[HBR] HBR 16 Owner Pondering Building My Own

[waltah at earthlink.net]

Lorne Barber wrote:
> I've been noodling on building a later model ham receiver and I'm
> considering the HBR along with some others.  While I know its like
> asking whats the best car or the best color of something, is there
> a best HBR? 

My impression as a non-owning student is that they're all good if 
you apply the standards of the 1960's -- they'll drift considerably 
during warm-up, for example.

Generally I think the later designs should be somewhat better 
performers.  One exception is that using the sharp cut-off pentode 
half of a 6AZ8 as an RF amp in the later HBRs was a bad idea 
compared to the use of the 6BA6 remote cutoff tube in the earlier 
sets.  

One option might be the 'Deluxe HBR' featured in Bill Orr's *Radio 
Handbook*, 17th and 18th editions.   The thing's amazingly 
elaborate, with 'hang' AGC and a separate S-meter amplifier stage 
but you can reduce the 19-tube count considerably by substituting 
solid-state diodes.   And many of us wouldn't need the voltage 
regulator tube either -- most power lines today are reasonably 
stable.  The Q-multiplier is a nice feature but could be deferred.   
The 7360 product detector is excellent but at $40 I'd suggest 
substituting a 6ME8 or 6JH8 -- both cheap tubes; bias voltages 
might have to be adjusted.   

If you're willing to make circuit changes, then the RF and IF amp 
stages in any of these receivers should be replaced with 6EH7's -- 
unbeatable for their combination of linearity over a wide AVC range 
and high gain.  Both mixers can usefully be replaced with the 'large 
signal' dual triode circuit found in many publications -- 6ES8's are 
best but 6J6's work very well and are 7-pin.   This mixer will deliver 
both better signal handling ability and lower noise than a pentode 
circuit and is slightly simpler.

The separate BFO of the Deluxe HBR can be folded into the 7360 
(or other tube) product detector.   There's no reason I can think of  
for having separated it.   The 7360 tube data sheets have the circuit 
but it can be used with any of the sheet beam tubes.  

One man's opinions ... mileage varies.

Walt
KJ4KV