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This one is a bit different for me. It's not the usual thing that requires me to spend a week or two in the shop, indulging in circuit design, panel graphics, sheet metal
fabrication, soldering and testing. I said indulging, because that's what I do ... I like doing it, I want to do it, and ... I do, do it.
Still, this isn't the typical radio that's fun to turn on and swing the VFO up and down in an effort to find something pleasant or interesting to listen to for hours on end.
As the great goddess, Electra, will tell you, "...
there's plenty of weather radios around this guy's house already."
She's right. And I agree. Besides, realistically, how many does a guy need? How many can you listen to? How often do you listen?
All good questions - I have no legitimate answer, except I wanted to build this one ... and that's good enough!
Anyhow, here it is. It's all stuffed into a 1U (1.75
In) rack chassis. It's a very basic PLL FM receiver
design borrowed from the many thousands of
engineers who have gone before me.
Most of the controls should be intuitive. The
audio section has a Detector Gain control ahead
of the Audio Amplifier for the convenience of not
overdriving anything from the Line Output while
the Audio level is turned up or down. This is kind
of a standard feature for broadcasters where
Line Level is set and fixed, but the monitor level
may be varied as convenient.
The PLL tuning is accomplished with BCD switching. I decided
on having two ways to input frequency. The primary is with a
multi-gang rotary switch that is wired as a binary encoder and a
digital BCD encoded thumb wheel switch for the "Home" or
primary station frequency ... kind of like a scanner's Primary
Channel.
The "Lock" switch disconnects the "Tune" and "Pri" controls
and the radio remains as it has been tuned.
The chip logic may be inhibited or enabled with a pulse from the
"Hold" or "Reset" buttons. This acts like a soft turn on/off mode.
The Audio may also be muted without affecting the Line Feed. There is a 10-segment VU bar graph meter calibrated as dB and milliwatts into 600 Ohms. There is avariable "Hash" filter
that cuts audio above 4KHz with a slope of up to 12dB/octave. Internal or external speaker may be selected, as can headphones only.
Okay, there you have it. It's a radio that works well for what it's designed to do. It's way over designed for the average family room, and could only possibly be (realistically) found in some
crazy Ham's Shack or maybe a studio control room somewhere.
I must say, listening to NOAA's WX B'casts is rather annoying. The digitized machine voices, both male and female, sound like the crankshaft bearings in my old Camaro; rough and
grating on the nerves. But the weather is a major part of our lives. It controls everything we do, plan for, and respond to, throughout the day. Weather monitoring, whether achieved by
the traffic and news girl on your kitchen radio, or through this monster, is one of those necessities of life ... I suppose it's kind of like having in-laws.  [3-7-11]
Counter
But wait, there's more! When I posted the pics of the NOAA receiver, I said I'd try to have the "Time" receiver done sometime in April. Well, it's still March and it's done. I can thank some
cold, wet New England weather for that.  [3-28-11]
So here they are. I call them the
Utility Twins
Coming soon: A 60 KHz WWVB Time Receiver. Basically a digital, LF-band receiver with a 6-digit, decoder time
display. These receiver/clocks are accurate to within a few milliseconds (propagation delay) and use the same
technology that your home "Atomic Clock" uses.

But this one will be different ... but you already expected that ... huh?
Here's the "Twins" sitting on top of a custom RACAL RA6790/GM.
Ever see a black RACAL before?
No? Then look
here.
This radio is pretty similar to the WX unit above, but
it's an 11 transistor superhet with the requisite HF
twiddlers (knobs), like an low-pass "L" tuner, and
selectable antenna matching for seriously
out-of-range antenna loads. The tuner can be
completely bypassed when not required, but then
switched back in without resetting all the twiddles.

Note that it retains the original 7.3 CHU frequency
which a part of the original circuit design. I kept it in
since it makes an interesting beacon (type) setting
for checking relative propagation qualities on the
40-meter band.
My receiver designs usually include a true
RF Gain control. Because of that, I usually
incorporate a (true) IF Gain control ... which,
by the way, is what a lot of manufacturers
call RF Gain. But as we all know, that ain't
true.
They cheat with stepped attenuators !
But that's another story for another time.

Both radios incorporate what I call a hiss
filter which is really nothing more than a 4
KHz rolloff trimmer - kind of like a treble cut
control, but with a knee two octaves higher,
above the normal speech range.
Also there's a 10-segment audio bar graph
VU meter driven from the detector preamp
(line audio).
See them both here
wx receiver
and here
time receiver