Conference vmszoo::rc

    Bummer, Dan!  Why don't you give cars a try, at least they are safer
    and tend to survive crashes better.  :+)
    
    Speaking of interference and such, what limits on transmitter power
    are there for R/C radios.  Would it be legal to boost your output
    power to 'a few watts' for emergency use to overcome interference?
    What is the normal power output of R/C transmitters?  Maybe when
    my modules come back from FUTABA I'll check with my power meter....
    
    Willie

Legal power is 1 watt, measured at the input to the final RF
amplifier.  It is not legal to boost it beyond this point, though
a pretty good idea.  As far as modifying the amp, final RF amp
design is quite tricky with the impedance matching and harmonic
suppression that needs to be done. 

        Re: .731

        You're right about the 1 watt input limit for the unlicensed units
        (27/72/75 MHz). On the Ham band (50/53 MHz, license required), 1KW
        would be legal, although somewhat impractical. I don't think you
        would be able to carry the transmitter, nor would you want to
        stand that close to the antenna any more :-) 

    Gee what a great idea with 1KW you could fly your model and roast
    hot dogs on the antenna at the same time ;^). Actally Hams are
    also resticted to 1W for model radio control, even on 50/53
    MHz. 

        Re .739 (whew, this note is getting long, and covering a lot of
        topics - maybe they should be in seperate places for indexing) 
        
        Hams are NOT restricted to 1W anywhere! A local club may restrict
        me on their field, I may have to log all my transmissions, I may
        not be able to find a transmitter without building it myself, but
        I am NOT restricted in any way as to power output or even what
        frequency I use or what I do with it, within the 1KW and 50-53.99
        MHz range. The FCC is the controlling body for these frequencies,
        not the AMA, the ARRL, or any other group that might issue
        "frequency plans". This is not to say that I don't follow these
        guidelines; just that there is no legal requirement that I do. 

    Re .741 (your right this note does cover a lot of stuf)
    I believe if you take a quick look throught part 97 of the FCC
    rules and regulations, you will find that you most certainly ARE
    limited to 1W Max for model radio control purposes.
    This rule is not dependent upon license class.
    I don't have the rule book handy right now,
    or I would qoute the paragraph for you. I don't know how long
    this restriction has been in place since I only recently got my
    ticket.
    
        You are absolutly right that the AMA and ARRL plans are not law.
    However the ARRL band plans are commonly accepted as a standard
    for operation, and to ignore them is inviting disaster as far
    as model operation is concerned (my opinion). Recently there has
    been a great deal of pressure in some areas from reapeater operators
    to use the upper part of the 6 Meter band. Due to this the ARRL
    RECOMMENDS that the previous R/C frequencies be vacated by 1990.
    

Its possible that Tim created a spark transmitter by connecting
his battery, but because I have never heard of this type of
interference (it would be common knowledge if it were true, since
this particular action happens frequently), I would say that your
glitches were caused by something else.

Now, the interference on the ground is a little more plausable,
especially if he were pitted next to you, but still hard to
believe by the standard of everyday practice.  I've had my servos
go crazy when someone on an adjacent channel, or on one of the
known interference channels pits near me or passes by with their
TX on and mine off.

I, at this time must restrain myself from further comment, for I
think that the best manufacturer of RC equipment is Airtronics...
:-)

    Airtronics are not immune either!  I have seen the same problem with my
    Vanguard 6 ch rx also.  Not with someone starting their engine, but
    someone being on a frequency close to mine.
    
    Robert

> I, at this time must restrain myself from further comment, for I
> think that the best manufacturer of RC equipment is Airtronics...
> :-) 

--- still doesn't stop the 'bad' tx's coming by does it !  8-)

Can the servo rattle be stopped ? I don't recall having the problem
when I had a remote glow connection. 

Eric();

Eric, you just introduced something new in talking about your
"remote glow connection".  How does this fit into the
picture...does Tim have one by chance?  If so, then it could be
the antenna for his spark transmitter, though I still think its
far-fetched. Perhaps there's a Ham out there who has experience
with this kind of noise interference and can say if its
plausable or not.

John,

Neither of us have a remote glow at present on our planes - just the good
old clip on type. I would have liked to put one in but the socket I have hadn't
enough depth for the fuse. 

I am going to do some tests this afternoon with the glow connection and see if
I can get some eye openers on it.

Eric();

    I've built spark transmitters back in my tech-weenie youth.
    
    Basically, any abrupt change in current (like a spark), can radiate.
    Making a connection to the glow plug can cause AMPS to flow. Radiation
    is possible only during connection & disconnection. Once the current is
    flowing constantly, nothing radiates (this is why remote glow operation
    is probably OK). When making a manual connection to the glow plug, it's
    possible to have thousands of make-break connections occur.
    
