Conference vmszoo::rc

Well, you didn't say if you're in the continental U.S., but I assume so...

Digital proportional means that the control surface deflection is
proportional to stick movement.  Usually it is a perfectly linear
function, though that can be changed in some radios.  It is not
really digital, actually the deflection is coded in terms of a pulse
width that is sent out for each channel, then separated in the
receiver.  The PCM sets are true digital, as we computer folkies
define that term.

As far as your radio goes, I think you got a white elephant.  The 36
Mhz band is not used in this country (U.S.), and it would be major
to convert the equipment...Since radios are so cheap, I'd suggest
putting yours in mothballs and buying another one.  However, if your
are up to a challenge.  ACE, a manufacturer of kit radios, sells a
transmitter module for $20 or so.  If you can supply +9.8V, ground,
and a good modulation signal to it, you're on the air.  The trick is
in finding that modulation signal.   Then there's the matter of
modifying the box to take the ACE module. 

Aristocrat is sold by Polks Hobbies, 346 Bergen Ave, Jersey City,
NJ, 07304.  Toll free 1-800-225-POLK (from pg 21 March '87 Model
Aviation).  Maybe one of their people could change the module or
sell you one to change yourself.

> Well, you didn't say if you're in the continental U.S., but I assume so...

  Yes, I am U.S.  Acton Ma.  AKO1, but the radio is from Hong Kong.

> As far as your radio goes, I think you got a white elephant.  The 36
> Mhz band is not used in this country (U.S.), and it would be major
> to convert the equipment...

  I called Polk's Hobbies and they sell crystal sets for $6.40.  The 
crystals are simple plug-ins that are externally located on both the
receiver and transmitter.     

> .............However, if your
> are up to a challenge.  ACE, a manufacturer of kit radios, sells a
> transmitter module for $20 or so.  If you can supply +9.8V, ground,
> and a good modulation signal to it, you're on the air.  The trick is
> in finding that modulation signal.   Then there's the matter of
> modifying the box to take the ACE module. 

  Would this be necessary with the replaceable crystals?


  Jim C.  

Jim, I would bet that it needs a new transmitter module. 

Just occured to me that you might not know that U.S. aircraft RC is on
72 Mhz, while cars and boats are on 75 MHz.  Doesn't sound like the
Polks folks are very up on that either!

But, if all it needs is new crystals, I'm almost 100% certain that
the transmitter must be tuned up when you replace those crystals.
The only reservation would be that they may have invented a circuit
that I've never heard of.  The output coils require retuning even
with in-band changes; least of all a change as great as this.  Any
retuning must be done by an FCC licensed technician. 

Forgot to mention the receiver; the same remarks go for the
receiver; it probably must be replaced for the U.S. frequencies.
Only difference is that you dont need FCC blessings to work on it.

  

  Yes, I do realize that I need 72 Mhz.  That is the whole reason
for getting the new crystals.  It would be a real bummer if I have
to scrap the radio.  Polk's said they do not make a 36 Mhz crystal.
So I have no idea where this crystal came from.  The back of the 
radio says that it was made for Aristocraft of New York.  The unit
was made in Korea.  I don't know if the crystals were put in to
conform to Hong Kong laws and never tuned or what!?!?!

   OK, what would be the worst I could expect if I changed the 
crystals to 72 Mhz and did not get it tuned? Would it damage the
radio or just make it not function right?
   Is there anyone local who handles tuning?


  Jim C.

Hi! Jim,

36Mhz is our Australian frequency. The RF modules are basically the same as the 
European 35Mhz with a minor coil change. 

I give you a 100% guarantee that you will have to change RF modules to go from 
36Mhz to 72Mhz. I changed a radio from 40Mhz to 36Mhz and that was outside the 
tunable range of the Tx and Rx RF modules.

< OK, what would be the worst I could expect if I changed the 
< crystals to 72 Mhz and did not get it tuned? Would it damage the
< radio or just make it not function right?

