STORNO NMT PRM6662 as Amateur Radio Transceiver

This information bases on the modification hints of Bo (OZ5AFJ). Uwe (DL6INT) modified the software in the following details: You can download the binary files here. Updates will follow on this page.
Date Version Comments
2001-12-19 afjint01.bin This version is not very well tested and may have some errors.
2002-01-11 afji3003.bin Some bugs fixed: Menu settings can be switched on and off now; volume does not toggle the handset speaker; all 3 transmit power levels work.
2002-01-19 afji3103.bin Some bugs fixed: Memory and VFO-settings are correct after power-on; correct behaviour in the "save to nr?" dialog.
New features: Large key is PTT; "B"-key is call tone; "A"-key is save to memory; seven repeater shifts selectable; handset speaker works with squelch.
2002-01-25 afji3107.bin Bugfix: External PTT does not activate call-tone
2002-02-09 afji3126.bin power-on-message "Amateur UHF", repeater shift is shown in main display
2002-03-23 afji3144.bin Bugfix: no crash on intel-CPUs
New features: #-key changes repeater shift, D-key toggles between memory- and vfo-mode; additional 2.0 MHz repeater shift; info can be aborted with any key
2003-12-14 afji3201.bin New feature: Automatic power-off-timer shuts down approx 10 hours after last action. This feature can be disabled with menu setting.

Some Things are To Do:

  • check band borders when operating with repeater shift
  • Your callsign in the power-on-message

    You can use a hex-editor (e.g.HEXEDIT  ) to modify the binary file so that the radio will show your callsign on power-up. Search for the "HELLO WORLD" at the bottom of the program and replace ist by everything you like. Don't use lower case letters, this will not work.

    Additional Hinds (tnx Joachim, DJ7TA and Peter, DJ5YG)

  • The PLL must be able to lock in a range of 20 MHz (10 MHz transceiver tuning range plus 10 MHz TX/RX offset). With an additional capacitor 3.3 pF or 3.9 pF in parallel to C 603 the PLL should lock in the whole range.
  • To avoid auto-turn-off after 30 seconds of transmitting, add a resistor 5.6 kOhms in parallel to C101 (10 uF) in CF6002.
  • Some control logic boards (CL6002) make problems to turn on the radio. Try a capacitor 22 nF from pin 1 to pin 20 of the U908 or U909 (74HC374).
  • The call tone frequency is 1800 Hz with the original 1.008 MHz xtal at the FX 409. To change the frequency to 1750 Hz, replace this xtal by a 680 mH coil. To get the exact frequency, add some pF's in parallel to C910.
  • Hardware modifications

    Change and add 3 capacitors. Add an antenna switch. see needed hardware.

    Changes to the RF part (RF6662)

    Mount a 2.2pF in parallel with the SMD capacitor C633 that is in serial with the trimmer C601. This is done to make sure the synthesiser can lock in the low part of the 70cm band. Put the RF6662 PCB back in place connect the antenna switch and maybe place some shielding around it.

    Changes to the CL6002 (CPU controller part)

    The only change to be done to the CL6002 is a new connection between 8031(CPU) pin 16 and 2816(eeprom) pin 21, and the SMD component R925 should be removed, it is a 0-Ohm resistor. It is near the pin 33 of the CPU on the solder side of the PCB.
    Remove both proms 27128 and 27256 make a new prom with the software and place it in the socket far from the CPU, the other socket is left empty.

    AF board CF6002

    I have chosen to use a 12V-antenna switch, and the relay should be connected to the DB25 connector pins 2 and pin 17. Pin 2 is +12V and pin 17 is grounded on PTT. Add an antenna switch See needed hardware.
    According to Storno max current draw on pin 17 is 100mA. Also place a reversed diode over the relay.

    First power on

    On the first power up the radio should give a beep and give a text in the display.
    “LOW POWER” can be displayed, this is caused by a supply voltage below approx. 10V.
    I have chosen to keep the watchdog function, so if the CPU locks, and the radio keeps transmitting the radio will turn off after 5 sec.
    Now adjust the radio after the Storno description, but I recommend not to retune the IF part.
    If the radio is set for 434.000Mhz, the injection frequency is 434.000Mhz + 45Mhz = 479.000Mhz.

    User guide for the software version afji3201.bin

    The radio remembers volume, frequency, output power and more, but is only stored when the radio is turned off with the ON/OFF button.

