Conference vmszoo::rc

    It has been pointed out elsewhere that the Airtronics Vision
    transmitter is not compatible with Futaba FM receivers even 
    though the ATRCS conversion of the MD7SP (the ancestor to the
    Vision) did provide Futaba compatibility.

    The May 1990 issue of R/C Soaring Digest (vol 7, no 5, pgs 18-20)
    has an article on adding this option to the Vision.  It requires
    soldering and mechanical skills, naught else.  You move a resistor
    and add a chip, wires, and a switch.  With this change you can use
    the Vision transmitter in PPM mode with FM receivers made by
    Futaba, World Engines, Challenger,and possibly others..  And with
    this change you void your warranty.
    
    That little magazine is a gem.
    
    Alton

    re .109
    
    This mod should work ok, but I have a few nits with his choice of
    components. The 7486 quad ex-or gate that he specifies is an obsolete
    part. Better to use a 74LS86. Current draw with the 7486 is ~50ma
    compared to ~10ma for the 74LS86. The very last thing you want in
    a Vision xmtr. is anything that draws more current. For even less
    current draw, a 74ALS86, ~6ma, could be used.
    
    Also, with an open switch position, using a 7486, the floating input
    without a pullup resistor (which he doesn't specify) is a no-no
    in terms of good design practice, although in this application it
    probably is pretty non-critical. Again, the use of a 74LS86 would
    cure this, because it has an internal pullup resistor, and inputs
    can be left floating without fear of glitching.
    
    I don't have any Futaba style rcvrs. to use with my Vision, so I
    won't be trying this mod.
    
    Terry
    

    Quickie re. compatibility: I have ried 2 Airtronics 4 ch micro FM rcvrs,
    model # 92245 with my Expert xmtr and Futaba micro-servos and neither
    has worked; at all. Yes, I did swap the 2 wires per the guidance
    somewhere in this file and, yes the servos work, as does the xmtr.
    
    I looked in this note and found nothing, except a note on the PCM
    problem, relating to this. I suppose it could be 2 bad rcvrs...
    
    Grazie e ciao, Ed

    You have been had by the FM/FM incompatibility referred to in 51.109

    As I remember it, the problem is in the video used to drive the FM 
    modulation stage.  Airtronics and Futaba are incompatible in that 
    the video of one is inverted relative to the video of the other. 
    Your World Expert (or is it Royal Expert?) transmitter may be like
    the Futaba in this regard.

    Have you tried the Airtronics transmitter with the flight system(s) 
    you have installed?  I'd guess that it will work with either of the
    Airtronics receivers.  I'm assuming that the "swap the 2 wires" 
    reference applies to the servo leads; the circuitry modification
    mentioned in 51.109 applied to the Vision transmitter.  I don't know 
    of any published changes to the receiver to invert the video.

Grazie BRAT::RYDER.... the 2 wires are indeed on the servo. So, know anyone
selling an Airtronics xmtr .. ;-[  I'll send back to Tower and buy some
other toy when I'm in the US December. Guess I'll stick to Futaba-compat.
stuff. Too bad as the Airtronics is about 1/2 price. I can get a World 
Expert rcvr. here for about $100 so I'll be in support of the local economy
for now. Getting tired of swapping my one non-Panic rcvr between 4 gliders/cum
electric sailplanes.

Ciao ciao e buon volante! Ed
    

>Grazie BRAT::RYDER.... the 2 wires are indeed on the servo. So, know anyone
>selling an Airtronics xmtr .. ;-[  I'll send back to Tower and buy some
>other toy when I'm in the US December. Guess I'll stick to Futaba-compat.
>stuff. Too bad as the Airtronics is about 1/2 price. I can get a World 
>Expert rcvr. here for about $100 so I'll be in support of the local economy
>for now. Getting tired of swapping my one non-Panic rcvr between 4 gliders/cum
>electric sailplanes.
>
>Ciao ciao e buon volante! Ed

I'll be glad to sell my Airtronics Vanguard 4 channel transmitter for $50
with NO extras - (no servos, no charger (it will work with a Futaba Tx Charger),
no nothing (well - maybe a box).

For what it's worth - Futaba is not compatible with JR either.

The assumption is that JR must talk to Airtronics?  But I don't have
sufficient frequencies to test that.

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

>>  The assumption is that JR must talk to Airtronics?  

    I'd like to move this from conjecture to fact or falsehood.  I'm
    seriously considering getting a JR 347 on 32 to join my two Airtronics
    Vanguard FM systems on 32.

    Is the Airtronics FM receiver compatible with the JR 347 tx in FM mode?