If you don't tune the radio to the new crystals the best you can expect is a
few feet range, the worst and most probable, it wont work. Forget it and buy
new RF modules in if you intend to use the radio otherwise you will never get a 
satisfactory performance.

John.

  @@*&**!!!%##  (translation:  OH Darn!)

  Well, I guess I'm not going to get much use out of my radio as it is.
I will have to see about changing the modules.  Well, there is nothing
to prevent me from using the servos is there?  I got 3 servos with it. 
Connectors might have to be changed to fit my other receiver, but no big
deal.


  Thanks for the info...Jim C.

 

The servos should be compatible, but the wires may not be in the
same order.  That is, you cannot change pin 1 for pin 1, etc, on the
two connectors.  If you need further help on this, post a note; I
have servo connections for several manufacturers.

    Will the manufacturer take your 36Mhz radio into their repair shop
    and turn out a 72Mhz radio ready to go?  If yes, evaluate the price
    too!

    
    	I would call Polk's. Let them know of the circumstances of
    the purchase. Most dealers of RC equipment are responsive to
    the public needs. You may find they will do an exchange free
    of charge. What do you have to loose. If you call Polk's I
    would as to talk to a manager. They may be a little more helpful.
    
    					Tom

  Well, I called Polk's and got an operator that was of no help.
She said I have to call back on Monday and talk to Nat or Lewis 
Polk personally. 
  I will post whatever info I get from them.

  I also called ACE radios and they are sending me one of their
catalogs.  
  I will check prices and 1) Exchange the unit 2) Have Polk modify
it 3) Modify it myself via ACE 4) Make a book end out of it.


  Jim C. 
         

Jim, a thought occurred to me on the way home last night...You said
in the base note that the frequency of the radio was 36 Mhz.  Was
the radio actually marked as having an output frequency of 36 Mhz,
or did you infer that the output frequency was 36 Mhz because of the
marking on the crystal?  The reason that I ask this is that some
transmitters, for instance ACE, use the second harmonic of the
crystal; an ACE crystal ordered with reference to a 36 Mhz
frequency, but is crossreferenced to its actual 72 Mhz output
frequency in the catalog. 

It does seem strange that a radio made for a company in the U.S.
would have an illegal frequency...

Hi Jim,

I picked up our local Mag last night and saw your radio advertised. It is as I
understand it is manufactured in Korea and is being sold at a very ECONOMICAL
price (cheap) here in Australia. It is being sold in Australia by one of the
oldest and most reliable Importers who are known for doing their homework
properly so I imagine it should be reasonable. I have not used this radio but I
have been told it is a good sport radio but not suitable for serious
competition work. Looking at the servo output arms I would have my doubts that
the servos would be strong enough for large models. 

<  One last question, I want to pick up some ni-cads, charger etc...
<  Where is a good place to buy/order from and what should I look for?
<  I see the rechargeable batteries at the local hardware store. I think 
<  they are General Electric batteries, are these any good?

I have never used GE batteries but a lot of the supermarket batteries cannot be 
fast charged (> 20% of rated O/P). If you wish to field charge check the specs 
of the cell first. I have always used Saft cells, they are reliable and take a 
lot of abuse. They have also been good supporting our sport in this country so 
I buy there product.

John.

re .12


>Jim, a thought occurred to me on the way home last night...You said
>in the base note that the frequency of the radio was 36 Mhz.  Was
>the radio actually marked as having an output frequency of 36 Mhz
>or did you infer that the output frequency was 36 Mhz because of the
>marking on the crystal?  The reason that I ask this is that some
>transmitters, for instance ACE, use the second harmonic of the
>crystal; an ACE crystal ordered with reference to a 36 Mhz
>frequency, but is crossreferenced to its actual 72 Mhz output
>frequency in the catalog. 

 The radio is clearly labeled as having a frequency of 36 Mhz.  A large 
sticker on the front, around the opening for the crystal, says 36 Mhz.
My brother-in-law is not into R/C so he did not realize it is not
an allowable frequency in the U.S.  The shop owner that sold it to
him swore up and down that it was just fine for the U.S.  He obviously
lied.  
 
