> >> A single-layer choke of up to c. 60uH will exhibit no resonances below
> >> approximately 35MHz, however, larger chokes will.
> Which frequency?
Life was much simpler when we only built 5-band amps years ago. With the
addition of the 160, 60, 30, 17, and 12 meter bands, the choke building
business got more complicated. Chokes that worked great on the five bands
did not have enough L to do a proper job on 160 meters. More turns were
required, which brought resonances into the spectrum below 30 mhz. With the
additional bands, fewer places were available to "park" the resonances in a
portion of the spectrum far enough away from any amateur band to avoid
heating/smoke/fire. The folks that make the choke that RF Parts sells and
Ameritron uses in their products produced a good compromise that avoids
having to use two chokes to cover the 10 HF bands. This choke is c. 200 uh,
and the resonances are parked c. 11.5 mhz and 34 mhz. This varies slightly
with each installation and chassis position. It is reasonably priced. I keep
a stock here, and have used this choke on several projects with great
success. It can be easily duplicated if desired. Please do not use Teflon
rod as a poisonous gas is emitted when ignited.
Before this choke was available, I went through several trial and error
scenarios; some ending in disaster. Utilizing this product has been 100%
successful for me in several projects over the years. Just something I don't
have to worry about when lashing up a new amp.
(((73)))
Phil Clements, K5PC
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