[HBR] One more quick question

[Walt Hutchens]

Bill wondered:

> I'm sure there are a few out there we maybe should NOT part out : )  But,
> which one/s would you be out there looking for???  IF I don' start looking
> better, I'll still be looking haphazardly for the next few years : )

You know what my answer's going to be, right?   But there's a longer story
...

I think the problem is that most good receivers -- either a good design to
start with OR a so-so design but excellent condition -- are uncommon to rare
and tend to sell for high prices.   Pretty much anything that looks like a
W6TC  HBR and has all coils for one band is going to be in that category --
$200-up, I'd say.   Of course you wouldn't want to part out a really nice
one.

Other receivers ... well, there just weren't many that have good homebrew
potential.   I've worked on FT-101 redos: these are transistorized-to-hollow
state conversions and (although I didn't do it yet) I think they could be
excellent.  BUT this is a bandswitching double conversion project: The set
doesn't have either the proper tuning cap or dial scale for an HBR approach.

Other relatively popular homebrew multiband sets ... gee there I can't think
of ANY of those.   Really ...

I got the dial and tuning cap for the 'Long SLOW ...' project from a
parts-only G3RKK designed set (appears in one or two of the RSGB
Communications Handbooks) but that's the only one of those sets I've ever
seen and nobody knew what it was until I got it here and was able to ID it
from the book.   

There's the G2DAF homebrew design -- a few thousand are said to have been
built -- but that's a UK set, most survivors probably are still there, and
it's another crystal converter/tunable 2nd IF double conversion set, like
the FT-101.   I've never seen one on eBay.

There are plenty of home use 'shortwave' receivers but they're general
coverage sets with el cheapo dials and the wrong tuning capacitor.   You
could perhaps prune the cap to something that would work, but it's the
cheapest possible cap and you've still got a crummy dial.

Lafayette and others made some ham band only vacuum tube sets. One of these
might be a possibility but I have no clue what to look for.

A vacuum tube FM receiver with a slide rule dial and three-gang tuning cap
(some were two gang) would have a cap and dial mechanism, also perhaps the
power supply, though the later models were series string.   However you
wouldn't get usable IFTs ... you'd have to search out either a crystal
filter and compatible IFTs or find the parts for the real W6TC approach of
double conversion. 

The reason I landed on the HR-10 as the foundation for my current effort is
that many thousands were made, they're single conversion (to a high IF)
bandswitching ham-band only designs but they were not great sets to start
with so they're not highly prized today.     If you set up your bidding
properly you'll get one on your front porch from eBay in less than a month
for under $100 total and with any luck all the essential parts will be
there.  

These sets have:

1. A decent dial mechanism with an already calibrated dial.   This setup is
infinitely superior to the National MCN (etc.) 5:1 dials used on the early
'authentic' W6TC sets -- you absolutely can tune in an SSB signal.  It's not
quite the equal of an Eddystone 898 but the whole set will cost you about
what that dial would cost and the Eddystone layout and metalwork is pretty
much the hardest such work I've done.

(The Eddystone dial has anti-backlash gear drive for the tuning cap -- no
string drive is going to fully equal that.)

My second HR-10 came with the plastic dial face glued to the front panel,
probably as a solution to the warping problem.  I'm guessing it can be
salvaged but there would be some extra work.

2. A good tuning cap.

3. A crystal filter -- although the first set I got came with a bad crystal,
forcing me to pay another most of $100 for a second set.

4. A full set of IFTs and matching BFO coil and BFO tuning cap.

5. An S-meter and scale.

6. A usable 11" x 13" chassis -- I didn't have to do any cutout/new plate
work at all and this is a good amount of room for this project.

7. A transformer and power supply stuff.  Even the 6X4 and filter cap are
okay in my two sets.

8, Miscellaneous parts -- An output transformer, panel controls (though the
volume control is probably shot due to Heath having put the ON/OFF switch
there), a fuse holder, two 21 mmf air variables for dial calibration and
antenna coil peaking, knobs (my second set came with a bunch of oddball
ones), most of the nuts and bolts you'll need, and some smaller parts,
including some silver mica and temp compensating caps if you cut up the
(cheap!) bandswitch to get them out.

If you get a set with items 1-4 in working order, you are good to go --
that's all the stuff you could otherwise spend a couple years hunting down.
(Remember that because there were multiple approaches to W6TC HBRs not all
the HBR parts out there are compatible.)  Add coil forms (but you can make
those) sockets for the same,  some tube sockets, the usual batch of small
parts, wire, a new cabinet and probably a new front panel and you have the
whole kit.   

>From what I know now, the HR-10 is the way to go.  Having done the basics,
I'm pretty confident that a decent HBR design can be built in that chassis;
I just haven't done it yet!   And anyway the first step after buying one is
to get it working as-bought because you want to be sure that all the key
parts are in good order before starting your own project.

If in the end you don't do the HR-10 to HBR conversion you can almost
certainly dispose of a 'seller refurbished' unit for more than you paid for
a 'used -- not working' one.   :-)

Walt 
KJ4KV