Posts Tagged ‘Radio Shack’

Useful Gadgets: Indoor DTV Antennas – The Third Time’s The Charm

Earlier this year, I posted a couple of product reviews of indoor digital TV antennas. The first test, posted on April 6, concluded that there isn’t a heck of a lot of difference between a $5 bow tie and a $40 ‘flat’ antenna when it comes to VHF and UHF TV reception.

The second test, posted on May 29, gave one manufacturer a ‘do-over’ as their original product didn’t perform all that well and was judged to be defective. And that test also included a newcomer who didn’t make the original cut. (Believe it or not, both tests grew out of a more impromptu test in my house of a couple of panel antennas!)

Since the Round 2 results were posted, three things transpired. First, I became aware of yet another indoor DTV antenna, called the Clear Cast X1 and sold through Sunday newspaper inserts, magazines, and even on this Web site.

According to Clear Cast, “Advanced patent pending design of the X-1 digital antenna pulls in free over-the-air digital and HDTV broadcasts in your area so you can leave behind cable-only channels & expensive cable & satellite bills. Receive crystal clear digital picture on any digital TV in the house with NO monthly bill, easy install and setup plus NO waiting for the cable guy.” OK, I was intrigued enough to order one (they’re not cheap!)

Secondly, the PR firm that represents Antennas Direct – the company that shipped me a Clear Stream Micron XG for Round 2 testing – inquired why I hadn’t tested the accessory reflector with the antenna. (Simple: As Steve Martin used to say, “I forgot!”)

Finally, the Mohu Leaf Plus that self-destructed in Round 2 had been replaced and was ready for another go. (The amplifier failed, a problem Mohu was aware of and corrected in subsequent production.)

So it was clearly time for one last trek to Mountain Lakes, NJ to put all of the antennas from Round 1 and Round 2 through one more workout. I loaded up my spectrum analyzer, computer, several spools of coax, and a few splitters and headed out to put this test to bed once and for all.

THE TEST

For Rounds 1 and 2, I used the same window as the desk in front of it was unoccupied at the time. This time around, I opted for a slightly different location between two desks so that I wasn’t interfering with everyone’s work. Additionally; since the test position had now shifted by about six feet, I decided to re-test every antenna from Rounds 1 and 2 to be consistent and fair to all.

Here's what the test site looked like.

 

And here's the 'reference' bow tie antenna taped to the window.

I was assisted in my endeavor by John Turner, the owner and president of Turner Engineering and a long-time veteran of the broadcast systems integration world. Using AVCOM’s PSA-2500C spectrum analyzer, we positioned a $4.99 Radio Shack bow tie antenna (no longer available) for best reception of WNJM-51 (now known as “NJTV”) out of Montclair, NJ.

I also connected a Hauppauge Aero-M USB stick DTV received to pull in each station, in tandem with the TS Reader MPEG stream analyzer program to verify reliable reception (i.e. low bit rate errors). Each antenna under test fed the spectrum analyzer and Aero-M through a two-way splitter, and each antenna was placed in exactly the same spot on the east-facing window, using four pieces of masking tape as markers for alignment.

For each test, I scanned for channels using the Aero-M receiver. Next, I scanned each physical TV channel that was received with TS Reader to see how clean that stations’ MPEG stream was. Finally, I captured screen shots of the actual waveforms from each station I received. And if those three steps didn’t prove which antenna works the best, I don’t know what would!

THE RESULTS

For the record, here are all of the test antennas:

 

Radio Shack bow tie ($4.99, no longer offered, but you can find them on eBay)

Clear Cast X1 ($68 plus shipping)

Walltenna ($35 plus shipping)

Mohu Leaf ($38 plus shipping)

Mohu Leaf Plus ($75 plus shipping)*

Winegard FlatWave ($40, free shipping through August 31)

Antennas Direct ClearStream Micron XG ($100 plus shipping)*

* – amplified, or comes with optional amplifier

 

For my tests, I scanned for all New York City and New Jersey DTV stations within range of Turner Engineering. One local station (WMBC-18) was so strong that I essentially discounted it from my test results – it would have come in with a paper clip!

