[MRCG] [MMRCG] Teletype paper
Tim
timsamm at gmail.com
Fri Mar 15 00:21:29 EDT 2019
Hi Jim (been awhile!) Yep, I know my PRC-47 - CV-2455 lashup is
non-authentic but its the best I can do without a proper terminal (and
space for one...) It is an AFSK system and it has decoded you just fine -
the RX Mk/Sp filters seem to be quite sharp and up to the task...I had to
build a Loop-to-RS232-to-Loop circuit as an interface though...Full
disclosure: I can barely spell "Mechanical Terminal"
It has worked John's GRC-46 system and one or two Dovetrons with no
problems - except that I recall I had to insert a manual carriage return
and line feed before hitting column 72. Probably related to the reasons
you cited.. The DOS computer runs an ancient RATT program written by
VE3LNY that I have used since the 1980's.(Improvise, Adapt, Overcome...)
Cheers! Tim
N6CC
NNNN
On Thu, Mar 14, 2019 at 6:39 PM Jim Haynes <jhhaynes at earthlink.net> wrote:
> On Thu, 14 Mar 2019, Tim wrote:
>
> > I'm running a PRC-47 with the CV-2455 RATT converter. Unfortunately no
> > mechanical terminal here so I have to use an ancient DOS laptop as a
> glass
> > terminal (horrors...). We ran the weekly net for several years, usually
> on
>
> While that is non-authentic, it's good for about 15dB in SNR improvement.
> The reason is that a mechanical teleprinter without a regenerative
> repeater in front has that problem with mechanical selectors. If the
> STOP pulse is missing or if there is a false START pulse the selector
> clutch is released and START-STOP synchronization is destroyed. There
> are usually several errored characters resulting from that one errored
> bit.
>
> The ancient laptop has an electronic receiving distributor which gives
> it the ability to detect a missing STOP pulse and stop anyway, and to
> detect an recover from some abnormally short START pulses. Some of the
> late FSK demodulators incorporate regenerators made from UART ICs that
> have the same capability, or you could build your own. Or there are
> older electronic regenerators out there, even going back to vacuum tubes
> if you want to be whimsical.
>
> In fact I remember now when I was participating in Clatternet that I was
> amazed anybody could copy me with the PRC-47 setup because it is such a
> simple demodulator. And maybe the laptop is the explanation. I gave
> away my PRC-47 setup without ever using it for RATT.
>
> Jim W6JVE
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