This zip file contains modified firmware for the Kenwood TS-850S/AT
HF amateur radio transceiver and DSP-100 unit that provides
DSP-generated HiFi TX audio in AM mode as well as sideband.

This modified firmware was created by Bill Paul N1GPT. For questions or
comments, you can contact me through:

Web: http://qrz.com/db/N1GPT
E-mail: wpaul@windriver.com

Special thanks go to:

- Tom K6AET for finding both the NEC uPD781x user's manual and
  the unidasm.exe disassembler tool for me

- Rick VE6CQ for prodding me into doing this

- The MAME developers for writing and releasing the unidasm.exe tool
  http://mamedev.org

The provided files include:

original/TS850.bin 	- Original Kenwood firmware
original/TS850.txt	- Firmware disassembly

patched/AM850.bin	- Modified firmware
patched/AM850.txt	- Firmware disassembly

docs/uPD78C18.pdf			- NEC uPD781x user's manual
docs/uPD78c10agq36.pdf			- NEC uPD7810 datasheet
docs/TS-850S_Service_manual_and_nodes.pdf
					- Kenwood TS-850 service manual

tools/unidasm.exe	- MAME disassembler tool

README.txt		- This file

NOTE: this firmware is being provided as-is, with no warranty for any
purpose. The author disclaims all liability for any losses or damage that
may result from its use. If it breaks, you get to keep both pieces.

NOTE2: strictly speaking, you don't need to use the DSP-100 for HiFi AM.
Using the DSP-100 for AM will get you about 6Khz of frequency response,
just as you can achieve with ESSB. If you have already 'VooDoo' modified
your TS-850/DSP-100, then this will let you use your radio for AM as well
with minimal changes (you just need to swap the firmware chip). However,
you can get up to 10Khz of response on AM without the DSP unit with some
fairly simple mods to the rig alone. You can find out more at:

http://people.freebsd.org/~wpaul/ts-850/850.html

NOTE3: this is a prototype implementation. It may change in the future.

BACKGROUND
----------

Like the Kenwood TS-950SDX, the TS-850S/AT and DSP-100 are a popular
choice for HiFi ESSB audio afficionados. The DSP-100 unit can be set to
produce 6Khz wide audio by changing the settings of some DIP switches
on the rear panel. However, like the TS-950SDX, when the DSP-100 is set up
for HiFi in this way, it only works on in SSB mode.

Ideally, the radio should be able to operate in HiFi mode in AM mode as
well as sideband, but due to a design quirk, when LPF the setting is in
the "off" position, the radio won't transmit a carrier in AM mode. (The
relays click and the "on air" light comes on, but there's no output.)

This appears to be due to a glitch in the DSP gate array logic. However, I
discovered by accident that there is a way to work around this glitch:

- Begin transmitting in AM mode, with the DSP set for HiFi
- Without releasing the key, press the LSB/USB button again to switch
  to SSB mode
- Again without releasing the key, press the LSB/USB button one more
  time to switch back to AM

The only problem is that this must be done for every transmission, which
makes operation clumsy.

THE SOLUTION
------------

There are two possible ways to achieve HiFi AM operation with the
TS-850S/AT without requiring additional manual intervention on every
transmission.

The first is to use an external computer assist program. This program
monitors the radio via the serial port, and when it begins transmitting
in AM mode, it can automatically toggle modes from AM to SSB and back
to AM again. This solution has already been implemented, and it works,
but it has some drawbacks: 1) you need a computer, 2) you need to buy
or make a special level converter cable to connect the computer to the
radio, 3) you can't use any other CAT software with the radio while the
program is in use, and 4) the rate at which you can query the radio
is limited due to the serial port speed, which means it can take a half
second or so before the program senses that the radio has started
transmitting and switches modes. (This same program also works for the
TS-950SDX.)

The second solution is to patch the firmware in the radio so that the
CPU tells the DSP unit to swap modes from AM to SSB and back to AM
again automatically. This can be done by sending some special commands
over the radio's serial interface to the DSP unit as soon as the radio
starts transmitting. The only limitation to this solution is that the
radio must be disassembled in order to swap the firmware chip. (Luckily,
the chip is socketed so this process is relatively simple.)

After a bit of work, I have managed to produce such a patch, and I'm
releasing it for free for the benefit of other TS-850S/AT owners. All
you need to do is program the firmware into a 27c256 32KB EPROM and
swap it for the one already in the radio, and you'll be able to
operate the radio in HiFi AM mode as well as SSB. Documentation, tools
and a technical description of the firmware code and patch are also
provided.

Note that unlike the firmware patch for the TS-950SDX, the user must
enable the mode swap function manually. This can be done as follows:

- Start with the radio off
- Press and hold the AM/FM key while turning the radio on

Once this is done, the firmware patch will be turned on, and the radio
will transmit properly when in AM mode and the DSP unit is set for HiFi
operation. To disable the mode swap function, simply perform the same
steps:

- Start with the radio off
- Press and hold the AM/FM key while turning the radio on

The feature is also disabled if the user performs a full CPU reset, by
holding the A=B key while turning the radio on.

Share and enjoy!

Bill, N1GPT
