On Mon, 30 Oct 2000 21:55:51 -0500 "Tom Rauch" <w8ji@contesting.com>
writes:
Hi Tom,
>I've designed switchers and cleaned up switchers for amateur and
>commercial use at HF stations.
Keep up the good work!
>> 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.
The 19th harmonic of 100KHz (first thing you have to worry about; on
160 meters) is down about 25dB; before 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.
My TV antenna is located 15' directly below my HF ham antenna.
I have ancient 5" Sony set in the shack which can connect to either
the main TV antenna system or rabbit ears. I'm clean on it either way.
The TV contains a couple of switching supplies, in addition to the H
sweep, and it DOES interfere with my VLF endeavors!
>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.
True... sorry for the for apple (HF TVI) & oranges (SPS RFI) example.
There are way too many additional considerations to make that an easy
valid comparison!
>You should do more of them then, and sell them. Most other
>people aren't as successful as you are.
I don't believe it would prove to be an economically successful
undertaking.
>
>You win. These endless arguments are too time consuming.
Merely an exchange of radio experiences -- which only seems endless
when the topic wanders so. :-)
>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.
When I build radio projects, I tend to ignore the cost/benefit ratio
(bearing some similarity to the US Government approach) but, rather
concentrate on the technical performance.... and matching knobs.
Few "consumers" would appreciate (or pay for!) my design tradeoffs!
73,
Marv WC6W
*
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