Servo problem

HUH? You are getting random movements when the transmitter is in OFF position and you consider that a problem? I consider you lucky one of the servos hasn't hit a stop and stripped something. Do a proper range check with the radio on, the antenna down and you ~75 feet away, and if everything works as expected, fly the plane. Getting random glitches on a PPM receiver when there is no transmitter on is pretty normal. The normal order of operations for ANY RC system is to power the transmitter up first then the receiver. Never the other way around. Especially with an electric power system.

Jim

Never power up your receiver unless your transmitter is on!!!! That is the problem!

Good flying, desmobob

Well, as you can see I'm not very experienced in R/C, especially since I got into the hobby myself without any outside help (resulting in several planes that had very short flying careers.) I had no idea that you weren't supposed to turn on your receiver without your transmitter being on. In fact, that's how I determined that there wasn't any outside interference! Maybe that's why that other servo died. Hopefully everything's ok and I'll be able to fly tomorrow.

Thanks for the quick reply and blue skies.

Well, as you can see I'm not very experienced in R/C, especially since I got into the hobby myself without any outside help (resulting in several planes that had very short flying careers.) I had no idea that you weren't supposed to turn on your receiver without your transmitter being on. In fact, that's how I determined that there wasn't any outside interference! Maybe that's why that other servo died. Hopefully everything's ok and I'll be able to fly tomorrow.

Thanks for the quick reply and blue skies.

Hope you get in some flying! Have a ball!

Good flying, desmobob (another self-taught R/C'er)

A lot of receivers do this. Basically its noise. It may be low level interference, or just 'hiss'

A good design will try and mute the receiver if there is not enough signal to give a reliable output, but many don't bother.

Transmitter off means the rx is picking up RF noise so the servos jitter. This is normal. It is also not a good thing to do. You should always turn on the tx first. That random RF noise can move the servos beyond their normal range and damage em.

I understand. I taught myself to fly also. It wasn't until I had several hours in the air that I found a club. The bummer was that they had a training program and I could have probably saved a few repairs if I had known ahead of time. Your best bet is to do the one thing we don't like to, read the manuals that came with your gear. Dollars to doughnuts the proper order of operations is mentioned in there. That prop can (and will) bite, you should do the reading first the flying second.

Jim

Yeah, I have lots of entertaining crash stories due to being self taught. Looking back, I think I would have saved myself a lot of money and headaches if I'd gone to the trouble to seek out a club or at least a more experienced R/Cer. There's still a lot of stuff I don't know. For example, my most recent crash involved my prized Goldberg Electra motorglider that was the first plane I ever flew. I thought I had everything covered in my preflight checks. Unfortunately I neglected to check the rubber band that holds the motor in, which was apparently so old that it was at the breaking point. The predictable result was the motor coming out several seconds after launch, resulting in a spin at

30ft, a head on crash into the ground, and severe damage. Now I know that ALL rubber bands need to be replaced regularly, not just the ones that hold the wing on!

On a side note, I flew the Slinger yesterday and everything seems to be fine, so I lucked out there.

This suggestion is a must for FM receivers. PCM receivers do not have this issue. In this case I have leared to power the receiver first (without turning the radio) just to make sure that no one else is on my channel or I'm not receiving any spurious signals.

This practice is gonna cost you $$, or pain and agony, one day....

The reason that it is standard operating procedure to turn on the Tx FIRST is to avoid spurious signals to the Rx, which can cause the servos to overrun their limits and damage themselves.

ALWAYS turn on the Tx first, then the Rx, AFTER checking the board for frequency use.... Believe me, you DO NOT want to find out you're on the same frequency as someone else using your method... It may earn you a fat lip....

Bill

This practise has actually saved me (or the other guy) twice! With the advent of park flyers, it turns out that in a nearby grass field a couple of kids were flying their park flyer totally oblivious to the fact that there is a public field nearby and a frequency board rule in place. And the second time one of the guys in our field had simply forgotten to put his card in. With an FM receiver I understand what happens when there is no signal as servos move all over and you could could potentially ruin something on the servo or plane. When there is someone else's signal, your servos would react and in that case there is a possibility that you could go beyond their travel limit and strip a gear or break/pull a horn. With a PCM receiver when there is no signal they do not react so no chance of damage here. However when there is a signal, well your servos could react and you could get into trouble like an the FM case before. Your point is well taken but I rather have my plane experience glitches and potential servo damage on the ground as opposed to in the air. In all what I really need is a frequency checker but until I get one, I will be following my practise.

When you receiver is turned on first the AFC circuit is wide open to any and all RF in the neighborhood. Sooner or later one of them is bound to be full throttle. :-(

And here all these years I thought PCM receivers were FM. FM is how it is modulated, PCM is how that modulation is coded. Receivers are either AM or FM. If they are FM they can be PPM or PCM but not both at the same time, some transmitters on the other had can programmed to transmit in either PPM or PCM mode. At least that's how I thought it worked. Or have the semantics confused me?

RS

Tower Hobbies sells a 72 MHz frequency monitor, if you are operating in North America, for around $50. In a couple of replacement servos purchased, you have paid for the frequency monitor.

Not all servo damage that can cause your model to crash is apparent on the ground.

Ed Cregger

You're correct as a PCM receiver is indeed an FM receiver. My point is that a PCM receiver does not misbehave when there is no signal (basically the fail-safe mechanism). As for my practise, the throttle could potentially go full on but that is OK because my engine is not running anyway.

In regard to Ed's comment - yes the purchase of frequency checker in on my list of things to do. In two incidences that I've experienced my servos merely moved according to the other guys transmitter. No damages though because, first servo centers and travel amounts do not vary significantly from one plane to another and second I turned the switch off after I noted the signal to my PCM receiver. This is to say with my practise I momentarily turn the receiver switch on & off to check for signals and I do this with my PCM equipped planes.

Just because YOU have not suffered any ill effect YET, does not mean that it is the right way to do things, PCM or not. Bottom line, no matter what your rationalization is, turning on the receiver first is the WRONG way to do it, period. I'm happy you have gotten away with it so far, but if I saw someone doing that at the field they would be corrected. If it continued they would be reported to the club's safety officer. Take a look at some of the flap/spoiler setups out there and tell me they couldn't be damaged by being controlled by someone else's radio.

Jim

I see your point with flap/spoiler but I don't use them or have them on my PCM planes anyway. The same safety rules state that one ought to put his card in when flying and people should not operate a radio in a nearby field but like many rules, they're broken sometimes. At this stage I respectfully disagree with your rule as it pertains to my special case. In future I might be proven wrong as I gather more data but so far my procedure has saved me (or the other guy) twice in a

3-year period.

It's sad to say, but there are no rules or laws that state that someone can not fly in a field next to a cub field. They have as much right to use the frequency as you do.

I see no harm that snipped-for-privacy@yahoo.com can do TO anyone if he sticks to what he says, let him be. No hard feelings to anyone unless OTHERS safety is involved. mk