Posts Tagged ‘Kowatec’
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.
Useful Gadgets: Super-Flat Indoor TV Antennas – Do They Really Work?
- Published on Tuesday, 03 January 2012 20:03
- Pete Putman
- 0 Comments
Depending on you believe, Americans are fed up with ever-increasing cable TV bills and are bailing out by the thousands on channel bundles, opting for free, over-the-air HDTV and movies and TV shows streamed over Internet connections.
Or maybe not.
While there’s no question that a cord-cutting movement does exist, it’s hard to tell how big that movement really is. But the allure of dropping $50, $60, $70, or more from your monthly Kabletown bill is strong, and the recent battles between Time Warner and MSG network over rights fees only serve to highlight the inflationary spiral of pay TV services.
If you live in a metropolitan area and have the major networks (CBS, ABC, FOX, and NBC), chances are you already have access to quite a bit of sports programming. Maybe not the 24/7 deluge from ESPN, but you do have NFL games through 2022, selected Major League Baseball games, the NBA Finals, the NCAA Final Four tournament, college football and basketball, and numerous golf and tennis tournaments. (Oh, and let’s not forget next summer’s London Olympics on NBC.)
And if you aren’t into sports, that’s all the more reason to stop paying for programming you don’t watch. There’s still plenty of good prime time programming available for free, not to mention reruns of older cable network shows (Curb Your Enthusiasm was available recently on UHF channel 17 in Philadelphia).
With that in mind, I recently tested a pair of flat TV antennas for indoor reception. The first is the MoHu Leaf antenna (http://www.gomohu.com/) ,available direct from MoHu for $39.95 plus shipping, and the second is the Walltenna (http://www.walltenna.com/) , sold by a company known as Urban Freedom LLC for $40 (also at online stores).
Both are marketed to cord-cutters. Both companies cite the trend away from pay TV services “…as more and more viewers look for higher value alternatives” and “…and to get free from recurring monthly cable or satellite bills, high-maintenance rooftop antennas, or bulky tabletop models.”
Do they work? I tested both recently for wall-mount and window DTV reception, alongside two other stalwarts – Kowatec’s UHF panel antenna (discontinued) and Radio Shack’s model 15-1874 ‘budget’ TV antenna. Let’s see how they stack up.
My house isn’t in the best location for indoor DTV reception. Although it’s less than 25 miles from the Roxborough (Philadelphia) digital TV antenna farm, there is a slight hill and a bunch of tall trees in the way. Only a couple of UHF stations (17, 26) and one VHF station (6) are strong enough to come through without separate amplification.
The back side of my house looks north towards Allentown, which has DTV stations on channels 9, 39, and 46. And they’re not all that strong, either. In short, I have the perfect location to test these flat antennas – weak signals, but just strong enough to lock up a tuner.
To quantify my tests, I looked at the received waveform for each DTV station on an AVCOM PSA-2500C spectrum analyzer. And I used Hauppauge’s WinTV Aero-M USB stick receiver to verify reception and get some screen grabs of the stations that came in reliably.
MoHu’s Leaf antenna looks mysterious and ‘stealthy’ with opaque black and white sides, but hold the black side at an angle to a bright light and you’ll see exactly what’s going on under that “luncheonette counter menu” plastic housing: A pair of dipole antennas with X-shaped capacity hats at the ends.
The Walltenna takes that design and makes it larger, except you can see exactly what’s embedded in the plastic – copper foil shaped much the same way as the Leaf antenna. It just doesn’t look as nice on the wall as the Leaf, but then again, some of the best antennas have little eye appeal. (In the eyes of us RF enthusiasts, however, they are things of beauty.)
The significant difference between both antennas – and one which I figured ahead of time would give the Walltenna the edge in receiving more DTV channels – is that the elements on the Walltenna are electrically longer than the Leaf. This means the antenna should be resonant at lower frequencies.
I should point out that neither antenna uses a traditional collinear dipole array, as many rooftop and wall-mount UHF antennas do. With a collinear design, the physical connection ‘crosses over’ from one dipole array to the next, so that each X-shaped dipole array is out of phase with the one behind and/or in front of it, creating a broadband response. In the case of the Leaf and Walltenna, the physical connection to each ‘X’ element remains on the same side of the antenna.
Both antennas are designed to be stuck to a window or fastened to a wall. Mohu doesn’t provide mounting holes, but Walltenna does. On the other hand, Mohu has encased the coaxial cable connection to the antenna in a solid plastic block, while Walltenna simply solders a balun to the copper strips and attaches the balun to the plastic cover with a rivet.
I do not like the latter method at all. First off, inserting a piece of metal between the balun legs at such close range de-tunes the balun lines. Secondly, the balun is stiff enough that it provides too much torque on the base of the antenna when bent – you must be careful not to put too much strain on the connector, and the supplied RG-6 cable jumper is too stiff and heavy for the balun.
