ORIGINAL MESSAGE:
On Thu, 29 Jul 2010 21:02:30 -0400, Roger <sub1@rogerhalstead.com>
wrote:
>
>Radio Handbook, 20th edition (17.22), " In the process of adjusting the
>resistor coil combination, it may be found that the resistor runs too
>hot. The heat is usually caused by the dissipation of the fundamental
>power int he resistor, which is an indication of too many turns in the
>suppressor coil. Just enough turns should be used to suppress the
>parasitic oscillation, and no more. Once the circuit is properly loaded
>and the parasitic suppressed, no parasitic power will be present and no
>power other than primary power will be lost in the resistor of the
>suppressor."
REPLY:
Correct.
Just to be clear: It is not the choke that does the suppressing, it
is the resistor. The purpose of the choke is to provide a path for the
lower frequency HF energy around the resistor. That is why too many
turns cause the resistor to overheat by forcing more HF energy through
the resistor, most noticeable on the higher frequencies like ten
meters. Likewise, too few turns reduce the effectiveness of the
resistor at the VHF parasitic frequency. As I said, getting the number
of turns right is a balancing act for the designer.
For some reason, Carl is unable to absorb (pun intended) this concept.
73, Bill W6WRT
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