Signal Testing With USB DTV Tuners
| Fig. 1: DViCO Signal Checker|
| Fig. 2: Autumn Wave OnAirGT|
| Fig. 3: Pinnacle operating screen|
Last year, I provided a quick overview of ATSC USB tuners. This month, I'll provide a detailed comparison of three--DViCO's FusionHDTV5 USB Gold, the AutumnWave OnAirGT tuner and the Pinnacle HD Stick Pro. All tuners include software that allows scheduling and recording programs.OVERVIEW
Readers who bought DViCO's FusionHDTV5 USB Gold after reading my September RF Technology column may have been disappointed to find the tuner often crashed the computer, especially when receiving weaker signals. While I sometimes experienced the Windows "blue screen of death," the DViCO tuner was far more stable and sensitive than the V-Box USB receiver I previously used.
Upgrading the FusionHDTV5 USB Gold to the latest driver and software, Version 3.50.01, eliminated the crashes. During testing for this article, I didn't experience any blue screens or crashes while switching between the three tuners. The FusionHDTV5 USB Gold comes with a 22-3/4-inch whip and F-connector antenna that worked very well. When traveling, this is the antenna I use with all the tuners.
DViCO is the only tuner manufacturer to supply a program for checking signal strength that's easy to see from across a room. DViCO Signal Checker displays a large bar indicating signal strength and has a large readout of the signal's SNR (signal-to-noise ratio). (See Fig. 1.)
This makes it easy to optimize antenna pointing and check station performance. The tuner software is easy to use and provides readout of stations sorted by major channel number. A window can be opened with EPG (electronic program guide) data taken from stations' PSIP data. EPG data is stored as you move from channel to channel, so you can see program listings for channels you are not currently viewing.
The Pinnacle PCTV HD Pro Stick was the first USB tuner I saw in mass market retail stores like Best Buy. As with the DViCO tuner, the first software release had problems with excessive CPU use and it wasn't really possible to view HDTV signals on my 1.83 GHz Pentium M Thinkpad.
Later software releases, including Version 4.54.1151, installed just before I started this article, greatly improved program stability. No issues were noticed with the small thumb drive-sized tuner drawing too much power from the USB port. The PCTV HD Pro Stick comes with a 23-inch whip antenna mounted on a magnetic base with and a thin coax cable to connect it to the tuner. While handy for fixed use, this doesn't work well in airports and carrying a powerful magnet around could cause problems if you put credit cards in the same case!
The PCTV HD Pro Stick doesn't have a signal checker program, but pressing Alt-I puts two color graphs in the upper right corner of the video display; one for strength and one for quality. Both have a scale of zero to 100, (see Fig. 3).
This display can be used for antenna pointing, but the size of the numbers and low contrast make it hard to see from a distance. Pinnacle's Media Center software is used for viewing and recording TV. As far as EPG is concerned, forget it unless you subscribe to Pinnacle's guide service. PSIP EPG data is not displayed. A one-year subscription is included with the device, but it is useless for many multicast channels. KLCS in Los Angeles has four multicast signals, but only one has a program guide.
AutumnWave was kind enough to send me their OnAirGT and OnAir Creator tuners for testing. They sell these tuners on their Web site and also on Walmart.com. For this review, I tested the OnAirGT. It is slightly larger than the other tuners, but still small and light enough to attach to the back of my laptop screen with hook and loop fasteners.
It includes an 11-1/2-inch whip antenna with an F connector that attaches directly to the tuner via a short F-to-phono plug adapter. I installed the latest software off the AutumnWave Web site. This installation requires installing drivers and the AutumnWave program separately. Unlike the HD Pro Stick, no serial number or registration was required.
DTV signal information, both in a cell phone-like signal bar scale and a dB scale showing SNR, is displayed whenever ATSC signals are being received. (See Fig. 2.)
Unfortunately, the readout is even smaller than the HD Pro Stick graphs. This isn't an issue if you are aiming an antenna within arm's reach of the computer screen, but it can be frustrating if the antenna is further away.
Station PSIP EPG data for all channels, including multicasts, is available on the channel display, but only EPG data for the program channel currently viewed is displayed. You can add channels that aren't detected in the scan manually, which is useful if you know a station is available but need to tweak the antenna to receive it.