    Now that we've established that there is a large current change
    occurring, how does it get out?  Well sparks contain just about all
    frequencies simultaneously. The frequencies that radiate are a function
    of the antenna dimensions.  For example, the first Marconi transmitter
    was a giant spark generator connected to a tuned antenna. They didn't
    know how to build oscillators back then.  Nonetheless, the antenna in
    this case are the battery leads from the glow plug to the battery. At
    71-72 Mhz, a quarter wave antenna would be ~1 meter (3 ft).  My glow
    plug wire to the battery is about that long. Seems to me a spark
    would easily radiate a few hundred feet in this situation.  I'd guess
    one of those little Ni-starters wouldn't cause any problems at all,
    since the dimensions are so small. 
    
    Was the person on the ground using a wire connected glow plug battery?
    
    ...bill

    
> Was the person on the ground using a wire connected glow plug battery?

Yes. 

How about a glow driver that ramps the voltage up or turns it on after
sensing the plug resistance ?

aside...

Currently I am building a circuit to keep the plug glowing constantly
independant of the temp/dry/wetness etc of the plug. Its basically a
modulated current source fed by a sample and hold circuit. It doesn't
include a 'ramp up' when attached bit but I guess it could be added if it
would reduce the spark possibility. But then the old connector rattles
normally anyway and, guess what, more sparks. So it is probably down to as
short as possible leads from the battery. 

Eric();

    Guys,

    You need voltage to make good sparks.  Glow drivers are only 1.5 volts.
    I suggest you buy a D-Cell battery, and sit down with your radio on,
    while you short + to - on the D-Cell.  I'de be REAL surprised if you
    could generate enough "noise" to even glitch the radio (even if you held
    the D-Cell right up to the receiver).  Remember, the interference lasts
    only as long as the duration of the spark.  This could, at most, be just
    a few Milliseconds.  That ain't long enough to cause any noticable
    jitter in the radio system.

    I think you're worrying about something that doesn't even warrant
    consideration.  The distributor in most cars generates a hell of a lot
    more RF as it commutates than you could ever produce with a glow driver.
    

    
    re: .-1 Randy, I strongly disagree!!!  The noise generated by the plug
    warmer _is_ enough to glitch your receiver, especially with an antenna.
    Stop by my Citabria next time we're at the field and I'll give you
    a demo.  The wires on my on-board glow system make a good antenna,
    and my Airtronics AM receiver is susceptible to this kind of
    noise.  It's not bad enough to give me problems but it _is_
    definitely noticeable.
    
    Let's think about it a little more...  If a transmitter can put out
    enough energy with 9 volts to control a receiver over a mile away,
    why couldn't a transmitter with 1.5 volts do the same to a receiver
    a few inches away?  And like Tim (I think) said, the spike of current
    puts out all kinds of frequencies.  The key is better receiver design,
    which the newer FM and PCM systems have.  I don't think they should
    react to this type of noise like my AM receiver does.
    
    Bill

        Re:                       <<< Note 1101.10 by LEDS::LEWIS >>>

                I have  seen  glow  drivers  affect receivers many times,
        including on my own planes. The effect is real.
        
                      _ 
                     / |
        |  _====____/==|
        |-/____________|
        |    |        o \
             O           \ 
                          O
         Hang in there! o_|_
                          |
             Anker      \_|_/

    Yeah, ok, but...

    My electric motors certainly put out more RFI than a glow driver ever
    could, but I don't see problems with my radios.

    I understand that electric motors can have an effect (witness the
    trouble Mr. Miner is having with his Astro 15), but mine don't, even
    though I can clearly see a little arcing at the commutator when the
    motors run.  My big electric glider uses an 05 Cobalt, without a
    capacitor across the brushes, no problems at all.

    If you're using a glow driver that does "pulsing", I'de be more willing
    to accept the RFI theory, but the simple connection of a glow driver to
    a plug?  Maybe a millisecond of noise, maybe, but I really have trouble
    swallowing the supposition that it generates enough sustained noise to
    crash an airplane (or was it a heli?).

    Anyway, Bill, what the heck are you responding to notes for?  You're on
    VACATION, D*MMIT!  CUT IT OUT!  Don't you have any airplanes to build,
    or fly?

    

I fly Airtronics FM Dual Conversion radios (2). I assure you that *EVERY* time
I pull the glow plug clip off the plug I take a minor hit. Among other things
it usually blips the throttle so if its at idle it kills the engine.
The duration of the interference is exactly equal to the amount of time that
contact is iffy. If I get a good pull and get the clip straight up and off its
almost immeasurable. If, on the other hand, the clip catches and/or drags on the
plug on the way up the interference lasts much longer. (Still much less than a 
second though - we're talking very short periods of time in either case)

I do power the plug from a Tower power panel and long-reach glow plug clip.
I believe that this panel pulses the power to the glow plug. I've never noticed
this interference carry to others planes, but its worth a look the next time I'm
at the field. As for shooting a plane in the air down... I doubt it. The
duration is so short that its unlikely if not impossible that you'd even notice
the interference.

