Troubleshooting a Kenwood D710 TNC
dranch at trin net dot net

10/31/15


A D710 user was reporting that his radio was hearing packets with full deflection
on his S-meter display yet no packets were being decoded.  There were the next
steps I offered to him to troubleshoot the TNC.


Few ideas here to test the TNC itself:  While your D710 is configured for:

   - 1200baud APRS packet on VFO-A (left hand VFO - keep tapping the right side TNC button until the LCD says APRS12)
   - Menu 102: Modulation: FM
   - Menu 105: S-meter squelch: Off
   - Menu 106: S-meter SQL Hangup: Off
   - Menu 110: Wather Alert: Off
   - Menu 517: ext. data band: B-band (that's the right side VFO)
   - Menu 601: Internal TNC - Band: A-Band, speed: 1200 bps, DCD: D or RxD band, delay: 150ms
   - While on VFO-A (the "PTT CTRL" is on the left side, ensure no PL tone is enabled (shows on the LCD as "T" or "CT" or "DCS"
   - tuned to 144.390

1) Turn up the AF volume on VFO-A. How do the packets sound?  Are they clean?  Are there any background noise, pops, etc. that are interfering?  The D710's TNC based on a TASCO chip is pretty good but it's not excellent so the packet signal needs to be quite strong and clear.  What's the indicated signal strength (out of 7 bars)?  Not all stations will be clear but hopefully a local digipeater will be clear.

2) Tap the bottom left side "key" button until you see the item "P.Mon" option show up.  Tap that and now you should see the raw APRS packets coming in (not decoded) where only valid (ok CRC) packets will show up.  Do you see anything?  If nothing is showing up, it would seem the TNC isn't receiving signals.

3) If you're not seeing anything, double check the RJ45 cable connection between the main body and the control head.  Check the pins and their connections on each header and socket too of that cable.  Make sure they are clean, If you have an RJ45 crimper, maybe give a re-pressing of the connector a try on both sides.

4) The next thing would be to see if the TNC is really working or not.  Depending on your computer operating system, load a serial terminal program like Hyperterminal (windows), Putty (windows/Linux), minicom (linux), etc:

   - Menu 528: COM port: 9600
   - Menu 529: int data band (packet) - A Band (left side VFO)

Set the serial program to 9600 baud, 8 data bits, 1 stop bit, no parity.  Now on the D710, tap the TNC button until it says PACKET12 (using the APRS12 mode won't show anything unless Menu 604 is turned on) .  At that point, you *must* see something like the following in the terminal program:
--
Kenwood Radio Modem
AX.25 Level 2 Version 2.0
Release 09/Mar/11 3Chip ver 1.02
Checksum $1859

cmd:DA 151030083600
cmd:HB 1200
HBAUD    was 1200

cmd:W6ESZ-7>SX4QYY,K6FGA-1,N6ZX-3,WIDE2*:`1-'l"#R/`"4H}_#
--

The top part shows you that the TNC loaded up, it's version, and it's config checksum is ok.  The next two parts is the system showing it's current date (check this) and RF speed.  Finally, the last lines shows an undecoded APRS packet I received.

If you do have Menu 604 turned on and set the TNC to APRS12, You would see something like:
--
cmd:KWXIMON  was 0
cmd:UNPROTO  was APK102
cmd:cmd:KI6ZHD>S7RPVQ,WR6ABD*:'1Wl -/]=
--

The first two lines come from the TNC setting itself up and the bottom line is an undecoded APRS line

5) If all of the above doesn't help, the first place I'd start is by replacing the battery (search the email archives here on how to do that).

--David
KI6ZHD