On 10/02/2013 01:39 AM, Markku MarkkuWW1C Oksanen wrote:
I was simulating (with LTspice) a three phase power supply where the secondary
is in star configuration with full wave rectification. You can get also a
second voltage from this by connecting to the center of the star, this voltage
is half of the full wave rectified voltage and is only half wave rectified (per
phase), 3 pulse in stead of 6 pulse for the higher voltage.
It turns out that even relatively high value (tens of uF) filter capacitors
would leave some 10% of ripple on the lower voltage. Now the question is: How
much plate modulation this make? The ripple frequency is 150 Hz and to me this
looks like your regular high level, plate modulated AM transmitter. Why do we
not hear this on a typical signal if it is there?
In commercial television transmitters this lower Voltage, frequently
used for the aural HPA (with 10% of the visual power requirement) is
hum-less by virtue of the Pi network filter system used. Made up of two
oil filled caps and a choke. Just like the higher Voltage supply.
--
Ron KA4INM - Youvan's corollary:
Every action results in unwanted side effects.
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