Randy

Using my Silver Seven AM receiver, I've had the servos jitter
when connecting the plug.  You might be able to duplicate this by
rubbing the connector around on the engine head as you connect
the plug.  This is usually how I've seen it.  And if you kept it
up you could create a fairly constant jitter that could throw 
the servos around a bit.  But turn on the Tx and away that goes,
so at 200 feet from the glow plug --- naw.

    The RF energy is a function of the power dissipated in the spark,
    not the voltage across is. Glow plugs draw a couple amps, I believe,
    so even 1.5 V at a couple amps is quite a bit of power.

    Congratulations, you've rediscovered the earliest method of radio
    communications - the spark-gap transmitter. The first transmitters
    were in Morse code, using a spark gap to generate RF. Your receiver
    could be pretty non-selective for this to work. It's also the cause
    of a long-term annoyance I have many mornings when some arcing/sparking
    something nearby my neighborhood puts out bursts of buzzzzzzzing
    sounds in my alarm clock/radio. Wish I could track it down!

    Dave

    There is another thing going on that most of us have seen:  The metal
    to metal contact causing RFI.  Try touching a screwdriver to your
    engine while it's running and you will probably see some servo jitter.
    No battery here.  I believe what's happening is change in the receiver
    and antenna efficiency affecting the signal rather than generated RFI.
    Metal clevises on metal fittings can do the same thing.  I bet that you
    can get the glow driver effect even without the battery making
    connection.  
    
    Charlie
    

I went flying Sunday in the drizzle and got a hit when a dirt bike rode across
under my plane as I was setting up an approach. My son mentioned that he hadn't 
seen me do a barrel roll that low before. Fortunately, the plane was coming
towards me and was out of the interference before it was out of altitude. I
passed on the next flight. I had just watched a show on The Learning Channel
about Marconi and his trans-Atlantic messages with "a spark transmitter!" on
saturday morning so I waited until the dirt bikers left the area before going
up again. I'm flying a Futaba AM Attack (but looking at an FM this week).

BTW: I also had the fun of discovering a 200 foot ceiling as I flew out on my 
takeoff. Damn good thing I didn't blink. I guess I was just a die hard this 
weekend but I had been looking forward to it so my buddy and I figured we'd
give it a try. Brought both planes home in one piece but it made it more 
interesting having to fly low and close. I was also surprised that the 2 cycle
engines didn't mind the 99.9% humidity.

    I would like to add that I have seen the same thing with my glow
    plug clip.  Even with my Tx (Futaba AM) turned on next to my plane,
    the servos glitch when I hook up my home-made plug warmer.  This is
    simply an old 35mm plastic film canister with a C sized NiCad in
    it.  There is 2 to 3 feet of wire connecting to the glow plug clip.

    RE: 1101.12 From Randy (LEDS::) Cohen

    Randy, I'm VERY surprised that you are running an Astro cobalt 05
    without a cap. and not getting radio interference.  Have you ever
    been flying when someone else got shot down?  Is your radio AM or
    FM?

    I'm still having problems with ElectroStreak #3 running either a
    cobalt 05 or cobalt 15.  It still hasn't flown.  It was a bummer to
    be at the KRC Electric Fly this last weekend with over 100 other
    electric fliers and to have my plane be "Static display only".   :-( 
    (More on the KRC Electric Fly in another note later.)

    Assuming you are using AM, I would like you to perform an experiment
    for me tonight.  (If it's FM, don't bother - FM should work fine
    under these conditions.)  Take your plane to the field (or your back
    yard if appropriate) with a helper and do a range check on the plane
    with the Tx antenna collapsed (down) all the way and the motor off. 
    When you get far enough away that you begin to loose control (50 to
    100 feet?), step 5 feet closer and turn on the motor.  (Warn your
    helper first though.  :-)  Do you still have control?  If not, move
    closer until you regain control.

    When I do this, I can get only 1/4 to 1/2 the range (about 15 to 30
    feet) as when I have the motor turned off.
                                              
    So, since we're on the topic of radio interference, I'm going to ask
    y'all for some brain power help.  Here's the story...

    I have an Electrostreak that has radio problems.  

      - The 'streak has a pull-pull rudder cable system that is made up
        of 2 steel wires.  The antenna runs parallel to them.  

        Theory: Rudder wires are acting like antennas and inductively
        coupling noise into the Rx antenna.

        Disproven: I removed the Rx and ran the antenna perpendicular to
        the rudder wires.  No difference.  Not only that, but there were
        probably 10-15 'streaks at the KRC Electric Fly this weekend and
        none of them seemed to have problems.

      - Theory: Maybe Rx is bad.

        Disproven: My channel 34 Tx/Rx (Futaba AM) has been used in my
        Skooter (w/ O.S. .25) for the last 2 months with not even a
        single glitch.  I also tried my channel 44 Tx/Rx (also Futaba
        AM).  No difference.

      - Theory: Maybe the speed controller is causing the problem.

