donderdag 8 juni 2017

Filling the Racal Cougar Crypto Keys using an Arduino Part II

This post will be about the protocol used by the Racal Cougar to fill the keys into the Crypto Board.
Before reading this post i recommend to read my previous posts about the mechanism used to program the Cougar: Program the Racal Cougar - Part 2 & Part 5

MA4083(G) Fill gun

Reverse engineering (again)

Like i did when figuring out the protocol used by the E.C.U and programmer to control the Cougar and fill the channel information, the first thing i did was hook up a fill-gun filled with known keys to the Racal Cougar and using the tap-cable making the data visible on an oscilloscope  (actually i used 2 fill-guns but more on that later) .

Tap cable
The difference compared with analyzing the date before was i now had a technical manual for the MA4073 programmer which provided me with useful information and hints.

Two different PWM data streams:

The datastreams used to fill the Racal Cougar can be divided in two types of data:
  1. Racal Cougar control data
  2. Key fill data

PWM timing

Control data:

The control data stream is described in the previous posts mentioned above, it uses PWM data modulated with a frequency of ~4 Khz. where one period takes 250 μS.

A logical '0' is send by pulling the F pin low for ~64 μS and high for 186 μS and a logical '1' is send by pulling it low for ~186 μS and high for 64 μS.

Control data takes 4 bytes (32 bit) and expect a echo to be returned from the Racal Cougar.

Key fill data:

The key fill data stream uses the same PWM modulation but with some differences compared to the control data. First of all the frequency of the PWM data is lower, it is ~1.42 Khz and second it is one continuous stream of 520 bits.

A key fill PWM modulated bit has a period duration of ~700 μS where a logical '0' is send by pulling the F pin low for ~96 μsec and a logical '1' is made by pulling it low for ~224 μS.

Fill commands and data

When sending key data to the Racal cougar the key fill data is preceded with 3 control commands each expecting an echo response :

  1. FTL command (HEX 7F8B)
  2. DSN command (HEX 7F03)
  3. ZA command (HEX 7F07)

After the ZA command, zeroise keys, is received the Cougar is generating a 1 Khz alarm tone on the audio line indicating the unit doesn't contain any crypto keys (you would get the same alarm when using the zeroise button on your Racal Cougar and select a crypto channel).

Next the 520 bits of key fill data are send which is handled directly by the crypto module. When no error's occurred the keys are stored in the crypto module which in turn disables the key alarm indicating a successful transfer.

Simplified overview of key fill commands

Key fill data

Information about the commands being send can be found in the technical manual of the MA-4073 and it tells you what in the previous paragraph but it doesn't tell you the actual structure of the key fill data. This is where the fun started :-)

Key fill data

Every transfer of key data starts with a fill instruction command, this command shouldn't be confused with the normal command structure, the fill instruction command are 8 bits preceding the actual key data and have the hexadecimal value of 30 (00110000).

Next there are 512 bits of key data, 128 bits for each key. 4 keys in total where the keys are stored in the following order: B, A, D, C.

Although the Racal Cougar can only handle 2 crypto keys, A & B, the crypto module can store 4 of them.

The 128 bits of a key contains the following data:

  • 12 bits of a predefined value, this is value is hard wired in the programmer and can be changed on customer's request. In general these are 12 one (1) bits.
  • 108 bits of actual key data, 36 octal (0...7) digits each using 3 bits.
  • 8 bit CRC using a different CRC-polynomial value for the different crypto boards.

Key data:

After the 12 predefined bits comes the actual key data, for every of the 36 digits 3 bits are added to the key data stream. The three digit bits are representing a binary value of 0 to 7 (octal) in Little Endian order (least  significant bit first).

The bit (LE)  values for the octal key digits:

0 1 2 3 4 5 6 7
000 100 010 110 001 101 011 111

To illustrate this, imagine we have a key made up of 8 digits with a value of '01234567'. The key data part of the stream would be the following 3 bytes:

Byte 1: 00010001
Byte 2: 01100011
Byte 3: 01011111


The last part of the 128 bit key data stream is used by a 8 bit CRC (cyclic redundancy check) value. This CRC value is used by the crypto module to check if all received bits are correct and the data hasn't been corrupted during communication between the programmer/ fill-in and the module.

CRC calculation is done by using a 8 bit CRC-checksum using a specific polynomial value. The crypto modules requiring a 'C' programmer/ fill gun are using a different polynomial value then the modules requiring the 'G' version.

