[Hallicrafters] Digi-crafters

[ah7i at atl.org]

I'll play devils advocate here.
Say you've got an old BA RX.
It's not an uncommon model.
It's your only RX.

You want to use it!
You want it to do the job as well as it can.

So, you might add a 6DJ8 first mixer and 7360 product detector.
Heck, you might even glom a DDS with digital readout and a tayloe mixer
in there and maybe a A/D and DSP where the final detector used to be.
The tube type IF chain is fine for bandlimiting prior to the A/D, and AGC
coupled back to the IF from the DSP will do a good job. You keepthe nice
tube audio stages though as there's nothing like that tube sound.

Now you have an accurate, fairly robust in terms of signal handling,
modernized, BA.

Sure, I can see doing this. Especially if you've only got a small shack
and room for just the one receiver.

It's better fate than the metal bin at the local recycling center and a
nice blend of homenrew with commercial gear.

Would I do this to a Drake 1-A or a Cosmophone (anyone got a spare
Cosmophone kilowatt that they want to part with?). But, a Hallicrafters
SX-117? maybe. Mine's already got the 7360 product detector and will be
getting the better 6DJ6 mixer. The digital portion? Well, I think I'd be
happier with DSP in place of the 7360. I don't like the BFO on this RX and
for weak signal work, it's either build a Q-multiplier or go DSP. The 50kc
last IF does a great job of band limiting and a 96kHz sound card has a
fast enough sample and hold to work at the 50.75kc IF. This is also a very
nice general coverage, 85kc-30Mc, RX. But there are not enough crystal
sockets for full coverage and the crystals are expensive. For the same
money, I can add an outboard DDS. Control this from the same computer that
holds the sound card and I have a receiver that I couldn't duplicate
without spending > $3K. Of course the DSP audio will go back through the
tube audio amp in the 117! The Tayloe mixer (2 Ohm on resistance MOSFET
switch is very low noise compared to tubes) might beat out the 6DJ8 but
that would be my last 'hack'. Hack out the analog dial, no need. But what
if I had a SX-117 with a mangled tuning mechanism on the VFO? Is it better
to 'part it out' as I see a lot of folks doing with more common RX that
are cosmetically flawed or in need of a hard to find major component? Or,
is it better to make something useful out of it?

73,
-Bob






On Tue, 20 Apr 2004, Al Parker wrote:

> Thanks for saying it John.  I'll bet 95% of us who have been watching this
> thread agree with you.  If the other 5% or 1/2%, whatever it might be,