[JMS] Millen 90800/90831 power supply and 90881 amp

Thu, 19 Feb 2004 14:10:26 -0700

If you don't get enough drive for your amplifier, consider shifting to =
the pi-filter for more voltage.

73,

Jim
  ----- Original Message -----=20
  From: [email protected]<mailto:[email protected]>=20
  To: =
[email protected]<mailto:james_millen_society@mailman.=
qth.net>=20
  Sent: Thursday, February 19, 2004 1:38 PM
  Subject: Re: [JMS] Millen 90800/90831 power supply and 90881 amp

  Hi Jim:

  No full wave BRIDGE rectification here. Just a diode on either side of =
the windings with the c.t. going to ground. I was considering a =
pi-network filter but it shouldn't be a big deal shifting one of the two =
22 uF/450 VDC caps to the output of the supply. It will be choke input. =
The power supply will be supplying both the modulator and the =
transmitter.  Output will be "QRP", that is, the transmitter will supply =
around 17.5 watts input to the 90881. Hope the power supply does the =
trick if I restrict the power level of the modulator and the transmitter =
to these levels. Cal, N6KYR.=20

  Cal,

  If you use a bridge rectifier on your power transformer you will get =
twice the=20
  voltage output but the rated continuous current will drop to half of =
the 250 ma=20
  value, so be a little careful about how warm the transformer gets.  =
You can pull=20
  only so many watts out of the transformer.  I would also suggest you =
consider=20
  making your filter a choke-input design with the capacitors on the =
output side. =20
  That will limit your high voltage output to about 0.9 times the =
transformer RMS=20
  voltage less the drop across the choke provided the choke inductance =
is above=20
  the "critical" value, L(henries) =3D Load Resistance (ohms)/1000.  A=20
  choke-input filter will also improve the regulation of the power =
supply.

  Jim Hanlon, W8KGI

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