C polynomial value: 1 11000000
G polynomial value: 1 01000010

By changing this polynomial value to match the target crypto module both can be programmed using the same Arduino programmer.

zondag 28 mei 2017

Filling the Racal Cougar Crypto Keys using an Arduino Part I

After being able to fill the Racal Cougar with custom channel frequencies using an Arduino the next step was being able to add new crypto keys using an Arduino also.

After spending a couple of days doing some reverse engineering using both a C and G MA7083 fill gun filled with known keys i was able to write a little Arduino Sketch that recorded the PWM modulation being send over the F-pin of the audio/fill connector.

At first the data stream didn't make any sense but after looking at it using a scope i noticed why the grabbed data looked like garbage and i had to change the grabber sketch to show the correct data.

Reading both tech manuals for both the programmer and a 4515 i got some info on the commands needed to be executed to do a key-fill and these were quickly identified in the datastream. The 'difficult' part was the key-data datastream and CRC checksum used.

In the movie at the top of this post you can see me changing and testing the Crypto Keys of two Racal Cougars.

Next post(s) will be about the commands and key-data datastream used.

maandag 22 mei 2017

Racal Cougar Standalone Programmer - Part 2

After playing with the initial version of the Arduino Racal Cougar standalone Programmer i decided i didn't like the cheap stick-on 4x4 keypad used so i replaced it with a different one. After make a new 3D model of the case and printing it this is the result:

Version 2 of the standalone programmer

Wonder what's inside it ? Besides a 4x20 LCD, Arduino Nano and a 4x4 keypad there is also a 3.7 volt 1200 m.a.h rechargeable battery with a Adafruit charger/ booster inside the case.

Inside the programmer

Programmer in action:

Besides working on the hardware i also completed the Arduino Sketch making the programmer fully functional and able to program the PRM-4515. 

An introduction and programming a cougar using the programmer can be seen in this video:

Used components:

I used the following components in this programmer. Please note that the provided links are displayed for  reference purposes and i am not affiliated to both shops.
Besides the component mentioned above i also used some items you probably have in your spare box:

  • DB9 female connector + mounting screws
  • Small power switch 
  • Power adapter  9 - 12v DC + chasis connector 
  • 2N7000 N-Channel mosfet
  • 10K resistor

dinsdag 16 mei 2017

Racal Cougar Standalone Programmer - Part 1

After completing the first version of the Racal Cougar Programmer i decided to make a standalone version of this programmer.

This post is a little sneak preview of this project i am currently working on.

 Development version of programmer with 4x20 LCD and keypad.
After collecting the required parts like an Arduino, 4x20 LCD, 4x4 keypad and rechargeable battery i started working on the user interface and menu. This was taking longer as expecting mainly because the existing menu libraries didn't fit my needs so i needed to write my own menu code.

At this moment the menu and user interface are complete, all features of the programmer can be controlled using the keypad and all what is left to do at software level is copying the code which is handling the actual programming  from the original programmer and execute it when the program menu option is selected.

The hardware displayed on the picture is a 3D printed case i made with the purpose of keeping all parts together while writing the Arduino code.

Development version inside view.

As you can see on thee picture it is missing some essential parts like a bottom and parts like the rechargeable battery and controller are just tossed in there.

So on the Hardware part there is still a lot to do and this will be next on my to do list.

Programmer in action:

If you are in a hurry and looking for a working solution to program your Racal Cougar PRM4515 check this post were you can find the schematic and a linkt to the Arduino sketch of my console-based programmer using an Arduino.

zaterdag 4 maart 2017

Program the Racal Cougar - Part 7

This week i added support for the PRM 4515 H (132-174) models to the Arduino Racal Cougar Programmer.

PRM 4515 H

I received a package from the UK containing a PRM 4515 H model from a fellow OM for me to use to test the programmer for this particular model. (Thanks Dave !)

After making some changes to the frequency logic in the programmer code, mainly add support for the 100 Mz digit which was hard coded to '0', the programmer was able to program this model also.

Model selection:

When the Cougar is turned on it sends a 52 bit datastream, 7E 0D 7E 0D 60 4C 4, which i thought was some kind of model identification used by peripheral devices. This could be useful for the programmer to automatically select the right model and frequency bounds supported by the model.

The fist thing i did after receiving the H model was slide it in a S.M.T. and hook it up to an Arduino using the tap cable between the S.M.T and E.C.U and turn it on to register this data datastream and the result was a bit disappointing: the same datastream as the L model was send by this model. This means it's not possible to automatically identify the model connected to the programmer so this has to be done manually.

Main menu with model selection option.

