[Kenwood] TS870 Band Data to switch Dunestar filters

[Bob Henderson]

One area where Yaesu has always won out over Kenwood is in the provision of
4 bit band data at an accessory outlet on the back skirt of the radio.  No
such output has been provided by Kenwood so doing automatic antenna and
band-pass filter switching has always been a problem.  Sure some logging
programs provide band data output from the LPT port on the computer but if
you are operating a multiple radio set-up and your computer crashes then
your filtering can drop out and your radio can be fried.

Today, I decided to solve this problem once and for all.  A quick look over
the 870 circuit and then a look at the rig itself gave me the answer.  The
external ATU socket on the 870 is redundant, certainly as far as my needs
are concerned.  I removed this (a very straight forward operation) and
replaced it with a 9-way female Cinch connector to which I attached a very
small piece of strip board on which I wired 6 npn open collector buffers.  I
connected the buffer transistor bases via 5k6 1/4W resistors to the
collectors of Q10, 11, 12, 14, 15, 16 on the foil side of the Final unit
filter board using a piece of ribbon cable.  This was pretty easy too, as
Kenwood put spare pads here which were very convenient.

This simple mod gives me decoded & buffered band data output suitable for
directly switching antenna selector relays and band-pass filters.

Now this is WAY better than the Yaesu band data output as I don't need to
invest in a Band Decoder.

Whole mod took me about 2 hours.  If this is of interest to anyone I can
probably put together some further details should anyone need them.

73

Bob 5B4AGN, P3F, ZC4ZM