I've designed switchers and cleaned up switchers for amateur and
commercial use at HF stations.
> If you can keep the 2nd & 3rd harmonics of your KW amp from futzing up
> the neighbors (or your own TV's!), then you can certainly deal with the
> 20th - 300th harmonics of the switcher.
No sale.
1.) The switcher is a square wave, or at least it should be close to
one. The PA is a half-sinewave or better, and is already 20 dB
down on low order harmonics without any filtering.
2.) The TV set is likely on an antenna a long distance away from
the transmitter, and hopefully not wired into the same outlet and
sharing the same feedline that connects directly or indirectly to the
same chassis.
3.) The HF receiver is more sensitive, partially because it has
narrower bandwidth and hams regularly depend on hearing signals
at noise floor or just above.
> You could actually shut down the output (phase controlled converter)
> section of the power supply in receive -- while leaving the PFC running in
> a discontinuous mode. The plate supply would come up before the antenna
> relay can switch, so there would be no noticeable delay.
That might be an acceptable solution.
> >Shielding a high-power high-frequency switcher from a receiver
> >connected to an antenna that might be fractions of a wavelength
> >away is a royal pain.
>
> It works fine when I build it here.
You should do more of them then, and sell them. Most other
people aren't as successful as you are.
> I have two "factory made" switchers in my 4CX1500B amp (one encased, the
> other open frame). They were both noisy as hell in the open monitoring
> with a receive antenna a couple feet away -- you could hear them all the
> way up to 30 MHz! In the cabinet, and properly line filtered, you can't
> hear a squeak out of them.
You win. These endless arguments are too time consuming.
I do suggest you go into business selling them, because every last
one of the switchers in the amateur market can be heard on
receivers when the antenna is close by. The switcher that came
inside my IC751A is laying in the scrap pile, waiting for a magic
touch.
73, Tom W8JI
w8ji@contesting.com
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