>........
>I believe the purported reason for using a progressive shorting switch is to
>reduce or eliminate the tesla coil effect of having the unused portion of
>the coil step up the voltage.
I Agree. The safest way to remove L is to short it out.
>In certain cases, an extreme high voltage
>could be developed. In the Heath, something was always connected to each
>end so that effect could not happen. ...
Amen
>
>The progressive shorting of the coil presents problems for the amplifier.
>In particular, shorted turns will act like a shorted turn of a transformer
>and can lead to large circulating currents.
I do not believe that this problem exists in the Heath SB-220. Perhaps
the reason why is that the two sections of L in the tank are not
electromagnetically coupled to each other.
cheers, Colin.
>I found an article in the May,
>1963 issue of 73 magazine by Bert Green, W2LPC. Bert wrote the article
>while working for Amperex. He made distortion measurements of the amplifier
>after construction and stated that "the distortion was decreased even
>further by leaving the unused turns on the plate tank coil unshorted when
>switching from band to band instead of shorting them as was done when the
>amplifier was first constructed".
>
>I installed the replacement wafer with no shorting contacts and had no
>problems.
>
>So, the question for home builders is " to short, or not to short?"
>
>73, Colin K7FM
>
>
>--
>FAQ on WWW: http://www.contesting.com/FAQ/amps
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>
>
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|