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Dec 22, 2017, 10:10 PM
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Bookstar75's Avatar

Receiver Antenna Question

Hello so I have a spectrum 400 longer-range receiver in my airplane. There are two antennas. One is a short one which is inside my airplane and the other antenna is a long one which I have sticking out of the side of my airplane going a different direction. My question is I do not have the full length of the antenna hanging out of the airplane. I only have a quarter of it sticking out otherwise it would hang out and Possibly hit the propeller. So I am wondering if that would reduce the range of the receiver if I keep most of the receiver antenna inside the fuselage? Or will that not matter? Thank you
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Dec 23, 2017, 01:04 AM
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O3D's Avatar
Inside or outside only matters if the frame absorbs 2.4 Ghz RF (such as Carbon fiber). Most frames are fine.

Other considerations:

- If you have 2 receiver antennas, put them at 90 degrees to one another
- Try to keep the antennas away from batteries, electronics and other wires
- Keep the antenna ends straight. For the Spektrum AR400, only the end of the longer wire is the antenna, not the whole wire.
- Try to keep the receiver itself away from other electronics
- Make sure the BEC can provide sufficient current to the receiver, even if a servo binds.

And always do a range test (using your radio's range test mode) after making any changes
Dec 23, 2017, 10:55 AM
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Ken Myers's Avatar
Just to clarify. The antennas are the same length, about 31mm. The thing that is different is the coaxial lead length. 03D already implied that in his response.
Dec 23, 2017, 07:32 PM
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Bookstar75's Avatar
O.k. perfect...yes the plane is just EPP foam and yes they are at a 90 from each it looks like I did everything right...thanks again!!
Dec 26, 2017, 06:31 AM
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Grup's Avatar
What I have done is to glue in a length of straw, one vertical on inside of fuse, the other horizontal on floor. I then run the antennas into those sections of straw.

- The straw keeps the antenna fairly close to 90 degrees apart from each other
- The portion of the lead between the Rx and the actual antenna may not be oriented at 90 degrees; but as Ken and 03D have noted, orientation of those leads does not matter
- Should you have a hard landing, or forget that you have antennas and pull the Rx out, the antenna is free to move so it doesn't get detached from the Rx. I've done this a couple of times in the past.

Other's have also suggested fuel tubing, this should also work as well
Dec 26, 2017, 12:15 PM
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O3D's Avatar
That's a great tip, Grup!
Dec 31, 2017, 09:05 PM
Registered User
Small strawas are great for keeping antennas in place and also protecting them.

I have also used the plastic tubing that is used as control rod guides.

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