Category: Archives

Memo to 3D TV manufacturers: First, you build the highway. Then, you build the cars!

The latest PR blurb from CEA headquarters shows that, in a survey taken of 250 sales associates in retail stores, consumer enthusiasm for 3D is strong, with 50% of customers reporting a positive response to 3D technologies, and only 2% reporting a negative response.

That’s not necessarily good news. Do the math, and you’ll see that 47% of customers had no feelings about 3D TV one way or the other, or didn’t respond. (Or were distracted by their teenagers repeatedly begging Mom and Dad for an iPhone or iPod Touch.)

The CEA report does go on to say that “…While nearly 70 percent of sales associates feel well trained to answer questions about 3D, there is still consumer confusion. According to the retail associates interviewed, roughly half of consumers had some confusion about the technology.” That pretty much covers the 47% who didn’t respond positively or negatively.

And now for the devil in the details! “…For most retail associates, 3D content is pivotal. Nearly 80 percent of the associates interviewed believe sales of 3D technologies will not be strong until more 3D content is available.  Moreover, some of the most frequently asked questions by consumers revolved around the availability of 3D content. “

World Cup in 3D…Been there, done that. What else ya got?

There’s the rub. 3D may look great in the store, but how much 3D World Cup coverage can you watch before nodding off? (Hey, did you catch Paraguay and Japan fighting to a 0-0 tie?) And there are only a couple of 3D Blu-ray discs out there that haven’t been exclusively linked up to a 3D TV bundle promotion.

DirecTV is taking some steps to solve the problem today, announcing the launch of its 24-hour 3D channel in conjunction with Panasonic at a New York City press event. That’s good news for DirecTV customers, but it’s not much help to cable or Dish Network subscribers who are currently limited to ESPN 3D.

If this seems like déjà vu all over again (apologies to Yogi Berra), it is. Remember the start of the digital TV transition in 1998, when exactly two DTV stations went on the air? (For trivia buffs, they were WRAL (CBS) in Raleigh, NC, and WFAA (ABC) in Dallas-Ft. Worth, TX.)

Set-top boxes cost about two grand. You needed component inputs on your TV that could accept the 1080i signal from the box (good luck with the 720p outputs), plus an antenna, and maybe a preamp, and a bunch of coax, and a compass to tell you where to aim the antenna.

Oh, and yes – you needed HDTV content. But there was very little of it back then, aside from some CBS prime-time programs and the ABC Saturday Night Movie. It wasn’t until four years later (2002) before most of the TV networks were carrying a majority of their evening programs and sports coverage in HD. Can 3D TV manufacturers afford to wait that long?

It’s encouraging that 70% of the sales associates interviewed by CEA felt competent enough to answer questions about 3D. But that’s not the problem, based on my experience last Sunday at Best Buy. Only two out of four 3D TV demos in the store were actually working, and one was located in the worst possible spot for a demo. The other had only one pair of working 3D glasses. How do you answer questions about 3D, when customers can’t even see a demonstration of it?

This is where a company like Sony has a leg up with their Sony Style company stores. They can ensure (and they’d better!) that potential customers get the best possible 3D demo, with a large screen LCD TV and comfortable seats positioned at the correct viewing distance. And they can put together a nice mix of live 3D (Sony is a World Cup sponsor) and clips from Sony Pictures 3D movies (think Cloudy with a Chance of Meatballs).

Samsung’s ‘experience’ store in the Time-Warner Center in New York City is also an excellent place to demo 3D. (Hmmm. Maybe Samsung should be thinking about opening their own company stores!) Alas, Panasonic has no such showcase and is at the mercy of Best Buy and Sears. And Mitsubishi (who has some of the most compelling 3D TV value propositions right now) has no 3D showcases at all. (Too bad they can’t just truck their June NYC line show around the country!)

Now, THIS is how ALL 3D demos should look. (Dream on…)

But all the demos in the world won’t do any good if there is nothing to watch in 3D. And for the vast majority of potential 3D TV customers, there just isn’t enough to watch in 3D right now, so the credit cards and checkbooks are staying in pockets and purses.

