction in range. This is certainly true of the classic Vee antenna
we use for video, so no surprise that it works for UHF. Anyway, it means
that running the UHF dipole through the wing, with upper half held straight
and lower half left to dangle, can work just fine for most flying.

ian
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Old Jan 30, 2013, 02:53 PM
Crashomatic
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United States, CA, SF
Joined May 2010
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I generally mix up range and "reliability" because they're related. As daemon says, you're more likely to lose signal in a bank. While the "hanging ground" of the dipole seems to work quite a bit better than monopoles, having it properly straight / mounted does extend range and thus reliability when you reach the limits.

But at the ranges I fly at in general, its plenty enough (better than the monopoles), and its easy to convert to a "proper" dipole.

I also checked that with a frequency scanner, and I get a much higher RSSI with the dipole "hanging ground" than a regular monopole. I get a little more with a "straight ground".

I haven't found any antenna that offers a better reliability/range / ease of manufacture and installation ratio.

So yeah, what Daemon wrote
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Old Jan 30, 2013, 03:07 PM
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Powder Springs, GA
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^ Check your frequency scanner at 1 mile - with a fan "blowing around" your dangling ground plane (simulating it flapping it in the wind)... vs the goodluck buy common mode (or the worst antenna you can buy) staying put at the same range. You might be in for a surprise.

Remember... moving 1 or more poles on a dipole is how it's tuned (remember your rabbit ears on the TV set??). I will never agree to have nature freely "tune" my antenna while my plane is in flight. You may argue that banking and piloting is essentially doing the same - (or at least has the same effect of changing reception)... BUT, I can level off my plane at will to GUARANTEE max reception only if I can control both poles. The only way I can control both poles is to install them in a way where they are consistent in flight.
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Old Jan 30, 2013, 04:20 PM
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Lakewood, Colorado
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My ground plane wire is stiff enough that it doesn't really "blow around". It just bends back
a bit at highest speeds and if I'm forced to land on it. And in my testing even having it
folded over 90 degrees, it still outperformed all the monopoles. Generally speaking
the sloppiest dipoles have outperformed the best monopoles, during ground testing
or in the air.

ian
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Old Jan 30, 2013, 04:36 PM
I LIKE WAFFLES....
SENTRY 62's Avatar
Powder Springs, GA
Joined Sep 2010
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My argument isn't that the monos dominate. My point is simply that I just feel that it's definitely worth it to take the 120 secs needed to spring-load the ground plane on the dipole.

Peform my 1 mile test (or attenuate if you don't have a mile) - there will be enough of "low-to-no reception" moments (based soley on RSSI) when the ground plane is flapping, that's all... and as we know, that effect is increased when there is real range, atmosphere, or LOS violations (which we all love - lol).
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Old Jan 30, 2013, 04:52 PM
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Not clear to me what I'm supposed to see at 1 mile. My Rf RSSI is usually still close
to 100% at 1 mile, with ground plane wire dangling below the wing of my X8. I've
done various ground range tests all the way out to 30 miles. In the first 15 or so,
the orientation and configuration (straight or bent) of the dipole doesn't matter much.
And as I said before, I've often found that with some bend in the ground plane wire I get less
pronounced nulls directly above and below which can be useful for proximity flying
and such. At 20-25 miles, I've found that a dead straight dipole will lose the
signal completely if one tip or the other is pointed at the Tx, but put a little bend in it,
and I still get a solid signal with active element vertical, and a usable signal with either
tip pointed toward Tx.

In the range that most people fly, the orientation of the ground plane doesn't matter.
If you've seen an issue as close as a mile, then something else was wrong.

ian
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Old Jan 30, 2013, 05:58 PM
I LIKE WAFFLES....
SENTRY 62's Avatar
Powder Springs, GA
Joined Sep 2010
2,452 Posts
The "issue" is dancing rssi when the dipole is flapping. I can clearly see this in the hours of FPV ground footage I see - and the general response of all the PMs returned when I ask is that they are running a dipole and letting it flap. It takes nowhere near 30 miles to show this phenomena. It appears that your dipole is "bent" in a certain orientation (you use thick wire?) instead of flapping as I am describing (as they do in flight)?? Over any given period of time - this "dancing" RSSI spends more than enough time at "low-to-no" RSSI value (or much lower than normal), even when the plane is generally the same distance away. Now add LOS violations (which is my flying style) to this phenomena.

These are my observations and why I decided to not let the ground-plane dangle. By all means - there are clearly plenty of people that do, and that's a personal choice. For me - my flying locations and flying style I can't leave it to fate when I can clearly see the performance enhacement of controlling both poles - and I need maximum control and elimination of variables... antenna position on the plane (when the plane is straight and level) is a variable I don't choose to live with when it's easily preventable.

@ Crash --- since you have a frequency scanner it would be great data to see how much moving the ground plane (not moving it and holding it - but actually having it flap) affects actual freq. I don't have one and only used RSSI for my tests - which admittedly is making some assumptions... although some very good ones.
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Old Jan 30, 2013, 07:31 PM
BEOWULF
North vancouver, B.C. Canada
Joined Apr 2008
18,680 Posts
Quote:
Originally Posted by heinduplessis View Post
I'm currently flying a small wing using RangeLink with this antenna from TBS:




Apparently it's far from perfect because it's made for a diversity receiver setup.

Would I be better off with this antenna from ReadyMadeRC:




Or could I get away with using this little thing from Goodluckbuy:



Or should I just build a turnstile antenna - I don't know if it's going to fit on the wing.

I'm confused as to the pro's and cons and would like to save a few $ not ordering the wrong one.

Can someone explain the difference?
You should have no problem with orrigionl antenna you post

I fly long range with no collector antenna but just a wire

Pointing down works best as is is clear of stuff that blocks reception

Same goes for video tx antenna mount it upside down if your plane lands in tall grass as example

Rc car antenna tubes they use for rx Antenna is nice and stiff and aerodynamic

People put on way too much antenna mass on their planes to improve reception
Like v antenna on UHF rx and cloverleaf or cp antenna for video

If you want to go fast use small antennas

As all this mass of antennas on the plane is a real drag
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