    Re: last-7,
    
    This is precisely why I advocate determining what system one prefers,
    for whatver reason, then _sticking_to_it_!  I see naught but problems,
    smoked radio gear and busted aircraft resultant of such
    "experimentation."
    
    I, personally, have nothing but Futaba equipment (well, one Cirrus but
    that's a Futaba too and I'll probably lose it as of 1/1/91) and, voila,
    I have no compatibility problems whatever.  My buddy, Chuck Collier
    flies nothing but JR...same story, no problems.  He has some features
    I'd like to have and I have some he'd like but we just bite the bullet
    and do without rather than risk the compatibility problems described
    herein.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

I'm glad someboy finally settled the question of World/Airtrinics
receiver compatibility for me.  I suspect that nothing is
compatible with Airtronics, since after getting my MD7 last
Spring, I have occasionally turned on my receiver while somebody
was flying on my channel and have noticed no control surface
movement (which I would get if my receiver was compatible).

Now, for World/Futaba compatibility, when the earlier reply
mentioned this, it rang a bell for me.  In another note I
mentioned an incident when I was in a Reno hobby shop.  The
owner was giving me a sales pitch on World, and mentioned that it
used the Futaba plug-in transmitter module...Of course, now I
understand why!  Actually, he said that they used the exact same
parts in many cases, such as the sticks.

Since the MD7 receiver is quite expensive for an FM receiver,
about $110 from Tower, I plan to buy one or two Vanguard FM
receivers and associated transmitter modules as spare flight
packs.  I'm mainly waiting for the odd channels equipment to be
available...well, there's a side issue of birthday/xmas money
too.

I stopped by the local purveyor of helicopter parts the other night and found
out some interesting info. He had three of those RCD recievers on the shelf 
for $70 and I asked him whether or not the Airtronix version was compatable
with JR. He said they were and that RCD now had a specific flavor out for JR.
Then he said to take a look at the crystals. None of the recievers in the case
had crystals. He said the original RCD recievers came with crystals installed
but they've found that the recievers are so tight that they just ship the 
dealers the recievers and crystals separately and the dealer just plugs in the
crystal for the channel you want. Extra crystals are $10.  

    Following up on the question posed in 945.7, I called JR and asked, and
    today Dan Snow and I tried out the JR X-347 transmitter in PPM mode
    ("FM") with the Airtronics FM receiver.  They are compatible with a
    minor caveat; the Airtronics receiver servo jacks swap the throttle and
    elevator connections relative to the positions on the X-347 receiver.
    To use the x-347 transmitter with a Vanguard FM receiver, connect those
    two channels accordingly, and include a tx-stick-to-control-surface
    verification in the pre-flight check list.  (I've learned the hard way
    to do that check anyway --- even with single manufacturer equipment.)

    Evidently it was this minor difference that prompted the "technical
    expert" at JR Service to simply state flatly that "the big three (JR,
    Airtronics, and Futaba) are all incompatible with each other."  We now
    know that at the video level Airtronics and JR are compatible but
    Futaba is inverted, and that at the channel commutation level Airtronics
    and Futaba might be compatible (inferred in the Vision modification 
    article) but not with JR.  The PPM encoding of a channel is the same 
    or sufficiently so.
    
    FWIW (not much!), here is the stick-to-servo translation for Airtronics:
    
    The servo jacks on the Airtronics 92765 receiver are numbered from 1 to 7.
    They are controlled by the sticks on the VG6DR transmitter as follows:

    	jack      transmitter control           used for   as tested
    	----      -------------------           --------   ---------
    	  1      right stick, fore & aft        pitch      elevator
    	  2      right stick, left & right      roll       rudder
    	  3      left  stick, fore & aft        throttle   throttle
    	  4      left  stick, left & right      yaw        
    	  5      left  switch, "gear retract"              
    	  6      right switch, "aux"            
    	B/7      none on the six channel TX     battery    battery

    From page ACRO 6 of the X-347 instruction manual, I see that this
    encoding is identical except that the throttle and elevator jacks are
    reversed.
    
    Conclusion: Airtronics FM flight systems can be used with the X-347 TX.

I caution you to not count on servo jack connections to channel
mapping for any manufactures radios for the long hall.

A long time ago I called up a 3rd party receiver manufacture
(forgot the name but it was before RCD) and they no longer made
two channel receivers for that very reason.

They could not count on which pulse would be assigned to which channel
coming from the transmitter.  

