This document describes how to connect Nokia RD58 (also Rx58 by slightly
modificating the component references etc) to packet radio.

-------	Text of OH8HUB
-------	Translation OH8HBG
-------	Note: 9k6 is not working with this, about 4k8 is maximum data speed

RD58 has a female D25 -connector for handset. For packet you should nee

Name	Pins		Remarks
---------------------------------------------------------------------------
GND	1,2,4,8,10	GND for current supply
MIC	3		Microphone in (to radio), impedance >= 2,2 kohms
MICGND	4		GND for microphone
PTT	5		Push-to-talk, ground this to transmit
ERP	9		Line out (from radio), about line level signal
ERPGND	8		GND for line out
ON/OFF	11		Radio ON/OFF, ground this to turn radio on, this
			should be properly grounded (with short wires to gnd)
			and it sometimes requires that it must be grounded
			about 0,5 secs _after_ attaching power to the rig,
			so the rig does not necessarily switch on 
			automagically after power-on... unfortunately

And same in text: Connect pins 1 and 2. COnnect pin 11 to 1 and 2 to swicth
on radio. GND in pin 10 is also possible, but it is not wired in some 
peripherals (car adaptors). Also switch is possible for this.

Connect pin 5 to 1 and 2 to transmit. So connect this to PTT-circuit of modem 
(etc).

Cable used was cutted from car adapter kit of RD58, which had own shielded 
cables for MIC and ERP. It is also possible to use pins 1 and 2 to ground MIC
and ERP too, but it is recommended to use shielded audio cables and specified
MIC and ERP GND-lines for grounding.

PTT-circuit schematics is available from:

http://www.baycom.org/~tom/pcf/ptt_circ/ptt.html

Linux AX25-HOWTO could have a wrong URL...

Serial port PTT switch is working fine. It could be build in the small 
vero-board and fit into the case of D-connector (in PC-end or in RD58 end). 

If you want to be sure about ground levels, optoisolator is recommded for PTT
and 1:1 transformers for audio. Iron nail and 50...100 turns of emaled copper
wire will do its task. But no additional info from this, so please inform 
others if you make the isolation.

> -- 
>  Ossi Herrala  |  oh8hub@sral.fi  | LOC: KP28QB98
>  OH8HUB        |  QSL via OH8TA   |

-------	Text by OH3GI
-------	Translation by OH8HBG

Asko, OH3GI, printed in RATS-magazine 1/1996

Receiver:

First IF filter is 15kHz wide. It could be broadened by connecting 470 ohm
resistor from XF1 output to ground.

Second IF filter (XF2, CFK455G) is replaced by broader one, CFW455B (30kHz),
which is smaller. It could be wired on the top of the RX PCB. CFS455B is also
OK but it's bigger and requires longer wires.

Detector (IC2, SA604AD) has C46 capacitor. Add 330nF parallel to it to allow 
lower frequencies to pass. Audio amplifiers IC3/2 feedback has capacitor C47.
Remove it to allow hiogher frequencies to pass.

Tune detector coil L13 to optimum frequency response. This is done by 
monitoring. RX PCBs connector RP/4 has audio output for 9600 bps modem.
Level is around 0,5 Vpp which is enough for RUH at least.

Transmitter:

Sythetizator board (V8DTB) connector VZ pin 3 is removed to prevent audio from
phone. Modem audio ouput is connected to end of R1 to synthetizator PCB. 
Required audio level is about 300mVpp.

Transmitter is activated by grounding phone connectors CA pin 5. Current is 
about 15mA. TX-delay value requirements of radio is not testedm but 350ms
is working fine.

*******

No exact measurements for radio has not been done, but it is working,

Relayed to moppe-lista -posting list by Arto, OH2BGN