[AMRadio] Transformer help

[Bill Smith]

Part of the design criteria for a power supply is to make sure the
inductance of the filtering network does not match a "critical" value, at
which the filtering network approaches resonance.  Of course at resonance
high voltages and currents are generated in the network, which is quite
opposite of the intended effect from a power supply.

A swinging choke's inductance varies with load.  The reason they are not
used with SSB gear is because of the extreme current fluxuations with SSB
driven amplifiers, especially when there is little modulation (no current
draw).  At this point, the critical value of a supply using a swinging choke
becomes very hard to avoid.  Swinging chokes work much better in a AM
transmitter with a relatively constant current draw.

73 de Bill, AB6MT
billsmith at ispwest.com



----- Original Message -----
From: "Gary Schafer" <gschafer at mediaone.net>
To: <amradio at mailman.qth.net>
Sent: Saturday, February 16, 2002 2:56 PM
Subject: Re: [AMRadio] Transformer help


> Thanks Russ & Jim.
>
> That Is what I remember from long ago but now I am wondering if it would
work ok
> with a large filter cap like around 25 mf.  In the days when swinging
chokes
> were used a lot large values of capacitance were hard to come by.  I would
not
> be depending on the choke for any filtering, only voltage regulation.
> Any thoughts ??
>
> 73
> Gary  K4FMX
>
>
> Tommye & Jim Wilhite wrote:
>
> > Russ is right about the swinging choke, Gary.  Good for AM, not good for
ssb
> > for the reason you cited.
> >
> > Jim
> > de W5JPW
> >
> > >
> > > Speaking of choke input, I wonder if a swinging choke only, will cause
> > > problems on SSB. The supply that the transformer is going into has a
20-4
> > > henry swinging choke. It was used that way before but I am not sure it
is
> > a
> > > good idea. I seem to remember from the early days that a swinging
choke
> > was
> > > not recommended as power supply dynamic regulation would suffer badly
?
> >
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