On 2023-09-01 12:55, Michael Carter wrote:
Hi Jerry,
There is no simple access to band data in
the K2 unless you want to reverse engineer
the AUXBUS protocol.
*** Considering that it's probably a low-speed
async protocol, that might not be that hard.
Depending on how
your homebrew amp selects its lowpass
filter options, you may be able to pick up
the relay control signals for the K2's bandpass
and lowpass filter banks and use those
to encode a band data word in the format
used by Yaesu.
*** Yeah, I was thinking of doing just that. Little
green wires and a pin header. Then a little board with
a microprocessor to convert the 1-low-per-band to the
needed 4-bit word. Might be able to do it with a diode
matrix.
There is no isolated connector
on the K2 Front Panel, Control, or RF boards
that makes available those relay control lines,
so you would have to tap the traces where
those control signals are exposed.
Perhaps you can comment more on the
homebrew amp design with regard to
lowpass filter selection?
*** Sure. The amp uses a W6PQL RF deck and LPF. It has a
four-inch touch screen and a Teensy 4.1 microprocessor card. I
wrote the software. It's my third recent solid state linear, and
I burned out my share of devices on the other two. Didn't want
to burn out this one - it's a $230 chip soldered to a heat spreader,
and would be both expensive and a PITA to replace. So there is no
bandswitch. In addition, there is a protection card that turns off the
power to the RF deck for
* Excessive drive
* Excessive drain current
* Excessive power output
* Excessive antenna SWR
* Wrong LPF selected
Even with that last, I prefer to have the linear set its band
from the exciter data. Belt & suspenders...
People have commented that I should find Elecraft's universal
adapter.
My answer to that is - yeah it would be easy, but not much fun. I have
plenty of radios
The band data is a four-bit word. 1 = +5V, 0 = 0V.
0000 - illegal.
0001 - 160M
0010 - 80M
...etc.
1111 - illegal
It works flawlessly with my FTDX10. It also works with my T41-EP
homebrew
transceiver. The linear doesn't have true TTL
inputs: its internal CPU is a 3.3V device, so there is a voltage
divider at each
band data input.
I see that the aux bus cable - for PC connection - is documented. Looks
like pin 1
is the shell, pin 2 & 3 are the RXD and TXD, and pin 5 is the common.
And the protocol
is async RS-232 4800 baud, 2 stop bits. There is also power available (
I assume 12V )
max 50mA on pin 8. I think an AtTiny84 would do it - but I'd need to
also put in an
RS-232 converter chip to deal with that pesky negative voltage.
There's another pin called "AuxBus". That's probably a more difficult
nut to crack.
- Jerry, KF6VB
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