>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input supplies were troublesome and out of date.
Choke (choke-input) filter supplies are out of date because they are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
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