[aprssig] AIS and DSC - lots of questions

Stephen H. Smith wa8lmf2 at aol.com
Tue Apr 5 12:47:33 EDT 2005

joe at dellabarba.com wrote:

> last question - radios with TNC
>connectors (FT-1500M and others), do these support the 9600 baud data
>or do I still have to wire up to the discriminator output?
>73 de N3HGB
The standard 6-pin mini-DIN "packet" or "data" jack provides  access to 
both the discriminator of an FM radio and to the (normally) 
de-emphasized squelched speaker-like audio but at a fixed level. 

Full details on the MiniDIN 6-pin "DATA" connector follow.  All these 
observations apply directly to the FT-1500 and similar radios. This is a 
reprint of a post I have made many times on various groups and mailing 
lists about this issue.....

======  PASTE ========

The 6-Pin MiniDIN "DATA" or "PACKET" connector is an industry standard 
adopted by all the Japanese ham mfrs.  It is now superseding the various 
proprietary 7, 8 and 13-pin full-sized DIN connectors used by various 
manufacturers.  The contacts on this connector provide access to:

1)  TWO kinds of receive audio:
    Raw non-deemphasized discriminator output sometimes labeled "9600 
Baud Receive".
    De-emphasized squelched audio similar to what comes out the speaker, 
but at a fixed level unaffected by the volume control. It is sometimes 
labled "1200 Baud Receive" or "RXD".
    On multi-mode radios (Yaesu FT-817, Yaesu FT-100, Icom 706, etc), 
only the "1200 baud" output will be live on AM, SSB or CW since the 9600 
baud output is associated only with the discriminator of FM receivers. 

2)  TX audio input (sometimes misleadingly labeled "TX Data Input" or 
"TXD")  In some radios, a menu setting for "1200" vs "9600" baud will 
determine if this input goes either into the same channel as the mic 
input (but at a higher audio level) for 1200 baud packet, SSTV, 
EchoLink, AFSK RTTY, etc,   or is DC-coupled directly into the TX 
modulator (for 9600 baud packet).

3)  TX PTT (confusingly labeled "Standby" by Kenwood) -- normal 
ground-to-transmit line  just like most mic inputs. 

4)  Receiver Squelch status line (normally no sig-squelch-closed = 0V, 
signal active-squelch open = 5V). Sometimes labled "COR" (Carrier 
Operated Relay - an archaic term from the early days of FM repeaters),  
"COS" (Carrier Operated Switch), "RX", "CD" (Carrier Detect), "Activity" 
or "Busy". 

5)  Common/Ground.

Note that despite the misleading labels referring to data input and 
output, the jack only carries AUDIO, AUDIO, AUDIO!    THERE IS NO ACTUAL 
RXD or TXD DATA in the sense of RS-232 or TTL-level streams of 1s and 0s 
anywhere on this connector!!!

This connector is the perfect point to connect packet TNCs, soundcard 
interfaces, phone patches, IRLP/EchoLink controllers, APRS trackers, 
paging encoders, or any other device that needs access to the transmit 
and receive audio of a radio. 

These audio inputs and outputs are high-level (100-300mV), similar to 
home stereo "LINE" input level seen at RCA jacks on tuners, amps, tape 
decks, etc;   NOT the the 5-10mV level seen at most mic input jacks. 
     NOTE that this means that you have to set the audio output 
("TRANSMIT") level of sound card interfaces, TNCs, data controllers, 
APRS trackers, etc to a MUCH higher level than you would for a normal 
connection into the mic jack.  With some devices you will have to shift 
internal jumpers,  or exercise software menu commands to increase output 
level (recent Kantronics TNCs for example).

On most radios with this port, grounding the DIN-6 PTT line mutes the 
front panel mic input to prevent extraneous shack noises from getting 
mixed with whatever you feed into the transmit audio input. 

You can connect a TinyTrak here very effectively if you:
1)  Change R5 (220K resistor) on the TT to about 27-33K to boost the TX 
audio level from mic level to line level.
2)   Connect the direct DC-coupled "CARRIER DET" line of the TT to the 
MiniDIN "SQUELCH" or "COR" line. 

An annotated pinout diagram of this connector, useful as a worksheet for 
making up cables,  is on my website at:

Click through the link on this page which will take you to a directory 
of assorted downloadable files, not a web page.  Look for the file   

Note that this connector is exactly the same one used on PS/2 keyboard 
and mouse cables.  A  PS/2 keyboard extension cable is an excellent 
source of a plug and cable assembly to mate with the jack on the radio. 
[at a fraction of the cost of the optional Kenwood or Yaesu cable 
assemblies! ] Cut the female end off, strip the bare end and connect the 
bare leads to the appropriate pins of whatever mates with your tracker, 
TNC, or soundcard interface.

Stephen H. Smith                   wa8lmf (at)  aol.com
Home Page:                                         http://wa8lmf.com
Ham Radio/Mobile SSTV page:         http://webs.lanset.com/wa8lmf/ham
APRS Stuff                          http://webs.lanset.com/wa8lmf/aprs


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