[Collins] Transformers

[james.liles at comcast.net]

Hi Jerry:

That would be true if there was almost no load at all because that would be 
the only time that the primary would display measureable inductive 
properties.  If there is any load at all the capacitor would see resistive 
properties passed back from the secondary.  The load that the filaments 
alone provide in a 100 watt radio with a 30uf series cap render the 
magnetizing inductive properties irrelevant.  The first thought that comes 
to mind is the series resonance effect from the capacitor will cause 
catastrophic current in the primary.  Not so.  Try it it will be worth your 
time.

Kindest regards Jim K9AXN



-----Original Message----- 
From: Dr. Gerald N. Johnson
Sent: Thursday, August 29, 2013 6:13 PM
To: james.liles at comcast.net
Cc: collins at mailman.qth.net
Subject: Re: [Collins] Transformers

The right value series capacitor drops voltage, the wrong value
resonates the inductive load and raises the voltage. I have used a
series capacitor to slow and quiet an AC fan. But I believe I could run
a 220 volt fan on 120 with the right capacitor to come close to
resonating the higher voltage winding. And have 220 volts RMS on the
motor winding.

A receiver load is a bit volatile too, especially one with a standby
switch and/or class AB or B audio. Generally in a communications
receiver the RF gain changes the plate current of every gain stage but
audio and oscillators, as does AGC.

73, Jerry, K0CQ

On 8/29/2013 5:49 PM, james.liles at comcast.net wrote:
> Hi Gerry:
> Might consider a polypropylene film capacitor in series with the
> primary. Provides about the same effect as a series resistor without the
> heat loss. Works well in receivers that use gas voltage regulation for
> the oscillators. Use 30uf per 100 watts for a 6 volt reduction in line
> voltage. Reduces in rush, has about the same line voltage regulation as
> the bucking transformer but regulation is sensitive to load like the
> series resistor. Can't be used in a transmitter where the load is
> volatile. There, the bucking transformer or autotransformer are the 
> answer.
>
> Kindest regards Jim K9AXN
>
>