To select the model connected to the programmer i added the 'm' (lower case M) menu option which brings up the model selection sub menu:

Model selection sub menu
Model selection is needed to define the lower and upper bounds of the programmable frequencies, use the correct Eeprom stored frequencies and determine if the model supports disabling the transmitted 150 hz pilot tone.

By default the programmer starts up with the L model selected, this can be changed in the Arduino sketch by changing the following line:

uint8_t selectedModel = MODEL_L;

uint8_t selectedModel = MODEL_H;

H model frequencies

The PRM 4515 H model operates from 132 to 174 Mhz in 20 Mhz bands. Which band it operates on is defined by the model number:

ModelBand startBand end
H3TAU132 Mhz151.9875 Mhz
H3TBU134 Mhz153.9875 Mhz
H3TCU136 Mhz155.9875 Mhz
H3TDU138 Mhz157.9875 Mhz
H3TEU140 Mhz159.9875 Mhz
H3TFU142 Mhz161.9875 Mhz
H3TGU144 Mhz163.9875 Mhz
H3THU146 Mhz165.9875 Mhz
H3TIU148 Mhz167.9875 Mhz
H3TJU150 Mz169.9875 Mhz
H3TKU152 Mhz171.9875 Mhz
H3TLU154 Mhz173.9875 Mhz

This band can be changed by changing some resistor jumpers as described on the site.

It is important to know the band your H model is operating on before using the Arduino Racal Cougar programmer. Trying to program a frequency outside your model its band will result in a program error.

150 hz pilot tone

The PRM 4515 H model doesn't support disabling of the 150 hz pilot tone using the programmer. This setting will be ignored when programming the H model.

Arduino Sketch

The new version, lets call it v0.0.3 to illustrate this is experimental software, can be downloaded using this link.

See my previous post on the Arduino hardware used and installation instructions.


zondag 12 februari 2017

Program the Racal Cougar - Part 6

Arduino boxed up and connected to the E.C.U.

This post is about the hardware and software i used doing my experiments.

I used an Arduino Nano V3 (cheap clone) with a minimum of additional components, mostly to perform the level shifting and have a visual indication of the programming result.

At this moment there is no support for the Fill Gun functionality yet. This will be added in future version.


The Arduino is powered using the USB Host using an USB cable and requires no external power source.

The schema is simple, the most important parts are the Arduino itself and the level shifter made using the 2N7000 mosfet. A bicolor led is added to have some visual confirmation of the programming result and a reset button for reseting the Arduino program.

Installing the Arduino Sketch

After you have downloaded and installed the Arduino IDE (Arduino Getting started) it is best to test your Arduino by connecting it using an USB cable and load the "Blink" example available in your Arduino IDE.

If you have the "Blink" sketch running and the led at pin #13 is blinking you have successfully installed the IDE and managed to load a sketch to your Nano.

Next is the Racal Cougar Program sketch which can be downloaded using this link.

After you have downloaded, unzipped and opened the sketch (file ending with the .ino extension) in your Arduino IDE you can upload it to your Arduino. After successfully uploading the sketch it will start running and the red led and green led should light up for 1 second in turn indicating it is ready to go.

Next is opening the Arduino Monitor (console) which you can use to control the programmer. This can be done by pressing Ctrl + Shift + M. Make sure the line ending and baud rate of the monitor are set to "Both NL & CR" and 19200.

After opening the monitor console the following should be visible:

Main menu

More information about the programmer menu and functions is described in a previous post.

Supported PRM models

At this moment the software is configured and tested for use of the PRM4515L (4 meter) model only.   Although programming the other PRM4515 models is based on the same principal i haven't implemented this yet, mainly because currently i have no other models available to test the functionality with.

If you have one of the other models and want to test the programmer for a particilar model please let me know and i will make some changes to the software for you to test.

Update 05-03-2017:

Version 0.0.3 of the Arduino Racal Cougar Programmer now supports the PRM 4515 H models, see next post.


This is an experimental project and you are using this software at your own risk. I am not responsible for any damage to your precious Racal Cougar !

zaterdag 11 februari 2017

Program the Racal Cougar - Part 5

The Racal Cougar uses PWM serial data over the audio connector its F pin to control and program the tranceiver. (see part 2). This part describes the commands i recorded using an Arduino and a tab on the cable between the Racal and E.C.U. (Remote Control Unit MA-4730) or Fill Gun (MA-4083)

Tap on F & E pins


Every command send by the ECU and Fill Gun / Programmer consists of at least 4 bytes of data; a header and instruction byte repeated twice, so byte 1 and 3 are similar and so are byte 2 and 4.

