>Here's a message received from a guy I knew at university aeons ago. He
>reads
>the archives but is not a subscriber. I'm not sending it because it carries
>any personal baggage for me but because it's an input from a highly
>qualified
>and very experienced rf engineer.
>
? The presumably highly-qualified and very experienced engineers at a
well-respected West-coast amplifier manufacturer have managed to design
three amplifiers which use 4.75 - 5.25 V rated filament tubes that have
5.79 - 6 V on the filament. Using the formula emissive lifetime =
[e1/e2]^23.4, the life expectancy of the cathode is c. 0.5% of normal.
- The presumably highly-qualified and very experienced engineers at Ford
Motor Co. mounted the electronic-ignition module behind the hot exhaust
air from the radiator. This decision probably saved Ford hundreds of
kilodollars in wire+labor that would have been used to mount the
electronic ignitition module in the cooler airflow out in front of the
radiator. The only tradeoff was occasional failure of the module on hot
days. Dozens of people died when their "better idea" Fords stalled on
freeways due to failure of the ignition. After a decade of saving
chump-change on wire, the recall is going to cost over $2-billion. If
the "slow-speed chase" of O. J. Simpson's white Ford Bronco had taken
place in July/August, and the car stalled on nation-wide TV because the
ignition module shorted out, the publicity would have probably
embarrassed Ford into fixing the problem early-on, and the company would
probably have saved >$1-billion.
-- RE: "subharmonics": Without 2-freqs and a mixer, they are an
old-wives' tale. Another clue is that parasites very rarely happen at HF
and parasites normally send grid-current through the roof. The moral to
the story is better to measure spurious outputs using a resistive
termination. In days of yore, copper-oxide was used to make rectifier
diodes.
cheers, Steve
>
>---------- Forwarded Message ----------
>
>Subject: Amps Reflector
To: <amps@contesting.com>
>Date: Tue, 21 May 2002 12:50:04 +0100
>
>I saw the comments on the amps reflector archive (I'm not a list member)
>about sub harmonic generation and the assertions that it cannot happen. It
>does happen and is often referred to as half carrier regen or parametric
>division. There are numerous references around on parametric dividers.
>
>It is a nonlinear phenomenon and happens particularly with low voltage
>semiconductor PAs when driven hard with the right/wrong kind of matching
>environment. You need assymetrical waveform clipping to take place in
>order to halve the period of what started out as a sine wave. It's also
>a major pain the the ass!
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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