My Airtronics Vanguard 4ch was not compatible with my Airtronics Vision
on the same receiver.  I was assuming that I could always use the Vanguard
as a backup radio for the Sagitta since it was originally installed in the
plane before I purchased a Vision - wrong.  To switch radios I had to 
get at the receiver and swap two servos around.  There is an interesting
set of maps that comes with Vision documentation that attempts to show
you which functions go to which channels on which Airtronics Receivers.

For example the table for my Lovesong looks like this:

Receiver Connections
        Receiver Type
     8CH 8CH 7CH 6CH 4CH
     PCM PPM PPM PPM PPM
    +---+---+---+---+---+
LAil| 4 | 4 | 1 | 1 | 1 |
    +---+---+---+---+---+
RAil| 7 | 7 | 3 | 3 |N/A| 
    +---+---+---+---+---+
Flps| 8 | 5 | 7 | 6 | 4 |
    +---+---+---+---+---+
Elev| 1 | 1 | 4 | 4 | 2 |
    +---+---+---+---+---+
Rud | 5 | 6 | 5 | 5 | 3 |
    +---+---+---+---+---+
Splr| 2 | 2 | 2 | 2 |N/A|
    +---+---+---+---+---+
Gear| 6 | 8 | 6 |N/A|N/A|
    +---+---+---+---+---+

If you think you spot any consistency like the Spoiler is at least always
on channel 2 if you have enough channels - forget it.  On the configuration
for flaperons the Spoiler is on channels 8, 5, 7, and N/A for the first 4
receiver types.

Which stick moves which servo is also a function of Mode.  What is right
stick for and aft could be throttle or elevator.

The Bottom line is when you actually set one up you just keep swapping
plugs till you find the right one.

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

Speaking of compatibility - here is an interesting tid bit.

I've been saving this - hoping to give Futaba another call some day soon
but I don't have the need or time or energy right now.

Perhaps someone else (Al?) can fight this battle - but...

I had asked them (Futaba) on the phone about a month ago about PCM
compatibility and they told me that the only PCM radio that was compatible
with my 9VAP transmitter was the R129DP.

This if a bit frustrating because it cost $200 without any servos, switches,
batteries, chargers, etc.

Anyway this rolled across the usenet:

>Article         3476
>From: [email protected] (Glen "Crash" Stone)
>Newsgroups: rec.models.rc
>Subject: Futaba PCM systems- Some Info
>Date: 14 Nov 90 22:56:41 GMT
>Sender: [email protected]
>Organization: Apple Computer, Inc.
> 
>Hi,
> 
>A while ago I posted a message asking about Futaba PCM Conquest systems 
>and their compatibility with the Futaba PCM 1024 systems. No one answered. 
>So, I bought both systems and did some testing. They do seem to be compatible. 
>I used the 1024  stick to control the "512"  seven channel receiver that came 
>with the conquest system. It worked fine and also responded to the 
>programmable fail-safe modes th
>happy as I can by the "cheaper" pcm receivers. I wanted the 1024 stick as 
>it offers a whole range of functions not offered in the conquest systems. 
>There you go.
> 
>Glen

Sorry about the hacked off text - but that is all I have.
So someone is not telling the whole story here?
I would love to know exactly what is not compatible about the non 1024
system?  What happens when you send a 10 bit digital signal to an 8 bit
D/A converter?  Do you just have less resolution but he same throw?
It would appear so.  It would appear that they actually made something
upwards compatible.  One could properly worry about the Fail-safe modes
and it certainly might have the hold/last and throttle channel in the 
wrong place?

Inquiring minds need to know.
Don't you just love it when the marketers hide technical details from us.
Of course we could find out a lot of the answers ourselves like this
fellow Glen from the usenet.  This probably isn't the right note
for forming a chart - but if we had a list of 1024 owners and frequencies
and a list of non-1024 PCM owners and frequencies - then maybe the right
two could arrive at the next DECRCM meeting!

My 9VAP is on channel 38 for what it's worth.

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

On the channel compatibility with Airtronics.  My MD7 was made to
work with an early FM receiver, but when I got it last spring it
had the '91 rated 92585 receiver.  Included in the documentation
was a tx channel/rx channel compatibility chart, which I've
entered elsewhere in this conference.  It really screwed the
channels from 4 thru 7.

I made a little conversion chart in postscript and pasted it
inside the back door of the Tx for reference.  Causes a little
head-scratching at installation time, but that's not too often so
its a pretty minor inconvenience.

I'll expect to have to switch things around again when I get the
back-up Vanguard receiver.

Of course, its my luck that the compatible receiver would be JR,
probably the only thing on the market that's more expensive than
Airtronics (well, there IS Millcott), and NEVER on sale!  Anyway,
its a boon for the JR guys.  Maybe a few of you will get the
Airtronics receiver and find out what real quality is all about
:-).