The Clear Cast X1 is definitely NOT worth $70. Let the buyer beware!

 

But other stations weren’t quite as strong. WABC-7 is a good test of high band VHF reception, inasmuch as every antenna in the test is supposed to pull in both VHF and UHF signals. WNJB-8 in the Watchung Hills of New Jersey is another good test of VHF reception.

For UHF signals, I checked out WNYE-24 (atop the Empire State Building), WNBC-28 (also on Empire and usually strong), WFME-29 (in West Orange, NJ), WFUT-30 (on Empire), WCBS-33 (Empire), WWOR-38 (Empire), and WNJM-51 (Montclair, NJ).

I didn’t expect the antennas to have much luck with WABC or WNJB, as they are too small to have much gain at VHF frequencies. The amplified antennas were a different story, though. If you are aggressively marketing indoor TV antennas for ‘all band’ reception, then you’d better deliver!

Table 1 shows how the unamplified antennas compared to each other. Satisfactory reception is indicated by glitch-free video streams for at least one minute and a ‘clean’ reading with TS Reader, while Table 2 shows how the amplified antennas (or amplified variations) compared.

Yes, you can actually attach the Micron XG to glass with masking tape! (The reflector was a tad more difficult to install...)

 

Note that the ClearStream Micron XG was tested three different ways –‘ bare bones’ with no amplifier or reflector in Table 1; with its amplifier switched to 15 dB mode in Table 2, and with the amplifier on and the accessory reflector attached in Table 2.

 

Antenna

WABC-7

WNJB-8

WNYE-24

WNBC-28

WFME-29

WFUT-30

WCBS-33

WWOR-38

WNJB-51

RS Bow Tie

Yes

No

Yes

Yes

Yes

Yes

Yes

No

Yes

CC X1

No

No

Yes

Yes

Yes

Yes

Yes

No

No

Walltenna

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

Yes

Mohu Leaf

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

Yes

FlatWave

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

Yes

Micron XG

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Table 1 – Unamplified antenna performance

 

Antenna

WABC-7

WNJB-8

WNYE-24

WNBC-28

WFME-29

WFUT-30

WCBS-33

WWOR-38

WNJB-51

Leaf Plus

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

Yes

Micron XG w/amp

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Micron XG w/amp and refl.

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Table 2 – Amplified antenna performance

 

Oddly enough, the Micron XG was the only unamplified antenna to pull in WWOR-38. But it was ‘tone deaf’ when it came to the two high band VHF stations. Neither version of the Mohu Leaf could snag WWOR-38, either.

As for the vaunted Clear Cast X1, it was unresponsive to any VHF channels and couldn’t hear local station WNJM-51. In contrast, the late, lamented Radio Shack bow tie worked exceptionally well on just about every UHF channel.

Bonus reception: WNJU-36, which is a tough signal to pull in at this indoor location, was successfully reeled in by the Micron XG with amplifier and reflector. So was WXTV-40, also pulled in with and without the accessory reflector.

THE CHARTS

I’ve included a few charts to show what the actual DTV received signals looked like on the AVCOM analyzer. You may be surprised to see how small the differences are between each antenna, and you will also note that the reflector didn’t improve reception at all on the Micron XG – in fact, it actually made things worse, probably due to all of the signal reflections and multipath at the test site.

As a reference, the actual signal levels shown are about 12 dB stronger at the displayed resolution bandwidth (300 kHz).

Here's what the RF spectrum looks like from channels 18 to 51, using the bow tie antenna.

 

And here's the same spectral view using the Clear Cast X1...

 

...using the ClearStream Micron XG...

 

...and using the Mohu Leaf (no amplifier).

 

Here's channel 51, the former WNJM, as received on the bow tie...

 

...and here's the same station on the Clear Cast X1. No improvement.

 

Winegard's FlatWave pulled in channel 51 more robustly...

 

...as did the Walltenna.

 

Finally, here are received waveforms for WNJU-36 and WWOR-38, using the ClearStream MIcron XG with the amplifier set to 15 dB, but minus the reflector...

