Python Technical Report

FCC ID: BRWPYTHON

Test Report

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FCCID_120324

Page 1
Technical Report
Transmitter Model PYTHON
FCC ID# BRWPYTHON

T A B L E O F C O N T E N T S

1.0 INTRODUCTION

1.1 Definition
1.2 Application
1.3 Construction

2.0 ENCODER THEORY OF OPERATION

3.0 THEORY OF OPERATION

3.1 General
3.2 Block Diagram

4.0 FAILURE ANALYSIS

5.0 APPENDICES

5.1 Transmitter Block Diagram
5.2 Transmitter Schematic Diagram
5.3 Transmitter Photographs and ID Labels
5.4 Transmitter Tune-Up Procedure
5.5 Quarts Crystal Specifications
5.6 Test Data

Page 2
Technical Report
Transmitter Model PYTHON
FCC ID# BRWPYTHON

1.0 INTRODUCTION

1.1 Definition

The Model PYTHON is a transmitter for the Remote Control
(R/C) of models such as cars, boats, etc.

This Transmitter is for AM System, available for the PPM(Pulse
Position Modulation).
This Transmitter is a part of the HORIZON HOBBY DISTRIBUTORS, INC.
AM"family" of Remote Control Transmitters which at this time
consists of:

Transmitter Model # FCC ID #

Beat GEAR NET-102 BRWNET102
PYTHON NET-112 BRWNET-112

Separate Applications for each transmitters and for the
receivers are submitted as required by the Commission.

The Manufacturer, Japan Remote Control Company (JR),
manufactures all transmitters and receivers.
The AM family of R/C systems is exported by JR to the United
States of America, and several European and Asian Countries.

The Applicant for this Equipment Authorization, HORIZON HOBBY
DISTRIBUTORS, INC. will, following receipt of Grant of Equipment
Authorization, import only those versions of these R/C radios
which are allowed for use in the USA under the Rules and
Regulations of the Federal Communications.

The 75 - 76 MHz version of this transmitter is the subject of
this Application; these are the units which will be offered
for sale to the general public.

Page 3
Technical Report
Transmitter Model PYTHON
FCC ID# BRWPYTHON

1.2 Application

The Model PYTHON R/C transmitter utilizes "Amplitude
Modulation" to convey the PPM encoded position of its
control handle and trigger switches to its companion
R/C receiver, where the PPM encoded pulse train is
demodulated, decoded, and supplied to a number of servo-mechanisms
for positioning of control surfaces, throttle etc. on the model.

Both transmitter and receiver are very narrow band units; they
have been designed to comply with the European requirements of
10 KHz channel spacing.

1.3 Construction

The Model PYTHON Transmitter all consists of a plastic case.

(Reference is made to Fig. 5.1, Transmitter Block Diagram)

* control handle and trigger
* a 8cells dry battery
* an analog-to-digital converter (ADC)
* a microprocessor to create the PPM pulse train
(TMP87C408N)
* a modulator driver stage
* a RF power stage
* a telescopic antenna

This Transmitter is to be made available by the importer
only on those carrier frequencies in the 75 - 76 MHz frequency
band which are at present authorized for R/C use.

Page 5
Technical Report
Transmitter Model PYTHON
FCC ID# BRWPYTHON

3.0 THEORY OF OPERATION

3.1 General

Reference is made to Figure 5.1, Transmitter Block Diagram.

The HORIZON HOBBY DISTRIBUTORS, INC. Model PYTHON R/C Transmitter
is handle and trigger type Transmitter.

It operates on any of the R/C frequency (Channels)
allowed by the Commission in the 75 -76 MHz frequency band.
Selection of the desired RF channel is made by Quarts crystal.

3.2 Block Diagram

(Reference is made to Figure 5.1)

The (up to) four control potentiometers are at the right side
of the schematic drawing.

The control potentiometer, which is mechanically coupled to
the control handle and trigger, is supplied with the regulated
5.0V voltage. The wiper on this pot is exactly centered in
the neutral control stick position. All analog processing
is performed as deviations from this center (reference)
voltage.
After the mixing of each channel, control voltage is changed to
Pulse Train, through encoder circuit.

The oscillation is oscillated by Transister Q51 with
Third-over-tone, 37.5 MHz then, is dubled by Dobrer Amp. And
Transister Q53 on 2nd stage to reach 75 MHz.
After this, it is amplified by power Amp. Transister Q52a,
and is supplied to the antenna through band pass filter.

Page 6
Technical Report
Transmitter Model PYTHON
FCC ID# BRWPYTHON

4.0 FAILURE ANALYSIS

A failure analysis was conducted to ascertain that
single-component failure will not result in unauthorized
radiation.

It should be noted that component failure would result in
return of the unit to the factory, or to an authorized repair
station.

(Reference is made to Figure 5.2, Transmitter Schematic Diagram)

Failure of any of the transistors (predominant failure mode:
emitter-collector short) will result in the unit becoming
inoperative:
In the case of Q51 oscillator short, RF output will be
non-existent.
Q53 failure will result in very low, if any, output.
Failure of Q53 will register on the unit’s meter which
indicates collector current into the PA stage.

Failure of the MOD IN input (latch at 0 or 6.0 Volt) or
modulator transistor Q2, will result in either the non-modulated
or small modulated being transmitted.
Although this failure render the unit inoperative,
the frequency tolerance would still fall within the channel
bandwidth and tolerance requirements of .002% of
75 MHz = 1.5 KHz.

Failure of the quartz crystal, X1, will inevitably result in
no, or strongly reduced, output.

All other incidental failures will render the unit inoperative
and because for return of the transmitter to the service facility..

Page 7
Technical Report
Transmitter Model PYTHON
FCC ID# BRWPYTHON

5.4 Transmitter R.F. Tune-Up Procedure

1. Remove 9 screws from transmitter. Break seal on case and
remove PC assembly. Put PC assembly on bench,
component side up.

2. Refer to transmitter schematic Figure 5.2.
Soften bee’s wax on cores in L58 and L53.
Starting at L58, adjust these cores for maximum wave form of
oscilloscope with small 50 ohm loop and L53, adjust.

3. Repeat step 2.

4. Using spectrum analyzer with small 50 ohm loop,
verify that sub harmonic and harmonic components are at
least 50 dB below carrier component. Pay special attention
to 112.5 MHz and 150 MHz components.

5.Remove PC assembly from Transmitter. Re-apply bees wax to
L58 and L53. Put PC assembly back into its case, replace
the four screws and re-seal opposite edge...

page 8

FCC ID# BRWPYTHON Figure 5.1 Transmitter Block Diagram

page
9

FCC ID# BRWPYTHON Figure 5.2 Transmitter Schematic Diagram

Document Created: 2000-08-03 17:01:36
Document Modified: 2000-08-03 17:01:36

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