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HelicopterMain Discussion › Radio Glitch
06-07-2009 07:42 AM  8 years agoPost 1
planeguy12

rrNovice

MI, USA

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Hi Guys

Just finished building a Raptor 90se. I have a Futaba PCM receiver. I installed a whip antenna and mounted it to the landing gear base plate. It ran up past my Gemini switch. I encountered a few glitches on the test hover which caused a fail safe situation. I thought the switch might be generating some RF noise so I moved the antenna. It is now mounted horizontal to the radio tray and is attached to a vertical plate that is part of the engine shroud. The antenna is pointed out toward the front of the heli. The following test revealed that it doesn't glitch as much but still suffers occasional radio interference.

PS I have used whip antennas countless times before with great success. Receiver/battery is mounted in foam. Antenna is now farthest away from all other electronic components as possible.

Any ideas?

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06-07-2009 08:31 AM  8 years agoPost 2
duceduc

rrKey Veteran

Saitama-Ken, Japan

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I never liked the idea of cutting down the stock antenna to begin with. I have used a deans antenna (I think that is what it was called) when I had my 72mhz tx. It didn't work for me though.

Duc S
Do It! Do It!™
AMA:REVOMIX
RCK:24005615-01

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06-07-2009 08:55 AM  8 years agoPost 3
Keith_C

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Weirsdale,FL-USA

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2.4

Documentation is a lot like sex When its good its verry good When its bad its better then nothing

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06-07-2009 09:06 AM  8 years agoPost 4
nivlek

rrProfessor

Norfolk England

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I thought the switch might be generating some RF noise so I moved the antenna
I don't know what a Gemini switch is , but I would just plug a 4 cell nicad/nimh directly into the receiver and see what happens then .

At the end of the day , it gets dark .

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06-07-2009 12:50 PM  8 years agoPost 5
Steff Giguere

rrProfessor

St-Eustache, Quebec, Canada

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Also make sure it does not touch CF.

Team Synergy, Rail blades, Team Scorpion, V-Team

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06-07-2009 06:48 PM  8 years agoPost 6
ch-47c

rrElite Veteran

san jose, ca

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I used Deans antennas for years with no problems. I cut my atenna down to no less than 12 inches. I never used them with a voltage-regulated system like the Gemini. I mounted them under the radio tray along the longitudinal axis of the heli. If the antenna hits the front inside of the canop, I bent the antenna up to 135 degrees back over itself if necessary and always did a range check.
You said it happened while hovering, does it do it when the engine is not running? Just trying to troubleshoot.

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06-07-2009 07:03 PM  8 years agoPost 7
Gyronut

rrProfessor

Martinsville In.

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I flew Deans Ant's for many years even in planks with great success.

Always cut the factory ant's down on the rcvr's too.

Rick

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06-07-2009 07:25 PM  8 years agoPost 8
Maverick3n1

rrApprentice

San Diego, CA

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Have you tried a range test on your heli? At what distance does your signal cut out on your range test? I've used those antenna's as well, and just tested mine to find a sub-par range test.. with a futaba 9C transmitter with just the thickest portion of the antenna extended, I couldn't get more than 30 feet from the heli without losing signal. With one of my airplanes in the exact same position without the deans mod, I walked 90+ feet and still had full control with the same remote.

I don't know whether mine is just because I cut the antenna and am off by an inch or so on the cutting or something along those lines, or if it's a receiver issue, but my next step is to attempt re-soldering an antenna to the little bit I have hanging out, and then seeing what I get for a range test.

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06-07-2009 10:36 PM  8 years agoPost 9
planeguy12

rrNovice

MI, USA

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I haven't done a range check with it yet as I have only been hovering the heli 10 to 20 feet away from me. The glitch has always occurred when the engine was running. I doubt there would be a way for one to detect the glitch with the engine off as the only way I notice it is the sound of the engine throttling down during a fail safe event.

I will range check it without and with the engine running and see what results I find and let everyone know. Also I will try it with and without the whip antenna, (maybe I got a bad antenna from the factory?) And yes, the antenna is allowed to touch the inside of the canopy when installed. Perhaps that is a variable to check into as well.

I know 2.4 would be the way to solve it, but I don't have the capital to invest in new gear at this time. Some day....

BTW I am using a 9c transmitter.

