■
Fig. 1 Reference antenna spectrum
■
Fig. 2 Yagi U-PA antenna spectrum
Transmitter Frequency [MHz]
561
634
666
U-PA Antenna Output Power [dBμV]
57
55.2
50.4
Multi-element Yagi Output Power [dBμV]
60.5
59.8
56.9
Transmitter Frequency [MHz]
561
634
666
U-PA Antenna MER [dB]
31.8
31.9
25.4
Multi-element Yagi MER [dB]
33.2
32.7
31
■
Table 1: Antenna Measurements - Gain
■
Table 2: Antenna Measurements - Quality
86
TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine
— 03-04/2014
—
As can be seen in Table 1, the
difference in antenna gain was
from 3.5 to 6.5 dB. This means
much less than what we expect-
ed from the specifications. This
point clearly goes to the Yagi
U-PA!
Then we observed the full
spectrum at the output of the
Yagi U-PA and the output of our
reference multi element yagi. As
you can see in the pictures, the
difference is indeed surprisingly
small.
Please note: at the left hand
side of the picture you can see
the VHF radio band. None of
these antennas is suitable for
the reception of this band – so
the difference between them
does not matter. What counts
are the three peaks in the right
hand side of the spectrum which
are 561, 634 and 666 MHz, rep-
resenting the terrestrial UHF
transmitters available at our
test location. It is clearly visible
in the screen shots that the dif-
ference between the antennas
is just a few decibels, matching
the results of the channel power
measurements we did before.
Naturally, if the signal at the
antenna output is weaker, than
its separation from noise de-
creases. We measured MER for
both antennas to evaluate qual-
ity of the output signals.
MER was almost equally good
for the YAGI U-PA as for our
much bigger reference antenna
for 561 and 634 MHz. Only for
the third lower power transmit-
ter at 666 MHz we noticed a de-
terioration of the signal quality.
However, it still had almost 4 dB
(3.9 dB) noise margin. So, even
in worse weather conditions you
should not be afraid of loosing
the service.
To sum it up, the Yagi U-PA
performed very well for its
class. If you receive a signal
from typical local TV transmit-
ter you can expect solid recep-
tion within a distance of 30 km
or so around the transmitter
site. If you put the antenna in-
doors the practical range will
decrease to 20 ~ 25 km.
