Conference vmszoo::rc

    Hi Walt,
    
    	Listen to your son. If you go to a race, you'll see two things.
    
    	1. Virtually all of the controllers are the pistol grip type.
    
    	2. Probably 90% of those with be the Futaba "Magnum" series
    	   ones. Either the Magnum Junior, or the Magnum Sport.
    
    	Get the pistol grip type because their easier to drive. Not
    	too many companies make the stick type anymore and future
    	repairs (if necessary) would be easier. Can't think of anything
    	off the top of my head where you'd use a third channel under
    	normal circumstances, but who knows what they'll come out
    	with in the future. The Futaba's are excellent radio's.
    
    
    Steve

    
    	Walt, 
    
    		From what I've observed in rc off road racing is that
    wheel radio's are the only way to go . The first radio i bought
    was a Futaba "Magnum Jr." and I've added others to this list since
    then . The only use for a three channel radio is in independent
    front and rear wheel steering trucks that require 3 channels, one
    for each axle and one for throttle . Also , there's a few models
    of trucks that have a 3 speed transmission that would require a
    three channel radio . I've been going to an indoor race track here
    since winter of "86" and have observed these radio's with the following
    results .
    
    		Both my and other racers Futaba "Magnum Jr.'s" and "Magnum
    Sports" have been excellent radios with minimum interference on
    at the starting line , while the worst radio (very sensitive to
    crystal changes and interference from other radio's nearby at the
    starting line ) was the "Challenger" by Aristo Craft . All in all,
    my favorite radio though is the "KO Propro EX-5" . the advantage
    of independent left and right steering volume , "Legal" crystal
    changing , and on the fly trim's that were easy to get to were it's
    best selling points . As far as it being on 27Mhz, I've participated
    in many races with radio's only two or three feet apart , and while
    other racers' cars were getting RFI and prematurely jumping off
    the starting line , MY and others radio's were rock solid .This
    is one radio that has made the grade for me !(and even won "A" main's)
    
    
    	So , I hope that this will help you in your decision if he's
    serious in racing . One more point of intrest , I don't know if
    the Futaba radio that your looking at is the new PCM type, but if
    it is , I would highly recommend it also .I just noticed that Futaba
    had PCM radio's in the latest issue of RC Modeler made just for
    rc cars . PCM is the latest and greatest in rc technology .I fly
    rc aircraft and this is the top of the line in "interference free"
    control . Unfortunately, so is the price ; about $200.00 .Whether
    you pick KO Propro or Futaba , you can't go wrong .
    
    						Keep em' Running,
    					
    							Carl
    

	re:.0

	Walt,

	I've been using a Futaba FP-3PG (Magnum) for a couple of years.
	It is an excellent radio and has some nice features as well as
	a couple of drawbacks.

	It seems that the radio was designed with gas powered vehicles
	in mind as it has a "warmup" function which, by throwing a toggle
	switch on the front, will cycle the throttle by a variable amount
	at a variable speed. Nice conversation piece when you're racing
	electrics. I've heard that the third channel, which is controlled
	by a knob on the front, can be used for movable wings/spoilers on
	the large cars (where the weight of an additional servo is of
	little consequence) or possibly perform a useful function on a boat?

	My primary motivation for purchasing this particular Futaba was
	the exponential response adjustments for both throttle and steering.
	I use this radio for 1/12 on-road racing which requires a rather
	light touch and precise control. I use a more conventional (ie no
	exponential control) radio for 1/10 scale racing where I find that
	that degree of control is not really necessary.

	Other regular features like separate left and right steering throw,
	thumb controlled dual rate steering, front panel brake and high
	throttle trim, and brake limit are all there. 

	Features unique to this model (compared to the other Futaba) include
	a swivel top (which is nice) and a removable battery compartment,
	you can put the pack in your pocket and connect it with a cord.
	The radio comes complete with a nicad pack. It comes standard with a
	75 MHz transmitter but the transmitter section is plug in and can
	be swapped with a 28 MHz transmitter section if you want without
	opening the unit. There is a three position throttle trigger
	adjustment with a special position for gas cars.


	On the down side....if you do put the nicad pack in your pocket it
	throws off the balance of the radio, well I don't like it. The
	radio is a bit heavier than most pistol grip types. You pay $50-$60
	dollars more than the Magnum Jr. (although the price includes the
	nicads and slow charger and micro sized receiver). The price should
	be getting down there with the introduction of the 3PB PCM, but who
	knows.

	If you plan on buying one for use with 1/12 or 1/10 electric, consider
	getting the "cheaper" servos (it's available with either the S131SH
	or the S132H). The S132H is smaller, faster, and lighter. The S131SH
	does supply significantly more torque.


	Chris

    Thanks for the info Chris.  It looks like my son has settled on
    the Magnum Jr. for his RC10.  Apparantly there was a RC show 
    somewhere not too far from where he lives, and he had the chance
    to handle both units and prefered the Jr.

    From what little I know, Futaba seems to almost have a lock on the 
    market for these things.  Anyone know why this brand is so popular?
    
    Now all he needs is this motor controller I am cooking up.

    Walt

    I had a chance to do some bench tests of the Magnum Junior last
    night as I was setting up my solid state speed controller to 
    this unit.

    I had designed my motor speed controller on the assumption that the
    idle throttle pulse width was 1.5msec, max fwd throttle was 2.0msec
    and max rev throttle was 1.0msec.
    
    I found that the Magnum, when in normal mode was set up to 1.5msec,
    with an idle offset adjustment range of 1.3-1.7msec.  Unfortunately 
    they program fwd to be 1.0 msec and reverse to be 2.0.   My speed
    control uses different numbers of MOSFETS for forward and brake/reverse
    so I couldnt just live with swapping a couple wires.   They do have
    a pair of servo reverse switches for steering and throttle so I
    switched it.  Unfortunately, the center idle point in the rev mode
    was 1.3msec, and is just barely adjustable to 1.5 if the offset
    is moced to the extreme position. Since this left no room for field
    adjustments, I elected to recalibrate my speed controller idle to 1.3msec.
     
    The Junior has nice maximum fwd and reverse adjustments (which they
    call maximum and minimum).  They also permit setting the mechanical
    throw of the throttle trigger to permit one of 3 fwd:rev throw ratios.
    1) equal throw, 2) 75% fwd:25% rev, 3)100: fwd.  This combination
    lets you set up the throttle for your particular speed controller
    and style, including how much forward throttle and reverse/brake
    can be applied.  This is not only useful to be sure you get 100%
    of what you intend to apply, but you can turn it down some for a
    novice and not have to worry about them having too much throttle
    while they learn.
    
    The steering has the usual racing tire control knob and electrical
    center control. I mentioned the reverse switch.  The unit also has
    steering drag adjustment and a steering sensitivity control, both
    of which are easy to dial in.
    
    The unit my son bought is in the 75MHz region (I cannot remember
    exactly what frequency).  One thing that I was unaware of is that
    FCC/US rules prohibits the user changing channels in the field at 
    these frequencies. The 27MHz units can be changed by the user by 
    purchasing additional crystals.

    Walt