A major feature of the PK-232 that Don does not mention is the ability to
easily interface an external "front end" to it. It is easy to bypass the
PK-232's filters (that were _never_ optimum for 170 Hz RTTY anyway) and
replace it with more optimum circuits to convert the tones into 5-bit TTL
level signals.
I have used an old highly tuned ST-6 with near optimum post-detection 45
baud low-pass filtering for years in this configuration by tapping in just
before the ST-6's loop keying circuit and converting it to TTL. It's copy
far surpasses the early sound card demodulators. I have more recently used
a second PC running a copy of MMTTY, directing it's output to a COM port on
that second PC, then translating that port's voltage level to TTL and
patching it over to the PK-232, which is feeding WL on the first PC.
In the above configuration, I get to continue using the PK-232 as FSK keyer
and CW keyer while still taking advantage of possibly better external
demodulators.
The external demod input is on the back of the PK-232 - you have to rewire
jumpers inside the case to enable it. The manual covers it well.
I am rebuilding my station now, integrating my new IC-756PRO into it, and
considered tossing the PK-232s, but decided to keep them in the rebuild
because they do such a good job of FSK and CW. I may drop the ST-6, though
- I have to compare it carefully to MMTTY running on that second PC before
I am sure.
I use these PK-232's exclusively for 45 baud RTTY, and those needing other
modes would also need to provide for switching the original PK232
filters/demodulator back in for those modes. This can be done with an
external switch.
Jerry W4UK
>SNIP
>
>Why do I still use a PK232 if I rate is 4th out the 5 I've use?
>I use it as the main FSK generator on one of my radios. If I
>had a second DXP38, I would retire the PK232, but for now it's
>OK on receive. Since I run MMTTY to back up the receive of
>my PK232 on one radio and the DXP38 on the other radio, I am
>not worried about receive. If one device misses print, the
>other usually copies under most conditions.
> <SNIP>
>That's the real ticket.
>
>73, Don AA5AU
>
>
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