Hopefully, that problem will sort itself out by year’s end, when we should see a flurry of 3D BD releases, more coverage of sporting events, the launch of Discovery’s 3D channel, and maybe even some 3D streaming from Netflix. (That last possibility assumes Netflix can get over some significant technical hurdles, such as bandwidth.)

Hint to TV manufacturers, and to Fox Sports: S-U-P-E-R B-O-W-L I-N 3-D. (Think that was subtle enough?)

So, we’re back to 1998. Grab some shovels and picks, and let’s get started on those highways! (Maybe there are still some stimulus funds available?)

Product Review: Three For DTV…Reception (February 2009)

I recently had an opportunity to test indoor DTV reception at a potentially “tough” location in New York City. This particular apartment requires an indoor TV antenna and sits about 3.5 miles from the Empire State Building, alongside Central Park.

The apartment is on a lower floor and next to several tall buildings that contain lots of steel and glass in their outer structures. The challenge was to come up with a model that would provide reasonably strong signals with minimal multipath, looking through or positioned just below a couple of small windows that face west, looking out over the northern section of the park.

Seeing as how RCA had just sent me their ANT1450B amplified VHF/UHF panel antenna (MSRP: $49.95), this seemed like a perfect location to give it a test drive. For more fun, I also packed up Terk’s HDTVa VHF/UHF indoor antenna (MSRP: $59.95) and Radio Shack’s “bare bones” 15-1874 VHF/UHF indoor antenna (MSRP: $11.99), along with a spectrum analyzer to accurately see how each antenna was working.

For test receivers, I packed up the AutumnWave OnAir Solution HDTV-GT receiver (5th gen) and my Acer notebook PC, plus a new entrant to the set-top box field – Aurora Multimedia’s V-Tune Pro HD ATSC/NTSC/QAM/IPTV receiver (MSRP $1,299). This box has RS232 controls and supports both component video and HDMI outputs – plus, it’s LAN-ready for streaming video and updating software and hardware.

THE LOCATION

The test apartment is currently undergoing interior re-decorating, so I simply placed each antenna near one of the two small living room windows and peaked it for best analog TV reception on as many channels as possible. The quality of each channel varied considerably, as you can imagine – multipath was so bad on some channels that it was difficult to get any reliable NTSC signals.

I then did channel scans with both the V-Tune Pro HD and the HDTV-GT, to see how many signals locked up both receivers. MPEG stream analysis was also done with the HDTV-GT and TSReader Pro, so I could check modulation errors. The results were surprising, to say the least.

The active DTV stations I was trying to receive included WNYE-24, WNBC-28, WPXN-30, WPIX-33, WNJU-36, WWOR-38, WXTV-40, WNYW-44, WABC-45, WNJM-51, WCBS-56, and WNET-61. Some of these stations have very strong signals, and I can pick ‘em up at home, 65 miles away in eastern Pennsylvania. Others aren’t quite as loud.

Figures 1a-b. Radio Shack’s 15-1874 “budget” VHF/UHF indoor antenna in a formal pose (top) and in action (bottom).

RADIO SHACK 15-1874

This antenna is about as simple as it gets. It consists of a small plastic base with a metal bottom, a thin-wire UHF loop that snaps into place, and a pair of thread-on, telescoping VHF rabbit ears. The 15-1874 is the kind of antenna many folks might use with NTIA DTV converter boxes, to replace their old, broken rabbit ears.

After peaking for best analog reception, I did a channel scan and was able to pull in 7 of 13 stations currently broadcasting digital TV signals from the Empire State Building, 4 Times Square, or other locations. For what it’s worth, two of the stations that didn’t make the grade (WNJU-36 and WNJM-51) currently broadcast from towers in New Jersey, and were just too weak to be picked up even though I spotted ‘em on the analyzer.

Figure 2a. Qualcomm’s MediaFLO service on UHF channel 55 (left waveform) and WCBS-DT on channel 56 (right waveform), as received by the 15-1874.

