MODEL RADIO CONTROL ELECTRONICS 
ALL OF THE NORCIM WEBSITE NOTES ARE FREE
TO USE IN PART OR FULL ON YOUR WEBSITE OR TO COPY AND USE FOR ANY REASON YOU
WISH.
MODEL RADIO CONTROL HISTORY AND TECHNICAL INFORMATION
by Terry Tippett and David Caudrey.
MANY THANKS for technical input from Dave McQue,
Mike Hawkins, Barrie Allen, Mohamed Shiraz Kaleel, Alan Pratt,
George Beeler,
Malcolm Perry, Ron Jay, Peter Keirle,
Peter Allen, Nicholas Ingle,
dave1993, Randal Munroe.
THE NORCIM
WEBSITE……a collection of technical data and history of model radio control
systems.
Please enjoy!….and thanks for reading!
YOU
ARE PROBABLY WONDERING WHY THE STRANGE WORD ‘NORCIM’ IS USED FOR THIS WEBSITE. well during
the early 1970s, a
In an attempt to provide Hints, Tips
and advice regarding R/C kit building, the NORCIM
WEBSITE was born. Note
that if you view NORCIM in a mirror,
then it reads MICRON !
Slowly, and with the help of several
Radio Control pioneers, the NORCIM
website has broadened its technical notes and historical content. Upwards of 17
LONG pages are now available.
Terry Tippett and David Caudrey now run
the NORCIM WEBSITE. We welcome any
Pictures, Hints, Tips or Notes of similar interest. We can use any of these
sent via Email. Inclusion of suitable input to the website is usually within a
few days. We have over a hundred readers
each day in many parts of the world. We hope you will join us !
Recent Visitor Map by Statcounter.com 22May2012
NOTE
THAT THE NORCIM WEBSITE IS A ‘FREE INFORMATION WEBSITE’ no money or reward of
any kind is accepted by the site
owners
or contributors of material to the website. NORCIM is purely an enthusiast
website for enthusiasts!
To contact us via email, use…norcimguy
at gmail dot com and we will reply. Thanks for reading !
NORCIM
NOTES1 home page. Micron R/C fault find both Transmitter and Receivers. DC
receiver circuit.
Field strength gadget for R/C transmitters.
Numerous R/C web links. Bang up to date model reviews! (note
you are here!)
NORCIM NOTES2 40 MHz conversion of Tx and Rx plus Glow control and PCM thoughts
NORCIM NOTES3 35MHz transmitter circuit. Electric glider design. 459MHz conversion
notes.
NORCIM NOTES4 Economy electric flight. 15 amp relay switch circuit. Lost model alarm.
History R/C.
NORCIM NOTES5 Receiver sensitivity test results from Dave McQue including receiver
circuit notes.
NORCIM NOTES6 History of R/C systems including early PPM encoding and decoding
circuitry.
NORCIM NOTES7 Miscellaneous model information plus electronic components and some
2.4GHz stuff.
NORCIM NOTES8 mainly unique model design for radio control and vintage radio control
electronic circuits.
NORCIM NOTES9 nostalgic transmitter circuits collected by David Caudrey. Also some
original circuit designs.
NORCIM NOTES10 further nostalgic original circuit designs for radio control by
David Caudrey.
NORCIM NOTES11 original R/C circuit designs from David Caudrey and some electric motor
testing.
NORCIM NOTES12 RON JAY’s circuit pages. Simply a multitude of alarm circuits, timer
circuits, LED circuits, Tutorials,
Choosing parts and components,
useful free circuit software, free circuit simulator. Magic Stuff !
NORCIM NOTES13 DAVID CAUDREY’s world of the Operational Amplifier. A page devoted to
the ‘OP AMP’ with possible
applications within radio
control systems. Many original design circuits. (content still being added Sept
2011)
NORCIM NOTES14 a discussion of tuned circuits used in model radio control from DAVID
CAUDREY and TERRY TIPPETT
NORCIM NOTES15 DAVID CAUDREY’s in depth look at
discrete transistor amplifiers, both Bipolar and Field Effect (JFET) types are
covered In great detail.
