Version 2022.01.15 of k2av.com is up. Current release "Versions" content:
*V.2022.01.15*
- [Home Page] In "Very Useful Details" added item (n) referencing and
linking to added content in "Taming the Inverted L": Using a special jumper
to eliminate false readings sometimes experienced measuring at the
Isolation Transformer. Sneaky problem not limited to inverted L's, FCP's,
or IsoT's.
- [Various] For situations needing common mode chokes, direct users to
K9YC's most recent designs. Added references and links to K9YC's 2018
reference PDF: *"A New Choke Cookbook for the 160–10M Bands, Using
Fair-Rite #31 2.4-in o.d. (2631803802) and 4-in o.d. (2631814002) Toroids".*
- [Field Adjustable IsoT] New article details winding a robust
*field-adjustable* step-up isolation transformer to deal with isolating and
matching an L/FCP feed R's 23-39Ω or 27-46Ω to 50Ω in a single device wound
on a 4 inch core. A limited version on a 3 inch core is included.
Particularly intended to support "taming" the L/FCP when using Method B in
"Taming the Exasperating Inverted L".
- [Various] Many textual improvements and small additions in older articles
needing references to and from the Field Adjustable material.
- [Various] Readability Improvements and Clarifications.
The "Special Jumper" and accompanying text addresses a common problem with
tuning vertical or partly vertical antennas fed at the bottom of the
vertical member, which includes an L/FCP, that can invalidate an
RF-analyzer-generated antenna tuning. This was a solution to a major WTF
conundrum in the adjustable IsoT Field Trial. I had one of those
troublesome just-exactly-the-unfortunate-length coax runs.
Specifically included direct recommendation of and linkage to K9YC's 2018
cookbook. This came about when common mode chokes (CMC's) per K9YC's design
and chosen material outperformed some commercially available CMC's when
cleaning up CMC on coax in the field trial of the adjustable IsoT. Wanted
folks to know about that.
Added an article to construct a field adjustable turns ratio isolation
transformer (IsoT). These have a step-up turns ratio to convert the low R
of an efficient L/FCP to 50 ohms while the installer trims the far end of
the horizontal wire for X = 0 at the chosen center frequency. This has been
a recurring request since the NCJ article in 2012. Direct link is
k2av.com/FieldAdjIsoT.html .
In comparing instructions for fixed 1:1 ratio bifilar IsoT and the field
adjustable versions, a majority of the text is identical for both with the
field adjustable directions comprising nearly all the difference. The field
adjustable article contains the material not in common. Added links to and
from the main IsoT article.
The field trial at K2AV is described.
The field trial uncovered quite a bit which fed back into the particulars.
Some obvious inclusions to the loss list are in the works but not available
now.
Enjoy.
73, Guy K2AV
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