Figure 2b. DTV waveforms from WNYW-44 (left) and WABC-45 (right), as grabbed by the Radio Shack antenna. Note the strong tilt on WABC’s signal.

Figure 2c. WWOR’s digital signal on channel 38 was problematic, and that big notch in the middle of the 8VSB waveform was the reason – it kept fluctuating up and down.

Of the remaining stations, one (WNET-61) is operating with very low power and is beaming its signal west towards Newark, NJ – its city of license. I could see it on the analyzer, but it was just too weak to pull in. (WNET will go back to VHF channel 13 after the analog shutdown, and should be plenty strong in the metro NY area, based on tests conducted in early January.)

The other two stations (WPXN-30 and WWOR-38) just had tricky multipath that the RS-1874 couldn’t do anything about. After all, it’s basically a dipole antenna on UHF with little directivity. I don’t expect the rabbit ears to make that much difference with high-band VHF channels, either. Still, for $12, this antenna did a fine job and is a low-cost solution for city dwellers that live 10 or fewer miles from the transmitter site(s).

Figure 3a-b. RCA’s ANT1450B in a beauty shot (top) and on the front line (bottom).

RCA ANT1450B

I’d tested the non-amplified version of this antenna (ANT1500) back in the late summer, and found it wanting for indoor reception at my location. The ANT1450B also uses a similar etched strip-line VHF/UHF antenna design, but included an in-line amplifier module to boost overall signals levels.

Given that my home location is 23 miles and over a hill to the Philadelphia antenna farm, I figured the New York location would be a kinder test of the RCA’s abilities. Once again, I positioned it near one of the windows and peaked it for best NTSC reception, and then did a channel scan.

Figure 4a. WCBS’ digital signal on channel 56 was a real challenge for the ANT1450B.

Figure 4b. WNYW-44 (left) and WABC-45 (right) looked a bit better through the RCA antenna.

Figure 4c. WNYE-24 had a booming signal at the reception location.

The results? Without the companion amplifier, the ANT1450B pulled in 6 of the 13 available DTV stations, once again skipping WNET-61. It also missed WPXN-30, WNJU-36, WWOR-38, WFUT-53, and WCBS-56. This antenna is just as non-directional as the 15-1874, and equally susceptible to multipath. With re-positioning, I was able to pull in WCBS-56, but dropped WABC-45 and WPIX-33.

Adding the amplifier accomplished two things. First, I was now able to add WFUT-53 and WCBS-56 to my original list, although the latter channel showed “hits” now and then. Second (and unfortunately), the noise floor on VHF channels 7 through 13 was elevated by 20 dB! That’s not a good development, and one that spells trouble for WABC, WPIX, and WNET when they go back to their original high-band VHF channels 7, 11, and 13, respectively.

Figure 5a-b. Terk’s HDTVa antenna looks aerodynamic just sitting still (top) and like it’s ready for takeoff when in use (bottom).

TERK HDTVa

This antenna continues to impress me, although its UHF section isn’t much of a mystery – it’s the Antiference Silver Sensor, coupled to an internal amplifier. The VHF element is a bit more pedestrian, with a pair of telescoping rabbit ears. They are robustly built, though.

After waiting for the usual channel scan, I discovered both the Aurora and OnAir receivers had logged 12 of 13 DTV stations (nope, still no sign of WNET-61). More importantly, only two (WPIX-33 and WPXN-30) showed any signs of “hits” from time to time. Impressively, I could now watch WNJU-36 and WNJM-51, previously missing in action.

Figure 6a. WWOR-38 came in beautifully through the HDTVa.

Figure 6b. WNBC-28’s 8VSB waveform, although ragged, was rock-steady with the Terk.

Figure 6c. WNYW-44 and WABC-45 looked best with the HDTVa.

