expo

My Feedback: (20)

Buncha rx questions:
Will a futaba crystal work in a Tower Hobbies 3000 rx?
What does dual and single conversion mean?
How about + or - shift?
PCM over FM--is the only advantage the failsafe feature?

redfox435cat

the tower system 3000 rx is a R127DF Rx. look under the label. So a futaba duel conversion RX crystal will work.

the single conversion crystal filters the signal once and dual conversion crystal filters the signal twice and there use depends on the Rx. The Rx you use depends on the Tx. All you need to know is use a dual conversion crystal in a dual conversion RX and a single conversion crystal in a single conversion Rx.

plus and minus shift refers to the pulse shift of the digital signal to the servo. this is dependent the manufacturer. futaba\hitec negative and JR\air pos. most of the servos made today can accept either. but the pos or negative shift does have to match the Tx. Basically if you have futaba stick to futaba. if you have JR stick to JR. unless you know it'll work. hitec most of the stuff is shift selectable.

Personally in aircraft I don't see the point of failsafe. cutting the throttle can reduce the risk but when the **** hits the fan the plane is gonna break and if it hits someone it's gonna hurt. Guys swear up and down by them, others laugh at em. I'm indiferant. I'd probably buy more PCM RX if they offered a PCM flight pack, but I'm cheap so I stick to FM for most my stuff. The PCM stuff I have I have becuase it came with the Tx and use them in my more valuable models but have yet ti set the failsafe becuase I've seen it bring down a couple models becuase of a mis setting.

Rodney

Shift has absolutely nothing to do with servo signals. A positive shift receiver sends the identical same signal to the servo as a negative shift receiver does and visaversa. Shift is the direction the frequency deviation of the transmitted signal takes from the "no modulation present frequency" to the change in frequency with a data pulse. Positive shift causes an increase in transmitted frequency (about 5KHZ) and negative shift causes a coressponding decrease in transmitted frequency during the data pulse.

aerowoof

on ignition engines pcm rx will still work where the fm rx is picking up and reacting to ignition noise.the correct thing to do is to get rid of the noise causing the problem for the fm rx but a few people are just using pcm rx as it is easier and quicker.

expo

My Feedback: (20)

Interesting responses--thanks. Aerowoof, do you know how the interference would be eliminated without the PCM?

Rodney

PCM does not eliminate interferance, it just masks it. If the interferance is minor, you may get by but you may just be asking for trouble unless you first find what is causing the interferance. Note that PCM is FM, the same as PPM which many mistakenly dub as FM.

aerowoof

pcm or pulse code modulation sends a coded signal to the rx,if the rx recieves a signal without the code it ignores it and waits for a correctly coded signal,obviously this is a shortened version of what really goes on.
there are alot of things to do to eliminate noise that are different for ignition engines .
metal sheild covering the firewall
all wiring kept as far away as possible from the engine
use a r type plug
no metal pushrod to the engine.nyrod type.
kill switches[two] mounted on engine side of metal firewall shield.
bosch plug cover
no metel to metal contact
there are other things to do but can not remmeber all of them.these are the major things to check.