When adding channels manually, a window is displayed showing lock status and PSIP acquisition status. This updates continuously, allowing you to move the antenna until the OnAirGT locks and acquires the PSIP data. Overall, the program was easy to use.PERFORMANCE
When comparing tuners, the ability to receive signals under difficult conditions is important. All of the tests here were done with indoor antennas in a second-story room near the southeast corner of the intersection of the 10 and 405 freeways in Los Angeles.
The Santa Monica Freeway obstructed the path to the Mount Wilson and Mount Harvard sites. TSReader Pro was used instead of the manufacturers' software to scan and decode channels. Only UHF channels were scanned, as there are no VHF DTV stations in the L.A. market.
The first test used a Terk HDTVi amplified log periodic antenna. I found little difference between the tuners, although both the Pinnacle and AutumnWave tuners detected a DTV signal from KVCR Channel 26 in San Bernardino.
During one test, the AutumnWave even locked onto a San Diego DTV station on Channel 19! However, neither channel could be decoded with either tuner. As far as picture stability on weak signals, the AutumnWave was best, followed close by the Pinnacle and, slightly worse, the DViCO tuner. Overall, however, the differences weren't that great, especially between the Pinnacle and DViCO tuners.
I realized that to really test these tuners, I needed a bad antenna! I did several tests using the short 11-1/2-inch whip antenna supplied with the AutumnWave receiver. The tuners were mounted one at a time on the back of my laptop screen, using hook-and-loop fasteners. Tests were repeated using the mag mount antenna supplied with the Pinnacle HD Pro Stick.
A 60-year-old National No. 697 power supply (used with my HRO receivers) provided a good base for the antenna. I checked reception both with the antenna fully extended and with it fully collapsed. To make reception harder, in all tests the antennas were oriented vertically. No adjustments were made to improve reception.
The Pinnacle and AutumnWave receivers detected 22 stations on all but the 11-1/2-inch whip and in one test the AutumnWave detected KVCR, for a total of 23 stations. When it came to decoding PSIP tables with TSReader, the three tuners were much closer.
While the DViCO detected fewer stations, it was close to the others in the number of stations where PSIP tables could be decoded. In terms of decoding PSIP tables and decoding MPEG-2 video, the DViCO and Pinnacle were very close, although overall, the Pinnacle had a slight advantage. The AutumnWave was the best performer, often decoding MPEG-2 video from one or two more stations than the other tuners. Depending on the antenna, it was possible to decode video from eight to 14 stations.RECOMMENDATIONS
While the AutumnWave OnAirGT consistently had the best performance, the difference is small enough that the other tuners may be worth considering, depending on your needs.
If you are doing field tests with a laptop and outside antenna, you will appreciate DviCO's signal checker, which makes it easy to peak the antenna and obtain SNR readings. With the latest version of DViCO's ATSC software, you shouldn't have to worry about it crashing your computer. If you want to record or view ATSC signals using Linux software, the FusionHDTV5 USB Gold is the only tuner tested with Linux support.
If you want a very small tuner you can throw in your laptop bag and use wherever you happen to be, its hard to beat the Pinnacle HD Pro Stick--just watch where you put that magnetic antenna base. Unfortunately, if you want to do field measurements with it, you will need TSReader to display the SNR and EPG data.
Considering the bugs in early software releases, manufacturer support is critical. AutumnWave is active on AVS Forum and regularly updates their software.
AutumnWave, under the name SASEM, was the first to offer a USB ATSC tuner. DViCO was slow to fix the problems with FusionHDTV5 USB Gold, but the last software release has proven to be very reliable.
Pinnacle has also been offering frequent updates, and perhaps someday we'll see a "PMC Lite" that offers fewer transcoding and Internet radio features but displays EPG data. Adding DTV closed captioning would be nice--none of the manufacturers include it in their software.
Broadcasters looking for a simple way to monitor their ATSC signals should look at AutumnWave's SignalSleuth package, which combines their OnAirGT or OnAir Creator ATSC tuner with Rod Hewitt's excellent TSReader Pro, which I'll take a closer look at next month.
As always, comments and questions are welcome. E-mail me at firstname.lastname@example.org