Jan 01, 2011, 10:47 PM
Registered User
replayreb's Avatar
Quote:
Originally Posted by IBCrazy View Post
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The truth is that the shield of the cable will acts partially as a counterpoise unless you alter the geometry a little. If you look at how I build mine, I keep the active element right in line with the cable and have the counterpoise at an angle. This mitigates the RFi and keeps the signal almost perfectly level.

It's amazing how much detail and analysis can go into something so simple

-Alex
I consider myself a relatively smart person but I think this antenna stuff is more art than science...or maybe voodoo.
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Jan 01, 2011, 10:50 PM
Engineer for Christ
IBCrazy's Avatar
Quote:
Originally Posted by replayreb View Post
I consider myself a relatively smart person but I think this antenna stuff is more art than science...or maybe voodoo.
Not really voodoo. Black magic actually
Jan 01, 2011, 11:03 PM
Registered User
replayreb's Avatar
Quote:
Originally Posted by IBCrazy View Post
Not really voodoo. Black magic actually
lol. No wonder so many people when they see a long range FPV video demand that the pilot tell them EXACTLY what equipment they used! The air stuff was easy for me...I just threw a 1-watt transmitter up into the air with the stock rubber duck and it worked flawlessly for me up over a mile away but this ground-based FPV range problem really has me confounded.
Jan 02, 2011, 07:39 AM
FPV is my cup of tea
blupp's Avatar
Quote:
Originally Posted by IBCrazy View Post
Sort of...

The truth is that the shield of the cable will acts partially as a counterpoise unless you alter the geometry a little. If you look at how I build mine, I keep the active element right in line with the cable and have the counterpoise at an angle. This mitigates the RFi and keeps the signal almost perfectly level.

It's amazing how much detail and analysis can go into something so simple

-Alex
http://www.antennex.com/shack/Dec06/cps.html
For clarity and better understanding, this antenna have no counterpoise.
It have two radiators, and the two radiators as a unity should be referred to as a radiating element.
Am I correct?
Jan 02, 2011, 09:10 AM
FPV maniac
bah7566's Avatar

coax question


If I wanted to make an extension from my video RX on my ground station to put the antenna on a pole. What coax would be best for about 25' ? Is this a possibility or a pipe dream? I want to have my yagi on a pole but the RX on or close to the ground.

Thanks in advance for any advice you may have.
Bruce
Jan 02, 2011, 09:19 AM
Thou who know not
Po73's Avatar
Quote:
Originally Posted by bah7566 View Post
If I wanted to make an extension from my video RX on my ground station to put the antenna on a pole. What coax would be best for about 25' ? Is this a possibility or a pipe dream? I want to have my yagi on a pole but the RX on or close to the ground.

Thanks in advance for any advice you may have.
Bruce
LMR-400 would work fine at 25'.
Jan 02, 2011, 09:20 AM
FPV maniac
bah7566's Avatar
Quote:
Originally Posted by Po73 View Post
LMR-400 would work fine at 25'.
Thanks!
Jan 02, 2011, 09:25 AM
Thou who know not
Po73's Avatar
Quote:
Originally Posted by bah7566 View Post
Thanks!
No problem. Keep in mind it's not very flexible so you want some slack near a point that will move IE; near the last clamp on the mast if you are rotating the mast.
Jan 03, 2011, 05:03 AM
FPV is my cup of tea
blupp's Avatar
Sorry if I sound arrogant and rude, I don't mean to. I just have to stick out my tongue sometimes.
Many here possess more knowledge and experience than I probably ever will.
Thank you for sharing and helping! Thank you Alex!
Jan 03, 2011, 08:42 AM
Well, now that you know ...
Bigster's Avatar
For my issue with the video breaking up on the return trip, watch here. At about 5:40, I turn around. Sorry for the boring video. My view isn't great - I need a different camera mount.

I'll shoot some pics of the plane and antenna/mount.

DragonOSD FPV (13 min 23 sec)
Jan 03, 2011, 08:52 AM
Engineer for Christ
IBCrazy's Avatar
Seems to me something on the airplane was blocking the signal. Do you have a picture of the antenna mounted on the plane?

-Alex
Jan 03, 2011, 11:51 AM
Well, now that you know ...
Bigster's Avatar
Here are a couple of pics. The wing does have a carbon spar, fwiw.
Jan 03, 2011, 01:44 PM
FPV is my cup of tea
blupp's Avatar
All electronics, wires, magnets and the carbon spar will interfere.
Maybe not much, but still.
I would move the antenna away from the aforementioned and as low as I could.
Possibly onto the tail fin. And tilt it slightly forward counter clockwise.
That would put the front lobe slightly angled downwards, below the motor, electronics, etc.
Last edited by blupp; Jan 03, 2011 at 04:17 PM. Reason: I changed my mind about the CP case, sorry :)
Jan 03, 2011, 07:10 PM
Engineer for Christ
IBCrazy's Avatar
Quote:
Originally Posted by Bigster View Post
Here are a couple of pics. The wing does have a carbon spar, fwiw.
Flip that antenna upside down. The way you have the coaxial cable coming into the center causes the shield to angle the signal skyward. Flip it over and it will send it downward where you want it

-Alex
Jan 03, 2011, 08:05 PM
Well, now that you know ...
Bigster's Avatar
Awesome! Thanks Alex - I'll try it!


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