        Disproven(?): The speed controller is totally isolated from the
        Rx circuit by an optocoupler.  By disconnecting the motor from
        the speed controller, but leaving everything else the same, the
        problem goes away.  [To be certain it's not the controller, I
        should get a HUGE resistor to connect in place of the motor to
        simulate the motor load.]

      - Theory: It's the motor itself.

        This is all I'm left with as far as I can tell.  Here's what
        I've tried so far:

        1)  Disconnect the motor and motor battery from the speed
            controller.  Then, connect the motor and battery directly
            while they are totally outside the plane.  Move the battery
            and running motor close to the plane.  Still have noise
            problem.

        2)  Try different motors.  I've tried my cobalt 05, cobalt 15
            and a friends cobalt 05 geared.  Same results all around.
            (ALL motors have a cap on them.)  My friend's motor has been
            working fine for him but, on the other hand, he's using FM
            so he probably wouldn't have a problem anyway.

    I've gone through MANY other theories, etc. and have turned up
    nothing but the possibility that it's the motor.  However, as best
    as I can tell, all motors I've tried are fine.  Also note that my
    cobalt 05 never gave me problems in 'streak #1.

    Charlie, can I arrange to come over to your plant sometime with my
    motor and radio so we can look at all this on a spectrum analyzer?
    It would be good if you could bring your 'streak and if Randy could
    bring his glider for comparison, too.

    I'm stumped and need some help.  There is another competition this
    weekend that I really, REALLY want to enter the 'streak in...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    Geeze, Dan, you covered a lot in that last note.

    I have done the range check experiment you asked for, already (it's the
    first thing I do before I fly a new plane, one bad experience,
    dontchaknow).  I swear, there's just no problem with the motor on.

    Maybe there's something flakey in the battery you're using.  Have you
    tried a different pack?

    I fly my glider quite far away some times, I can only recall one
    instance when I had trouble with it.  It was our DEC funfly last year,
    the plane didn't have the Cobalt in it at the time (just a hi-po Kyosho
    motor), and the problem turned out to be an adjacent frequency
    transmitter left on in the impound.  Symptom?  Servos went hard over in
    short bursts.  I'm sure the plane survived only because I was at such a
    high altitude at the time, I was able to just wait it out (and the
    "pulses" only lasted as long as it took the servos to go to their
    limits and come back to their proper place.  Less than 2 seconds,
    probably less then 1).

    Had to go back and reread your note.

    Disconnecting the motor from the speed controller, and having the
    problem go away, DOES NOT ABSOLVE the speed controller from being the
    culprit.  In fact, since you presumably run the 05 and the 15 with the
    same controller, it kind of suggests that it is the source of your
    problem.

    When you removed the motor, you left open the battery-controller-motor
    circuit.  This circuit switches a lot of current using PWM, probably,
    and is a REAL likely source of RFI.

    I'de go to a hobby store and buy a car-type mechanical speed controller,
    hang it on a servo, and put it in your plane.  Then see if the problem
    goes away.  I bet it does.  There's a lot of semiconductor junctions in
    a speed controller, any one of which might emit some interference if it
    were flakey.

    Check it out.  Speed controller would have been the second place I
    looked (first being replace/add noise capacitor to motor brushes).


    As an aside, I recall having seen, in a recent model mag, an New Product
    announcment for an LC tank, on a circuit board, that could be soldered
    right up to the back of a electric motor.  They claimed that it's much
    more effective at quieting noise than just a Capacitor.  It probably is.

    Since I only get MAN and MA, it had to have been in one of these, not
    more than 5 or 6 months ago.  You might want to see if you can find it.

    Randy

  Dan,

  Have you tried running your motor next to someone else's plane to see if it
causes interference to them? 


   Jim

    RE: .19 (Dan's note)
    
    Hello Dan.  I have some ideas that may help.  First of all, I'm not
    "real" familiar with electric planes, so bear with me.
    
    1. Motor capacitors are not created equal.  There are many (most)
    capacitors that have awful high frequency characteristics.  The actual
    value of the cap doesn't seem to matter as much as it's high frequency
    characteristics.  The smaller they are physically the better. The
    little caps used on DEC's modern PC boards are wonderful.  I could get
    the P/N if you're interested. 
    
    2. A choke or inductor in series with the motor will also help.
    Unfortunately, these thingies are heavy.   The secondary of a good old
    radio shack 6.3V filament transformer works fine. This would be heavy
    though.  The problem with choke/inductors is that they need to pass BIG
    currents. (This solution will help, but I'd guess it's not practical).
    
    3. Ferrite beads placed on the power wires to the motor will dissipate
    high frequency energy much like a choke/inductor. These things are a
    modern miracle, and they keep DEC in business.  They are light, cheap,
    and they really work. I don't know if R/S sells them, but I could get
    you some if you like.
    
