| by Peter Putman, CTS, ISF
Over the past five years, I’ve tested DTV reception
in such diverse locations as Los Angeles, New York City, Philadelphia,
and Atlanta. I’ve employed all kinds of antennas, hooked up over
a dozen different models of set-top receivers, and shot hundreds of
photos of waveforms, antenna set-ups, and surrounding topography.
Back in those days, receiving DTV and HDTV signals off-air
was largely a black art. Receivers weren’t all that good at handling
weak signals and multipath. Today, receivers have jumped ahead significantly
in terms of performance. Now, off-air DTV reception problems are largely
due to MPEG encoder problems (incorrect or conflicting program PIDs),
electronic program guide snafus, and incorrectly set system timetable
clocks.
According to the National Association of Broadcasters,
there were 1186 DTV stations on the air as of May 10, while the Federal
Communications Commission counted 1411 DTV broadcasters. (Heck, Philadelphia’s
got ten by itself, plus another four in nearby cities!)
So there are plenty of stations to tune in and watch.
The question is; has off-air DTV reception gotten any easier?
STEP RIGHT UP!
It has, according to Winegard, the antenna manufacturer.
Their new $149.95 SS-1000 Square Shooter antenna is billed as a “install
anywhere, indoors or outdoors” product that (I quote from its
box) “receives and modulates analog and digital TV signals up
to 50 miles away” and “outperforms all but the largest competitive
antennas”.
1a. Here’s a view of the Square Shooter
with its cover on…

1b. …and with its cover removed.
Note the half-circle element shape.

Never mind that antennas are passive devices and can’t modulate
anything – all they do is resonate at different frequencies and
pass along RF signals to a receiver. Even so, I got several email inquiries
from colleagues and friends asking me if this really was a worthwhile
product and if it worked as advertised.
A quick call to Winegard secured a review antenna. But
this was destined to be more than a simple review.
Over the years, I have compiled lots of data on comparative
antenna performance for indoor and outdoor reception. Many of the antennas
I have used are still available for purchase, albeit with updated model
numbers or features.
Considering how far DTV reception science has progressed
since then, it made sense to haul out these ‘golden oldies’
to see how they’d do with a state-of-the-art receiver, and how
their performance compared to Winegard’s ‘new kid on the
block’.
For reception, I selected a ‘bare bones’ inexpensive
terrestrial-only tuner -- LG’s LST-3100A ($399 MSRP). This tuner
uses LG/Zenith’s 4th-generation 8VSB chipsets and provides a very
user-friendly operating interface. Not only that, it scans DTV channels
really quickly (typically 30 seconds for a scan from 2-69) and also
allows you to do overlay scans, adding new DTV stations to those already
in memory.
2. LG’s LST-3100A was the reference DTV receiver.

To add to the fun, I resurrected a pair of homemade UHF antennas (one
measuring 17 inches with five elements, and one measuring 5 inches with
two elements) used in many of my original field tests. One was built
from $10 worth of plumbing parts in a hardware store, while the other
was fabricated in about 15 minutes from scrap metal and tubing on my
workbench.
There were two parts to this test. The first part took
place in my studio in Doylestown, PA. This location is about 22 miles
from Philadelphia transmitting towers, and the path is partially obstructed
by a hill. The second part was staged outside my office with all antennas
mounted on a 5’ tripod in the parking lot.
During these tests, I monitored each DTV station’s
8VSB signal waveform on a Sencore SA1501 spectrum analyzer and measured
its strength on a Sadelco Mini-Max 800 meter. Once each antenna was
aimed and connected, I performed a channel scan with the LST-3100A,
and then checked to see which stations made it into the tuner’s
memory.
3. A spectrum analyzer and RF signal meter provided baseline measurements.

