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Nokia Mobira R58 series (band versions RB58, RC58 and RD58)

This page is intended to be a collection of modifications for R58 series radio, to be used for both operating radios and R58's used as repeaters, duplex gateways etc.

CTCSS generation/encoding for non-repeater use

Introduced at firmware 3.Yz, requires R58 firmware 3.Zi or or higher to operate as follows:

The RX front-end DAC can be used for generating CTCSS waveform for TX. The modification is easy and requires just two components, a polystyrene 100n capacitor and a 10k resistor to be installed on the A8 audio board beneath the P8 processor board. All settings are adjusted by the handset.

Solder points for the components
Components laid in place


01 GE:CtCSSt CTCSS frequency in hertz. For frequencies with decimals, use the nearest full Hz. eg. 118.8 Hz would be 119 and 74.4 Hz would be 74

816 PH:CtCGEn option rFcdAc selects the RX RFC DAC output to be used as CTCSS waveform generator during TX.

817 PH:CtHAnG sets the TOC time in millseconds. TOC eliminates the squelch crash at the receiving station, suspending the CTCSS tone transmission prior to the drop of the carrier.

818 PH:CtGAin sets the amplitude of the generated waveform, must fit between rfc and abs(-rfc)

921 rF:rFc sets the DC bias of the DAC, please remember that this value has individual settings for each full 1 MHz band

Improved CTCSS tone filtering / Parannettu aliäänen suodatus

Replaces 330kohm resistor and 100nF cap: Korvaa alkuperäisen kytkennän.

  >--- 22kohm ---+--- 22kohm ---+--- 330kohm ----- 15 nF ----> output
                 |              |         
                === 15nF       === 15nF
                 |              |
                 |              |
                GND            GND 

Capasitors can be between 10...20 nF, resistors 18...27 kohm.

Filter simulation

CTCSS generation/encoding for R58 repeater

The procedure above works also in a repeater. However, as the receiver runs full time, the RFC CTCSS will introduce aplitude modulation for some extent in reception. Thus there must be a fixed RFC voltage generator circuit.

See one approach by OH3MBC [[1]]

CTCSS decoder installation for R58 (both repeater and non-repeater use)

A de-facto CTCSS decoder (and encoder) is Selectone TS-32. Wiring the TS-32 to R58 radio for repeater or end-user radio is fairly easy and requires the following connections. Other decoder models can be used with the similar details;

  • Power 5V or 12V to the decoder unit and ground
  • Unmuted audio for CTCSS tone detection (flat audio preferred)
  • Tone decode output, which is a signal which represents successfull decode (presence) of defined CTCSS tone in the received signal. The decode output can be either logic 0 or logic 0, R58 software supports both.
  • Optionally, the RX audio can be passed through the TS-32 to filter out subtone frequencies below 300 Hz.

In the example below the TS-32 CTCSS decoder is installed in the duplexer chamber next to the P8 logic board.

R58 TS-32 wired in.jpg

Decoder wiring

Necessary connections for the decoder input are available on the connector PP2 on the P8 processor card;

  • PP2 pin 7 = (Optional) Audio filter output
  • PP2 pin 10 = Ground
  • PP2 pin 12 = Audio input
  • PP2 pin 18 = (Optional) Audio filter input
  • PP2 pin 19 = +Vcc to decoder board

R58 CTCSS-TS-32 lines-1.jpg

The decoder output is connected to the IC24 pin 36. The path to pin 36 needs to be cut underneath the board!

  • IC24 pin 36 = Decode output (logic low or logic high)

R58 CTCSS-TS-32 lines-2.jpg


26 Sq:CtCSS set to AND. Normal squelch and CTCSS tone presence are both required for receiver unmute criteria.

814 PH:CtCPol to POS or NEG, respectively to the configuration of TS-32, does its output go negative (ground) or positive (+V) when correct tone is detected.

02 GE:CtCSSr to something else than zero. 1 or tone you're running (without decimals) work, as a reminder. This does not affect anything but enables the CTCSS part of the squelch.

General-purpose outputs

DTMF decoder installation for R58 (both repeater and non-repeater use)

Wiring R58 for external controller usage (both repeater and simplex gateway use)

R58 firmware wishlist

The latest firmware is 3.Zi.

Level control does not work in RFC DAC CTCSS generation (works at least in 3.Yz).

<bold>Solved. In later versions, 818 CtGAin must fit between 921 rfc and abs(-rfc)</bold>

Repeater mode needs two additional parameters: one to define minimum length of overs and another to define the number of overs to trigger the shutdown ID. This is needed to make the repeater as quiet as possible in case of kerchunking or somebody just ID:ing or calling another station with no QSO resulting.

There is a special build of the firmware with RSSI reporting to the handset MBUS line, this should be incorporated in the future mainstream builds. There is at least one SIO port available, maybe its application should be considered, too.

Do the offset and multiplier parameters (881-813) work? Do they also work if the LO signal is divided to HF?