Useful Gadgets: Wall-Mounted Indoor DTV Antennas
- Published on Friday, 06 April 2012 12:47
- Pete Putman
- 0 Comments
A few months back, I ran a test of several indoor DTV antennas that you can mount on the wall, or on a window. Specifically, I looked at Mohu’s Leaf antenna and the Walltenna, and compared them to a baseline UHF table-top antenna and a $12 Radio Shack set of rabbit ears and a UHF loop.
Since then, I’ve received a few more samples to test against the Mohu and Walltenna. Mohu shipped me the amplified version of their Leaf (Leaf Plus, $74.99) while Winegard dropped off a sample of their FlatWave indoor antenna (FL5000, $39.99).
Well, nobody enjoys a good antenna test more than I do – except perhaps John Turner of Turner Engineering in Mountain Lakes, NJ, who offered to let me use his facility for these tests. So, I piled all of the flat antennas used in the December tests plus a Kowatec UHF panel antenna, a $3.99 Radio Shack bowtie, an AVCOM PSA-2500 spectrum analyzer, and a pile of coax jumpers into my car and headed north one fine day in late March.
At the test site, I was directed to use a large office window that faced east. A nearby desk provided a home base for the PSA-2500C and my laptop computer, which would simultaneously mirror the spectrum analyzer screen while running a Hauppauge Aero-M ATSC/MH USB stick receiver and the TS Reader MPEG stream analyzer program.
The methodology was to tape each antenna into the same position, connect 20’ of coax through a two-way splitter, and scan for channels while looking at each received DTV waveform. The TS Reader program would then confirm whether I was actually receiving a signal reliably, by providing me a read-out of the MPEG transport stream and the bit error rates (BER).
Speaking in plain English, this test was conducted as fairly as possible, favoring no antenna. I made no effort to try and ‘peak’ antennas for more reliable reception – I just taped them up and scanned away, just as the average consumer would do. Next; for every DTV station I supposedly ‘received’ on the Aero-M, I checked the quality of their signal before giving them a thumbs-up.
Simple enough! Once each antenna was mounted to the wall (the Kowatec was attached to a tripod and placed in the same position as the other antennas), I performed a channel scan with the Aero-M, looking for both ATSC and ATSC MH (mobile) DTV signals.
After each scan was completed, I looked at each channel that was detected to see if a signal was actually present. (Sometimes ATSC receivers grab just enough PSIP data from an othwerwise weak signal to ‘capture’ it, which is why you have to verify reception.) If the signal played back reliably for several minutes with no drop-outs, I gave it a thumbs-up and moved on to the next detected channel.
After this process was completed, I then used TS Reader to see just how reliably each signal was coming through. TS Reader shows the accumulated number of dropped bits (BER) as you watch the program. The lower the BER, the more reliable the signal.
After compiling a list of stations received with all antennas, I then picked the seven that showed up repeatedly, whether received reliably or not. They were WABC (physical RF channel 7) from New York City, WNJB (physical channel ’8′) in the Somerset hills in central New Jersey, WMBC (physical channel 18 from Montclair, NJ), WNBC (physical channel 28) from New York City, WWOR (physical channel 38) from New York City, WXTV (physical channel 40) from New York City, and WNJM (physical channel 51), also from Montclair, NJ.
According to the TVFool Web site, WMBC and WNJM are just 11.7 miles away from the Turner offices and are both ‘line of sight’ (LOS) paths, while WFME-29 (which didn’t come in reliably on any antenna save one) is a hair closer at 11.4 miles, LOS. WNJB sits 19.4 miles over a LOS path, while WWOR-38 in New York is 24.9 miles and also LOS.
WABC-7 and WXTV-40 were both shown as 1-Edge paths from the Empire State Building and also 24.9 miles away, while WNBC-28 was listed as a 2-Edge path (lots of multipath) from the same distance. So I had a nice mix of strong, ‘easy’ signals to go with some weaker, ‘tough’ signals.
Table 1 shows the results. A ‘yes’ indication means that the station was received without drop out for at least two minutes AND had a very low or almost zero bit error rate, as verified by TS Reader. A ‘no’ indication means either the station was not received at all, or was detected by PSIP but had too many dropouts to be reliable.
Not surprisingly, the Kowatec antenna couldn’t pull in either high-band VHF stations 7 or 8. That’s because of simple physics: It has no gain at those frequencies, and its antenna array is too small to be of any use with channels 7 through 13.
I didn’t expect much from the Radio Shack bow tie, but it did OK by grabbing channels 8, 18, and 51. Not surprisingly, these are the three strongest signals at the Turner office location, so every other antenna should have pulled them in (which they did).
The Mohu Leaf gave a decent accounting of itself, grabbing channels 8, 18, 28 (one of the strongest UHF stations in New York City), 40 (also a powerful signal), and 51. The Walltenna equaled that performance with the same channels – no advantage here.
The FlatWave was a big disappointment, faring no better than the $3.99 bow tie – and it costs ten times as much! Most of the antennas in this test use variations on collinear antenna arrays, but aren’t electrically long enough to have any gain on channels 2-6 and 7-13. But the FlatWave didn’t even have that much gain at UHF frequencies.
I saved the Leaf Plus for last. Comparing an amplified antenna to non-amplified versions isn’t a fair test, and as expected, the Leaf Plus pulled in all of the listed stations reliably, except for WWOR-38.
However, it added WFME-29 (West Orange, NJ), WFUT-30 (Telefutura from New York), ION-30 (also New York), WCBS-33 (New York), and WNJU-36 (Telemundo, New York) to the list of ‘thumbs up’ stations.
Note that a few of these signals are listed as 2-Edge paths with much weaker signal levels on TVFool.com. So this antenna does perform very well, although a bit pricey at $75.
Reliable digital TV reception is all about having enough signal presented to the receiver so it can do its job. That also means high enough carrier-to-noise ratio (CNR) for the adaptive equalizer circuits to smooth out echoes and other signal reflections caused by multipath.
In general, any late-model TV built in the last four years has good-enough adaptive equalizer circuits to accomplish this task if it is presented with enough signal. For people who have problematic over-the-air DTV reception, low signal levels are usually the culprit. I’d suggest using the non-powered antennas if you live 15 miles or less from a DTV transmitter, and switching to an amplified antenna at greater distances. (Once you get much past 25 – 30 miles, you should really put up an outside antenna for best results.)
The Mohu Leaf and Walltenna work quite well for close-in DTV reception, while the Leaf Plus makes a big difference at longer distances. The FlatWave is a disappointment – save your money and go with the Leaf or Walltenna instead. Or, try a simple bow-tie or even Radio Shack’s 15-1882 VHF rabbit ears / UHF loop combo instead – for $12, you can hardly go wrong.