[Premium-Rx] Cubic 3030 Rx

[Carcia, Frank A. HS]

Hi All,
I went back for a third time and measured the dynamic range of my 3030A. I
compared it to a stock RA6830 I built for a friend. Again
I verified the numbers. At 2 KHz spacing the RA6830 was 8 dB better
and at 40 KHz spacing the RA6830 was 17 dB better. It was about even at 80
KHz spacing but at 100 KHz the 3030 showed a dynamic range of almost 110 dB.
My hot rod RA6830 is about 105 dB.
I measure synthesizer noise by the ARRL method which appears accurate. It is
easy you just measure MDS off center frequency
and compare the difference at CF. I'm only using a pair of 
HP8640Bs for sources so numbers are not absolute.
I started looking into the synthesizer modules and one thing jumped out.
78XX voltage regulators need good bypass on both sides. We
had phase noise problems with these regulators when I worked for
Andersen Labs. They used them in saw oscillator hybrids with typical
ceramic bypass caps. We found they need at least .36 UF on the output to
tame them. A reverse diode would have to be added if
large caps are installed and that is my plan.
Reverse voltage on these regulators is instant death. The synthesizer
modules have only a few .01 UF bypass caps on the power bus. I'm thinking of
a ground lug on the regulator mounting screw
to be the place for caps to bypass the regulator and a diode across the
input and output to protect it. The gain distribution of this radio is quite
good and maybe we can improve the synthesizer enough to take advantage of
it. The nice part is there is plenty of room to play inside these modules.
Now has anyone removed the cover of the key pad to stretch it flat
and reinstalled it? I have a bag of new ones but the second functions are
not printed on them.   fc

-----Original Message-----
From: Herschel McCullough [mailto:w5mc at austin.rr.com]
Sent: Friday, September 12, 2003 1:32 PM
To: refmon; premium-rx at ml.skirrow.org
Subject: Re: [Premium-Rx] Cubic 3030 Rx


Thank you John.. it was starting to look a little  " BASH 'E "  for the 3030
and 3030A  ..
mac/mc

----- Original Message -----
From: "refmon" <monitor at referencevideo.com>
To: <premium-rx at ml.skirrow.org>
Sent: Friday, September 12, 2003 6:18 PM
Subject: Fw: [Premium-Rx] Cubic 3030 Rx


> Hi Group,
>
> I had inadvertantly responded directly to Richard.  As I am always
trolling
> for ideas, I'd like it to go to the list in case there's any other 3030
work
> going on that I don't know about.  I have added a few additional points
> since my original note to Richard.
>
> Soooooooo.....
>
>
> > Hi Richard,
> >
> > I generally agree with the info you're receiving thus far as regards the
> Cubic
> > R3030 series receiver in it's stock form.  First warning---do not
confuse
> the
> > R3030 series with the current 3000 series receivers.
> >
> > Keeping in mind that many if not all Premium Receivers are intended to
run
> in
> > automated or semiautomated systems, here's what you can expect to
> > find, all of which are annoying from the perspective of a user who sits
at
> > the receiver for hours of weak signal searching:
> >
> > Idle gain on an empty channel is far too high by 30-35db...result is an
> > exhausting roar rather than the gentle rush with static crashes
> > intermingled.  This is can be fixed.
> >
> > AGC is the hang-type, and is set up such that return to "no signal" is
> quite
> > fast.  Result is severe pumping on SSB or CW signals.  This can be
cured.
> >
> > There is a heavy click when the receiver is hit with the leading edge of
a
> > strong signal.  This can be cured.
> >
> > The receiver radiates fairly heavy digital noise which in a home setting
> may
> > be picked up by your antenna.  This can be fixed.
> >
> > The R3030A, in particular, has bouncy keypads and often has loose keypad
> > legend overlays.  This can be fixed.
> >
> > The R3030, in particular, has no speaker outputs.  This can be fixed.
> >
> > I have never found any two receivers that track in terms of alignment or
> > meter readings.  This can be fixed.
> >
> > Hobbs-style hour meters tick rather loudly...slow torture...easily
fixed.
> >
> > Synthesizer phase noise is a little high ... mods are being considered.
> >
> > There are a few other issues that are no big deal.  By the way, this is
a
> > nitpicked list of items that I expect is no longer and is much simpler
to
> > deal with than with many other Premium Receivers.  Note that the Cubic
> > receiver, in spite of its sealed case, > does not suffer from overheat
and
> > meltdown.
> >
> > The great thing about this series of receiver is that it is built like a
> > battleship, uses discrete IC and transistor circuitry, so is easily
> modified
> > or repaired, and it uses plain old everyday parts.  I have developed and
> > installed modifications for each of these issues and will be releasing
> them
> > to the Premium-RX list.  Most of the modifications are resistor changes
or
> > additions, capacitor changes, addition of shielding.  Some of the
> > modifications require signal generator and spectrum analyzer or
> pan-adapter
> > for fine tuning, but I've gotten reasonable results without.  A couple
of
> > other list members have been digging around in these receivers and we've
> > been exchanging ideas on these mods.
> >
> > Note the AM demodulator is not all that great and modifications have not
> > been done at my location.
> >
> > I am currently working on LabView 7.0 applications which include the
> > R3030 control via GPIB.  The 3030A is by RS-232, which I have not
> > played with, although the protocols are quite straight forward.  My
> > applications currently concentrate on automated sweeps and record/plots,
> > scans with audio recording and logging, etc.  Also integrated into the
> system
> > are Watkins Johnson 86xx receivers, HP spectrum analyzers, etc.  In the
> end,
> > coming up with a control console for the R3030/R3030A should be fairly
> simple.
> > The problem will be that I am not in a position to develope a
> comprehensive
> > system...mine will be more task-specific.  I also cannot define a time
> frame,
> > as is evidenced by the time it has taken me to get my modifications
> package
> > "almost done".
> >
> > Spares for these receivers are pretty rare...that is, modules, boards,
etc
> > are few and far between.  The receivers are not particularly prolific
> > either, although there are occasional bursts of availability.  I'd
expect
> to
> > pay real money for these in good shape and intact.  Take a look at Ebay
> > prices asking and sold-for...surprisingly, these track private sales
> fairly
> > well.  Any sign of fiddling or missing modules and I'd cut the price big
> > time.  The point is, no need to buy a beater...patience will net you a
> good
> > condition, complete receiver.
> >
> > good luck in finding a receiver, whatever it may be
> >
> > John Collins
> > ______________________________________________
>
>
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>
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>



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