I also photographed dozens of 8VSB signal waveforms for each antenna/preamp
combination and location, and verified reception on every channel. During
the course of these tests, one local station – WPPX-DT, on UHF
channel 31 – shut down its transmitter for a brief time, then
came back on. All others stayed on with constant power output.
INDOOR TESTS
The indoor tests weren’t too complicated. I simply
placed each antenna on a counter in my middle office and aimed ‘em
towards the Roxborough antenna farm. The yagis were leveled with whatever
boxes I had on hand, while a $2.99 RadioShack UHF bowtie antenna was
taped to a handy cardboard box. I even located a collapsible 20”
whip antenna in my junk box, and hooked it up to see just how little
signal the LG tuner could work with.
Both of my homemade UHF yagis made it into this test,
along with the Square Shooter, Terk’s TV55 VHF/UHF omnidirectional
bar antenna ($99.95), Zenith’s directional UHF Silver Sensor ($24.99),
Channel Master’s omnidirectional 3000A VHF/UHF SMARTenna ($76.55),
and Radio Shack’s omni/directional 15-1880 VHF/UHF amplified indoor
antenna ($49.95).
From the start, I was surprised at how easy it was to
pick up not just one, but also multiple DTV signals indoors using the
LST-3100A. For the worst-case reception scenario, I extended the whip
antenna completely and simply laid it on its side. That allowed the
LST-3100A to pick up exactly one station, WPPX-31 (PAX) on UHF channel
31.
4. The simplest antenna of all – a vertical collapsible whip.

Standing the whip antenna up straight brought in five more stations,
including KYW-26 (CBS), WPSG-32 (UPN), WYBE-34 (non-commercial), WPHL-54
(WB), and WCAU-67 (NBC). While that was impressive, the $2.99 bowtie
pulled in eight stations, adding WTXF-42 (Fox) and WPVI-64 (ABC) to
the above line-up. Plugging in the Silver Sensor was actually a step
backwards, as the LST-3100A could only find seven DTV stations with
it (KYW was the casualty).
5. This UHF bow tie antenna isn’t too fancy, either.

One of the most pleasant surprises of this test was Radio Shack’s
15-1880. Its predecessor, the 15-1862, was an antenna that did really
well in my previous DTV reception tests, but one that Radio Shack discontinued
shortly thereafter (it figures!). Good news – it’s back,
and with a better-looking cabinet.
The 15-1880 raised the reception bar with its rotatable
double UHF loop and built-in adjustable preamp. I was able to lock up
ten different stations in no time, adding Allentown-based PBS station
WLVT and Univision’s WUVP on channel 66. For about $50, it’s
a “best buy”.
6. Radio Shack’s 15-1880 was resurrected from a premature death.

How’d the heavy artillery do? The Square Shooter was braced on
that same shelf and pulled in nine stations (missing WLVT), many with
beautiful 8VSB waveforms free of multipath. Adding a low-noise UHF preamp
didn’t result in any more stations, but did boost signal headroom.
In this test, the Square Shooter beat out the TV55 (six
stations received) and the SMARTenna (seven stations). Both of my ‘scrap
pile’ yagis held their own in this test with each logging nine
UHF DTV stations.
7a. ‘Junkbox’ UHF yagi #1, made in minutes from scrap.

7b. ‘Junkbox’ UHF yagi #2, built from plumbing supplies.

8. A composite of indoor 8VSB waveforms from KYW-26.

9. A composite of indoor 8VSB waveforms from WTXF-42.

The next test involved indoor amplified antennas. RadioShack’s
15-1880 carried the day here by grabbing ten different stations with
its amplifier turned on (it really doesn’t work at all with the
amplifier off). An unusual catch was the 8VSB carrier from Allentown,
PA-based PBS station WLVT on channel 62, as the 15-1880 was oriented
almost 90 degrees away from that direction.
The Square Shooter came in a close second here, equipped
with the Channel Master Titan 2 preamp. It sniffed out nine stations,
missing only WLVT-62. Channel Master’s SMARTenna came in third
with eight stations picked out of the ether, and Terk’s TV55 brought
up the rear with six DTV stations.
10. Received 8VSB waveforms from WPPX-31, WPSG-32, and
WPHL-54 using indoor amplified antennas.

