Bread slicers have their issues and are not really the best solution.
Using a fixed high current mica G2 broadcast capacitor of a higher value
than you need, and making it variable with a series inductor is the way
to go. This is what broadcast stations do in their ATU's. I haven't
ever seen a bread slicer in a radio station ATU. A good high current
mica cap and a flat wound taped coil IMHO is the way to make everything
work well with no breakdowns. For a wide range of matching consider a
bridge T with fixed components and taped coils. Go to W8JI's wonderful
site for the values you need based on the impedance presented to your
feed-line.
Herb, KV4FZ
On 11/8/2016 6:55 PM, Rob Atkinson wrote:
A vacuum variable for L impedance matching is unnecessary. Vacuum
variable capacitors leak eventually. It take a long time for them to
go through their ranges and you have to have the mechanics outside if
you perform remote tuning, to sense or count turns to track when the
v.v. is nearing its maximum or minimum. It is far far easier and
faster to use an air variable that rotates freely. You only need to
keep it sheltered.
Elevated radials are fine provided they are high enough to be
decoupled from earth, which for most hams is difficult to accomplish
on 160 m.
73
Rob
K5UJ
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