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Inflight Glitching- Due to Antenna Routing

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Old 10-09-2004, 06:16 PM
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Cyclic Hardover
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Default Inflight Glitching- Due to Antenna Routing

Heres a good story which just happened to me this weekend. I guess you could take a particular problem with theses planes and it may be one of 50 things that went wrong. All my planes are on the same frequency. And I have never had a problem with glitching or radio problems on any area around the flying field.

Now on my Shoestring which is one of my more regular planes meaning it always flys when i go out to the field even if something else happens to another plane. I know this plane very well and every time I pass over the same spot in the pattern I get a quick glitch which rocks the wings for a second and then its gone. This has been a steady problem with this plane for over a year.

It happens every time, so for the most part avoid this area but to test it I'll have somebody wtch and sure enough , I pas over that area and a fast twich happens . Can understand why it does not happen to my other planes until now.

There was this guy who did a demonstration one time. I forgot what his name was or job but show up at a meeting once with all his equipment. He profession was this "RF" stuff. He took a reciever and strung out the antenna straight out. As soon as he put his testor right in line with the antenna, the signal was immediately cut in half but if he went off just a few degrees up to 90degrees it was fine.

The point he was making is many of us to include myself run some antennas through the top of the plane and straight to the rudder, then loop it back around so its nive and pretty. This is very bad. Frank when your flying your plane and it passes in frint of you and heads straight out away from you, it's a coin toss on every lap whether that thing gets stuffed of not.

Some also like me run it under the plane in the same manner. The best thing he said to do is if you run it to the rudder or underneath, take whats left over and just let it hang off of run it 90degrees and attach it to something like the stab.

Whatever the case is not to have it run straight out, have a few inches at the end hanging or secured in a different direction.

So I re-routed it all and the problem was gone!
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Old 10-10-2004, 11:31 AM
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Default RE: Inflight Glitching- Due to Antenna Routing

In the begining it was usually regarded best to have the antenna be a wire extending straight up from the center of the airplane. It was only pointed at you when it was up over your head. This evolved to going to the top of the tail and now we run it to the tail under the fuse.- not the best way. Its pointed right at you just after take off or just before landing. It would be better to run it out the wing.
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Old 10-10-2004, 11:03 PM
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Default RE: Inflight Glitching- Due to Antenna Routing

I always wondered why there should be a correct way to route the antenna... Can't radio waves penetrate the "undense" structure of model planes? After all, they do pass through walls... and if this holds true, then shouldn't it be safe to have the antenna completely hidden within the fuselage? Maybe its for that same reason that TV antennas all point to the same direction to receive a particular station - to get the OPTIMUM reception. And when it comes to a plane in the air, anything less than OPTIMUM is not good enough right?
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Old 10-11-2004, 12:02 PM
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Default RE: Inflight Glitching- Due to Antenna Routing

The best way to get optimal antenna operation is to use circular polarization. I don't think you would want to carry around the necessary transmitter antenna. The very first successful RC airplane by an amateur I ever saw was flown by George Trammel in 1947 and used circular polarization.
You can put the antenna internal as long as you don't use metal for the skin of the airplane or paint it with some kind of metal based paint. Use non metallic push rods to be safe.
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Old 10-13-2004, 01:43 PM
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Default RE: Inflight Glitching- Due to Antenna Routing

Dirtybird, does this apply to a plane with aluminium colored monokote? I would expect that some form of metallic powder would have been used in the coloring process to make the monokote look metallic. I'd better hang more of my wire out on my next flight...
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Old 10-13-2004, 03:18 PM
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Default RE: Inflight Glitching- Due to Antenna Routing

ORIGINAL: MeanMustang

Dirtybird, does this apply to a plane with aluminium colored monokote? I would expect that some form of metallic powder would have been used in the coloring process to make the monokote look metallic. I'd better hang more of my wire out on my next flight...
Don't know. I would keep my antenna outside to be safe.
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Old 10-13-2004, 04:56 PM
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Default RE: Inflight Glitching- Due to Antenna Routing

There is no metal in aluminum or metallic MonoKote.
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Old 10-14-2004, 12:03 AM
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Default RE: Inflight Glitching- Due to Antenna Routing

Think of it like this - the radio antenna is the flyswatter, and the radio signal is the fly. Catching the fly (radio signal) isn't too hard to do when the swatter (antenna) is broadside, but, turn that swatter sideways and the fly is a lot harder to hit (signal harder to catch). The discussion on polarity is on target, and in addition ya gotta remember that most antennas are directional - even dipole antennas have some gain one sides and some loss on ends.

Not much one can do about it tho. I worry more about my dumb thumbs
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Old 11-14-2004, 08:36 PM
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Default RE: Inflight Glitching- Due to Antenna Routing

I ended up just replacing the whole receiver
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Old 11-15-2004, 07:51 AM
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Default RE: Inflight Glitching- Due to Antenna Routing

This thread seems to imply that an antenna mounted in the fuselage should be doglegged. Or maybe the last few inches or an exposed antenna should be flapping in the breeze. Or maybe the antenna should go up the mast above the fuselage before heading towards the vertical fin.

It’s unfortunate that tools to verify the effect of an antenna change are not easily usable/available. Often I have wanted hard evidence of the net result of a change. The evidence is never found in my fingers and eyeballs.
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Old 11-15-2004, 02:15 PM
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Default RE: Inflight Glitching- Due to Antenna Routing

One thing that is not obvious is that your Tx also has a role in signal strength to the receiver. Your signal radiates out of the sides of the antenna in a big disk. The point of weakest radiation is the tip of the antenna. This is why that if you are having control problems, you need to aim the side of the antenna at your aircraft. Alway avoid pointing the tip of your Tx antenna at your aircraft as you risk losing contact.
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