    4. Grounds. I bet you have a ground  potential problem. Without getting
    in to why, try this:
    
    (I assume there are separate batteries for the receiver and motor)
    
    I know you have an opto-coupled Speed controller, but the speed
    controller needs power to run its electronics. I assume this comes from
    the motor battery. Connect the (-) terminal of the receiver battery to
    the (-) terminal of the motor battery.  Make this connection directly
    to each battery. This will keep the receiver ground and the motor
    ground at the same potential. The receiver will still be "isolated"
    electrically from the speed controller, but the return potentials will
    be the same.
    
    ...bill

        Re:   <<< Note 1101.23 by TALLIS::SAMARAS "New England: July-August & winter" >>>

        Bill,
        
                I would  like  to  highlight  one of the points you made.
        The speed controller  could  be  the culprit!  I suggest Dan runs
        the motor without it and checks the interference.
        
        Anker

    This isn't exactly the sort of interference thats being discussed
    here, but it's equally destructive and can happen to anyone.
    
    At our field we use a ply board with small squares painted on the
    edges, one per frequency. Before turning on, we place a clothes
    pin with our name and freq. on it, on the appropriate square.
    Having each pilots name on the pin gives some indication as to how
    long he'll be up, wether we should run for cover when he lands,
    etc.
    
    Yesterday a guy showed up at the field who was a very experienced,
    well known flyer locally, but hadn't flown at our field before,
    a fact no one realized beforehand. He proceeded to check the board
    before turning on, then removed the chan. 40 pin from the board,
    which was being used to control a Sagitta 600 airborn at the time,
    walked over to his own plane, turned on and shot the Sagitta down!
    After the screaming and shouting was over, it turns out this poor
    guy honestly thought that the freq. control system worked the other
    way around. A pin on the board means the freq. is clear. At the
    power field across town thats the way it is. I think we'll
    be putting up another sign explaning that we're "backwards".
    
    Terry
    

                                 
       I was in 3 clubs last year, and they all used different methods of
    frequency control.
    
             - Club A uses the method of placing the clothspin marker on
               the board when using the freq. Everyone has their own pins.
               Check your slot on the board, if open, place your pin on the
               proper place.
    
             - Club B uses the opposite method. There is only one pin for
               each freq. When you go to fly, check to see if the pin is
               on the board. If it is, take it and fly. If it isn't, you
               wait until the pin is returned.
    
             - CLub C also has one pin per freq. They are stored under the
               board (which only has 4 slots, the maximum allowed to fly
               at one time). When you want to fly, look at the 4 slots, if
               your pin is not on the board , and there is an available
               space, get the pin from underneath, post it, and fly.
    
    
               As you can see, all the different methods can be confusing.
     Until a universal standard is reached, it is the responsibility of
     a new pilot at a field to understand what method is in use before
     turning a transmitter on.

    
    I personally prefer the method used at CMRCM - you take the clothespin
    off the board and clip it on your transmitter before removing your
    transmitter from the impound rack.  That gives you an easy check
    (the pin clipped on your transmitter) to make sure you didn't forget.
    It also makes it easy to catch someone with a transmitter not on the
    impound rack without a pin.
    
    I hate flying at fields that do not have an impound rack, and I don't
    like the "bring your own pin" concept.  Without an impound rack, it
    is too easy to make a mistake and switch on without checking.  It
    also makes it very difficult to catch someone who has just shot you
    down, since it only takes a moment for him to switch off and it isn't
    "illegal" for him to have his transmitter sitting in his flight box.
    
    Of course this is personal preference and CRRC seems to be perfectly
    happy with the "bring your own pin" scheme.
    
    Bill
    

    Bill, I think you hit it right on the head.
    
    	FIELD DESIGN AND LAYOUT &  ENFORCED DISIPLINE
    
    are the key factors. If you don't have both and don't use both you
    haven't an effective control system.
    
    
    Tom

        Re:                   <<< Note 1101.28 by HEFTY::TENEROWICZT >>>

                The problem  with  CMRCM is THAT THEY DONT USE IT ALL THE
        TIME!  Most  times  there  is NO frequency control system because
        they have become tired  of  people  walking away with their pins.
        This  is  the  biggest problem  with  the  subtractive  frequency
        control system. 
        
        Anker

    
    	The two systems I've seen work the best and survive are;
    
    	1) You supply the pin and attach it to the frequency
    	  board when you want to fly. My club uses this particular
    	  method. The pins are white with the frequency number
    	  on them and the pilots name. 
    
     	2) The other method has slots for each frequency. The pilot
    	  puts his/her AMA card into the slot when they wish to fly.
    
    
    Tom 

    Re. Anker
    
    There's also something to be said for training/field rules, common courtesy,
    and common sense. Your right, we don't use it all the time. It usually
    comes out when it starts to get busy. HOWEVER, I don't remember
    ANYONE getting shot down all last year. Only one instance of a radio
    being left on in the impound (antenna completely down) which only
    affected one plane as it passed the impound. The affect was a little
    jitter for maybe a second or two.
    
    Steve
    

We have a system at the PPRC club that works very well.

