FrSky Rx Antenna placement and rules

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FrSky Rx Antenna placement and rules

Postby takilara » Tue Jul 20, 2010 10:41 pm

Hi, my FrSky set is the first 2.4Ghz Tx/Rx i have ever used. I was wondering bout how to best place the Rx antennas, and how to "fix" them (or get them to point in the desired direction)

I've understood it so that the antennas should be 90 degrees to each other, but how do I achieve this? Especially without reducing performance/range
I have the following ideas:
1. Heatshrink, to make the antennas stiffer and pointing in the correct direction
2. Two pieces of normal antenna tube, shorten it, and fasten it to the airframe somehow, stuffing the antennas in the tubes
3. Two pieces of drinking straws fixed to the airframe somehow, stuffing the antennas in the straws
4. Tape?
5. Tiewrap?

I don't know how much plastic or rubber will affect the reception of the Rx, if plastic is not a problem, i think either the heatshrink or the normal antennatube is the way to go.

This is going in a T-REX 600 with Carbonfiber frame
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Re: FrSky Rx Antenna placement and rules

Postby RCModelReviews » Tue Jul 20, 2010 10:57 pm

In a helicopter, you want the antennas at 90 degrees and spaced (where possible) by at least a couple of inches but you also want to make sure that they're as "visible" as possible from the widest range of angles.

This means that you don't want both antennas on the same side of the model so that they end up being blocked by the frame/motor/servos or whatever when at some orientations.

I'd be tempted to have one pointing vertically down between the skids and the other running *almost* parallel with the tailboom (but well spaced away from it and slightly to the side.

Fortunately, virtually all modern 2.4GHz radios have enough headroom that (at typical helicopter ranges) the antenna placement isn't as critical as you might think. The bottom line is to keep them away from the carbon/metal components (ie: don't tape them to the boom :-))

As for how to secure them -- well you can use the drinking-straw method (bearing in mind that they shouldn't be able to vibrate out, no matter how many G's you're pulling).

I haven't got a heli in the air at the moment so all my installations are in fixed-wing models where I just tape them to the sides (internally). Of course I never crash so I'm unlikely to end up pulling an antenna out of the receiver due to the tape holding it firmly in place while the receiver moves (yeah! right!).

Plastic (other than the carbon-reinforced type) will have no effect on the 2.4GHz signal but carbon, aluminum and wire will).
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Re: FrSky Rx Antenna placement and rules

Postby takilara » Tue Jul 20, 2010 11:10 pm

Ok, I was thinking one down along the skid leg, and the other along the boom support. The skid leg is plastic, so that should be fine, but the boom support is CF, so ill find another route for that one, i'll see if i can get it straight to one side or so

I don't crash as often anymore. I also see that my crashes more and more often tend to be mechanical or electrical fault, and less and less pilot error. So at least i'm learning something. (however learning that i'm a horrible mechanic at the same time)
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Re: FrSky Rx Antenna placement and rules

Postby jomarx » Thu Jul 22, 2010 5:55 am

I will also recommend option 2. I had a bad experience with option 4 (especially in a crash).

Well if your RX is the 8ch variant, HiModel have replacement antennas in stocks just in case if it breaks.
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Re: FrSky Rx Antenna placement and rules

Postby takilara » Thu Jul 22, 2010 9:36 am

Thanks :)
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is getting what you once wanted...
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Re: FrSky Rx Antenna placement and rules

Postby takilara » Sat Jul 24, 2010 10:22 pm

I went with two pieces of normal antenna tubing.

I mounted one horizontal, but 90 degrees to the frame, tiewrapped this to the mountingtray for the Rx.
The other i mounted close to vertical. I drilled a hole in the mounting tray above the Rx, and CA'd it there.

You think that this will be adequate? (see images)
(Note. Servo cabling is not yet complete. Please disregard the mess :)
Image
Image
The price of getting what you want;
is getting what you once wanted...
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