NORCIM NOTES16
Micron Rx notes, Vintage model update to R/C,
Misc engine notes, ESC in-line buffer circuit, Special in-line converter for
The Futaba FASST 2.4G
system, Special D.I.Y anodizing project for model engine parts.
NORCIM NOTES17 Valve receiver technology
by David Caudrey. The lost and secretive art of the Super-regenerative
receiver.
THE NOTES KICK OFF WITH FAULT FINDING THE MICRON RECEIVER KITS:-
General If assembled correctly; all four
receivers in the micron range should perform correctly at switch-on. There is
little or no variation between range (sensitivity) and other characteristics of
correctly assembled versions of the same type. (It is even difficult or
impossible to pick out a ‘good one’ to keep for 
yourself).
The FET
receiver generally
will show slightly more range to complete loss of signal compared to the
other versions, (probably owing to increased front end stage gain.)
For receivers that don’t work on completion of assembly. These often have a built
in mistake and rarely suffer from a faulty component. Look for 4k7 and 47K resistors in wrong
places as reds and org colours are similar in artificial light. Also people get
4K7 mixed with 270K as they are the same three colours but opposite way round.
Coils that have been cut
wrong and mounted the wrong way round. IF
coils may have had the centre pin cut too short. The winding loops around this
pin and if cut too short will cut the winding. (Check primary pins for
continuity using low ohms on meter)
Sometimes capacitors get mixed up and you may find a 47p and a 47uf in the wrong places or similar.
Have a sample PCB to hand or do a ‘pencil rubbing’ of the boards before
construction, as it is possible for customers to join two small copper lands
with solder so that it looks correct as one land. (Particularly mini Rx)
Look carefully at the 104 caps, either the yellow type or the blue type as after soldering, the leg can
become detached from the side of the capacitor, shown by a crack around the
outside edge of the cap. This fault only occurs if the capacitors have been
mounted very close to the board where the thermal shock of soldering is
increased. If in doubt another 104 cap
can be touched to the bottom of the PCB, across the suspect cap, during test to
see if the problem clears.
Look for the obvious, as many
times, IC’s are put in the wrong boards or the wrong way round. Check that only
Futaba, Fleet, Multiplex, JR, or GWS, receiver crystals are being used in the
receiver.
Check that only the transmitter manufacturers crystal is being
used in the transmitter. (use of a different make of Xtal will almost certainly
result in an ‘off frequency’ transmission.
The decoders of the receivers rarely produce problems
providing component values are correct. Very,
very rarely a significant static shock (type that stings your finger when
closing the car door) can knock out the Cmos chip and this is shown by scope
input readings to the chip (normally clock @ 4volts & reset ramp of around
3 volts) being clamped at below 1 volt. Indicating that the chip inputs have
gone low impedance and the chip needs replacing.
Often customers use flux on the boards when soldering which
unfortunately has an acid content and therefore adds many unwanted resistors to
the circuit. This condition can be detected visually with residue on the
boards. The only possible cure is to
clean the residue from both boards using a toothbrush soaked in methylated
spirits but often the flux has impregnated the board and satisfactory
operation cannot be regained and the receiver is not recoverable.
Replacement is the only answer.
Receivers that work but show low range this mostly points to the antenna input
bits. Happily there are few of these
parts involved. (The 159 coil, the 27p capacitor, the antenna input cap and the
capacitor feeding pin16 input of the 3361 chip. Often the flex antenna can be
shorted to ground with a solder whisker on the PCB or a stray wire from the
flex antenna remaining on the board surface and touching the metal coil cover.
When cleared with a model knife, normal range is restored. Perhaps the wrong capacitor has been inserted
across the 159 coil. Is the coil the
correct way round? If the 159 coil
responds to tuning, then the lack of range could be further on in the circuit.
If the front end is checked out and OK then a possible lack of range could be
found in the filter section of the receiver.
‘The filter section’ has its input from pin3 of the 3361… filters the
10KHz spot frequency…feeding it back into the 3361 pin 5. The filters involved vary with the receiver
type. The standard and Comp receiver use a transistor between the filters with
associated resistors/capacitor. The filters
rarely go wrong but the transistor can be inserted with its legs wrong and
associated resistor values need checking.