Our frequency board has a 6" dowel sticking up for each frequency. On each
dowel sits an engraved plastic clip. The clip has a two-color face in the
old frequency colors and is engraved with the frequency number. The rule is
you don't fly without this pin on your transmitter.

In addition each flyer must have a clothespin or two with his name on it.
Here's where the extra length on that dowel comes in. If you want to fly
on a certain freq. you put your clothes pin on the bottom of the dowel for
the frequency you want to fly on. When your pin bubbles to the top you get the
Tx pin and go fly. When you're done you move your clothespin to the bottom and
return the TX pin to the top.

With this system we get three things.
	1. You can only fly if you have the TX pin.
	2. We have an automatic queueing mechanism that insures more-or-less
	    equal flying time to all flyers on a frequency.
	3. We always know who has a given pin.

Like any system this one works well as long as everyone follows the rules. It
dies, as do all such systems when someone doesn't.

For what its worth...

Randy

RE: -1
The only thing I don't like about this system is that often some
Bozo :-) drives off with the pin, thus rendering confusion on his
frequency.  The nice thing about the one that has pegs for the
frequency is that if this happens, all the people left at the
field need to do is verify that Bozo has gone and remove his pin.
Bozo is also saved a fast trip back to the field to replace the
pin, after he's had his post-flying session beer.

I do like the queing system, since all a pin-hog like me needs to
do is keep an eye on the board to see if there's someone in the
queue waiting to fly.

Now, how about a combination of the two systems?  With an UP
dowel to show that Bozo is on frequency, and a queue dowel to
show who is waiting.  We could use the same board, minus the
fancy channel pins we currently have.

Randy, were you there the last time someone suggested a change to
our frequency system at the club meeting? You'd have thought they
were discussing a mass castaration or something for all the fuss
and hollering.

    
    
           Anyone out there have any info or experience with
      interference form microwave towers?. The reason I ask is 
      just last saturday we (citizens of Auburn N.H.) were informed
      that MCI (the telephone co.) has obtained a lease for some 
      land in our town and is applying for a variance to install
      a 7 dish 280 ft tall microwave tower in an isolated area of
      town and there is some concern, mostly from neighbors about
      stray radiation (not my worry). My concern is since I tracked
      the direction of the proposed dishes (in line from portland ME.
      to nashua) it seems to be close to my favorite field.(my back
    yard). Can this type of broadcast affect RC?. I believe the freq
      is around 2-4 GHZ, but with the power of those tight beams I
      wonder if there is a danger. (to my planes).
    
       Any help or guesses might give me enough to stand up and fight
      em, but then again progress is progress.
    
      kevin p (scared of those little micros that cook so well)

Those microwave shots don't use much power...I'd be surprised if
it was more than 25 watts, probably closer to 5.  Now if it was
radar...

Re: Note 1101.40 

For many years (10+) I have been involved with model flying displays at the
local Aero Club. About 4 years back I was asked to organise another display but
noticed some Microwave dishes had been installed at the adjoining Navy training
base that directed across the normal flying site. The dish was less than 1/2
mile from the flying area. 

I had the same concerns so took a team of volunteers to the site to test the
effects before we would commit to doing the display. After confirming the
Microwave was operational we flew all day and only experienced a couple of
glitches when we believe the model was actually in the direct path of the beam.

We did the display over two days using about 40 different models and never
experienced any problem. 

As John says radar is different. I can relate the incident at the 1987 F3D
World Championship in Australia where we had to relocate the event from
Laverton to Point Cook because of weather radar interference. That was quite
dramatic and occurred every time the dish swept over the field. The effect was
even detected by a guy wearing a hearing aid. 

John 

    I am fairly new to flying RC planes and have just completed my second
    plane, a Super Kaos. I bought a new Futaba FP-6NFK radio channel 16 
    and checked the operation of all the controls. I took the plane to the 
    flying field and did a range check - OK.
    
    When I started the engine, a Super Tigre 61, I started getting
    interference and all the servos started vibrating. This continued even
    with the glow starter removed. 
    
    I tried various things but only managed to stop the interference when I
    swapped out the receiver for the one out of my trainer - problem went
    away (this receiver was on channel 48). 
    
    Has anyone else seen this type of problem. Is it simply a bad receiver?
    The receiver is a FP-T127DF.
    
    Any help or advice would be much appreciated.
    
    ....Dave.

    Could be a loose antenna wire (bad connection or partially broken).
    This could make intermittent connection and cause the effect your
    seeing. The other possibility is a cracked crystal. This is one of the
    reasons for doing an engine on range check after a crash.
    
    Since you said it's new, I'd send it back with a letter stating the
    conditions you mentioned in .43. Do it soon since it's still building
    season ;^)

    Re -2:
    Sounds like vibration's the problem.  You could have a defective
    receiver - not that uncommon with a new system, or you could have a
    vibrating metal connection that is creating interference.  Any loose
    metal fittings can do this - like the throttle linkage at the engine. 
    Since changing out the receiver helped, I would suspect that the
    receiver is more vibration sensitive than it should be.  Did you have
    it wrapped in foam?
    
