>
>on 5/28/01 5:16 PM, Tom Rauch at w8ji@contesting.com wrote:
>
>> The reason this argument continues is because many like to think
>> the model we use to "black-box" the source is actually what the
>> source looks like inside.
>
>I discovered a very apparent reason why this is so.
>
>I was cruising through my 1987 ARRL handbook the other day (yes, I have a
>newer one, but I am more familiar with the old one). In the PA section, it
>does the VERY thing Tom says you can't do. It talks about efficiency based
>on the resistance of the source. It goes inside the source model and acts
>like there is a dissipative resistance inside. They even show this nice
>graph of efficiency vs. match vs. power transfer to buttress this "fact."
>
>Most hams have not gotten a 4 or 5 year degree in Electrical Engineering.
>Of those that have, many took few if any RF classes. So we have a ham
>populace that reads a supposedly authoritative text (after all, it IS
>published by the League) and believes it as gospel truth.
>
>I should look in my 1999 handbook to see if this error still exists. If it
>does, then the next person to re-write that section should remove it!
>
>A lie, if told often enough, becomes believed as truth.
>
? Amen. For years and years, the Handbook has advocated putting gaps
in HV anode/plate chokes to ameliorate the resonance problem. For years,
I thought it was true - however, I am a curious person, so I decided to
build two HV-RF chokes that were quite similar except that one had gaps
and the other did not. Both chokes had similar resonances. Eureka! I
discussed this problem with a QST Staffer. He told me that if a specious
idea originates from an elderly League employee who has guru-status, it
is not easy to fix.
- The good news is that the new Handbook explains why so-called
'rectifier-equalizers' can lead to diode failure.
later, Jon
- R. L. Measures, 805.386.3734, www.vcnet.com/measures.
end
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