What is the difference between AM and FM channels. I was looking at a really good deal with an engine, all servos and radio gear and airplane for pretty cheap but the owner said it was AM. Is this any different good or bad or what? Thanks Xleem

Both AM and FM use the same 72Mhz frequency band.


FM signal changes the frequency back and forth between the carrier frequency and a shifted frequency that is very close the the carrier frequency.


An AM signal has a constant frequency but the signal is turned on and off to modulate or the signal.

Modulation is just a fancy word that means the transmitter transforms your stick movement into a language that the receiver understands. It's kinda like Morris code.


It's called Pulse Code Modulation. I explain it more in-depth [link=http://www.hooked-on-rc-airplanes.com/pulse-position-modulation.html]here on my website[/link].


AM uses signal on or off to represent pulses. FM switches between two frequencies to represent the pulses on or off.

Most radios today are FM.(or spread spectrum) Some say AM is more prone to interference, although I'm not 100% convinced that is accurate.

AM transmitters are limited to four channels, that's probably the biggest drawback I see.

If it's a really good deal I'd say get it. They work just fine.

But if it's a mediocre deal I would hold off and get FM or 2.4Ghz.

I hope this helps.

Thanks I appreciate the advice. I think I'll opt to get it.

It depends on the frequency. If it is a narrow band AM in the 72mhz band, it will probably be OK. I wouldn't put it in a 1/4 scale, but for close in flying it should be OK. If you want more than a 4 channel setup though, I would go with the FM or PCM radios or if the pocket book will allow, a 2.4GHz setup.

The AM is old iron. Doesn't mean it won't work, but it won't have any of the neat stuff avaiable now. Like dual rates, amd expo, let alone any computer mixing. It is pure basics, maybe with reverse on the servos. I have a Futaba FG series TX and Rx in front of me that has the gold ama sticker, A mandatory valadation to fly at any club field. It even has a RF module for the TX so you can easly change frequencys, if you can find another.

IF, and it a big IF, the Tx and the RX are compatable, Gold stickered, and you can get it for $20 or so, it may make a good first radio. You will have to get new batteries, which will run you anothe $40 to $60 bucks or so.

My suggestion would be to pass it up and spend the money on a more current radio. Nothing like a radio failure on your first flight to sour the experience. For under $200 you can get a new 6 chan computer radio with receiver and four servos. http://www3.towerhobbies.com/cgi-bin...=LXRXF5**&P=SM

It's hardly worth putting up with the headaches of the old iron.

Don

Agree with camp. Get the plane if you want it and it is a good deal, but if it was me, I'd ditch the radio.

I didn't have any problems with an AM radio . I purchased it with a a used model.
It was an old airtronics. It had a gold AMA inspection sticker on it.
I flew the model until i crashed it....it was the radio and not pilot error

The radio system that comes with R/C cars are AM. And don't say a $500 savage is worth less than a $500 airplane.lol

sorry...

Yes but a $500 Savage isn't going to fall out of the air and cause possible property damage or injury to bystanders if it loses a signal.Nor is it operated from a great a distance as airplanes are.

I garantee ya, if you ever had a runaway savage going into traffic...you'll have a differenent perspective.
Or if you ever been hit by a 15lb object going 40-45 mph.

There's a fail safe incase of runaways (Low batteries or antenna not being raised).
It dosen't came out of the box.

Where did you get the idea that only 4 AM channels are available? I have a couple of Futaba AM's with 6 and 7 channels. If speaking of 4 freqs/channels within the band, that is also not true. Not current production but still out there.

Morris Code? MORRIS code?????

Yeah, he was Morse's cousin I think. On his mothers side. http://en.wikipedia.org/wiki/Morse_code

I've been wrong before![X(] I made that comment because I personally have never seen an AM radio with more than 4 channels. So I assumed that's all that was available. Guess I shouldn't assume things huh?

If you don't mind sharing, what are the models of those Futaba radios you speak of?


And Morris is my cat...

Does Morris know code?

AM radios (partial list):
FP-5FG
FP-6FG
FP-7FG
FP-6FN
FP-5FN
FP-8JN which can be either AM or FM depending on the installed module
These can be found on the Futaba manuals site http://www.futaba-rc.com/manuals/index.html

Thanks!

I really appreciate you correcting me on that. I really don't remember how I got that notion in my head, but I'm glad you set me straight!


Matt

Nobody (that I know of) except maybe some of the "toys" are using AM in new gear these days and although AM usually works fine, FM is a better modulation scheme.