Just saw the following on the usenet.  I find the Futaba compatibility
fascinating.

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

Article         3712
From: [email protected] (Glen "Crash" Stone)
Newsgroups: rec.models.rc
Subject: RE: Futaba PCM and FM
Date: 9 Jan 91 22:09:26 GMT
Sender: [email protected]
Organization: Apple Computer, Inc
 
Oh Hi,
 
I have a bunch of Futaba stuff including 512 PCM and 1024 PCM.
They seem to be completely interchangable. My current setup:
 
Tx: Field Force Seven (FP-7UAP Super) 1024 PCM or simple frequency 
modulation
1 plane with 1024 PCM 9 channel
1 plane with a 512 PCM 6 channel
1 plane with a 512 PCM 4 channel.
 
All recievers work fine, including the fail safe modes that only the 9 
channel RX is supposed to have. Next reciever I'll by will be a simple 
FM one for my glider. I don't see much advantage to the PCM unless you 
like to fly low to the ground. I really like the transmitter unit, it 
holds config data for 4 planes/helicopters/
 
-Glen

Here is some frightening news from Model Builder magazines column "Electronics
Corner" by Eloy Marez.

Now keep in mind that Eloy used to work for Futaba and according to Al
Casey he left on less than favorable circumstances.  

But in the April 1991 issue of Model Builder (starting on page 7) Eloy
addresses the issue of 3rd party vendors auxiliary equipment that
plugs in to receivers.  Specifically they bring the subject up because
of the World Engines E.G.A.S. (Electronic Glow Adjustment Switch) system 
that doesn't work with a Futaba PCM radio.

Eloy says 
=========================================================================
"Robert, there is a cure, but let us first clarify a point.  The
fault is not in the E.G.A.S.  The Futaba R129DP receiver, as furnished
with the five, seven, and nine channel PCM systems, will sometimes not
work with auxiliary equipment, and a lot of after-market equipment 
manufactures and owners have found that out the hard way.  As a matter
of fact, the receiver will not always work well with earlier Futaba servos,
even some bearing the same numbers as those now being furnished with R129DP
equipped system.   Should you run into that, most of the servos can be sent
in for an update.

The reason is not that this is a PCM system, nor that the receiver is putting
out some sort of exotic control information to the servos.  In actuality, the
output is the same old PWM (Pulse Width Modulation) - output we have all been
using since the Orbit 714 in 1966.  The reason that this receiver is critical 
to add-ons is that it has been designed with a very marginal output pulse 
amplitude.  When any device with an impedance mismatch is plugged into it, the
signal dies or is reduced to a level too low for reliable control.

You say you like numbers!  Well in most receivers, the control pulse amplitude
is at least over four volts, often the same as the supply (battery) voltage.  
For confirmation, I hooked up my Airtronics 92784 FM receiver, which upon
being powered with a regulated five-volt supply, put out a steady stream of
five-volt control pulses which remained steady with as many as three servos
connected in parallel to one channel.

In turn, the R129DP, with the same regulated five volts in, emitted control
pulses of only three volts amplitude.  They remained usable with some 
combinations of two (Futaba) servos, but not with all and never with three
of them.

Why?  I can't even begin to guess, I doubt if a reasonable answer is known."

=============================================================================

It goes on for quite a bit after this.

Remember - I didn't say anything negative - I'm only  quoting the magazine
and I have no doubt that we may well read a retraction next month or so.
My next plane is slated to be the first to use my R129DP - but I don't intend
to hook any servos up with Y connectors.  Hmmmmmmmmmmmmmmmm

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

    Hmmmmmm...I've never experienced _any_ of the symptoms Eloy mentions
    and I'm using servos that go waaaaaaaaaay back, even before Futaba's
    original 512 PCM.  In 2 1/2 years of service, my R129DP receiver,
    actually the entire 7UAP-1024 PCM system has operated absolutely
    flawlessly.  I've never even _heard_ of these symptoms before and,
    thus, have to think we're dealing with isolated problems here.
    Quie sabe (who knows).....??
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

From:	US1RMC::"[email protected]" "Chad Leigh"   16-APR-1993 15:25:54.16
To:	3d::reith
CC:	
Subj:	Kyosho RX 

Hi Jim

Can you find out for me what the RCers know about Kyosho FM RXes

are they Futaba or JR/Airtronics compatible (signal phase etc) and
does anyone use them?  Tower has them now for $40 for 6 channels or
something like that.

Thanks
Chad