I am getting into larger aircraft, .60 & .90, And thinking of purchasing a Futaba 7CAP transmitter. Six of my seven planes have Futaba or Hitec radio gear and I presently have a Futaba T6EXAP. I just finished a Seagull Edge 540 .60 and want some more advanced mixing.

My question: Do I want a PCM of FM receiver and why????
Presently all my receivers are FM but some of the pilots at my club strongly recommend PCM for larger and 3D aircraft????

Thank you....

I fly FM in all my planes.

My current fleet:
LT-40 TH .75
Pacific Aeromodels Edge 540 TH .75
Fliton Edge 540 TH .75
Ultra RC Giles 202 w/MVVS 2.15 gas
CMP 3D Giles TH .75
World Models 80" Extra 300S w/G-62
Great Planes 1/3 scale Pitts w/Fox 3.2
Kangke Laser 87" w/G-62
World Models 90" Extra 330L w/3W-80XI
Carden 30% Cap 232 w/3W-80XI


Never saw the need for PCM. I'd rather have it twitch or wiggle if it gets hit anyway. That way I know it. With PCM--your just locked out and you sit back and wait untill it decides to let you back in. At least with FM you might have some control or intermittent control and can manage to fly the plane through the interference.

But, honestly:
When was the last time you were REALLY shot down by outside interference? I really don't think it happens as much as everyone claims.

I think mostly pilots thumb their airplanes and then say, "I got hit." Because they can't admit they made a mistake.

I'm in my 10th year in this hobby. I've been shot down by interference exactly ONE time. Been shot down by another TX ONE time. Thats it. All the rest of my crashes have been my fault for thumbing it in.

I'm not saying interference isn't out there. I've been hit before--lots of times--but not enough to knock me down.

If all your doing is 60 and 90 size stuff--FM receivers work fine. No sense in spending the extra money on PCM. You don't need it. I don't even use it on 27% and 30% planes with gas engines. Been working fine for many years.

If FM didn't work--then the industry would do away with it. It's that simple.

Same here I have been flying FM for a very long time now and not once have i been shot down. I have been hit but that was corrected when I yelled out, the guy then cut his transmitter off.

I guess the one of the reasons I have not swapped to PCM is because my FM is still working fine for me. I have used this radio for helicopters, sailplanes, small planes, .90 size planes, extremely fast planes and now bigger 50cc gas.

If I had to buy a new radio gear I would maybe go with PCM just t have it though i guess. Just I haven't not had to buy so thats why I am still using FM.

Either one you go with I think you will be okay and cant really go wrong.

One thing u mentioned that your club members strongly recommend for 3D and larger airplanes. The larger ones i heard people say that before due to ignition issues or vibrations. But I wonder why they strongly recommend for 3D? 3D planes still fly the same as the others.

To clarify the large plane issue. All of their planes are Gas engines which does bring up the ignition issue. For now my only decision is which receiver I buy. The 7C Tx can be switched to either FM or PCM.

I'm going to put it in my Seagull Edge 540.

Just get the FM for your smaller plane. PCM really gets usefull in Gas planes and Helicopters.

I check for interference with FM and then go with PCM on High dollar models. Both work but I think PCM maybe a little more precise and mask some FM(PPM) interference.

Nearly everyone that flies pattern uses PCM. I actually asked some top FAI pilots if they could tell a difference in then Futaba recievers(319/2048) and two of them said definately. They both claimed they had to add expo with the more sensitive RX.

For 60-90 I'd probably go FM/PPM.
BTW both are FM, they are just PPM and PCM.

I wouldnt get to carried away with either, I think spectrum 2.4 ghz will be the future.I just hope I just hope I only have to buy RX's and Module for my 9C.


rcpilet I see you like the Tower 75, Great engine that works as well as any OS I have ever owned.

Thats completely wrong. I'm sure this is what the guys at the local field are telling you---but it's completely wrong. Not every "expert" at the local field knows what he's talking about.

PCM will not STOP ignition noise. It can mask or hide the ignition noise for a period of time. Eventually, the RX will pick up enough ignition noise and lock out. Dead plane.

If you want to use PCM on a gas powered plane--then you should be doing all your initial range checks with an FM receiver. The FM recevier will not hide anything. If you got glitches--you'll know it. Thats exactly what you want. Find and diagnose any glitches BEFORE you put it up for the maiden flight. If you have any problems that show up during the range checks with the FM receiver--then you find it and fix it.

