[HBR] That General Coverage HBR Project -- 2

[Walt Hutchens]

I've got a temporary substitute for the choke and with that and a few
more hours work yesterday, the mechanical stuff is done for now.  Still
gotta make the bandswitch out of an FT-101 unit but it will be months
before that needs to be installed.  Not only will I work from the audio
backward but the bandswitch somewhat restricts access to the tube socket
level of wiring in the front end so I won't install it until that's done.

Metric hardware on the bandswitch -- I got the M3x0.5 die for the switch 
rods from Tower Hobby.  Does anyone have a favorite online hardware 
store with better prices?   $13 with shipping for a 1" die seems a bit 
steep.

I took some photos of the radio and should have them up somewhere tonight.

This is basically the circuit of the R8040A band imaging design with a
simpleminded crystal synthesized converter front ending it. I will 
improve the R8040A design with a 6BN6 product detector and a 12AU7 p-p 
audio output stage.  115 bands of 250 kcs from 1.75 Mcs to 30.75 Mcs. 
That's not using the first five crystals of the BC-1335 set; if they ARE 
used then you pick up the top of the broadcast band but with a 
substantial birdie where the band crystal(those would be 5675-5775 kcs 
inclusive) falls within the 1st IF, 5550-5800 kcs. It's 14 tubes, series 
string filaments so no filament or plate transformer.

I think the main risk areas are getting the synthesizer to work properly 
and building a ladder filter broad enough for SSB at 4.096 Mcs -- that's 
lower than generally recommended.

The R8040A used a 150 mA string but with the higher tube count this one
requires 300 mA.

Having seen the chassis corner gussets in the HBR-16 that just sold on
eBay, I thought I'd try them in the GC-HBR.  WOW, does that stiffen your
chassis -- the thing is almost like a brick.  Definitely worth the
trouble for any design where rigidity/stability is important.

One of the kinds of knowledge I have most regularly picked up is this
kind of "obvious once you see it."  No idea why I so rarely figure it
out ahead of time.

Walt
KJ4KV