Y10-7-13 VHF Antenna: two different
versions adding 3 and 5 additional directors and a planar reflector.
Approximately +2 and +3dB gain improvement, respectively.
DB8 UHF Antenna: swapped out the stock
combiner and harness, closed the triangles, and added a trough reflector.
Aproximately 3 to 4 dB gain improvement (this is the "Old" DB8).
CM4228HD Nist Harness Here is
an implementation of the harness design by Ken Nist, publisher of "The HDTV
The following notes apply to all hacks listed above.
- None of the
captures are intended to present actual (absolute) field strength or gain.
Each result is presented as a comparison between two antennas or
configurations, in a test bed with otherwise identical electrical and
physical aspects, except as noted. That is, the same Tx and Rx locations were
used, the same cables, Tx levels, etc. The single variable was the unit under
test (the stock and modified antenna).>
antenna test bed is by no means ideal. Almost every placement of Tx and Rx
antenna at these close distances and proximity to ground can result in
reflections that affect absolute receive levels at various points across the
spectrum, and to varying degrees. The general rule of thumb, however, is that
Tx and Rx antennas should be at least 10 wavelengths apart, and that rule is
- The test bed was established by
in both horizontal and vertical polarizations. I.e., after characterizing a
response with, say, a horizontal polarization, both Tx and Rx antennas were
rotated 90 degrees to a vertical polarization. If the results varied
significantly the Tx and/or Rx locations were changed. Both horizontal and
vertical measurements were repeated, and locations adjusted again if necessary,
until locations that produce similar results in both orientations were found.
It is an accepted practice in antenna testing that if the results are similar
for both orientations one can be reasonably assured that measured differences
are due to unit differences versus environmental differences.
- The measurements are made at the coordinates 39° 21’ 14.63” N 120° 5' 19.54" W.
The terrain is extremely mountaineous and rugged. Note that I do think
TVFool predictions serve well in LOS scenarios. However, at these
coordinates they're really more of a hint at reality, are not generally as good
as RFProfiler (I find), and neither one can nor does come close to accuracy for
this 1Edge and 2Edge, rugged mountain terrain location.