PCM ?
08-22-2002, 04:44 PM
#1
Banned
Thread Starter
Join Date: Jan 2003
Location: gone,
Posts: 4,923
Likes: 0
Received 0 Likes
on
0 Posts
PCM ?
PCM encodes the desired servo positions in a different manner than standard FM radios (which are "PPM")
Almost any PCM capable transmitter also has PPM capabiity, which means the "higher end" transmitter will function with the "lower end" recievers, with either the flip of a switch f a couple of button presses to set the signal mode.
The actual FM transmitter section is virtually identical. The difference is in the encoding, not the signal strength... just what's in the signal. (That's why its so easy to change modes)
The PCM radios have small computers in both the transmitter and the reciever. (one reason almost any PCM radio is also a computer radio... it has to have some computer capability to generate the encoding.)
The PCM receiver, uses its computer to determine:
Is there an FM signal on the tuned frequency?
Is the signal valid? (PCM encoded and not scrambled by interference)
If either is not true, the computer will check if the last valid signal included a "failsafe" setting for one or more channels. If the failsafe setting is present, it will mofe the appropriate controls to those settings. If the failsafe setting isn't encoded... it will set the controls at the last valid signal's "desired" position.
By setting failsafe positions, such as: Throttle to idle, elevator to slow flight neutral, ailerons neutral and rudder slight right turn, (some will only set those 4 channels... some will allow every channel to be set) you give the plane a chance to self-recover into a circling glide-speed (free flight style) descent. (if the plane is inherantly stable...) The reduced throttle setting helps to prevent as much damage as would be possible at full throttle, and is very important. (no guarantees... but it sure won't hit as hard.)
Most modern PCM recievers also have a battery low voltage sensor, which will set the throttle to the failsafe when the RX battery is dangerously low. (a sure indication that its time to LAND NOW! ) Note that if you use a 6 volt RX pack, the voltage failsafe won't kick the throttle down until its too late. And... if you didn't set the failsafe for the throttle... it defaults to hold the throttle... (and I've seen that one come up. Its ugly when the detected "hold" is full throttle.)
If yo use the PCM capabilities correctly... they are very worthwhile. If you don't actually set the failsafes... Why bother buying it?
Almost any PCM capable transmitter also has PPM capabiity, which means the "higher end" transmitter will function with the "lower end" recievers, with either the flip of a switch f a couple of button presses to set the signal mode.
The actual FM transmitter section is virtually identical. The difference is in the encoding, not the signal strength... just what's in the signal. (That's why its so easy to change modes)
The PCM radios have small computers in both the transmitter and the reciever. (one reason almost any PCM radio is also a computer radio... it has to have some computer capability to generate the encoding.)
The PCM receiver, uses its computer to determine:
Is there an FM signal on the tuned frequency?
Is the signal valid? (PCM encoded and not scrambled by interference)
If either is not true, the computer will check if the last valid signal included a "failsafe" setting for one or more channels. If the failsafe setting is present, it will mofe the appropriate controls to those settings. If the failsafe setting isn't encoded... it will set the controls at the last valid signal's "desired" position.
By setting failsafe positions, such as: Throttle to idle, elevator to slow flight neutral, ailerons neutral and rudder slight right turn, (some will only set those 4 channels... some will allow every channel to be set) you give the plane a chance to self-recover into a circling glide-speed (free flight style) descent. (if the plane is inherantly stable...) The reduced throttle setting helps to prevent as much damage as would be possible at full throttle, and is very important. (no guarantees... but it sure won't hit as hard.)
Most modern PCM recievers also have a battery low voltage sensor, which will set the throttle to the failsafe when the RX battery is dangerously low. (a sure indication that its time to LAND NOW! ) Note that if you use a 6 volt RX pack, the voltage failsafe won't kick the throttle down until its too late. And... if you didn't set the failsafe for the throttle... it defaults to hold the throttle... (and I've seen that one come up. Its ugly when the detected "hold" is full throttle.)
If yo use the PCM capabilities correctly... they are very worthwhile. If you don't actually set the failsafes... Why bother buying it?
