[Amps] Plate modulation from power supply ripple?

[Ron Youvan]

   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.