The transistor gives around 10/12dB gain when fitted correctly. If you
have an oscilloscope, the following can be checked. With the Tx on the bench,
with about 25 cm of aerial, pin 3 or the base of the transistor will show
around 0.1 volt of mixer output. If the transistor is working OK then there
will be 1/1.5 volts of IF at its collector. (as seen on the scope). It is worth
mentioning that the 3361 works well without this extra gain as in the mini
receiver.
The amp in the mini Rx is also used to
increase white noise of the whole circuit so that with the transmitter switched
off, there is a pile of noise activity at pin9, which bombards the 4015
decoder to keep its servo outputs quiet. Note: - the mini receiver
works differently and without the IF amp there is a much reduced noise level at
its 3361 pin9. This lower noise helps to keep the 4017 decoder servo
outputs quiet when the Tx is switched off.
Voltage levels around the circuit. I must admit that I do not have any record of voltage
levels. I often made sure that the receiver board was getting 4volts supply
from the decoder board (or slightly more,) but beyond that always used the
scope to prod around during faultfinding.
Remember that after trying to get a receiver with a
fault working, the coils could be well out of correct setting. This does not
matter for the 159-antenna coil, as the receiver will still work at close
range at any possible setting of this coil.
The setting of the IF coil however is
critical to a quarter of a turn to get any response at all from the servos.
Resetting visually as compared with a working receiver or a new replacement
coil is a useful start.
The ‘Transmitter Power Meter’ kit available from micron is sensitive
enough to detect the oscillation of a receiver Xtal stage if its antenna is
held very close to the crystal. Also but not so convenient maybe, a
spectrum analyser will pick up the receiver crystal stage by simply holding the
input probe close to the Xtal.
Mild jittering or servo noise using the
Micron FET receiver. Although range and general
performance of early dual conversion micron receivers seemed OK, reports from
some parts of the
MICRON TRANSMITTER
GENERAL NOTES:-
The very first ‘Micron’ transmitter circuitry
that I assembled was actually fitted into a ‘redundant’ commercial transmitter
case and sticks. The transmitter had 
developed a
fault that was not repairable but the hardware was still excellent including
sticks, switches, meter, antenna etc. Some ingenuity was necessary to secure
the two Micron printed circuit boards in place but the end result made an
excellent transmitter working on the 35MHz band!
Transmitter
electronics kits are not available from Micron now. The seven-channel circuitry changed in recent
years owing to the obsolescence of the dedicated ‘Motorola’ R/C coder chip. The
replacement coder is interchangeable with the earlier type and now uses
‘bog-standard’ easy to get electronic parts, which are readily available from
most hobby electronics shops.
There is
little point in commenting on the earlier circuitry as inevitably most problems
involved the special IC, which is now unobtainable. The only practical remedy
for repair of these is replacement with the later version coder board.
The photo to the left is now 37 years old! It shows one of the first
Having assembled several of the later coder boards
and seen other peoples efforts, the faults found were as follows: -
Blown 4017
IC. This is
usually caused by incorrect battery wiring giving a reverse input voltage! The
other circuitry survives but it is worth replacing the 22uF. Usually a new 4017
solves the problem but the battery wiring must be checked before
switching on again.
Note that the
coder circuit will run without the IC plugged in at around 1 KHz
which can be seen at the yellow output wire on a scope, or even heard using a
crystal earpiece. This test shows that most of the circuit is functioning
except the IC. If there is no life, check component position, in particular the
correct positioning of the transistor legs into the board.
Working but a
channel(s) is missing this fault can often be traced to an
incorrect setting of one of the joystick pots. All the stick pots must be
pre-set so that their wiper is at mid position, when the sticks and in-flight
trims are at a centre position. This can be checked using a multimeter.
It is also
possible that one of the crimped connectors of the plug-in flylead from the
stick, has not located correctly in the plastic shell and as a result, the
crimp has pushed out of the top of the shell. Relocating the crimp, making sure
that the small plastic fingers of the shell are pushed in to secure the crimp,
is usually a cure.
Another
possibility is a blown diode (usually caused by accidental shorting of the
board to the edge of the metal case, during testing and adjustment). Often this
can be 
confirmed
using a multimeter on low Ohms setting across each diode in turn (there are 10
of them!), to find the ‘odd one out’, followed by replacement.