 

...and here's what those same waveforms looked like AFTER I installed the reflector. Reception actually worsened, something I saw on numerous other UHF channels. Indoor DTV reception can be funny that way!

CONCLUSIONS

It’s hard to make much or an argument for spending very much money on an indoor DTV antenna when you see how well the lowly $5 bow tie design performed! This antenna design has been around since the 1950s and is just one of those things that can’t be improved on – unless you build an array of them. (‘X’-shaped colinear UHF antennas perform the same as the bow ties.) It’s just unfortunate that no mainstream electronics retailer sells these anymore. (Hey Radio Shack, are you listening?)

However, it’s easy to make the argument that the Clear Cast X1 is definitely not worth spending $70 on, especially since it was easily outperformed by the far less costly Leaf, Walltenna, and FlatWave antennas. Even the bow tie picked up six more stations than the X1 in my overall tests, two of them on VHF. I don’t know what’s inside the plastic housing, but I’d bet it is nothing more than a simple dipole, bow tie, or loop antenna (Clear Cast’s claims to having a ‘patent pending’ notwithstanding). Keep your wallets in your pockets!

Among the basic flat antennas, I still prefer the Leaf – it’s smaller and more esthetically pleasing than the Walltenna (which still  does a good job, better than the FlatWave) and it’s been a reliable performer everywhere I travel. The Leaf Plus is a bit pricey at $75, but the amplifier – while not as powerful as that on the ClearStream Micron XG – helps pull in marginal stations and doesn’t add much to the form factor.

As for the Micron XG, I had mixed feelings about it. It’s big and somewhat blocky, expensive, and based on my tests, you can’t depend on it for VHF reception in suburban locations, a chore the other ‘flat’ antennas handled without much difficulty. In its favor, the Micron XG did pull in WWOR, something no other antenna could do. (Maybe that outcome was just a fortuitous combination of antenna position and signal level?)

The Micron XG amplifier makes a big improvement, but I’d suggest running it no higher than 15 dB. The 20 dB setting creates too much noise and also degrades weak signals, as observed with the spectrum analyzer. The lower-gain 10 dB setting is also very handy in fringe urban areas where you don’t need tons of signal, but just need to boost the carrier-to-noise ratio (CNR) a bit.

And that reflector? It’s hardly worth bothering with, as it didn’t improve reception on any of the tested channels and in some cases degraded it. Those results were puzzling, because the reflector effectively converts the antenna pattern to something resembling a two-element yagi, which should have more gain as it becomes more directional. Maybe you’d have different results over a line-of-sight (LOS) path, but that’s hard to ensure when trying to grab DTV signals indoors.

In any case, you should be able to get a decent indoor DTV antenna for less than $50. Stay away from the amplified versions unless you live in a fringe urban or outer suburban area, where there are less likely to be out-of-band sources of overload and interference. Always place your antenna near a window and/or closest to the direction of the TV transmitter(s) for best results.

Good luck!

Useful Gadgets: Super-Flat Indoor TV Antennas – Do They Really Work?

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).

 

Figure 1. The Walltenna is transparent and flexible (and maybe not too attractive).

Figure 2. Mohu's Leaf antenna is also flexible, but opaque and a bit less inconspicious.

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.

 

THE TEST

 

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.

Figure 3. (clockwise from upper left) The Walltenna, Leaf, Kowatec, and RS 'budget' antennas in position.

THE CONTESTANTS

 

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.

Figure 4. (Clockwise from upper left) Spectrum analyzer waveforms of WPVI-6 as received with the Walltenna, Leaf, RS 'budget,' and Kowatec antennas.

Figure 5. (Clockwise from upper left) WBPH-9 and WHYY-12 as received using the Walltenna, Leaf, RS 'budget,' and Kowatec antennas.

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.)

Figure 6. (Clockwise from upper left) KYW-26 as receivedon the Walltenna, Leaf, RS 'budget,' and Kowatec antennas.

Figure 7. (Clockwise from upper left) WFMZ-46 as received on the Walltenna, Leaf, RS 'budget,' and Kowatec antennas.

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.

 

CONCLUSION

 

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. )