VCF 8.0 Pictures - test-drb@ccmp.vtda.org

11 Nov 2005

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Subject: RE: VCF 8.0 Pictures
   From: "Gooijen, Henk" <henk.gooijen at oce.com>
   Date: Fri, 11 Nov 2005 13:11:24 +0100
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

Allison wrote:

  > On
display I can have:
>
> 2) Homebrew pdp8/e running (slow) OS/8 or DMS  
 Howbout a 6120 homebrew running OS8?  The trick was real DEC 
 style IO rather than PIEs and cruft that leads up to os78 and os278. 
I don't have a 6120. The heart of my homebrew pdp8/e is a 6809! 
Ah, the 6120 is the PDP-8 on cmos core of the DECmate-III.  Thats 
different from an emulation.  

...
   > 3) PDP-11/03, a real one for a change :-) decoding
HAM radio RTTY  
 I've used the -11 for RTTY display.  You only need a modem to 
 decode the tones though having spilt screen, upper for 
 incomming and lower for outgoing  text. 
That is exactly what I intend to write. Not too difficult, I will
document this project on my website.  I am combining the actual
*use* of a PDP-11 for something, learn to write PDP-11 assembler,
and program ESC sequences for a VT220. Not just simple "hello",
but a project with a goal. 
Should be fun.  It's fairly straightforward.  Think ring buffer 
for incomming and long buffer for outgoing as the system tends 
to be half duplex mostly recieve.  RT-11 is an ideal OS for this.

...
   I'd like
to see PSK31 software for the -11. 
I have not looked into the details of all new digital transmission
modes that HAMs use (for example with MixW), but without any
knowledge, I wonder if a PDP-11 would be fast enough ...
any idea about that, Allison ? 

this is off topic and maybe outof band for this forum:
The real problem is doing the base band audio processing currently 
it's done with PCs and sound cards.  The modulation is narrow 
(200hz or less) band QPSK at around 31 baud or so. The usual reciever
is SSB so the challenge is that the audio stream is 500-2500hz 
bandwidth and multiple converstaions can take place so digital 
filtering is done to seperate and detect the signals.  Seems to 
require a P200 or faster. But I haven't dug deep enough.  I have
asked one question around but no one has answered and that is what
if the reciever (radio) was narrow selectivity (say 300hz) so that
only one data stream could be heard, would that simplify the 
filter/detect/decode process enough for a much slower processor?

Allison