Thanks for the suggestions thus far everyone.

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06-08-2009 12:39 AM  8 years agoPost 10
Maverick3n1

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San Diego, CA

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Make sure when you do the range check, you have the antenna completely retracted with the exception of the thickest section extended (So pull it all of the way out, and then colapse it down so you only have the thickest portion extended). You can overheat your module if you have it entirely retracted.

You should be able to take 30 paces from your heli (approx. 90 feet) and still have control of it. If you don't, you have a range problem. That should be a standard test that you do EVERY time you fly for the first time that day. There's always the possibility that the connector between your receiver and your whip antenna can come loose, or something else could cause an issue. You'd much rather find that problem before the engine is running, then when the helicopter is in the air and you lose control.

Standard test should include a range test, a test of all movable planes, making sure there is no binding, and then a tension test, giving each ball joint point a pull to see if you can pop it off by hand with ease. If so, you need to replace that socket.

If you are a member of a local AMA sponsored club, I'm sure there will be a club officer around that can direct you in all of the proper procedures for pre-flight checks/inspections. Helicopters have a LOT of things that can go wrong. Doing these checks can save the pocket book and potentially an injury, or worse, death. They may be considered toys, but these toys can be very dangerous. Be safe, always test, safety always comes before anything else. If you can't get crap for range, and can't fix it, send the receiver in for repair. A $20 diagnosis fee is a lot cheaper than a $300+ crash, or a medical bill and/or a lawsuit.

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06-08-2009 03:21 AM  8 years agoPost 11
RotorTech321

rrApprentice

Scranton, PA. USA

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Go for the 2.4 upgrade, its well worth it.

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06-08-2009 12:24 PM  8 years agoPost 12
chris6414

rrApprentice

Sneads Ferry, NC USA

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Cutting antennas on 72 Mhz systems
This a good read. Receivers are tuned for a specified antenna length. I know, some can be cut down and you have been flying like that for years. It's still wrong. A good whip is OK, but still takes away from the total range. With helos though, we usually don't fly an FM system out to the limits of our sight.

http://www.rc-cam.com/ant_exp.htm

Century Hawk Sport, OS .32, Futaba 7C, GY-601 9251
Predator Gasser SE G-23, Fut 3010 servos, JR gyro/servo

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06-08-2009 02:07 PM  8 years agoPost 13
MattJen

rrElite Veteran

UK

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sounds like a main mast bearing problem.

Unfortunaly spinning the head is not a good enough check, I did spin the blades on my large turbine, but it was only when i was advised to take the actual bearing out and spin them in my hand i realised how far they had gone..

A main mast bearing that is notchy will take you down, on 2.4 you are ok as the frequency is higher..

I would recommend you take them out and spin them in your hand, if they are notchy that is your problem.. i know it is a pain in the neck as you have to split the frames, but it is worht the effort.

Matt

All The Best

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06-13-2009 02:36 AM  8 years agoPost 14
Maverick3n1

rrApprentice

San Diego, CA

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Chris, that's a great antenna review. Gives a lot of good info. What it didn't cover and I'm suprised it didn't, is many people say that you can zig zag an antenna wire across a wing, but you can not cross the antenna wire, or it will be equivelant to having cut the wire at point of intersection. Have you or anyone else heard of this? I was kinda bummed they didn't try that out.

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06-13-2009 03:29 AM  8 years agoPost 15
ShuRugal

rrKey Veteran

Killeen, TX

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as long as your antenna is insulated so it wont short itself out that shouldn't be a problem. Winding the antenna back through airspace it has already covered seems a bit of a waste, but it shouldn't short the signal unless there is no insulation. I don't -think- that an antenna would have a strong enough flux to effect by laying it across itself...

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06-13-2009 11:25 AM  8 years agoPost 16
Eric Giorgianto

rrApprentice

New Jersey

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Glitch
Hey Buddy, this may sound ridiculous but I had a similar problem before I went 2.4, and my friend had me run a ground wire from my tail boom to one of the engine bolts,and bingo no more glitches, also check your voltage you might be a bit high at first and once the batts settle down the glitches will go away, also make sure that your fan is not rubbing on the top of the shroud as this can cause RF noise, hope this helps good luck. BTW please make sure to post your solution..
Eric G

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