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[aprssig] Looking for an EJ41U TNC

Scott Miller scott at opentrac.org
Sat Dec 16 21:09:30 UTC 2006

Anyone want to trade an Alinco EJ-41U TNC (the internal type for the
DR-135T) for a working but pre-production prototype T2-135?  It's a Tracker2
board designed as a drop-in replacement for the EJ-41U.  Its APRS support is
way better (SmartBeaconing, digipeating, waypoint output, weather station
support, etc) and unlike the EJ-41U it has flash-based configuration memory
and won't lose its config every other time you turn it on.  Retention should
be at least 10 years from the time the last config command is entered, in

The KISS buffers are small, but adequate for APRS, and it won't lock up or
otherwise freak out if you do overrun the buffers.  There's no connected
mode support (remote commands are via APRS messages) and no 9600 baud
operation, but aside from that it should outperform the EJ-41U in just about
every way.  Decode rate on the tested prototypes has been better than the
TNC2 clones I've tested against.

Oh, one other difference - the T2-135 has a pre-emphasis filter on the
transmit side.  The EJ-41U (like the D700) transmits flat, which is bad if
you're applying de-emphasis on the RX side.  In the future this will
probably be selectable by jumper, but for now it's hardwired.

I need an EJ-41U to do some head-to-head performance tests, but they're
getting a little scarce and they seem to be backordered most places.  It
might be a couple of weeks before I can have a T2-135 unit ready in exchange
(I'm waiting for parts now) but I might be able to have one ready sooner if
an alternate source for the connectors works out.



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