Coder board
quality, I have seen more than one coder Printed board now which
was not up to the usual crisp copper etch that is normally seen. On these
boards it was necessary to carefully inspect the copper lands and cut through
with a model knife, the several bits that not intended to be joined! So look
carefully with light behind the board.
The Transmit
Section is a smaller board that feeds the antenna and like the
coder board, if assembled correctly, does function at switch-on. The outputs of
this board has been passed by the ERA (Electrical Research Association) for
Not working at
all this points to resistors or capacitors in the wrong
places. Remember if you find one wrong then there will be another where that
one should have been! Look for coils that have had the wrong pins snipped. These
will need replacement. Check the transistor legs are going into the correct
holes on the board. Check that only Micron or Futaba crystals are being used
and ‘Tx’ is indicated on the crystal tab. Try another crystal in case the one
fitted is duff.
Reverse
Polarity fault. This always shows itself as a burned brown/black 100R
resistor in front of the output transistor. Unfortunately both the output
transistor and RFC will need replacing. The oscillator coil always survives, as
does all of the other circuitry.
THE MICRON
DUAL CONVERSION R/C RECEIVER
The
fundamental advantage of Micron’s receiver front end is acknowledged in the
RSGB 
‘Radio
Communications Handbook’, 5.16. As a result, the receiver Jfet does handle
strong out of band transmissions particularly well.
Microns use of
the FET is interesting in that some of the known disadvantages of this device
have been addressed.
JFET’s, used
in mixer stages, do like, a high oscillator drive to work well. Unfortunately
JFET’s also have poor isolation of the 
oscillator
frequency and this results in the oscillator frequency being transmitted via
the receiver antenna! Although this transmission could still be termed as
‘flea-power’; Just imagine thousands of such receivers on a good flying day,
all transmitting on a frequency that has nothing to do with radio controlled
model aircraft! The interference to other users of the radio spectrum would be
at risk and it is important that R/C receiver emission is kept to an absolute
minimum.
The Micron FET
receiver uses dual conversion
Another
problem with JFETs was the divergence of characteristics from one device to
another but technology has advanced and JFET characteristics are now much more
controlled, with even selected versions of the same 
device
available.
The Micron FET
receiver circuit diagram comes next and surprisingly, its
almost as simple as the Mini receiver that they do, except for the two
transistors added on at the front! I will try and run through the circuit as
best as I can without causing too much pain for the reader!
The 35MHz
parent transmitter signal is picked up by the 85cm flex antenna. (Length is not
critical). This excites L1, producing a 35MHz signal input to the BF244A
(gate). The 27p/4.7uH trap grounds the 13.5MHz image frequency and the 24.3MHz
oscillator leak through via the 15p cap. Meanwhile the 24.3MHz plug-in crystal
oscillator circuit output is injected via the 0.1 cap to the BF244A source
terminal and mixing of the two frequencies occurs, producing a 10.7MHz output
at the BF244A output. There are several other frequencies produced by mixing
but the 10.7MHz crystal filter rejects these.
The selected
10.7MHz signal is passed on to pin 16 of the Motorola 3361 chip. Mixing takes
place for the second time using the on-board 10.245MHz Xtal oscillator. This
produces a 455KHz signal at pin 3.
This signal is
filtered by the 10KHz filter (CFU455HT) and then amplified in the chip, with
the FM content being detected at pin 9.
The 4k7 and
.022 cap at pin 9 get rid of white noise on the output signal, leaving rounded
signal pulses (from the transmitter) of about 0.5v peak to peak. Note L2 needs
adjusting to achieve this. Pin 12 is an input to a squaring amp with outputs at
pins 13 & 14. These two outputs (4v pp) are used to clock the standard Cmos
counter chip, giving up to 8 servo outputs. The 2N3904 provides an extremely
servo noise free supply of around 4volts to the whole receiver. The ‘image
frequency’ rejection of this receiver is around 60dB which means that
transmitted signals on the 13.6MHz band (image band) would have to be a million
times stronger to cause a significant interference problem. This compares with
‘normal’ single conversion receiver image rejection figures of around 10dB,
allowing 34MHz band signals to cause havoc when only 11 times stronger! The
34MHz band is for ‘Ministry of Defence’ use and has been little (if any) used
over recent years.
