How do they rank? Over the majority of the UHF band the Channel Master
appears to be the better performer. The caveat is that above (about)
Ch 40, the Antennas Direct DB8 excels. Also, because the DB8 exhibits a slightly
stronger signal over most of the band below Ch 40 than the Winegard HD-8800, the DB8
appears to rank second, the HD-8800 third.
The Winegard HD-8800 was a little bit of a surprising disappointment, especially
for such a long standing company which has produced so many other quality
products. In addition to demonstrating a generally lower gain, it has a
few physical short comings. It was the most tedious to assemble because it
has the most nuts & bolts to install of all three; most of these to hold the
joining booms together. Some screws were also a little hard to reach,
lying in between the active and reflector elements. Finally, the locking
design of the "snap into position" active elements does not always yield a
strong lock. Some elements required very little pressure to push them out
of position. The top most element of the test unit could be pushed
downward with a fairly light touch of the finger. Repeated use as a bird
perch would easily displace the element, resulting in loss of gain.
On the other hand, along with its overall favorable performance, the Channel
Master was hands down the easiest to assemble. It ships in an over size
but fairly flat box, with all bays already ganged, and the active element boom
assembly pulls easily into position in front of the reflector.
The DB8 assembly comes out closer to the Channel Master than the Winegard.
Not quite as simple as the Channel Master, but it moved along quickly, and was
no where near as tedious as the Winegard.
Of the three, the reflector design of the Channel Master uses the closest
reflector spacing, and thus a higher number of reflectors for the same overall
area. This higher density of reflectors, along with a longer overall
dipole dimension, is a likely contributor to its higher low end gain (see the
sidebar below for more discussion on this).
Sidebar - Some Engineering Info and Discussion
It might be interesting to revisit those comments like "... most 8-Bay antennas
are optimized for the old UHF spectrum".
Here are the mechanicals for the three units tested here. The "old" DB8 is
just included for reference.
1/2 Wave Fo
Full Wave Fo
Do the measurement observations correlate with this mechanical data? Hmmmm....
not exactly. If the
longer length dipole is such a critical factor, wouldn't both the CM4228HD and WineGard
HD8800 outperform the DB8?
The implication is that dipole length may not be the only significant factor.
By observing the characteristic resonance frequencies for the
lengths involved, its pretty clear the "new" UHF spectrum is just as much within
the range of the "old" designs as it has always been. Its also clear
that for some channels these bowtie designs behave like a 1/2 wave antenna, and
for other channels they behave like a full wave antenna. What electrical
characteristic changes the most across this range? Impedance.
How in the world can one optimize the power transfer from an electrical source
whose impedance varies so dramatically across the spectrum of interest?
The answer is simply that you can't optimize for all frequencies; its only
possible to find a compromise. That is, a "best choice" center frequency
at which source and load impedances are matched optimally, and above and below
which things don't get so bad as to be unusable at the extremes of the spectrum.
The design choices that have gone into the
transmission systems and baluns of the various models must surely represent a
compromise aimed at centering optimal performance within the desired band.
If the center point of that band has shifted (as a result of the re-allocation
of the high end), then the only thing that should need to be shifted is the
center point targeted by the balun. So the suggestion is that while designs
like the DB8 do have shorter dipoles, their lengths are not out of the band of
interest, and by slight modification to their integral baluns, it might be
possible for them to peform comparably to longer dipole designs at the low end.