Small Fry

I was lookin at towerhobbies, and still cant figure out the difference between an FM Radio and a PCM. Can someone clarify?

Rodney

PCM is FM as is PWM and PPM in most modern radios although all can be done with AM. All are just different methods of coding the information from the transmitter. For most of us, PWM or PPM is more than sufficient. There are a few places where PCM might have an advantage but is usually not worth the additional cost.

Unstable

the diffrence in FM and PCM is that FM is analog, and PCM is digital.

with a FM signal a "sinc pulse" is sent to the RX followed by the pulses for the servo... the stronger the pulse the more the servo moves.

if something were to degrade or strengthen that pulse the servo would move acorrding to what it received, not what was sent. hence interference.

in PCM the signal is converted into a digital modulation (on or off) and the signal is encoded.

if something interferes with this signal it would not decode properly on the RX side and that "packet" would be discarded and the next one used instead. hence no "twitching".

also with most PCM systems if you loose signal completely it can go into "failsafe" the servo can be programed to either freeze in the last know spot (in hopes of recovering from the outage) or defaulting to a set position (throttle kill on loss)

for most sport flyers the cost isnt really justifiable but if you get into large scale, jets, or other things were reliability is a must then its time to start looking into PCM.

Small Fry

So, for a beginner like me, FM will do since I'm a ways off from the jets and large scale. This is correct?

4*60

My Feedback: (41)

This is correct.

FLYBOY

My Feedback: (11)

One thing to think about on radios is that it can last your for a long time. I used my last one 15 years. This one will last at least that long. FM will probably be fine for you, but don't get a radio that is too small, because you will have to replace it quicker and cost then. If you get a good radio now, it will last a long time. I could still be using my old one, but I had to have the 9chp. It is the coolest radio I have ever used.

Small Fry

FLYBOY, I was thinkin about the Airtronics RD6000 Super. I think you said in another thread, it's a good radio, and others have recommended it as well.

Rodney

Smallfry, check out torreypinesgulls.org/Radios.htm for detailed explanation of the various types of codeing and modulation used for RC.

FLYBOY

My Feedback: (11)

I wouldn't have said that about Airtronics. Must have been someone else. I have had very bad luck with the 3 airtronics radios I had. Will never use them again. I fly only Futaba. Been using them for over 25 years with not one problem. I am sorry I don't know that particular radio. If the guys at your field can buddy box with it, it will probably work. I did just go look at it at tower and it dosn't look like a bad radio. It will last you and would be a good choice for you. Just make sure that the people around you have something compatible. Nothing worse than going to the field and not being able to hook up to someone for training. Handing it back and forth causes crashes.

mattebox

Side note: For some reason Tower Hobbies has the Futaba 8 channel PCM receiver R138DP for only $99 (same price as the smaller gumstick style 8-channel FM receiver R148DF). For those of you with high end radios, like the 9C, that can modulate both PPM and PCM, you might want to check this out. I've never seen an 8-channel PCM receiver so cheap. Is this normal?

http://www2.towerhobbies.com/cgi-bin/wti0093p?&C=LDN

FLYBOY

My Feedback: (11)

They are having a sale this month on it.