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Consumer
Indoor Antenna Test Results Reported at the
NAB Broadcast Engineering Conference
On Monday,
April 14, during the "DTV Reception Issues" session
which was part of the NAB Broadcast Engineering Conference (BEC),
Dennis Wallace of Meintel, Sgrignoli, & Wallace gave a presentation
describing the testing that they performed on consumer indoor
antennas. One objective of the testing was to develop indoor "planning
factors" based on the measured capabilities of the products
currently in the marketplace. The facilities at Electronics Research,
Inc. (ERI) were used for the tests.
As background,
the presentation noted that indoor antennas will be important
for consumers in the DTV transition. The tests were to determine
the types and numbers of indoor antennas and to assess their performance
specifications versus measured performance and then based on this
data, suggest the antenna assumptions that might be used for indoor
reception/propagation models.
Their research
(in 2007) indicated over 107 available models:
8 VHF Only
Models
10 UHF Only
Models
89 VHF/UHF
Models
64 Antennas
with no electronic components (passive)
43 Antennas
had pre-amplifiers (active)
No "Smart"
Antennas were found (it was reported that some are in development
to use the CEA 909 interface).
The investigation
revealed that there was very little published performance data
on the antennas; rather they found lots of marketing hyperbole
about "Digital" or "HDTV" Antennas; "Low
Noise", "High Gain" and such. Further, there
was little measured data available. The presentation showed
each antenna with the available published data.
Measurement
of a selected sub-set of these antennas was undertaken using
ERI's Anechoic Chamber. Ten antennas were selected, a mix of
five active antennas and five passive antennas. The measurements
made included:
Gain of Antenna
Relative to Dipole
Azimuth Pattern
Elevation
Pattern
Polarization
Isolation
Output Return
Loss
Active Antenna
Gain/Loss
Active Antenna
Noise Figure
The presentation
included the measured patterns for each antenna (not shown here)
and summary tabular data, some of which is shown below.
The measured
passive antenna gains (dBd) for selected channels are shown
in the following table.
|
Antenna
|
Claimed
Bands
|
Ch.
7
|
Ch.
14
|
Ch.
33
|
Ch.
51
|
|
ANT
115
RCA
|
All
|
-5.2
|
-2.7
|
-6.2
|
-0.8
|
|
Silver
Sensor
Philips
|
UHF
|
-25
|
-3.1
|
-2.4
|
-3.0
|
|
SS
1000
Winegar
|
Hi-VHF,
UHF
|
-20.4
|
2.5
|
6.0
|
2.7
|
|
DB-2
Antennas Direct
|
UHF
|
-14.1
|
6.4
|
7.3
|
5.7
|
|
303F
Terrestrial Digital
|
UHF
|
-18.2
|
-1.4
|
-1.3
|
4.7
|
The measured
active antenna gains (dBd) for selected channels are shown in
the following table.
|
Antenna
|
Claimed
Bands
|
Ch.
7
|
Ch.
14
|
Ch.
33
|
Ch.
51
|
|
ANT
585
RCA
|
All
|
13.4
|
11.7
|
21.0
|
15.6
|
|
MANT
940
Philips
|
UHF
|
7.2
|
16.4
|
18.1
|
20.5
|
|
SS2000
Winegard
|
Hi-VHF,
UHF
|
-10.5
|
12.3
|
15.8
|
14.6
|
|
TV25
Terk
|
All
|
24.3
|
12.4
|
13.7
|
12.6
|
|
SS3000/HDTVIp
Winegard/Terk
|
All
|
-3.8
|
13.3
|
15.4
|
13.6
|
Each of
the five active indoor antennas was evaluated for preamplifier
performance. Selected results are shown in the following table.
|
Antenna
|
Gain
dB
|
Noise
Figure
dB
|
|
ANT
585
|
21.5
|
3.1
|
|
MANT
940
|
20.9
|
3.6
|
|
SS2000
|
8.8
|
4.6
|
|
TV
25
|
21.5
|
3.9
|
|
SS3000
|
8.6
|
4.7
|
Mr.
Wallace offered the following conclusions:
Some antennas
have very well behaved directional UHF patterns as exemplified
by the Silver Sensor, SS1000, SS2000, DB2, and SS3000/HDTVIp.
They typically had good Front/Back ratio (>10dB) and polarization
Isolation 6-10dB. The Sharpshooter behaved well at Hi-VHF
frequencies as well.
Hi-VHF
Performance for the UHF Only Antennas was generally poor and
variable. For example, the Silver Sensor Hi-VHF reception
was 90 degrees from "front" of antenna. Other antennas
were "Quasi-Omni-directional" (ANT115, ANT585, MANT940,
TV25, 303F) with broad patterns for azimuth and poorer polarization
isolation. Some of these had greater gain in vertical orientation.
Active
antennas generally had better return loss and would provide
impedance mismatch isolation to the receiver.
Generalizing
from the results these antennas suggest are appropriate, the
following preliminary planning factors were among those suggested.
|
Parameter
|
Hi-VHF
Passive
|
UHF
Passive
|
Hi-VHF
Active
|
UHF
Active
|
|
Net
Gain
|
5
dBd
|
+3
dBd
|
+11
dBd
|
+14
dBd
|
|
Pre
Amp Gain
|
NA
|
NA
|
+20
dB
|
+17
dB
|
|
Pre
Amp NF
|
NA
|
NA
|
3.5
|
4.0
|
|
Return
Loss
|
3
dB
|
6
dB
|
10
dB
|
10
dB
|
The presentation
is part of the BEC audio recordings which can be purchased through
the NAB Store online at http://www.nabstore.com/audio-products.html.
Several sessions are also available for free at NAB365: http://nab365.bdmetrics.com/SPC-8-11044/2008-NAB-Show-Audio-Recordings.aspx.
JUST
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TRAINING SEMINAR
Whether
you are a satellite uplink operator, engineer or even a technical
manager who just wishes to become more familiar with satellite
communications, NAB's Satellite Uplink Operators Training Course
is for you. This four-day course is designed to instruct students
in the proper technical and operational practices that will
ensure safe, successful and interference free satellite transmissions.
The course will be offered June 2-5, 2008 at NAB's headquarters
in Washington DC. For more information call Cheryl Coleridge
at (202) 429-5346 or go to NAB
Satellite Uplink Operators Seminar.
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TV
TechCheck will not be published on May 26 but will return
on June 2.
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May 19, 2008 TV TechCheck is also available
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