    Cancels the squelch, loudspeaker symbol blinks

    Up / Down arrow
    Adjust the volume in 15 steps

    One press gives a step down in frequency, if you keep the button pressed for more than 3 sec it will step down in frequency until it has reached 430.000Mhz or the button is released.

    One press gives a step up in frequency, if you keep the button pressed for more than 3 sec it will step up in frequency until it has reached 439.9875 Mhz or the button is released.

    This button is used to select between 3 output power levels. in the right hand side of the display is l for low power m for medium and h for hi (0.5w, 1.5w or 15w) or whatever you have adjusted r109,r103 and r111 for.

    Scan function of the whole band or (10 memorised channels) the radio will stop with carrier detect and will continue when the carrier disappears.

    Changes the repeater shift  1.6  2.0 7.6 9.4 MHz positive or negative and 0 simplex

    Saves VFO settings into one of the ten memory channels

    The call tone frequency is 1800 Hz with the original 1.008 MHz xtal at the FX 409. To change the frequency to 1750 Hz, replace this xtal by a 680 mH coil. To get the exact frequency, add some pF's in parallel to C910.

    is the confirmation key to write an memory channel

    D-key toggles between memory- and vfo-mode;

    Large key on handset is PTT
    PTT, on TX the red triangular symbol little key will lit

    Two small keys on handset change the handset volume

    Access, and scroll the menu, scroll to the end or press CL to exit. Menu only works in vfo mode.
    Use FLAG to change a menu item
    In the menu are the following items:
    -microphone on , off
    -handsfree on,off activate pre emphaser
    -speaker : loudspeaker on,off
    -handset mic on,off
    -handset spk : activate the handset loudspeaker the AF is not squelched
    -clear all: with D-key, all memorys are set to default settings
    -keyb light : keyboard light
    -info: shows an message with version number
    -start beep : power on beep
    -key beep : keypad beep
    -auto off: automatic power off 10 hours after last action

    The radio can be used in two ways, either in VFO mode or in MR memory mode
    VFO mode : Here you can enter frequencies in 12.5/25khz step "Flag/|" can be used to change the frequency.
    MR memory mode : Here you will have a digit (0-9) in the left side of the display indicating the actual channel. You can change the channel using the numerical keypad or "Flag/|"

    Memory input :
    1. Press "D" for VFO mode
    2. Choose frequency, output power, repeater spacing.
    3. Press "A" the display shows "SAVE TO NR? 1"
    4. Now you can choose the memory position you want to save in.
    5. Press "C" to actually save the data in that position,

    The radio has an incorporated field strength indicator, the 3 LED’s to the left of the display. The squelch opens on the first LED, and can be adjusted with R711; all 3 LED’s are lit with max signal strength.

    Connections on the 25 pin rear connector

    Pin Description
    25 -  GNU
    24 LS 2
    23 LS 1
    22 TX Line
    20 HF Mic
    19 MS Mic
    18 Signal GNU
    17 Antenna relay
    14 + 13.2 V
    13 -  GNU
    12 -  GNU
    11 HS RX
    10 RX Line
    9 + 5V output Max 0.8A
    8 On/Off Reset
    7 Bus data
    6 Bus request
    4 PTT
    2 + 13.2 V
    1 + 13.2 V

    MS Mic has an impedance of 600 Ohms, and has a DC voltage output of 8.5V.
    LS 1/ LS 2 is the loudspeaker output in 4 Ohms, 10W.

    RX / TX Line can be used with an external modem as Storno says, but they also talk about a 10Hz to 3KHz +/- 3dB frequency response.
    It is probably a good idea to use all the pins for the power connection, otherwise it can get a bit hot drawing 6A through 1 pin.


    PRM6662D15N Technical manual
    OZ1ASF article in OZ n 4/90 and 6/90
    OZ1HQR article in OZ 11/2003

    Needed hardware

    1  antenna Kit from DD9UG to Siemens C5  Fon: + 49 5617391134
    1  27C256 EPROM with the afji3201.bin software
    1  1 pF capacitor
    1  2.2pF capacitor
    1  6.8 pF capacitor
    RG174 or similar, 15-20 cm.

    Credit to 
    Uwe Hennig, DL6INT, 2003-12-14
    Source code
    Storno C
    Storno H
    Thanks to Bo  OZ5AFJ