[HBR] Anybody got a rotary switch shaft assembly -- and a question!

[hbr@mailman.qth.net]

Don Hendrickson wrote:
> See if these will work:

Gee ... they look perfect.  I just emailed him.   THANKS!

The question:  I have always used sections cut from an 'unrolled' tin 
can as small shields across RF stages, etc.  However, tin cans are 
rapidly being corrupted -- turned into corregated laquered steel which 
is about useless.   The short pineapple cans are still tin but that only 
gives you stock about 1-3/4" wide.   Does anyone know of a product 
that comes in a larger *tin* can? 

The front end of GCHBR is the most difficult design I've ever 
attempted -- 'very three dimensional' and thus very hard to visualize.   
I've settled on an 11" x 17" x 3" chassis even though I might have 
gotten it on something smaller; hopefully the extra room will allow me 
to make a few mistakes.   

After staring at it for a month, I think I've got the basic layout figured 
out.   The tuning dial (LM freq. meter) and two bandswitches are at 
the left side of the panel.   This wastes the least space and gives the 
strongest mounting for the synthesizer assembly.  The syn. drops 
into the bottom of a 5"x7"x2" chassis installed upside down under 
the main chassis.   

The 10-position bandswitch (0-9 Mcs) operates the cam for the 
synthesizer slug rack.   It's mounted on the front of the synthesizer 
and extends forward through the panel.  There's about a 2" wide slot 
in the chassis to clear the switch sections, with coils mounted on 
both sides.  The last switch section (next to the syn.) selects the Mc 
crystal and the shaft is about 1/4" above the chassis.   Right below 
the Mcs switch is the 6-position bandswitch (0-0.5-10-10.5-20-20.5 
Mcs) at about the middle of the 3" high chassis; it is mounted both 
to the panel and a shield separating the input and output tuned 
circuits for the RF stage.   

Above the Mcs bandswitch is the main tuning dial -- can't be 
perfectly aligned because the VFO box has to clear the synthesizer 
chassis.  The VFO is about 4-1/4" high over the bottom of the 
gearbox; I have to go to an 8-1/2" or 9" high front panel to get 
clearance.   

The tuning cap for the front end and syn. output is to the right of the 
0-0.5 ... Mcs. bandswitch, mounted under the chassis.  It may be 
possible to align the shaft with that switch, depending on my 
willingness to use spacers under the cap.  

The right half of the chassis will hold everything after the mixer, 
including the power supply.   Should be ample room.  

The two big risks are (1) Winding the slug-tuned coils for the 
synthesizer.  I don't exactly know how I'm going to do that, since 
they're in cans -- it could be a whole lot of trial and error.   (2) Stray 
capacitance in the front end.   It's *very* hard to keep that area both 
compact and accessible at the same time.

The first step -- started tonight -- is mechanical construction of the 
front end area.   Then I'll lay out the rest of the chassis and build the 
power supply.   Then build the synthesizer -- no mechanical work 
there because I'm using the ARC-27 20-30 Mcs IF assembly, but six 
tubes to wire and seven or eight coils to wind.  I can use the existing 
Butler oscillator without change and its coil may be close enough to 
just realign.   

This is gonna look like some of the military sets, with knobs located 
here and there around the panel.   Well, if it works I can live with that.

Walt 
KJ4KV