[RTTY] FSK Keying of TS-590SG

[Don Hill AA5AU]

I've been using the circuit shown on this page for over 20 years with success.

https://www.aa5au.com/rtty/fsk-interface/

Don AA5AU

-----Original Message-----
From: RTTY [mailto:rtty-bounces at contesting.com] On Behalf Of groupsrichart at gmail.com
Sent: Friday, February 23, 2018 1:49 PM
To: KenwoodTS-590 at yahoogroups.com; rtty at contesting.com; TS-590 at groups.io; TS-590S at yahoogroups.com
Subject: [RTTY] FSK Keying of TS-590SG

I would like to hear from anyone who is successfully keying the FSK and PTT lines via the ACC2 connector on the rear panel of the TS-590SG. What serial adapter and what hardware interface are you using to do so?

I have tried two different interfaces using optoisolators to attempt FSK and PTT keying from a serial card to the rear panel ACC2 connector. Both attempts have failed. I am using MMTTY software for keying and I do get the requisite signal change on TXD pin 3 (FSK) and RTS pin 7 (PTT) lines. I have also verified proper setup of the '590 by manually grounding the inputs PKS pin 9 (PTT) and RTTY pin 2 (FSK) on the ACC2 connector.

However, I *think* the problem lies with the serial card not providing enough voltage/current for the optoisolators to completely turn on and provide a hard ground to the ACC2 inputs. I have tried two different serial cards and one swings from -4.9 to +5.0 VDC on the data lines and the other card swings from -3.8 to +3.9 VDC. The cards I am using are a two port generic PCI Express SI-PEX15037 and a four port Perle Fast 4 PCI card. Does anyone know of a serial card that has a full -12 to +12 VDC swing?

One of the hardware interfaces has 4N25 optoisolators and the other uses Fairchild FOD852 optoisolators. There are 1K series resistors in the input line to the optoisolators and I have tried various values (100,
220 & 470Ω) with limited success but nothing consistent.

While my objective was to keep the rig isolated from the computer, I am thinking about building an interface that uses NPN transistors for keying. Is anyone using NPN transistors to key their '590? Are you tying the ground from pin 5 of the RS-232 port to the pin 4, 8 or 12 ground of the ACC2?

Any input is appreciated...I have been off RTTY since purchasing this rig in November and I want to get back on the bands.

Thanks,

Tim WS4V

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