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Old May 23, 2011, 08:57 AM
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Spain
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Quote:
Originally Posted by IBCrazy View Post
You meant the patch? yes. The Skew-wheel and cloverleaf? If it's 1.1mm wire, yes. I never thought about it, but bailing wire would probably work fine for this antenna too.

-Alex
Sorry for not being clear.

I'm referring to the wire for building the spw/cloverleaf..
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Old May 23, 2011, 10:02 AM
Whats the wrst that can happn?
AdamChicago's Avatar
Chicago, IL USA
Joined May 2010
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Hey is there anyway to go CP with UHF 433mhz Rx/Tx's. I imagine the Rx antennas would be to large, but is there a way around that?

I've been getting bad multipathing on the Tx/Rx flying in the city but don't know of a better solution. The signal will just drop out completely in a matter of 2-3 seconds! It can't be a null because the Tx is an omni whip and I'm no where near the top end null (out 4000 feet and maybe 600ft up) and I'm not far enough out to be losing the signal (4000 ft LOS using a Scherrer LR UHF on the 2w setting). The Rx antennas are positioned in an "L" shape on either side of the Skywalker nose). And I don't think this is from RF because it's happened in two totally separate locations in the city.
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Old May 23, 2011, 10:42 AM
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Amherst, VA
Joined Jun 2006
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Yes: turnstile antenna. It is circularly polarized.
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Old May 23, 2011, 10:45 AM
Whats the wrst that can happn?
AdamChicago's Avatar
Chicago, IL USA
Joined May 2010
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Oh I didn't realize it was a CP. What would be a good Tx CP mate for it? I imagine the stock omni whip (even when tilted on its side) wouldn't be as good as a CP antenna?

Quote:
Originally Posted by IBCrazy View Post
Yes: turnstile antenna. It is circularly polarized.
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Old May 23, 2011, 10:52 AM
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Amherst, VA
Joined Jun 2006
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I'm not sure if I'd use it as a TX antenna or an RX antenna. An RX antenna might be easier to mount. Eiher way, it should help with some of your problems. multipathing shouldn't be too bad for a control system unless you are flying very low to the ground.

-Alex
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Old May 23, 2011, 11:11 AM
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Spain
Joined May 2011
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Thanks for your answer. Do I have to adjust the measurements or can I use directly your formulas in order to use the galv steel wire?

Quote:
Originally Posted by IBCrazy View Post
You meant the patch? yes. The Skew-wheel and cloverleaf? If it's 1.1mm wire, yes. I never thought about it, but bailing wire would probably work fine for this antenna too.

-Alex
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Old May 23, 2011, 11:58 AM
Don't disturb the pilot !!!
saucisse's Avatar
Canada, QC, Quebec
Joined Jun 2008
2,190 Posts
Alex, saw this post from Sander ? Maybe it's the reason why the cp antennas don't work with the Lawmate Rx ??

http://www.rcgroups.com/forums/showp...postcount=1422
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Old May 23, 2011, 01:19 PM
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Canada,Quebec
Joined Jan 2005
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Quote:
Alex, saw this post from Sander ? Maybe it's the reason why the cp antennas don't work with the Lawmate Rx ??
They do work, install a 100ohm resistor between video and ground on the vtx side.
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Old May 23, 2011, 03:45 PM
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SW England
Joined Aug 2009
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Hugo, you use a 100pF capacitor in series with the antenna centre connection to block the DC flow.

Nigel.
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Old May 23, 2011, 04:01 PM
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Joined Oct 2007
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Quote:
Originally Posted by saucisse View Post
Alex, saw this post from Sander ? Maybe it's the reason why the cp antennas don't work with the Lawmate Rx ??

http://www.rcgroups.com/forums/showp...postcount=1422
Gee, I can't believe this internet rumor is still circulating. The Facts are:

1) Lawmate Rx work fine with CP antennas. I have six lawmate RX and they all work perfectly with CP antennas and all other antennas I have tried.