Depending on the type of command 20 additional bits of data are appended to the command maing the size of the data stream 52 bits.

(Almost) every command is echoed back by the Racal cougar after it has been processed successfully. The difference between  normal command and echoed command is bit 7 of the command header. On echo this is set to '0'.

The following command tables have an echo column which describe if an echo is to be expected.

Controlling the Racal Cougar:


Select channel

HEXByte 1Byte 2Byte 3Byte 4Echo
Channel 07F007F0001111111000000000111111100000000Y
Channel 17F087F0801111111000010000111111100001000Y
Channel 27F047F0401111111000001000111111100000100Y
Channel 37F0C7F0C01111111000011000111111100001100Y
Channel 47F027F0201111111000000100111111100000010Y
Channel 57F0A7F0A01111111000010100111111100001010Y
Channel 67F067F0601111111000001100111111100000110Y
Channel 77F0E7F0E01111111000011100111111100001110Y
Channel 87F017F0101111111000000010111111100000001Y
Channel 97F097F0901111111000010010111111100001001Y



HEXByte 1Byte 2Byte 3Byte 4Echo




HEXByte 1Byte 2Byte 3Byte 4Echo

Select Secure7E0D7E0D620C501111110000011010111111000001101Y

Use Cypher A7ED37ED30000101111110110100110111111011010011Y

Use Cypher B7ED37ED38000001111110110100110111111011010011Y

To select a Secure channel 2 commands need to be given, "Select Secure" and "Use Cypher A/B"

Programming the Racal Cougar


HEXByte 1Byte 2Byte 3Byte 4Echo
Init (FLT)7F3B7F3B01111111001110110111111100111011N
Start (FTXI)7F3B7F3B01111111001110110111111100111011Y
Disable Tone7FB37FB301111111101100110111111110110011Y
Channel 0 TX7E007E00240E001111110000000000111111000000000Y

Channel 0 RX7E807E80240E001111110100000000111111010000000Y

Channel 1 TX7E087E08E40E001111110000010000111111000001000Y

Channel 1 RX7E887E88E40E001111110100010000111111010001000Y

Channel 2 TX7E047E040C0E001111110000001000111111000000100Y

Channel 2 RX7E847E840C0E001111110100001000111111010000100Y

Channel 3 TX7E0C7E0CCC0E001111110000011000111111000001100Y

Channel 3 RX7E8C7E8CCC0E001111110100011000111111010001100Y

Channel 4 TX7E027E02AC0E001111110000000100111111000000010Y

Channel 4 RX7E827E82AC0E001111110100000100111111010000010Y

Channel 5 TX7E0A7E0A6C0E001111110000010100111111000001010Y

Channel 5 RX7E8A7E8A6C0E001111110100010100111111010001010Y

Channel 6 TX7E067E06820E001111110000001100111111000000110Y

Channel 6 RX7E867E86820E001111110100001100111111010000110Y

Channel 7 TX7E0E7E0E420E001111110000011100111111000001110Y

Channel 7 RX7E8E7E8E420E001111110100011100111111010001110Y

Channel 8 TX7E017E01220E001111110000000010111111000000001Y

Channel 8 RX7E817E81220E001111110100000010111111010000001Y

Channel 9 TX7E097E09E20E001111110000010010111111000001001Y

Channel 9 RX7E897E89E20E001111110100010010111111010001001Y


A program sequence is made up of the following steps where step 3,4 and 5 are repeated for every channel to be programmed:
  1. Init
  2. Start
  3. Disable tone (optional)
  4. Channel n TX
  5. Channel n RX
  6. End
The Disable Tone command can be omitted if a 150 Hz pilot tone is requested for the selected channel.

The Init, Start and End commands are needed to store the new channel data in the Racal's EEProm. Using the Program Channel commands without this results in the channel data only being stored in RAM and thus reset back to its original info after powering down the unit.

In the table above the following frequencies are programmed:

Channel 070.250 Mhz70.250 Mhz
Channel 170.275 Mhz70.275 Mhz
Channel 270.300 Mhz70.300 Mhz
Channel 370.325 Mhz70.325 Mhz
Channel 470.350 Mhz70.350 Mhz
Channel 570.375 Mhz70.375 Mhz
Channel 670.400 Mhz70.400 Mhz
Channel 770.425 Mhz70.425 Mhz
Channel 870.450 Mhz70.450 Mhz
Channel 970.475 Mhz70.475 Mhz

The "algorithm" to set a specific frequency was described in part 2.