[HBR] 'Transformerless' receiver design

[Walter A. Hutchens]

Rich said:
> I emailed walt about sharing his transformerless design as I need a
> project, I have a lot of spare time on my hands due to foot surgery on the
> 30th, and this looks like a good project to get me (and maybe some others)
> back into serious homebrewing.

I've had a couple of requests for this info.   I've been writing it up as the 
project went along and have started on the diagram.   I don't think it would 
be a good beginner's project because the IF packs quite a bit of gain into 
two stages and if there's any feedback at all, the shape of the bandpass 
will be crummy.   That has to be the case because there's no RF stage.   
Additionally, the 'six tubes plus rectifier' is really ten when you allow for 
dual-section tubes with the halves doing separate jobs -- but packed into six 
sockets plus one.   

'Transformerless' design gives you new issues that I think I have completely 
resolved (and documented) but that isn't a guarantee.   However someone 
who has build a several-tube design before should be able to get it working. 

I should have a diagram in a week.   I think I can resurrect a computer that 
will let me do a final version with software.    

Critical parts are three shielded coil forms 9/32" diameter with about an 
inch of winding space and four terminals (I used APS-13/APN-1 IFTs) plus 
one spare shield and base to house the crystal filter, a double gang BC 
receiver tuning cap, each section about 450 mmf (otherwise other values 
will have to be adjusted) with fairly low torque, another double gang BC 
tuning cap with equal sections, value >200 mmf/section, ideally with a built-
in 5:1 reduction, plus the usual main tuning dial (5:1 is NOT a high enough 
ratio -- I used one of the two-speed Miller drives) and other usual receiver 
parts.  Three crystals that will have to be special ordered -- most of $75 
for those.   Most tubes are uncommon but all are cheap.   

Walt 
KJ4KV