[MRCG] Poor conditions in Eureka

[Tim]

Hi Mark - Well you're right, there doesn't seem to be any documentation on
the CV-2455 RATT converter aside from what Dave Ross published (apparently
originally sourced by Dick Dillman).  That document is actually for the
Collins 700C-1 FSK converter built for a "commercial set".  No specs that I
have found.  The tones are generated by an LC transistor oscillator and it
does not look like there are adjustments to the L or C, according to the
schematic...So the tone spacing could be a little wider than 850 - but
again, what's the "systems" plus/minus spec?  Dunno....
And I'd bet my multi-kilobuck PRC-47s' primary oscillator standard is more
accurate/stable than my $100 Ramsey counter audibly beat against WWV...
LOL...

Then again, if I already knew everything there is to know about RATT and
this system, it wouldn't be any fun....but it sure is fun to watch it do
its thing!

Also, the "spur" that I saw on your signal was just on the lower frequency
audio tone (on the lower frequency side) - the upper one was clean.  I
still haven't figured out if that was the mark or space tone...LOL  The
active audio filters in this sound card are awfully good...the waterfall
display is the spectrum analysis products that Richard mentions...

much fun!
Tim

On Sun, Sep 7, 2014 at 10:39 PM, Mark J. Blair <nf6x at nf6x.net> wrote:

>
>
> > On Sep 7, 2014, at 21:33, Tim <timsamm at gmail.com> wrote:
> >
> > Hi Mark - well my CV-2455 filters could be mistuned.  I'll try to figure
> > out how to test the tone freqs to see if there is a detectable problem on
> > this end.  There's gotta be knobs in there someplace!  On receive, it was
> > working fine...  But it IS 50 years old.....
>
> Is real repair documentation available for that converter? I'd want to
> know what the specs are before turning any pots. 40 Hz might be well within
> the allowable tolerance range.
>
> With AFC turned on, Fldigi locked on to your mark tone, and your space
> tone was just a bit off to the right from the space cursor on the
> waterfall. Center frequency error was on the order of 10 Hz if I recall
> correctly, which is a lot smaller than the errors we'll expect to see from
> sets like the GRC-46 or GRC-26D. The main thing I'm curious about is how
> tolerant the CV-2455 will be on Rx. The GRC-46/etc. are going to be the
> hardest of the bunch to keep on Tx frequency without "cheating" with
> something like an outboard VFO (as I probably will do to be a well-behaved
> NCS), and the PRC-47+CV-2455 seems like the set with the fewest knobs for
> chasing off-channel signals around on Rx.
>
> Well, a big motivation for bothering to do this at all is to learn the
> operational intricacies that we can't pick up by just reading TMs. Maybe
> RTTY operators from mechanical VFO days just spent a lot of time tweaking
> knobs, and we'll learn to do the same? Or maybe the channelized sets were
> deliberately tolerant of the older sets, and it'll just work? Maybe our
> modern gear just gives us unrealistic expectations of how perfect things
> must be to get traffic through? I'm having a lot of fun learning about this
> stuff.
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