A HOT TIP !
If you use one of the cycle pump type
de-soldering tools, try pushing a short length of silicone fuel tubing on to
the nozzle end so that just a couple of millimetres protrudes from the tip. The
resulting ‘soft end’ seals around the solder joint better as the tool is used
and also reduces the recoil kick back. The silicone tube is also unaffected by
the solder iron heat!
MODEL
CONTROL TRANSMITTER OUTPUT TESTER CIRCUIT
This next
circuit lends itself not only for home checking but also club and quick
model shop checks. The circuit checks for correct power output of any 35
or 40 MHz radio control transmitter is shown. These things are called ‘field
strength meters’ and are a standard piece of electronic equipment in the
service workshop to check the output power of R/C transmitters. ‘Field Strength
Meters’ (as they are called) are usually based around a reasonable size
sensitive 50uA moving coil panel meter. These are now 
listed
(Farnell) between £20 and £30 each (before circuitry!). This circuit is based
around the National Semiconductor LM661CN Cmos quad op-amp IC. The circuitry
components should cost no more than £4.00! and it has greater sensitivity than
the standard meter type. Transmitter output strength is shown by four
Superbright red light emitting diodes. A correctly functioning R/C transmitter,
will illuminate three to four LEDs at a distance of 10 metres away. Adjusting
the length of the short telescopic aerial will allow all LEDs to operate at a
shorter distance for indoor checking. With occasional use, a four AA alkaline
battery lasts over a year (even occasionally leaving the thing switched on)
The OA47 diode
seems to work best but more difficult to get. L1 needs to be initially adjusted
to illuminate the maximum number of LEDs at a range of 10 metres or so. Once
set that’s it. The Toko coil used is no longer manufactured but many are still
in the pipeline and there are alternatives. Remember, if you set L1 using a
35MHz Tx then the unit will only check other 35MHz transmitters. If 40MHz Txs
are to be checked, set L1 using a 40MHz Tx. L1/C1 form a tuned circuit at
35MHz. A 35MHz Tx will excite this coil and cause a resonance of L1. D1 detects
this and a little current flows at 35 million times a second! into C2. This
increases the voltage across C2 (slightly) in proportion to the power of the
transmitter signal. The LMC660CN is a Cmos op-amp and has little effect on the
input circuit. The op-amps are arranged as voltage comparators using the
potential divider R1-R5. The resistor values are selected to give a 3dB step
between op-amps flipping on. (each one showing twice the transmitter power
output) So with a weak signal, IC1D output will illuminate LED4. As the
received signal gets stronger, the remaining LEDs will illuminate in turn,
until all four are illuminated.
An excellent
practical layout of this circuit using Veroboard and some up to date components
can be found at www.pm.keirle.com/
SOME USEFUL LINKS:-
www.micronradiocontrol.co.uk kits for R/C receivers, speed controllers,
servos, chargers, etc.
www.modelflying.co.uk ‘Radio Control Models & Electronics’ one
of the leading UK R/C model aircraft magazines.
www.rcmodelworld.com ‘Radio Control Model World’ one of the
leading
www.epemag.wimborne.co.uk ‘Everyday Electronics’ a leading
www.flyingsites.co.uk general information regarding radio control
model aircraft.
The UK Radio Control Council the Radio Control technical advisory council to
the Govt ‘OFCOM’.
www.rc-soar.com Info about radio control soaring models (and
independent coverage of micron receiver assembly!)
www.nikamelectronics.co.uk RF Electronics Company used by micron for
development of UK R/C systems.
www.ShortRangeDevices.co.uk companion site to above with possible model
to ground modules 433MHz to 5GHz.
www.elektor-electronics.co.uk edge of electronics UK/Netherlands magazine.
Electronic projects/PCBs.
http://home.HiWAAY.net/~mjn EF info plus PIC based speed controller design
absolutely free! See Radio2
www.customelectronics.co.uk flight simulator system for model aircraft,
speed controller & other items.