Although the HDTVa is vastly more directional than either the Radio Shack or RCA designs, its performance could be even better if it had a reflector behind its rear element. WPIX’ channel 33 waveform showed some pretty funky notches, and WPXN could have used a bit more signal overall. I also noticed hits on other channels that seemed to be tied to the passage of busses and trucks in the street below, but these primarily affected upper UHF channels (53, 56) that won’t be in use after June 12.

As well as the HDTVa performed, it also raised the high-band VHF noise floor by 20 dB or so, indicating the presence of some type of broadband RF emitter nearby. Perhaps that was a computer, or a security system sensor. (I’ve even seen high-band VHF RF emissions from a hand-held HD camcorder, believe it or not!)

Figure 7a. Here’s what the normal nose floor looked like underneath VHF channels 7, 9, 11, and 13.

Figure 7b. And here’s what the RCA and Terk amplifiers did to it – raise it up by 20 dB!

Figure 8. Aurora Multimedia’s V-Tune Pro HD did a creditable job pulling in the test DTV signals.

CONCLUSIONS

My tests at this site aren’t yet complete, and another round of testing will include antennas with improved directivity to help minimize multipath. But if I had to go with one of the test antennas, I’d pick the Terk HDTVa. It did the best overall job on UHF DTV and analog VHF signals, and the internal amplifier (although not a low-noise design) does make a difference – plus, it works a lot better than the in-line amp module RCA ships with their ANT1450B.

I was very impressed at how well the RS 15-1874 worked, but given its traditional design, a lot of the credit must go to the OnAir HDTV-GT and Aurora’s V-Tune Pro. Stand-along HDTV set-top boxes are getting harder to find these days, and one that’s integrator-ready like the V-Tune Pro are rare. It works very well, and its receiver is even a bit better with tricky signals than the Gen 5 HDTV, now two years old.

As for RCA’s ANT1450B, it would appear to work best in a location where it has a clear shot towards a transmitting antenna. Handling multipath is not its strong suit, but what can you expect from what amounts to a pair of folded loop antennas, mounted inside of each other’s radius? I’d skip the in-line amplifier unless you live in a less congested area – too much garbage gets pulled in and winds up degrading the noise figure of the receiver.

Radio Shack 15-1874

Budget VHF/UHF Indoor Antenna

MSRP: $11.99

http://tinyurl.com/2ml5re

 

RCA ANT1450B

Amplified VHF/UHF Indoor Antenna

MSRP: $49.95

http://tinyurl.com/b7ksnr

 

Terk HDTVa

Amplified VHF/UHF Indoor Antenna

MSRP: $59.95

http://tinyurl.com/arntk

Product Review: Optoma HD8200 Home Theater Projector (August 2009)

It’s funny how the fortunes of competing projection technologies have swung wildly over the past decade. Back at the turn of the century, most industry analysts (including myself) figured that Texas Instruments’ DLP technology had pretty much won the hearts and minds of CEDIA dealers, and that 3LCD didn’t stand a chance. LCoS? It was certainly out there, but mostly on the fringe.

Well, we sure got that one wrong. Three years ago, Mitsubishi pulled the rug out from under the DLP crowd with its eye-popping 3LCD HC5000, priced at $4,495 and completely upstaging new LCoS projector announcements from JVC and Sony. Epson and Panasonic also unveiled lower-price 3LCD chassis’ with great color, deep blacks, and plenty of contrast for similarly low prices.

Since then, 3LCD technology has taken mighty leaps forward, incorporating manual lens offset, dynamic irising, and improved black levels to become a can’t-miss value proposition. On the LCoS side of things, JVC’s DLA-series projectors are now the favorite of many prominent home theater enthusiasts and reviewers. So what’s happened to the DLP crowd?

One of the limitations with using single-chip DLP light engines is the difficulty in adding mechanical lens offset. Many early DLP lightboxes had a fixed lens offset and were intended for ceiling installation. But that severely constricted the installer’s choices when adding a projection system to an existing room, something the 3LCD and D-ILA camps were quick to point out.

