Receiver Choices

[RC Steve Sterling]

The 138DP is an 8 channel PCM receiver. PCM transmits a digital data stream
like a modem and the receiver has a microprocessor to decode it all.

The 148DP is an 8 channel PPM receiver. An old standby. PPM varies the width
of FM modulation pulses to communicate servo position.

The 149DP is a 9 channel PCM receiver.

PPM receivers see interference or low signal as some different pulse widths,
so they tend to cause the servos to jitter and jump and be pretty
unpredictable when there is a problem.

When PCM receivers get interference or low signal, they either just stay
put, or go to a pre-programmed setting, like low throttle, wings level.

PCM receivers generally have cost quite a bit more than the PPM receivers,
so the 138DP price is encouraging. There is much debate, particularly on
this list, on which is better/more reliable. PPM proponents say that they
see problems coming when the plane starts jumping around, and with the
warning, may have time to get down and solve it. PCM proponents say they
don't see as many problems in the first place, and would rather have their
servos do predictable things when faced with interference.

I run PCM in my pattern planes, PPM (cheaper) in my sport, funfly, float
planes, etc. No problem with either. Have seen others with failures in both
types of receivers. Because equipment does fail, you will get anecdotal
stories from both sides, but nobody has done a scientific study to really
determine which is better, and under what condtions.

-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of Brian Young
Sent: Friday, September 27, 2002 11:24 AM
To: discussion at nsrca.org
Subject: Receiver Choices


Im looking to buy a couple new receivers, flying
Futaba so thats my area of preference. I have an 8UAP
currently. I notice Futaba has available a new 8 CH
RX, 138DP for about $100, then they have 148DP for
about $130, and 149DP for $160.

Each of these receivers have the required capacity for
my plane. Can anyone enlighten me as to a method to
evaluate the price of the expensive one vs. the cheap
one? Does the extra money bring more reliability, etc?

The 138 is a new model, so may have the use of latest
technology, the other two have been around awhile so
maybe they are more of a proven design.

And if anyone has any spares they want to sell I may
be interested.

=====
Brian Young
Tulsa
b4598070 at yahoo.com
918-745-6046h
918-838-0900w

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