redtail53

My Feedback: (4)

Earlier this week, I was flying a nice Sig King Kobra with an os .61 sf, with futaba FM radio. I bought this radio new, and have never had any trouble with it. Anyway, on my second flight I started a turn and the plane just kept on going. No response on any channel. Plane went in full bore. After retieving the mess, I checked the 4.8v batteries voltage, it was 5.3v. So I'm left with either the switch going bad mid flight, or radio interference. If it was radio interference, would a pcm radio system have made any difference?
The club I fly at is next to a fair grounds, drag strip, go kart track and nascar track. Other members at the club say a lot of two-way radios are in use near by. And that some type of "harmonics" may have been to blame. Any help is appreciated. I feel that is it either safe to fly or it is not. I build most of my planes from kits, or plans, and have a lot of enjoyable time, but still lots of time, it each plane, not to mention $$. I would like to take all precautions possible to ensure I continue to enjoy this great hobby.
As stated earlier, all help appreciated.

Thanx, Jim

Rodney

You will get a lot of different opinions on this. In reality, both PCM and PWM are usually FM and both are equally susceptible to interference. It is just that PCM will sometimes mask the problem so you don't know its there until its to late. On the other hand, if the interference is very spasmodic and rare, you will fly right through it never knowing it occurred with PCM. In general, my opinion is that PCM does not give enough edge to pay for itself. I fly many big birds with magneto ignition, all on PWM, with no problems.

RCPilot100

My Feedback: (4)

You are probably going to start another firestorm discussion concerning PPM vs PCM, but to answer your question, I doubt that had you been using a PCM you would have had any better results. When you say that you lost all channels, it sounds like you had some type of failure. Failure, such as a busted antenna, bad power switch, or many other things that can happen will affect you regardless of receiver type. You don't say how old your radio system is, but the first question I would ask is when was the last time you had it checked out. I regularly have all my Rxs and Tx checked out.

Dan

MrDHEJ

My Feedback: (5)

Losing an antenna would cause the PCM reciever to go into fail safe, so would interfearance or low battery voltage.

It won't however save you if the battery is disconected via bad switch or being unplugged.

Dave Bowles

My Feedback: (7)

In this case, regardless of what system used it would have crashed. If it was interference it would Probably crashed in fail safe mode , but usually interference on PPM or PWM which ever term you prefer, would show signs of glitching or intermitting control . complete loss of all channels is generally a hard failure. If the signal would have cleared you would have regained complete control right away for PPM, If it cleared in PCM, you may have to wait a moment to regain control.

FLYBOY

My Feedback: (11)

Has your switch gone bad? Has it been wet? I have had them fail in the air. I change them usually after every season. I don't like a $4 taking a $500 plane.

Also, I do belive PCM is better. I have been shot down on FM and have been flying PCM for 15 years. I saw 2 gliders in a contest flying side by side, on the same freq. Neither one had a problem till one plane got right over the heads of both guys, who happend to be standing about 30 feet apart. The plane that went over them tucked into the ground then. They flew together about 7 minutes. No PPM would have stayed up when the guy on the ground turned on. I have also had guys turn on while I was flying my PCM and their PPM was going nuts on the ground and I was OK.

Just my experience. I still have both PCM and PPM though. Some planes just don't require the expence of PCM.

OOPSIDIDITAGAIN

My Feedback: (8)

My quesstimate is a failure of power to the receiver as described by everyone before me. What I'm alittle confused about is the general concensis that there is little to no difference between FM and PCM.
It's always been my understanding that PCM offered a stronger narrower band that was less susceptible to interference due to it's smaller area in which interference had a harder time finding and overwhelming. I know it sounds like I've been blinded by all the bells n' whistles radio systems have to offer, but someone please steer me in the right direction and put me out of my misery. Anybody for control line? chuckle.

Bonefrost

My Feedback: (6)

I've done away w/ some of the switches on my trucks.Too unreliable.
Does anyone know of a reliable switch?
Thanks,
BNZ'

sfaust

My Feedback: (11)

Just to clear up an old wives tale...

When the interference clears up in either PPM or PCM, you immediately regain control. There is no difference between then in this regard.

There is no delay with PCM before you regain control. In PCM, the receiver is designed to come out of hold/failsafe on the first good frame it receives. That means, as most there is a slight delay of a few milliseconds, which is insignificant and not detectable by the pilot.

I have verified this with JR and Futaba engineers.

LQUAN

My Feedback: (17)

RedTail53,

I had the exact same incident as yours a month ago and lost an antique Pacific Ace. I was using a Futaba 8AUP (PCM) at the time. As an RF/Microwave engineer, all I can tell you is that it doesn't matter which type of radio system you have, when interference finds its ways to your narrow band, your plane is as good as gone! Interfence has a tendency to stay for several minutes not seconds. Here is a scenario that caused your reciever to switch to fail-safe mode: If you look up your Frequency Chart, you will see the frequencies are 20KHz apart. For example, I am on channel 19; frequency number 72.1700MHz. If both of the upper and lower frequencies, 72.1600MHz and 72.1800MHz are being used, my reciever will switch to fail-safe mode. If only either one upper or lower frequency is being used, my reciever can still manage to distinguish the splatter from that signal. The signals in between our rc frequencies are frequently being use by train, or pager, or crane operator, ect in the area. Our rc recievers are not good enough filter out splatters from both upper and lower interference at the same time! Splatter happens on every RF transmitters, rc or not. This tells you how well the AMA is working to keep our 72MHz band clear!!!

The best way is to have a scanner to check from junk RF before you take off. I just recently bought a Yeasu VR-500 for $200 as a low cost flight insurance. You can get a Icom IC-R2 or IC-R10 also. They all do the same thing. The VR-500 and the IC-R10 can check on narrow band at step down to 0.005KHz while the IC-R2 can only go down to 5KHz step wide band. Remember, our rc transmitters are working at narrow band. Always perform range checking prior each flight on expensive airplanes. You will find out quickly if there are interference when you are 200ft+ away from your plane. Sorry about your loss.