    Charlie
    
    

I guess this is as good a place as any .....

I was flying on Sunday, practising approaches, when I approached a bit low (6 
inches below ground level!). OK, some damage, but not bad, and I'm getting used 
to this....

I was quite happy (!?) that this was my fault, when one of my fellow club 
members pointed out that he'd lost control in the same area shortly before, and 
said that he'd seen two kids pop up out of the heather nearby just before both 
incidents. He said that the kids had got some sort of box in their hands.

Now, this guy is at about the same level of experience as me, that is to say we 
manage reasonable landings most of the time, but every now and again we don't! 
We were both flying 35Mhz, but different channels (76 and 74 from memory). I'm 
just curious as to whether any device exists which could cause this type of 
problem. I'm 90% certain that we both just made mistakes (it was a gusty day), 
but I'm concerned that we may have been the victims of "enemy action".

So, am I right (we made mistakes), or do we organise a lynch mob?

Cheers

Nigel.

    Electronically everything is possible. I once built a simple oscillator
    and modulated it with a square wave. Needless to say, the whole TV band
    was affected. And this during the German Soccer World Championship
    somewhere back 1974 or so. I almost got lynched.....
    
    If those boys have a wideband transmitter or even one with tuneable
    frequency it could very well be a problem. So speaken I remember a
    Super Bozo, who, during an RC Airshow caused 8 beautiful planes to 
    crash before he got caught.
    
    Bernd
    

Soooo,

This weekend'd checklist: Plane, trannie, fuel, shotgun, cartridges..... 8^)

But seriously folks, we're going to take the club's frequency monitor to the 
field for the next few weeks, and keep an eye on it. If we DO find that some 
moron's trying to shoot people down I guess we'll have to inform the local 
police (criminal damage?).

Cheers

Nigel

There were old style Txs that were VERY broad band (super-regenerative) 
These were only usable one at a time. A Spark gap can also put out 
enough broad spectrum interference to mask most systems. It could be 
being done without being frequency specific. I think you can file a 
complaint for malicious intent as well but I'd leave the actual charges 
to the lawyers.

    If there IS someone out there intentionally shooting people down, AND
    you manage to catch them, AND you turned them over to the police, I
    would just say that they suffered an unfortunate "slip and fall" in
    the tall grass while trying to get away. That's how I'd explain the
    cuts and bruses and blood. 8^)
    
    S.

    Steve, 
    	How do you explain the antenna wrapped tightly around their neck?
    or placed where the sun don't shine? :-)
    
    
    

    Gee officer.......I had to wrestle this guy to hold him for ya and the
    next thing I know, there's this OS60 Long Stroke stuck up his A** and
    a 12x8 APC down his throat. Beats the hell outa me. Must be one of
    those real strange accidents you always hear about. 8^)))

Well Your Honour,

You see when the defendant switched on his equipment, causing my aircraft to 
crash it regrettably hit him. This explains the bits of wood in the various 
orifices.....

Cheers

Nigel

PS> I'll let you know if it happens! 

    << He stumbled acoss my winch line just when I launched my sailplane...
       and then the plane crashed right onto him that's where those marks
       come from.
    
    
    Hmmmpf

    
    Well, time has passed. We haven't seen the two lads again, and we've
    had more fun and games with (suspected) interference.
    
    It seems that the area around our field is susceptible to the odd spot
    of bother. It is however, the only field we can use in the area, even
    with major time restrictions. So we're just going to have to stick with
    it, and hope! 8^(
    
    Pity really, I'd rather have had a good explanation, even if it was
    "enemy action"!
    
    Cheers
    
    Nigel
    

    
    we had nothing to do with this interference, really !    :-)
    

    I'm posting this here because it is a question on interference not a
    crash analysis.
    
    On 11/5/94 at our Merrimack field, we had three planes flying - on
    channels 54, 58, and 13.  Suddenly, the planes on 54 and 58 were shot
    down, but the plane on 13 had no problem.  All equipment was
    gold-stickered narrow band.  Both of the crashed planes had good
    batteries in Rx and Tx.  Both planes had completed several trouble-free
    flights before this occurred.
    
    Everything points to a broadband interference that cut across the 54 to
    58 spectrum, but left ch 13 alone.
    
    WHaaa happened??   Is this possible?  Or is there some other
    explanation?  I might add that the weather looked threatening, and
    there was possibly electrical storm activity in the vicinity, but if
    this was the case, why did Ch 13 get spared?
    
    Inquiring minds want to know.
    
    Regards,
    Joe
    
    
    

If you've got some VERY local pager in the area between those frequencies that's
pumping out 500 watts, the bell curve distribution would probably bleed over
several channels at the one watt level. Of course, this is all conjecture. Both
planes lost control at the same instant?

>                     <<< Note 1101.57 by MKOTS3::MARRONE >>>
>                      -< TWO SHOT DOWN, ONE STILL FLYING >-
This sounds like a classic 23 channel interference problem.

