91XG versus thier New DB8
The captures below compare Antenna Directs's 91XG Yagi antenna to their new DB8.
One measurement note: the vertical height of a DB8 and other 8-bays is around
28" or so, and the 4 left & right pairs of active bowties sit at 4 different
altitudes (four slightly different horizontal planes). On the other hand
the 91XG Yagi design's sensitivity lies on a single horzontal plane (altitude).
All the 8-Bays all use two mounting clamps, one near the top and another near
the bootom spaced about 22" apart. Thus the 8-bay's
maximum height will always be limited by the point where the top most clamp is attached at the very
top of the mast. That makes the center of its sensitiviy about 11" or so
below that point, and for these comparison purposes the 91XG was mounted at that
point, about 11" below the top of the mast. [Given its mounting design,
the 91XG actually exhibits a small advantage over 8-Bays because its effective height
can be about 18" above the center of sensitivity of an 8-Bay. Not a
major factor, but in a marginal situation it couldn't hurt.]
Channels 15, 20, and 24:
Channels 23, and 26:
(Note: Channels 24 and 30 are
approximately 75 degrees off axis. The visible signal is an indication of side
lobe response only.
It is interesting to note the significantly lower side lobe
response of the 91XG's much morech more directional Yagi design
versus the fan dipole design of the DB8... as
would be expected!)
Channels 30 and 33:
Channels 44, 47, 49, and 51:
Which of these is "better" is a marginal call; it really depends on the channels
of interest. At the low end the DB8's response has some
short comings, as have
been shown else where, and the 91XG has about 3 to 5 dB
better sensitify at that end. Elsewhere across the
band the differences are minor; at some frequencies favoring the 91XG by about 1 dB or so,
and at other points favoring the DB8 by about the same amount.