Only AFTER you have a solid range check with the FM recevier should you go ahead and switch out to the PCM receiver.

Using a PCM receiver to cover up an RF problem is going to cost you a plane. Probably sooner, rather than later. []

I highly recommend you use this site to your advantage. It sounds to me like the guys at the local field already have their minds made up. And it sounds like they have some questionable practices. (like using PCM receivers to hide RFI) Might sound good while the guy is standing there telling you, but you don't have to take their word as gospel just because they are local and they've been doing it longer.

Go over to the Giant Scale forum and perform a search using the search bar at the bottom of the forum page. Search for RFI or PCM or PPM or FM or interference or ignition. Read as much as you can in that forum. There are a lot of very experienced members on this board and they know all the ins and outs of RFI. It's been written about probably 1000 times on this board. You really shouldn't take my word for it either. Go do a search in the Giant forum and read what other guys are saying. Get the information yourself and read it yourself instead of taking someone elses word for it. Then you can read it and decide whats BS and whats good info.

RCPilet, Thanks for the knowledgeable advice. I just read your post on PCM from 3/20/06 about the antenna mounting.

In my Edge 540 I have been having "Rudder Flutter" for two weeks. I have changed everything(one at a time). Different RX, TX, Battery, Switch,different freq,servos, leads,crystals and wound the 24" leads. Still had the problem except with a PCM RX. Which I felt only masked the problem, I wanted to know why??. On Saturday I tried another RX and the antenna was outside the fuse, rather than down the internal tube which runs it to the tail containing 3 servos and parallel to 9 wires and comes out the bottom and contacts a metal plate that holds the horizontal stab wires. I went back to my RX and if the antenna is in the tube I have the Flutter. If I take it out behind the cockpit to the Vertical stab. no problem. No matter how I arrange a tube in the fuse. to the tail I get the interference so outside it stays!!!

This is the first plane I have that has three servos in the tail so it's the first time I've had this problem. It now make perfect sense.

Thanks again for your advise. I think the FM Rx is the way to go for what I am flying at this time. Check My Planes on My profile page.

It really depends on your preference. There is no question that the encoded signal of a PCM receiver is more reliable and much less likely to recieve interference than PPM. Thats a simple fact due to the way the things are built and why the radio mfg's started making them. Now, do I think you NEED to put a PCM receiver in a small plane? No, not if you are willing to take the risk and you dont have interference problems at your field. If you are not willing to take the risk then spend the extra money and go PCM. There is a REASON why pattern and guys that fly big gas planes use PCM, they are more reliable. If they weren't they would be flying PPM.

FM has been working for years, and at some fields there is absolutely no problems with it. If you are only flying one place and there are no issues, sure fly FM on a small plane. I do. But I am being cheap and taking a risk to save $100 on a plane that costs <$500. If I wanted to decrease my risk, I would go PCM. That is what I fly on planes that I cannot afford to lose to a rogue hit.

This is all about to be moot anyway. Rumor has it that an aftermarket drop in Spread Spectrum Frequency Module and receiver for Futaba and JR systems are supposed to be coming out sometime in October. If/when that happens frequency and interference issues will become a thing of the past. And according to the website that is claiming release next month, the module and receiver will cost <$200.
http://www.xtremepowersystems.net/xtremelink.php

First off, do a little reading. http://www.torreypinesgulls.org/Radios.htm

There is no FM/PCM, they both use an FM carrier, they are different on how they encode the information sent to the reciever.

Ken is exactly right though, "fixing" a problem by using PCM isn't fixing anything its covering up a problem that will come up and bite you in the butt later on.

Really depends on where your flying.
When i started flying in kansas, lots of people were having fits with FM, supposidly because of a pager tower nearby. So i started with PCM and havent looked back. Since moving to Dallas, then Houston I havent seen anyone have trouble with FM like i did at that field in Kansas.

edit,

I do know that with my Futaba, if someone flips on their FM TX, it wont touch my PCM RX.

I use Both.... at the same time!

Our field is quite remote from any interference. I Do not know of anyone getting hit other than a TX turned by accident or stupidity. It's nice to know that a PCM would not be affected by this.