Pointing Antenna(s) at Phantom

Thanks for the shout out John.

While we're at it, it should be mentioned too that solder splicing coax is also a bad idea.

Sure it works, but you are actually degregating your ERP (effective radiated power) by causing reflections back into the Tx.

Kinda: 'two steps forward - one step backwards' sort-of-speak.

In the old days this could damage the RF amp [section] but it seems nowadays the designs and components are much more resilient.
 
Thanks John !

N017RW said:
While we're at it, it should be mentioned too that solder splicing coax is also a bad idea..

People also do not realize how much loss there is at these frequencies and how short a wavelength is. Very critical stuff. I mention wavelength because on the other end of the spectrum in the AM broadcast bands you can trim antennas inches at a time with little or no effect. At 5.8 ghz you about have to file the wire off! You really need to buy quality products and components. No messing around.

I also agree about the compromise too which is the reason I am running the shorter FPVLR Helix as I DONT want any less beamwidth than I have now.
 
MapMaker53 said:
..., I'm wondering why positioning the antenna horizontally (bent to the side 90 degrees like when you store it in a case) wouldn't be the optimal position since it would always be perpendicular to the UAV while you generally face it no matter at what altitude it is in the sky.
It has to do with signal polarization.
The best orientation is parallel. This gives you maximum power transfer between the transmitting antenna and receiving antenna.
Since the receiving antennas on the Phantom are vertical, you want your transmitter antenna vertical also so they are parallel.

If you rotate the tx antenna 90 degrees you minimize the cross section and cut the amount of signal that makes it across.
 

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Yep, got it. I understood the perpendicular aspect between antenna orientation and an invisible line to the Phantom, but I didn't know that you should keep the TX antenna as parallel as possible with the Phantom's antenna. Thanks, guys.
 
I don't have much experience at these frequencies but if I remember correctly at VHF frequencies I think there was about 20db loss when you are running vertical to horizontal antennas (meaning different TX vs RX antenna polarization). I would guess its closer to 30db or more at these frequencies. Someone with more RC experience might chime in but I bet I am not to far off.

To put that in perspective.... doubling your transmitter power only gains you 3db !

MapMaker53 said:
Yep, got it. I understood the perpendicular aspect between antenna orientation and an invisible line to the Phantom, but I didn't know that you should keep the TX antenna as parallel as possible with the Phantom's antenna. Thanks, guys.

In reality you wont have a lot of control over keeping them parallel. It is what it is based on the Phantom distance vs height.
 
So with the stock Phantom 2 directly overhead, what is teh best orientation of the stock tx antenna?
 
Carey said:
So with the stock Phantom 2 directly overhead, what is teh best orientation of the stock tx antenna?

Horizontal to the ground.
 
Carey said:
So with the stock Phantom 2 directly overhead, what is teh best orientation of the stock tx antenna?
Best would be pointing straight out or to the side, not straight up. That said, either orientation is still going to give you poor results.

The receiving antennas on the Phantom are still pointing straight down which means you are in the worst possible position from the Phantom's point of view.
You'll never get good range straight up unless you re-orient one or both RX antennas on the Phantom.
 
sbarton said:
Thanks. Didn't realize I was supposed to point the top of the repeater towards the Phantom. I thought it was supposed to be the side.

-Scott

Whoa... You don't want to point the tip of the TX antenna at the Phantom. When it is overhead you have to balance the radiation pattern of the TX antenna (which is strongest off the side) with the vertical polarization of the Phantom's antenna. So I would shoot for some where in between.
 
Sorry I misinterpreted you - you did say repeater.
The large flat side of the stock repeater should face the Phantom.
 

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