Mohu’s antenna comes with a long run of mini 75-ohm coaxial cable. This cable has higher signal losses per foot, but is much lighter and more flexible for indoor installations. Given the rough handling that such antennas are likely to receive, this is a much better approach.
THE TEST: ROUND ONE
My first test took place in an upstairs bedroom. I removed an oil painting and hung/clipped the antennas to the picture hooks. For comparison, I elevated the Kowatec and Radio Shack antennas and placed them in the same position. This wall position is on the part of my house closest to Roxborough.
After scanning for channels, the Walltenna snagged a few expected stations and a few that were not. Channel 6 (WPVI) runs tons of power to overcome interference from nearby FM stations (Channel 6 is at 85 MHz, and the first strong FM channel in Philly is 88.5). So it wasn’t a surprise to lock up.
Neither was WHYY-12, which also runs beacoup power now that they don’t need to protect channel 12 in Binghamton, NY. WHYY locked up just fine without dropout. WBPH-9 from Allentown was also rock steady.
So were UHF stations WPHL-17 and KYW-26, also a couple of powerhouses. WCAU-34 was mostly reliable with the occasional ‘hit,’ as was WFMZ-46 from Allentown, another strong station. (WBPH-9 and WFMZ-46 antennas were on the wrong side of my house.)
I could see RF carriers from other stations, but none were strong enough to lock up the Aero-M tuner. Even so, this was impressive performance from a so-called “all band” omnidirectional antenna. What the designer got right was to make the antenna elements longer, which helps with gain at highband VHF frequencies (channels 7-13). But it can also degrade performance in the UHF spectrum – you never get something for nothing.
By using a balanced line connection to the balun, that problem is overcome. At higher frequencies, only the dipole elements are active. At lower frequencies, part of the transmission line becomes part of the antenna. It’s a technique I’ve used for years on ham radio antennas and on my ‘ugly duckling’ UHF antenna prototypes from a decade ago.
So, how’d the Leaf do? Not too bad, but it only pulled in channels 6, 12, 17, 26, and 46 reliably. Channel 9 was nowhere to be seen, while channel 34 suffered from constant breakup. Odd, considering the Leaf is primarily a UHF antenna design and WCAU’s signal on channel 34 is one of the stronger signals around.
The fact that the Leaf pulled in both channels 6 and 12 is a testament to how much power both stations run. This antenna also uses a balanced line feeder to its coaxial connection, which provides resonance over a wider range of frequencies.
But the ‘X’ elements at the end of the balanced line are only 4.25” long, whereas the Walltenna ‘X’ elements are over 7” long. So the Walltenna has a decided edge in reception of VHF signals.
How about the two ‘control’ antennas? Kowatec’s panel antenna is usually a strong performer with UHF TV stations, but all it could receive reliably in the test position was WBPH-9, WCAU-34, and WFMZ-69. Radio Shack’s ‘budget’ antenna (UHF loop and rabbit ears) did marginally better, pulling in WPVI-6, WHYY-12, KYW-26, and WFMZ-46.
THE TEST: ROUND TWO
For the next part of the test, I hung or placed each antenna in a back bedroom window, facing north towards the Allentown and Bethlehem stations. Once again, channel scans were run using the Aero-M and screen grabs were taken of actual DTV waveforms.
I didn’t expect to pull in much from this location, save for WBPH-9 and WFMZ-46. The Walltenna met those expectations and also pulled in KYW-26 as a bonus, off the side of the antenna. The Leaf antenna located the exact same stations with comparable reception results.
The control antennas provided mixed results, but one did marginally better. Kowatec’s panel antenna snagged WPVI-6, WBPH-9, and KYW-26 (no sign of WFMZ-46 and its million-watt ERP signal), while the Radio Shack 15-1874 delivered WPVI-6, WBPH-9, KYW-26, and WFMZ-46.
Obviously all of the antennas could have been placed more carefully for optimum results. But how many readers have access to a signal level meter, or a spectrum analyzer? I’m betting not many. So my methodology of just picking an arbitrary antenna position yielded a fair set of results.
There’s definitely something to the Walltenna design, but it’s not black magic. Just make the elements bigger and you will approach resonance at lower frequencies. The X-shaped elements on the end act like capacity hats and do the trick! (A full wavelength @ 175 MHz – channel 7 – is 1.7 meters, while a full wavelength @ 665 MHz – channel 46 – is .45 meters.)
The Mohu Leaf is a solid performer on UHF and will pull in the odd VHF station, if it’s strong enough. Both antennas are easily concealed, but take care in what you place them behind or near, as metallic surfaces will detune each antenna and the balanced feed line, degrading performance. (Tip: If a metallic surface is placed ¼ wavelength behind each antenna at the desired frequency, it will become more directional on the opposite side.)
As for the control antennas, they held their own in at least one test, so I can’t say that either flat antenna had a distinct advantage over the Kowatec and Radio Shack entries. Where the flat antennas have the upper hand is in design – they’re easier to hide and to look at . (Although Walltenna should really take a page from Mohu and encase their product in an opaque plastic coating. )