[HBR] Another HBR Project

[john]

This was also implemented in the  design of the later model Meissner Signal
Shifters...

73
John K5MO



At 08:27 PM 8/25/03 -0400, you wrote:
>Kees said:
>
>> This business about using a turret tuner out of an old TV, like on
>> this 1956 radio of Cliff's, looks interesting also. Toroids should
>> make that very useable. 
>
>Yeah, wonderful idea.   The problem with those TV tuner bandswitch 
>designs in the past was that the coils were so small that you couldn't 
>get a decent Q but with toroids, that wouldn't be a problem.   You 
>might even put the toroid in series with the original coil and use that 
>as a trimmer.   Somebody on the list ought to try it!
>
>On the 'One Week HBR' project, I'm chewing now on the HV supply.  
>I like to keep it to around 150 volts to reduce the power consumption 
>(=heat) but nobody much made power transformers like that.  I have 
>found a few 'isolation' transformers in the 20-30 watt range but even 
>those are not common now.   I've done 'transformerless' designs but 
>having to decouple the negative line is a source of design problems.   
>Another trick I've used is to convert the primaries of two Radio Shack 
>filament transformers of the right size into a single 1:1 transformer -- 
>they are bobbin wound with equal bobbins for both windings so this is 
>easy to do once you get the transformer apart.  
>
>I have just tested a 15 watt 1:1 power supply:  with a capacitive input 
>filter it gives 110 volts at 90 ma which should be enough power for the 
>1WHBR.   The voltage, however, may be an issue.   I want to use a 
>12BH7 (dual medium mu triode) for p-p audio output, driving it with a 
>phase splitter; there may be trouble getting enough drive voltage.  
>
>We'll see.  Have to get going on the chassis.
>
>Walt Hutchens
>KJ4KV
>
>
>
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