[HBR] Another HBR Project -- Chapter 5 -- Pictures

[hbr@mailman.qth.net]

Eddy asked:

> BTW, how's it perform...? 

Not at all, yet.   Still have the front end coils to wind and a whole 
laundry list of small it-won't-work-until ... items to take care of.   
Hoping to finish in three weeks total -- that would be by this Sunday.  
 Lessee ... today is mow two acres of lawn, doctor visit, pack two 
items for eBay shipment ... bet I'm not going to make even 6 hours.

> Can you please expound a bit on that funky-looking dial ... 

Remember the 'command receivers'?   The capacitor shaft is parallel 
to the front panel, driven by a worm gear.   The dial drive mechanism 
is on the front of the capacitor frame and consists of a two stage 
spur gear reduction drive.   Anti backlash all the way except for the 
shaft to 1st gear on the dial drive.   The dial revolves about 330 
degrees for 31 or 32 shaft revolutions to move the capacitor through 
its 1/2 revolution.   It looks a little funky because I replaced a plate -- 
calibrated along the edge and thus applicable only to a single band -- 
with a plastic pointer with a hairline and an on-the-panel paper scale.  

The dial drive alone would have cost you $100 or so in 1950 or 60 ... 
that tuning cap is a genuine precision instrument.   But hams didn't 
homebrew that much, and the 330-degree rotation and need to solve 
the multiband problem seems to have limited the use of this fine 
instrument.   

Another way to get multiple bands is to use a rotating plate with a 
fixed transparent pointer bridged across it.   

Other tricks:  the control boxes have a removable dial drive 
mechanism that can be adapted to drive a straight (perpendicular to 
the panel) tuning cap.   It's not quite as good quality as the one on 
the cap, but it's still *way* better than the usual ball or pinch drive.   
You can also take the gear mechanism off the front of the receiver 
tuning cap (those caps that were trashed to build 10-meter receivers 
etc, etc, etc are prime candidates) and use it to drive a perpendicular 
shaft cap -- that would be my choice for a 'really traditional' HBR 
project.    In that case the dial rotation would be that of the cap -- 
usually 180 degrees.

There are a couple of temporary details (of the 1WHBR) that add to 
the funkyness quotient:  The hub of the dial drive shows at the 
center; it'll be cleaner looking when I paint this part of the pointer 
black.   Also, the paper scale just has three full circles.   When 
complete those will be 330 degree arcs with marks at the ends.    
The scale that's there now is just to get me started on the front end 
construction. 

A permanent possible piece of funkyness -- I happen to like crank 
dial drives so I adapted the crank from the control box normally used 
with the command receivers.   Most hams would use a round knob.

Another possible choice is the ARC #6473 local control knob but 
that's a bit too small to be handy.

One sub-theme for the project has been 'use as many command set 
parts as possible' and the crank was one of those.   In addition to the 
crank, tuning cap, coil sets, and IFTs I also used one of the 
trimmers, the 'Align input' cap from the front panel, a pointer knob 
from the control boxes, and probably a couple of other things I don't 
remember right now.   This stuff has been standard ham junkbox fare 
for over 50 years now ... I don't tear up restorable equipment to get it, 
but there's still lots of it to be had in my (and other) junkboxes -- 
heck, I still buy it when I get to a hamfest!

Walt
KJ4KV