[HBR] One Month HBR Doc Package (was 'Another HBR Project -- Chapter 9')

[waltah at earthlink.net]

Kees asked:
> Say Walt do you still have a documentation package available for
> your HBR receiver ? I have all your notes on the CD I'm sure but I
> did not get a copy of the diagram and chassis layout. 

I never did that documentation package.   There seemed to be no 
interest in it and documentation is a whole lot of work.   

Plus -- if you can believe this -- it's still under development.   About 
three months back I added an IF stage at 1665 kcs (1st IF) and 
now need to go back and add cathode resistors for that stage to 
each of the coil sets (I'm sure there's a spare pin available 
somewhere!) so that the overall gain will be the same on all the 
bands.   

Possibly then ... it did turn out quite nicely as a 'vintage design' 
vintage piece.   And while the mechanical issues of plugging in the 
coils through the panel are substantial, electronically it's an easy 
set to get working because the gain is distributed over all possible 
frequencies -- an RF stage, a single stage each at 1665 and 85 
kcs, and finish up at audio.   

Stability's quite good, considering, because of the cooling of the 
coils by inward/upward air flow.  

The coils are no fun though -- the space in the command set coil 
cans is so limited that I haven't been able to find room for 
compensating caps in there!   

Also I *think* I know why those command set 85 kcs IFTs have 
such poor skirt selectivity.   The wires that connect the plug on the 
bottom to everything inside run up very close to the (large!) coils 
and the outside of the coils is 'hot.'   Thus there's substantial 
coupling past the tuned circuits.  It didn't matter in 'range receiver' 
use -- might even have been an advantage to be able to hear a 
strong station that was somewhat mistuned -- but it's a serious 
flaw in communications work.

It is possible to put a bit of grounded tin between the wire and coil 
in these places to provide shielding and I have been doing that, one 
transformer at a time, as I feel inclined to remove four or more wires 
and eight tiny screws.  

More to come on that topic.  

Walt
KJ4KV