[R-390] Straight Key Night

[Michael Murphy]

Don,

CQ SKN! I am going to let loose with a "new" ARC-5 TX on 80M and the R390A
on RX. This T19/ARC-5 chirps like a bird so it should "ring in" the new year
if you have your passband too tight. I do not ever remember my novice BC-696
chirping this bad, and I was using unregulated supply per the handbook back
in the 70's.

When I started bringing it up last week it REALLYchirped... I have tried
everything to calm the beast down and things are better:

Fancy DC regulation on the oscillator and PA screens.

Isolating the 1625 fils with a common mode choke.

Beasty choke input HV Supply for the finals B+

Better grounding.

Neutralizing the finals critically (this had by far the most pronounced
effect on improving chirp, better in fact than the regulation).

Results: - It still chirps. It must be pulling pretty bad.

Mike WU2D

----- Original Message ----- 
From: "Don Reaves" <don at reatek.com>
To: <R-390 at mailman.qth.net>
Sent: Friday, December 30, 2005 10:57 AM
Subject: [R-390] Straight Key Night


> If this year's Straight Key Night is like last, here is a chance to
exercise
> your R-390A narrow CW filters.  Lots of crowded, slow speed signals
bunched
> up in the bottom half of the 80,40,20 meter ham bands.  Many of the
signals
> you hear will be rarely used vintage transmitters, so there is a challenge
> to twist knobs and track the chirpers and drifters and weak sigs.  Just
what
> R-390 receivers were born to do...
>
> New Year's Eve 7pm EST to New Year's Day 7pm EST.
> Details at
>
> http://www.arrl.org/contests/rules/2006/skn.html
>
> Hope to work some of you. Happy New Year
>
> W5OR
> don at reatek.com
> w5or at comcast.net
>
>
>
>
> > -----Original Message-----
> > From: r-390-bounces at mailman.qth.net
> > [mailto:r-390-bounces at mailman.qth.net] On Behalf Of
> > Flowertime01 at wmconnect.com
> > Sent: Thursday, December 29, 2005 7:22 PM
> > To: R-390 at mailman.qth.net
> > Subject: Re: [R-390] Trim Caps on Mechanical Filters
> >
> > DW Holtman ask,
> >
> > Was the modification that installed variable caps (C-569
> > through C-571) in
> > the input and output of the mechanical filters in the If
> > module applied at Depot
> > during rebuilds, or just put on newly manufactured modules?
> >
> > There are two flavors of mechanical filter caps in production.
> > What you see is what you get. The field never went back and
> > "upgraded" the
> > caps in the IF deck.
> >
> > Early production had selected fixed caps.
> >
> > Later production had 4 caps under the can and 4 more on the
> > side of the deck.
> > These units also had 4 more holes in the side of the frame to
> > access the side
> > caps.
> >
> > If you have an IF deck with side caps and no side holes in
> > your frame, you
> > have a swapped in IF deck. Conversely if you have holes in
> > the frame and no caps
> > you have a swapped out IF deck. This will start some chatter
> > and likely get
> > us another dead carcass. So near the new year and such tasks
> > to be dealt with.
> >
> > There was much todo about what to do if you had to replace a
> > mechanical
> > filter in a deck that did not have trim caps. The last word
> > in 1975 as I was
> > getting out of service was still to just put the filter in
> > and ignore the cap
> > optimization problems. Wisdom from management powers was that
> > once the caps were
> > properly trimmed they needed no further adjustment. If you
> > measured the output
> > before you tweaked on the trim caps, you likely found your
> > diddling produced no
> > further gain. Experience in the field did not support this
> > wisdom from higher
> > management. It was standard procedure to tweak all the filter
> > trim caps on
> > every PM event. We wondered why there was no modification
> > work order to at least
> > add the top caps to the IF decks. We could see why no one
> > wanted us drilling
> > into IF deck and installing caps in the bottom side.
> >
> > I think if we look at decks with and without trimmers on the
> > bottom side, we
> > will see that the decks have a lot of differences to allow
> > the caps to be
> > inserted. There was just not a big blank chassis wall space
> > there waiting for
> > additional caps. The extent of these changes may have been
> > why no field
> > modification was ever kited and fielded. The idea of
> > providing new decks with caps was
> > just a non starter from spending and contract point of view.
> > Letting someone
> > drill holes in the frame to trim decks in place was not a
> > popular subject.
> >
> > We always wondered how much better a deck would have been if
> > it had had
> > adjustable caps. Decks without trimmers still passed signal
> > to noise test like
> > every other receiver, so we believed the assembly folks did a
> > good job testing and
> > selecting the fixed caps.
> >
> > One myth was the early production was "selected" to closer
> > specification.
> > Once Collins had a big pile of good but not good enough
> > filters, a proposal was
> > produced and sold to get the trim caps in and the less exact
> > filters in. Myth
> > was that a well trimmed deck never needed adjustment. I have
> > no evidence to
> > support that statement.
> >
> > Hope this provides you some insight on the subject.
> >
> > Roger AI4NI
> > _____________________________________________________________
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>
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