Alan’s Hobby Web Links A comprehensive ‘A to Z’ of hobby
related web sites.
www.glue-it.com Model
enthusiast site with many links and info including model railway topics.
www.actionkit.co.uk electronic
kits for models and GCSE projects, see Radio3 bottom of page.
http://www.iroquois.free-online.co.uk Dave
Day’s Home Page….everything to do with model aircraft and more!
http://www.rcmodelreviews.com/
simply one of the best R/C electronic sites you are likely to come
across. Bang up to date technology explained.
http://www.webx.dk/index.htm superb website for R/C electronic
projects. Excellent circuit diagrams and assembly photos. By Thomas Scherrer.
A MAGICAL COLLECTION OF ELECTRONIC
CIRCUITS.
http://www.zen22142.zen.co.uk/index.html
CIRCUIT EXCHANGE INTERNATIONAL Website by Andy Collinson. Electronic and
radio schematics, design and simulation.
Welcome to Circuit Exchange
International. My site contains electronic and radio schematics in ten
categories. In addition, there are sections on circuit simulation, design,
analysis and a practical section containing tutorials. This is a free site and
mostly my work, however I do welcome contributions. Everyone who has helped in
the making of this site is listed on my credits page. This home
page has kindly been translated into several languages, and you can use google
translator for others. Thank you for visiting my site.
The following links come from ‘Alan’s Hobby Web Links’
(above) ….these links are just a tiny part of of Alan’s Dictionary of Model
Radio control but this tiny part fits with the content of this website perfectly…..many
thanks… my flying friend.
2.4-GHz
Spectrum Analyzer - Low Cosr
Altimeter - Winged Shadow Systems -
micro
Circuit Diagrams for Model Aircraft
Circuits for RC gadgets - Jo
Aichinger ***
Creating
Printed Circuit Boards - Easy DIY
Do-It-Yourself Radio Control Electronic Projects &
Gadgets
Dump "r" DIY discharge RX
and TX packs
Electronic projects and tutorials ***
Electronic Circuits for the Hobbyist -
Tony Van Roon
Electronic
Gadgets (Projects) for RC - Tony Van Roon
Electronics Pages - Circuits etc by
Tomi Engdahl's
LED Calculator - RC Cam Projects
Lost Model
Alarm (LMA ) - Plane Finder with fail safe
Plane finder
_ Lost Model Alarm
Newark Electronics, Catalog = Electronic Components
Optic Isolators - S.M.Services (U.K.)
Ltd
Radio
control electronics - DIY fault finding and repair [Norcim] ***
Radio Electronics Pages - Build your
own TX & RX
Ram Radio Controlled Models Home Page
Receiver
& Solenoid wiring for use with SLA (Gell Cell battery)
RC Groups
Discussion - DIY Electronics
RC Systems - DIY build your own &
other RC projects.
Schiepatti
Switch - for camera operation, glow driver etc
Stefan's Electric R-C Web Site
Supercircuits Inc. ..Micro video camera etc.
Sirius Electronics-TX Diodes bridging
Suding Associates Inc. - Main Page
Voltage regulator = BEC 5V & 6V for Boats, cars and airplanes
traffic
light security for external links.
Did you know that the new Spread Spectrum
(2.4 Gig stuff) technology has been around for
70 years? You need to watch this video right through, Don’t switch
off! thinking it’s not relevant, then ask your grandparents about Hedy
Lemarr! http://www.youtube.com/watch?gl=CA&hl=en&v=xUyhPDVBiaI
You can contact me….norcimguy at gmail.com
Thanks for reading!
Thanks for
reading !
The newcomers guide of Spread
Spectrum radio control simple
advantages of the 2.4 Gig radio control band for model control.
A change of subject ?.... The
energy saving light bulb Myth. How
for ‘free’ light bulbs that
don’t work!
A
simple demonstration of how to fly a model helicopter a superb video showing how to get started with model helicopters 
This can’t be real !
or can it? A full size airplane looses
a wing and the pilot lives??
Do we need the two new
UK aircraft carriers costing 5 billion pounds ? have a look at what the new generation of the Harrier Jet
looks like. Does it need a
conventional aircraft carrier ?????
MICROSOFT
ANTIVIRUS award winning security program for business and home computers at a
seriously competitive cost.
Norcim website
protected by symantec Norton.