>    Everything points to a broadband interference that cut across the 54 to
>    58 spectrum, but left ch 13 alone.
>    
>    WHaaa happened??   Is this possible?  Or is there some other
>    explanation?  I might add that the weather looked threatening, and

If there is a pager 22.5 channels from 13 and it was strong then
you have all you need to shoot down any single conversion receiver
(excluding the JR ABC&W receivers).

If that was the case - good riddance to bad rubbish.

I have seen lightning in the distance take out a plane on landing
but it was only a quick glitch and it was an AM radio.

If Jim's theory is correct - you can confirm this with a scanner - then
you wanna record all the technical details and check out the possibility
of legal action.  I have read many notes about pager companies illegally
increasing their power (to make more money).  Apparently it is quite common
and a large market for linear power amps put to illegal use.  The FCC will
slap their hand but the court can replace your airplanes.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################


    

We've just had a scan of our local channels done because of some
interferrence around ch 43.  It turns out that there is some wideband
pager activity going on across chs 40-45, though I too thought it was
not legal.  The gist of the problem though is that even with the
wideband radiation of the pager station, the narrow banding of our
receivers does not allow enough power to leak in to cause a crash,
assuming that the receiver batteries are up to snuff and everything is
on spec.  Our crashes occurred on chs 43-45, and there is some
question on the condition of the receiver batteries, etc to explain
the problem.

BTW, it seems to be a good idea to get a scan done every few years, if
for no other reason than to act as an advisory to club members who
want to buy radios and would like to know the safest channels to get.
Our club is going to use the scan data along with a database of member
channels for the members to access.  

    I wonder if you can get a list of broadcasting stations from the 
    FCC....  Don't the have state or regional coordinators??  
    
    It is quite possible that someone installed some new service on the
    micro-wave tower near our field..  
    
    Hmm, I will have to ask around...
    
    cheers,
    jeff
    

    
    
       As I mentioned in the Luchtime excitment note, I also believe
    my X-cell experienced catastophic interferance at Merrimcak this past
    Tuesday.

The problem with pagers is that you get a 10 second burst every once in a while
and then they're gone. If it's swamping that many channels, it could be a real
safety concern. You can generally get a list of the local transmitters from the
local ham radio dealer/supplier. They might even be able to point you to the
owner of the tower so you can get on his information list when a new service
emerges.

    We did a frequency scan on three separate days in July or August with
    the district scanner.  At that time, nothing suspicious showed up. 
    What was strange about this incident was that both planes were hit at
    exactly the same second.  I've never seen thi shappen before, that's
    why I speculated about some kind of broad-band interference as opposed
    to encroachment on only one channel.
    
    Dan, what channel were you hit on?  It might help to fill out the
    pattern.
    
    Time permitting (who am I kidding?) I will try to collect some info as
    suggested in the past few replies.
    
    Thanks,
    Joe

Keep in mind that JR has two "bands" on their rx line... there is a high band
and a low band. I don't know where the division is or if the two bands are
actually physically separated. That might explain why the ch13 was spared in the
weekend incident

    Didn't know that Jim.  I have been using JR for three years, and find
    them totally interchangeable with Airtronics, so I've never thought
    they operated on two bands.
    
    -Joe

    I think what Jim meant was that they are tuned to operate either in
    the higher or lower end of the RC spectrum.  So, basically what they
    are saying is that you can change crystals from CH14 to CH16 but you
    should not simply change the crystal from CH14 to CH54.  For that big
    a jump, you should have the Rx retuned..
    
    I agree with Kay that I doubt it is renegade.  While there are some
    nice fields just across the river, I find it hard to believe that 
    3 or 4 or 5 different channels have been hit.  What are the chances of 
    them using the same freq as we are, at the same time??  Also, we would
    be shooting them down as well and I would suspect that RC Buyers would 
    have heard about it (Bob has not heard of problems from anyone else 
    but us).
    
    I just called Americable, which is the cable company at the base of the
    tower.  They do not use/operate the tower and believed it is
    Cellular-1.  However, Cellular 1 does not operate in this area..
    
    He did state that they have intermittent problems on CH 4 and CH 5 and
    they believe it is Sanders.  They have no proof though..  When they 
    have problems, they have called Sanders, they dis-avow any knowledge,
    but then the interference goes away...  Al's son works at Sanders
    so I am going to have him ask around a bit...
    
    cheers,
    jeff
    

                              
    
      After further investigation, it appears my X-cell crash may have been
    caused by mechanical failure, and NOT a "radio hit" as I originally
    thought. I am still investigating, and will post any further
    information as I get it. Details in note 366.
    
      If it was a mechanical failure, that would be good for the Merrimcak
    field, as the only "radio hit" would be the one a week ago Saturday
    that took out two planes simultaniously. It would also reduce the
    "band width" of frequencies affected.
 
      It will also maintain my confidence in flying at the Merrimack field
    and in JR radio equipment.