Conference vmszoo::rc

    Anker,  
    
    The best [and easiest] defence against 3IM is distance.  We [the
    1/8 AF] started establishing and enforcing the use of flight stations
    separated by a minimum of 30' about 6-7 fly-in's ago.  We'd had
    no 3IM problems as yet and didn't want any!
    
    Since then, all valley clubs have followed our lead and establiched
    pilot-boxes, 30' apart, at all the local sites and, as a result,
    3IM has become a thing of the past locally.
    
    Of course, at our meets, frequencies are also sorted to specific
    flightlines to help prevent or minimize 3IM but our experience has
    been that the 30' separation, more than any other factor, is what
    has effectively eliminated the problem.  The only thing required
    is that pilots refrain from standing right on top of on another
    and maintain at least a 30' separation between transmitters...just 
    a little pilot discipline and you got `er made.   
    
    Kay and Kevin got a good look at our setup and I'm sure they'll
    be glad to pass it along.
    

      :
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    
    RE: .0 - No notes on 3IM????  Couldn't have looked very hard! :-)
    
    I've only been hit by interference once at CMRCM and it was a clear-cut
    case of 3IM - I was on 54 and two other planes were up - 52 and
    50.  I learned to respect 3IM at that point.
    
    I've heard rumors from time to time that lots of hits seem to occur
    at the left end of the field over the pond.  I also wonder how
    much interference we are going to get from the Microelectronics
    Center at the top of the hill when that really gets into operation.
    
    I've seen at least three instances where a single adjacent transmitter
    has shot down a plane, clearly a case of a receiver or transmitter
    being out of tune, or a transmitter putting out nasty sidebands.
    Did you happen to catch the channel number of the other guy that
    was up when your friend had trouble?  If adjacent I'd tell your
    friend to get his radio gear checked out just to be safe.
    
    Bill

    A couple of more questions::
    
    Lets assume you turn your receiver on but your transmitter id off.
    Is is reasonable to have the servos jitter, and perhaps jitter quite
    a bit?
    
    Turn your transmitter on, but the antenna is NOT extended, and is
    within 3-5 feet of the receiver. Is is reasonable to still see lots
    of jitter?
    
    If I make this same test at home, or at fields I've previously flown
    at I've never experianced this problem.
    
    I bought a PCM radio, and I'm sending back my old radio to futuba.
    
    Does anybody have any experiance with sending a radio back to futaba
    for checkout?  If so, can you fill me in on the details such as
    local service centers? (besides CA.), cost, time it will be out,
    plus any other details you wish to share.
    
    
    				Thanks, Dave
    

    Dave, Dave, Dave , DAVE!
    
    	If your servos jitter with the transmitter 5 feet away and the
    antenna collapsed you have a totally useless receiver. You obviously
    don't know how to do a range test. Collapse the antenna and walk
    at least 25 paces away. You should still have full control of the
    model. If you don't you cannot fly.
    
    Anker

    Another thought. At the AMA NATS this year there was a consideral
    amount of radio interferance in PYLON. I use this example because
    there are usually three or four flyers on the line at the same time.
    Also in PYLON certain frequencies are eliminated so ther can be
    no 3IM problems. So what was cousing all the problems? It is being
    looked into by the AMA. It's starting to look like AM and FM don't
    mix well with AM being the looser. There is talk about eliminating
    AM at some time in the future. 
    
    None of the FM's had any problems. 

    This is just a thought, but does anyone have any information on
    skip with our radios.  I know that the frequency is a good candidate
    for skip and that power is not a requirement.  However, our antennea
    (sp) is not the most efficient so that could reduce the skip potential.
    Many people have talked well over 1000 miles on 5 watt cb, so 3/4
    watt should have some potential.

		________
	 /	  __|__  
	=========[_____\>
	/	__|___|__/  BREAK A BLADE,
			    Ken    	

    
    Anker, it appears that many people, even supposedly experianced
    flyers do not know how to range check properly. As I was told by
    several people that what I was seeing was OK providing that when
    I extended my antenna, the problem went away, which it did. I'll
    assume from this point forward that you are correct, and that
    previous info was wrong "crashing wrong"
    
    
    						Dave
    

As one who has bench tested more than one rc receiver, I can say
without qualification; don't fly with that RX.  Actually, there are
several things that can be causing your problem.  One thing can be
tested by simply turning your rx on without the tx.  Any shaking or
movement in the servos, apart from the very obvious jittering of an
interferring signal, is due to a problem in the rx.  Usually, this
can be cleaned up with a re-alignment of the IF.  As I've said
elsewhere, the AGC on the typical rx is quite powerful, and will
cause feedback/oscillations/noise if not properly designed or tuned.

If your rx remains quiet, you probably have a fault that has reduced
the sensitivity of the rx.  This could also be due to IF
misalignment, a defective RF or converter stage, or, most likely in
the absence of a previous crash, the antenna becoming disconnected
or broken somewhere along its length.

The only good test for a receiver is as Anker says; walk of 50 or so
feet and check the controls with the tx antenna collapsed.  Should
be solid.  Additionally, I always turn the tx off, then on again to
check for instability, oscillation, or some other glitch that may
affect the ability of the receiver to "grab" the tx signal.

    re .-1
    
    Be sure there aren't any transmitters on nearby in the pits on
    adjacent channels. I've seen the "jitter" occur if you turn on
    your receiver but not your transmitter, and somebody on an
    adjacent channel has their transmitter on a few feet away. That
    kind of interference is not necessarily bad, so long as when
    you turn on your own transmitter with the antenna collapsed
    the jitter goes away. The 50' range check is the best check.
    But please note that you can get a big difference in range with
    just a couple inches of antenna. If you have your channel cards
    clipped to the bottom of your antenna, then you can't collapse
    it all the way, it's out about 4-6", and that will make a big
    difference in signal output. Collapse the antenna all the way,
    or go out further on the range check.
    
    Dave

    If other transmitters are on on an adjacent or near adjacent channel,
    it is not adnormal to get jitter with your receiver on and TX off.
    This is because the AGC circuit in the reciever cranks the gain
    wide open if there is no carrier on its channel.  Then it is very
    subject to glitching from other transmitter signals that get through
    the filters.  What Anker says is true if no other radios are turned
    on during the range check.  
    	Also, it is my experience that FM is the loser when AM and FM
    are mixed.  Unless the receiver is a dual conversion type, I wouldn't
    fly FM at our field.
    

    [moderator, this is the best place I could think to put this...]
    
    The back page, "Abort, Retry, Fail?" of this week's "PC Magazine" 
    (April 14) has a cartoon:
    
    Next to the building with a sign "Wireless LAN Research Inc."
    is a shop - "Walt's Remote Control Model Airplane Shop"
    with....  R/Cers' running in panic!
    
    	Dave.

    Most of the wireless LANs we're testing with Pathworks in LJO2 are
    infrared. I'm sure there are some others out there but infrared works
    good in most line of sight applications. Sort of like mini microwave
    towers on top of the cubicles 8^)
    
    The Hams have been doing work in this area for many years and we
    coexist with them pretty well.
    
    Anyone know what bannds the transmitting style LANs would be allocated
    to?