OUTDOOR TESTS
The outdoor antenna lineup included the Square Shooter
(with and without a channel Master Titan 2 low-noise UHF preamp), the
TV55, the SMARTenna, a Channel Master directional 3010 STEALTHtenna
($69.99, optional preamp also $69.99), Terk’s directional TV32
4-bay UHF screen antenna ($89.99, also with and without the Titan 2
UHF preamp), and my two scrap pile yagis.
The Square Shooter did very well, pulling in nine stations
(WPPX was briefly off-air during the test) including the weak, hard-to-receive
signal from Philadelphia PBS station WHYY on channel 55. Adding the
Titan 2 UHF preamp only improved signal levels across the board –
no other stations were scanned and put into memory.
The TV32 found the same nine stations, as did my two homemade
yagis. Terk’s TV55 received eight Philly stations and WLVT from
Allentown, while the SMARTenna could dig out only six DTV channels.
The “flying wing” STEALTHtenna hauled in eight
stations with or without its optional preamp. (WPPX came back on after
this last test was completed and was so strong that I scored it a ‘gimme’
for all of the outside antennas.)
Winegard touts the Square Shooter’s ability to be
rotated on-axis and elevated, so as to (hopefully) overcome multipath.
Do these features make any difference?
11a. Front view of Square Shooter rotated 45 degrees.

11b. Rear view of Square Shooter rotated 45 degrees.

In my tests, I was able to pull in some DTV signals with 45 and 90 degrees
of on-axis rotation. However, four previously strong DTV stations disappeared
altogether at the 45-degree mark (KYW, WPSG, WPHL, and WCAU).
12. A composite of outdoor 8VSB waveforms from
WPVI-64, WUVP-66, and WCAU-67.

The on-axis rotation and azimuth adjustments could be of great help
when trying to overcome multipath. However, without a spectrum analyzer,
aligning this antenna for best DTV signal reception could be a hit-or-miss
proposition. And while the Square Shooter does work well, it wasn’t
significantly better than some of the test antennas.
AND WHAT HAVE WE LEARNED?
For one thing, off-air DTV reception has gotten a lot
easier. It’s still not 100% plug and play, but the LST-3100A runs
circles around my 1999-vintage Panasonic TU-DST51A set-top DTV receivers.
If terrestrial DTV stations take the time to make sure all program packets
are identified and mapped correctly, a tuner like the LG unit can have
you up and running in no time.
Next, it doesn’t take a lot of signal to pull in
a DTV station. Look at the waveforms for reception of KYW-26 using the
whip, bow tie, and small junk box yagi. There wouldn’t appear
to be much clean signal present, but the LG tuner held KYW-26 steadily
with no dropout using each of these antennas.
WTXF-42, up the band slightly, wasn’t quite as easy
to pull in. Even with the almost non-existent signal on the vertical
whip, it locked up just fine. The playing field was much more level
here; there were scant differences between the scrap yagis, Silver Sensor,
Bow Tie, and Square Shooter.
Among the indoor amplified antennas, reception didn’t
vary by all that much except with Terk’s TV55 bar antenna, which
fared poorly across the board. Even though Channel Master’s SMARTenna
isn’t any more directional, it yielded much cleaner 8VSB waveforms
on channels 31, 32, and 54 with about the same overall signal level.
Another observation: Multipath correction is best done
with a directional antenna that has adjustable polarization. The Square
Shooter is semi-circularly polarized, but not a true CP design with
left-hand or right-hand polarization switching. Such an antenna product
has been called for by more than one veteran RF engineer. When will
we see it in production?
In the outdoor tests, rotating the axis of the Square
Shooter actually introduced more tilt to the signal of WCAU-67, making
it unreceivable. WUVP-66 was also intermittent at any but the 0 degree
alignment. Only WPVI-64 seemed unaffected by antenna rotation. Again,
you’d need some sort of spectrum analyzer to see if rotating the
Square Shooter or changing its azimuth was helping or hindering the
cause.
I look forward to testing the next generation of DTV receivers
using the 5th-gen Zenith chipset, which put forth quite an impressive
show at NAB 2004 and the annual ATSC meeting. ATI also stopped by my
place to test out their Theater 313 chipset; it too has excellent performance
with close-in echoes and varied multipath.
Copyright ©2004 Peter H. Putman / Roam Consulting
Inc.
No reproduction, in whole or part, via electronic or printed means
is allowed without the express written permission of the author. |