 
  Jim C

    Jim, I may have a solution for you:
    Since you are in AKOV01, and there is always someone or another
    going to Hong Kong from your building (GIA), why don't you just
    ask somebody to return your unit and get you the money back??
    
    Konrad
    
    

    or get the someone to exchange. send somebody that has good acting
    skills to give person who sold you this something to think about...
    
    

  Well I talked to Nat Polk of Polk's Hobbies.  He said he could not 
exchange the radio because they are made in Korea and shipped directly
to Hong Kong, or Australia, or the U.S. or wherever.  Since he can not
sell the radio as it is, he would have to ship it over seas and it would
not be realistic for him.  He also said that about the only way to 
change the radio to 72 Mhz is to replace the entire guts of the unit
which he was willing to sell me, but they cost about $50.00. So, I am 
going to see what the ACE catalog I have ordered has for the upgrade or
I am going to try to off load it to someone in a 36 Mhz country. 


  Jim C
    

Jim, some things you could do to test the feasibility of this project.

First, open the radio and locate the transmitter.  If its on the
same board as the encoder, you're in for difficulties because you'll
have to disable the transmitter portion while not affecting the rest
of the circuitry; very difficult without a schematic.

If the transmitter is on a separate board, the conversion is
possible (I believe most transmitters are).  The ACE module measures
about 3 inches long, by 2 or so inches wide.  That's what you'll
have to find room for.  

The existing transmitter board should have 3 wires; any more and
you'll have to figure out what the others are for.  The +9 and
ground wires shouldn't be hard to find.  The modulation wire should
be checked with an oscilloscope.  This is to verify that you have
the right modulation level for the ACE module.  Actually, I don't
believe this is critical, since I've hit the ACE module with some
terrible signals!  I think the modulation level out of the encoder
is pretty much the same across the board; at least it is the same
between my Futaba and ACE.  Also, as a confidence check; if your
transmitter uses the Signetics NE5044 chip, you've got it made,
since that puts out the correct signal automatically.

Once you've got those wires picked out, you can do the job with a
little ingenuity.  ACE sends a small instruction booklet with the
module; if you don't get one, let me know, and I'll send you the
info. 

I've been thinking about sticking an ACE module in my Futaba, since
it would allow me to change frequencies easily by simply plugging
in another board.  Also, I think the ACE module will be more compliant
with the FCC narrow band requirements that are coming in.  This is
the same module that they are using in the Silver Seven.

 Re .18

 Sounds pretty straight forward (famous last words).  I'll take
a look at this things guts this weekend and see what I've got.

  Thanks

	Is it correct that you can change channels within a band
	(ie 75Mhz) by simply swapping crystals with no retuning? 

	Chris

Yes, that's correct.  But I've been told that to change +/_ one
channel from the one the transmitter was originally set up on is OK.
What you're fooling with here is the tuning of the final output
stage.  The FCC specifies that the power at this stage must
not exceed 1 watt.  The way they set it is to monitor the collector
current of the output transistor, and calculate the output power
from there.  As the output load of this stage is tuned, the current
through the transistor changes.  They tune the stage such that the
output load is matched to the antenna, while the collector current
is at or below the specified value.  For each frequency, this stage
must be retuned to achieve proper match and current.  Of course, the
intervening multiplier stages must be retuned too, to allow the
transmitter to operate at maximum efficiency, but the important one
to the FCC is the output stage.  Because our RC channels are so
closely spaced, they will work pretty well on adjacent channels; but
that's about all.

Those transmitters that allow quick frequency change use one of two
methods; either there is some sort of quick change transmitter
module that plugs into the transmitter, or they use frequency
synthesis to generate the carrier.  

    
    	Does this (tuning) require shipping the transmitter to the
    	factory or is there someone local (NH/MA) that can/will do
    	it? I'm a little hesitant about sending my radio away for
    	(many?) weeks.
    
    	Do we have any FCC licenced mech/techs participating in this
    	notes file?
    
    	Chris