Also in reply to Charlie, re: why not used more often.
Back in bygone days we were allowed to run 1 KW power input for cw or 2000
watts input peak input for SSB and other modes. Many, if not most of the
commercial amplifiers were designed to tune up with a cw carrier and 1000
watts input power. These amplifiers typically had a cw/ssb switch on the front
panel that changed the plate transformer primary or secondary tap to cause
the plate voltage to increase about 40%.
The idea was you could tune up at 1000 watts input, make the switch, adjust
the drive level enough to increase the plate current about 40% and end up
with 2000 watts input power and the have the same plate load impedance.
It was illegal to make the switch and adjust the drive level using a cw
carrier as that would always exceed the legal input power limit of 1000 watts.
Of course no one ever did that, right?
So, the scheme has been around for a long time; just not described as we
have been discussing here recently.
73,
Gerald K5GW
In a message dated 7/24/2015 10:30:07 A.M. Central Daylight Time,
chris@chriswilson.tv writes:
Hello Charlie,
On Tuesday, July 21, 2015, you wrote:
> Along the same vein as Colin, I have an adjustable 0-4kv, 0-2.5Amp SMPS.
It
> has a switch freq of 18 khz.
> Will this allow to change the Ep, and not retune?
> If so, why not use more often? Seems like an efficient way to go. Much
> lighter, and voltage regulation is <1%.
> What am I missing?
> Charlie N6CFH
I would be most interested in seeing photos and a schematic of this,
or a similar high voltage, high current SMPS, either home brew or
commercial. The tight voltage regulation, and not having to put my
back out lifting huge linear supplies is very appealing!
A big thanks to Manfred too, for another fascinating post on SMPS
matters.
I run a big transformer that gives 5kV at well over an Amp off a 25
Amp variac. I mainly run it with the variac switched out, but it's a
very useful beast for general HV supply duty, and regulation, looked
at on a scope with a loosely coupled coil winding, is pretty good even
with the variac giving about 180V AC into it, instead of our UK 240V @
50Hz. It's just so *BIG* though, in a castored cabinet, and would need
dismantling to safely get it down the stairs from my upstairs "shack".
--
Best regards,
Chris mailto:chris@chriswilson.tv
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