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[WriteLog] RE: rtty RX comparation PK-232 front end

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Subject: [WriteLog] RE: rtty RX comparation PK-232 front end
From: jflanders2@home.com (Jerry Flanders)
Date: Thu, 13 Sep 2001 21:57:33 -0400
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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