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Old Nov 18, 2012, 03:09 PM
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Question
'Sander' 1/4 wave monopole - correct length for 433MHz UHF?

I am trying to determine the correct length to make a Sander Style monopole 1/4 wave antenna for my Dragonlink receiver (UHF 433MHz).

My initial search of the web found these links:
http://www.rcgroups.com/forums/showthread.php?t=1413650
http://www.fpvmanuals.com/2011/03/23...nd-turn-style/

where, when using an angled SMA connector, the legnth of the wire is 164mm (corrected from en earlier error), but there is still some confusion in this thread:
http://www.fpvmanuals.com/2011/03/23...nd-turn-style/

I initially built one with a wire length of 164mm, but had terrible range.

I then compared the one I built to one that was purchased from ReadymadeRC:
http://www.readymaderc.com/store/ind...oducts_id=1032

which is 174mm length!

Can someone please settle this - I'm tempted to just copy the bought one, but I'd like to be sure.

I'm using a standard right angle SMA plug:
http://www.jaycar.com.au/productView.asp?ID=PP0631
Soldered with Enamel coated wire, stripped at the end for the solder joint.

Any help much appreciated.

Roger.

(Edit: Did some more reading - seems that the external sleeve on the antenna makes a big difference. Perhaps I just need to do a field (RSSI) test and trim the antenna until I get to the peak voltage, then stop cutting.)
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Last edited by Kahnx; Nov 18, 2012 at 04:47 PM. Reason: more info found
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Old Nov 18, 2012, 07:16 PM
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In my micro-power range tests (and some full power range tests in the past),
I've not really been impressed with any 433Mhz UHF monopoles regardless of total
coax length. I'm not really sure what the attraction to them is, when as far as I can tell, even
the sloppiest built and installed (ground plane left to dangle in the wind) dipole will outperform it.

ian
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Old Jan 30, 2013, 02:44 PM
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I have a few extra SMA adapters but they are SMA male to female right angle and straight SMA crimp. Like this:



So I am guessing this may change the tune a bit. Is it the wire itself that is 164mm or just from the end of the crimp adapter? I think it's easier to understand as overall wire length without the connector.

Anyways, what do I need to do in this case to check that my antenna's are tuned correctly? Will using two connectors mated this way degrade performance?

Thx.
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Old Feb 01, 2013, 10:59 AM
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Quote:
Originally Posted by Daemon View Post
In my micro-power range tests (and some full power range tests in the past),
I've not really been impressed with any 433Mhz UHF monopoles regardless of total
coax length. I'm not really sure what the attraction to them is, when as far as I can tell, even
the sloppiest built and installed (ground plane left to dangle in the wind) dipole will outperform it.

ian
^Same as mine and Sentry's tests as well. Nothing beats the old fashoined dipole. The other alternative is a turnstile laid flat on the wng of your plane, but usually oinly fits on large flying wings.

-Alex
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Old Feb 01, 2013, 12:01 PM
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Quote:
Originally Posted by IBCrazy View Post
^Same as mine and Sentry's tests as well. Nothing beats the old fashoined dipole. The other alternative is a turnstile laid flat on the wng of your plane, but usually oinly fits on large flying wings.

-Alex
In my experience with antenna installs, it is usually the ground plane portion of a dipole that creates the most difficulty. Dangling is an option, but I've damaged alot of antennas that way. Eventually the wire breaks loose without good support, either from all the movement or belly landings.

Is there another way to make the ground plane portion of a 430-444mhz dipole besides a wire?
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Old Feb 01, 2013, 12:17 PM
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Nope. I don't think I've ever broken the ground side of a standard UHF dipole.
I usually break the center wire of the coax where it connects to the active element,
either from landing on it's head, or from bending over the stiff vertical during
transport in the car.

ian
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Old Feb 01, 2013, 12:32 PM
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@Ian, try 20 AWG solid wire and cover it in a layer or two of heatshrink tubing for rigidity. It still folds up great on landing and won't be damaged in transport. It also helps to use RG142 for the feedline as it is much stronger than RG316.

-Alex
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Old Feb 01, 2013, 12:35 PM
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Quote:
Originally Posted by billyd60 View Post
In my experience with antenna installs, it is usually the ground plane portion of a dipole that creates the most difficulty. Dangling is an option, but I've damaged alot of antennas that way. Eventually the wire breaks loose without good support, either from all the movement or belly landings.

Is there another way to make the ground plane portion of a 430-444mhz dipole besides a wire?
You can try this:

Build IBCrazys Turnstile LRS antenna for FPV (4 min 33 sec)


Lay it flat. You will also need to have your transmitter flat as well for best results. It is designed to be an "over the Horizon" antenna in that it behaves better when you have a disturbed Fresnel zone.

-Alex
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Old Aug 06, 2013, 11:17 PM
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Quote:
Originally Posted by IBCrazy View Post
You can try this:

http://vimeo.com/21420029

Lay it flat. You will also need to have your transmitter flat as well for best results. It is designed to be an "over the Horizon" antenna in that it behaves better when you have a disturbed Fresnel zone.

-Alex
for an atena like this would one need to make a matching one for the other end?

currently using the cheap hk clone orangerx openlrs for control and am tired of the cheap antennas that come with. what would you suggest as a good solution?
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Old Aug 07, 2013, 12:30 AM
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Also how well do you think piano wire would work as the antenna element on a sander style antenna for the Tx side?
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Old Dec 23, 2013, 01:11 AM
RC pilot by soul
Israel
Joined Apr 2005
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back to the original question - whats the best length to a monopole "sander style" antenna?

BTW - monoploes are very suited for multi rotors where its hard to install a dipole.
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Last edited by i3dm; Dec 23, 2013 at 01:17 AM.
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Old Dec 23, 2013, 09:19 AM
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Quote:
Originally Posted by i3dm View Post
back to the original question - whats the best length to a monopole "sander style" antenna?

BTW - monoploes are very suited for multi rotors where its hard to install a dipole.
http://fpvlab.com/forums/showthread....)UHF-antennas&
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