2) Sander's post was a speculative response about what could be the problem if there was a problem (but there really is no problem). He thought the Lawmate RX might have +5v on the antenna output to power an external LNA which could be shorted if a closed loop antenna was used. This is an easy test to make: test the antenna input of the Lawmate with a voltmeter. You will find there is no DC voltage there.

What typically happens is that someone has a problem with their system or testing approach, blames a particular component and then makes a post. I know that facts have little impact on beating down internet rumors but I can't resist trying.

OMM
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Old May 23, 2011, 04:10 PM
Don't disturb the pilot !!!
saucisse's Avatar
Canada, QC, Quebec
Joined Jun 2008
2,190 Posts
Sorry if my comment bugged you out that much! I don't read all post in here

Quote:
Originally Posted by Old Man Mike View Post
Gee, I can't believe this internet rumor is still circulating. The Facts are:

1) Lawmate Rx work fine with CP antennas. I have six lawmate RX and they all work perfectly with CP antennas and all other antennas I have tried.

2) Sander's post was a speculative response about what could be the problem if there was a problem (but there really is no problem). He thought the Lawmate RX might have +5v on the antenna output to power an external LNA which could be shorted if a closed loop antenna was used. This is an easy test to make: test the antenna input of the Lawmate with a voltmeter. You will find there is no DC voltage there.

What typically happens is that someone has a problem with their system or testing approach, blames a particular component and then makes a post. I know that facts have little impact on beating down internet rumors but I can't resist trying.

OMM
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Old May 23, 2011, 04:34 PM
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careyer's Avatar
Joined Feb 2011
183 Posts
Low range

Hi there

i've build one of those Skew Planar Wheel for my 910Mhz 800mw Hobbyking RX/TX Set but the result is extremely bad.

Though i tried to keep tolerances as small as somehow possible (<= 1-2mm) it does not give me more than 200m of range in direct line of sight. Tried all channels 1-4 (910-1040 MhZ) and channel 3 ist best. The Standard antennas even give me slighly more range and more robust signal. Any Idea what might be wrong?

Here's a pic of my two antennas:


P.S: 900M Mhz is the primary band for cellphones right over here. Might this affect the range that much? Cellphones are allowed to send 2W .... basestations about 8W.
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Last edited by careyer; May 23, 2011 at 04:40 PM.
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Old May 23, 2011, 06:15 PM
QiW
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south east asia
Joined Mar 2009
956 Posts
hi
i am using the hobbyking 200mW 900mW system ... and the cells in my country operates on GSM which is also around the 900mhz area
i am using the cloverleaf on my vtx and SPW on my vrx ... so far my signal has been good up to 700m or thereabouts (checked on goggle map)... cannot fly far yet as i do not have RTH and OSD (but they are on the way) ... i have even flown my plane to within 100m of a cell tower with mild interference and between trees too
in theory u should have at least double my range
i see u have the SPW on both vrx and vtx ... u might wanna give the CL a try on your vtx since this combo is highly recommended
there was one time when i was getting no more than 200m of range so i did some checking ... apparently one of the wires have a cold solder joint on my vtx and cracked on the solder breaking up the signal intermittently ... making the range much much shorter than it should be ... u should try checking the solder points on your vtx/vrx just in case
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Last edited by QiW; May 24, 2011 at 01:01 AM. Reason: typo
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Old May 23, 2011, 06:16 PM
Future-proof EVERYTHING
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NY
Joined Jul 2008
762 Posts
If your in Europe or another country using GSM, I wouldn't use 900 mhz.. The cell towers can and likely will trash the signal if you get in their beam.
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Old May 23, 2011, 08:07 PM
QiW
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south east asia
Joined Mar 2009
956 Posts
hi darkheli
i have set my vtx closer to 1ghz ... so far the gsm 900mhz has not really affected me seriously ... unless i fly really close to the tower(s)
yes ... i know its a bad idea/choice of frequencies on my part
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