[AMPS] to choke or not to choke...

[Rich Measures]

>Subject:     [AMPS] to choke or not to choke...
>Sent:        4/01/1997 12:25 AM
>Received:    4/01/1997 5:22 AM
>From:        Jim Henderson, jhenders@tdrss.wsc.nasa.gov
>To:          amps@contesting.com
>
>Esteemed Reflectees:
>
>        A couple weeks ago there was a thread about power supplies, and the
>desirability or not of choke input supplies. I have been considering a
>couple of used Henry amps using that design.
>
>        I recall comments to the effect that choke-input PS systems were the
>long engineering solution to a simple requirement, that Henry-style choke
>input supplies were troublesome and out of date. 
Choke (choke-input) filter supplies are out of date because they are 
suitable only for constant-current loads.  However, resonant-choke filter 
supplies are capable of handling rapidly changing loads--i.e., SSB 
amplifier service.  Resonant-choke filters provide Much better regulation 
than C filters.  The main trade-offs are weight and cost.   A fringe 
benefit is that a resonant-choke filter supply demands about 12% of the 
peak current from the electric-mains that a C filter supply with a 
similar V/I capability demands.  This means that the conductor diameter 
used in the mains can be considerably smaller (like #8 vs. #4) with a 
resonant-choke filter than with a C filtered supply.  .  
>        I wonder if this is true, as Henry amps do retain the image of
>battleship ruggedness and reliability, or did I miss something salient. 
.......
Henry resonant-choke supplies are pretty good, out of the box, but you 
will need to add a step-start circuit on most models.  One dpdt relay and 
a pair of wirewound resitors will take you there.  A resonant-choke 
should be *always* be potted, and Henry doesn't, however, you can take 
care of this yourself.  Both items are discussed in *Amplifiers* at 
http://www.vcnet.com/measures>
 Other electrical improvements that might be nice:
1.  high speed switching to reduce racket and to prevent hot switching 
with 
      modern radios..
2.  decreasing the vhf-Rp of the vhf suppressors to improve stability.  .
3.  isolating the c. 90MHz resonance in the Henry HV-RFC from the anode 
resonant circuit 
     with a ferrite vhf-attenuator bead and a c.1 ohm resistor.   
4. output compartment vhf resonance dampening loop (2k4, 3ka, et cetera). 
  This subject should probably be discussed privately, Jim,  so as not to 
arouse any quiesent lap-dogs.  
--Rich--


R. L. Measures, ag6k, 805-386-3734    


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com