[RTTY] PK232 & TS850

[Richard Ferch]

On Wed, 30 Oct 2002 09:07:54 -0000  G0URR wrote:
> Hi all, at G4RS we have an 850 and several pk232s. If you have got this
> combination running youre end, could you let me know how you got on wiring
> it up etc. Also if you are using a soundcard to generate fsk and feed that
> into the 850, what was the best way to make that work. Thanks all, seeya
in
> WAEDC (if i can work out qtc with w/l)
> Robert Webb
> G0URR

Hi Robert,

I can't help you with the PK-232 directly, but I used to use an MFJ-1278 TNC
for FSK with my TS-850. I took the TNC's receive audio input from an
outboard audio filter unit plugged into the radio's external speaker output,
but you can use a splitter on any of the radio's audio outputs. I used the
TNC to control PTT through the radio's REMOTE connector (pin 3). The 1278
has a separate FSK output which I plugged into the radio's RTTY keying jack.
IIRC, I had to fiddle with the polarity to get my tones right-side up,
either inside the TNC or via the radio's menu item 11 (I can't remember
which I ended up using).

I stopped using the TNC recently after I discovered: (a) soundcard programs
do a much better job on receive; and (b) my TNC generates enough RF noise on
receive that the soundcard receives better with the TNC off than it does in
"dual receive". The PK-232 may be quieter than my MFJ was, so don't let my
experience put you off.

As for FSK keying from a soundcard program, the soundcard itself has nothing
to do with this. The sound card program uses the UART on a serial port to
generate an FSK keying signal on the TxD pin (I understand that most
USB-to-serial adapters cannot do this, so it looks like you need a real
serial port). You need a keying circuit to convert the RS-232 levels to
switch the radio's RTTY keying line.

Most of the commercial sound card interfaces do not support FSK keying from
TxD. I believe one of the Rigblaster models (the Plus) can use TxD to
produce an FSK signal. Since I don't have a commercial interface, I made up
a box to control all three (FSK, PTT and CW) from a serial port a few days
before the CQ/RJ WW contest, and actually had it working for a couple of
trial QSOs, but the serial port in my computer died shortly thereafter. I
suspect I may have used too small a resistor in the keying circuits, which
could have drawn too much current from the serial port and fried the line
driver - at least, that's what the symptoms suggest (each of the serial
port's output lines worked for a while but then they each stopped in turn,
and now they are all sitting at a constant 0V). I ended up using AFSK
instead, and that worked well enough that I haven't bothered following up on
my serial port problems - but now I can't use the TNC any more because the
serial port it used is dead!

For AFSK, I feed the sound card's line output signal into pin 11 of ACC2 on
the 850. I use the radio's computer control to switch PTT, but you can also
use a hard-wired signal to pin 9 of ACC2. You can also get receive audio
from pin 3 of ACC2. With the sound card in my computer, I don't need an
attenuator between the sound card's line output and the radio's ACC2 audio
input. I set the two sound card sliders (Volume Control and Wave) around 50%
(low enough to avoid generating IMD products inside the sound card) and use
the TS-850's Mic control to keep the ALC reading on the radio's meter just
below the point where it starts to twitch, which maximizes the transmitted
signal power while avoiding nonlinearity. On my radio, the Mic control sits
around 9 o'clock, or position 2 on the front panel. I have to tweak it
slightly when I change bands to ensure that the drive is just at the point
below triggering ALC. I used exactly the same setup with a friend's TS-950
during the CQ/RJ WW contest, and the same volume control and mic gain
settings worked there as well.

Another advantage to using AFSK is that you can use the mouse for fine
tuning within the filter bandpass. You cannot do this in FSK because the
radio's transmit tones are fixed at 2125/2295 Hz in FSK. On the 850, you can
and should use the radio's CW filters in AFSK, but instead of centring
around 2200 Hz like they do in FSK mode, they are centred around 1400-1500
Hz in USB/LSB.

Hope to CU in WAEDC. I'll be using MixW in AFSK, and plan to do QTCs by hand
(with computer assistance - but that's a whole other story).

73,
Rich VE3IAY

PS: A couple of great resources on all of this stuff, thanks to Don AA5AU,
are at http://www.aa5au.com/rtty.html and http://www.geocities.com/writelog/
.