Optoma, the US branding arm of Coretronics, is a leader in sales of DLP projectors for both consumer and professional use. They’re had a few previous entries into the CEDIA channel that have done well, but the long-throw zoom lens issue had to be sticking in their craw.

So they did the smart thing by not getting mad, but trying to get even. And the HD8200 is all about “getting even,” leveling the playing field with 3LCD and LCoS projectors in design, functionality, and hopefully, performance.

Figure 1. Now, here’s a different look for an Optoma projector!

OUT OF THE BOX

The first thing that strikes you about the HD8200 is how much it looks like JVC’s DLA-series projectors, from the long, rectangular cabinet with smooth curves to the rich, gloss black finish, the lack of nomenclature around the housing, and the minimalist video input panel. It’s all about the quality of images, and not appearances.

As supplied, the HD8200 is fitted with a 1.5 – 2:1 manual zoom lens, and veteran projectionists know that longer lenses usually mean less problems with pincushioning, barreling, and other optical distortions. That in turn makes aligning the projected image to a screen a much easier task. And the longer lens provides more mounting distance options.

Of course, longer lenses also mean optically smaller lens apertures and dimmer images, unless a lamp with more horsepower is included. So Optoma has included a hefty 220W UHP lamp that can run in two modes – standard and bright. They’ve rated lamp life to half-brightness at 3000 hours in the first mode, and 2000 in the second.

The imaging engine uses a DarkChip3 DMD, combined with a Pixelworks PW9800 co-processor with DNX MotionEngine. Optoma claims the HD8200 uses 10-bit signal processing to correct for both motion judder and when deinterlacing and compensating 480i and 1080i content.

When it comes to input connections, you basically get one of everything – one composite, one S-video, and one analog component (YPbPr) input, plus one 15-pin RGB/SCART connector, and one DVI-D jack. The exception? Optoma has provided a pair of HDMI v1.3 input jacks and labeled them as being compatible with Deep Color spaces, a color gamut that no one currently uses for HD TV shows and movies.

 

 

 

REMOTE AND MENUS

The supplied remote control is also a departure from previous Optoma designs. It’s not all that large, but is very user-friendly with large, backlit buttons. Optoma has thoughtfully provided direct access to many menu adjustments, including brightness, contrast, lamp bright mode, digital image shift, aspect ratios, overscan, and edge masking.

You’ll also have direct access to any input, and you can set up the HD8200 to automatically detect active inputs or skip inactive ones. A pair of 12VDC screen triggers is yours for the asking on the IO panel, and you can operate a motorized screen directly from the remote with Screen Up and Down keys.

The operation and image adjust menus aren’t overly detailed, but get you to the critical adjustments quickly. Optoma has provided four factory image presets, labeled as Cinema, Bright, Photo, and Reference. There’s also a User selection, although you can recalibrate any of the settings for any preset.

In addition to basic image tweaks, you’ll find an Advanced menu that really lets you get to the nitty-gritty adjustments. There’s a ten-step motion adaptive noise reduction setting that’s intended to be use with interlaced content – separating noise from interlaced artifacts in 480i and 1080i content is a tough job, and you may find this control helpful in doing so.

Gamma is selectable over four presets – Film, Video, Graphics, and Standard. Note that these are all factory presets, which means you can’t go into a multi-step gamma adjustment menu and fine-tune RGB response as you can on JVC’s DLA-series projectors.

You’ll also find a black/white extension setting that’s ostensibly used to enhance contrast. Be careful – these settings usually play with gamma curves, often resulting in an unwanted S-shaped response (I’d suggest leaving this switched off).

There are three factory color temperature settings (Cold, Medium and Warm) that you can readjust, using the supplied red, green, and blue contrast (high) and brightness (low) controls. You’ll also spot a Dynamic Black mode in this menu, and it’s used to enhance deep shadow detail in low-level scenes. Again, caution is in order, as dynamic black enhancements will have an adverse effect on the projector’s gamma response.

In the press releases for the HD8200, Optoma made a lot of noise about its PureEngine imaging technology. (Shades of Pioneer plasma TVs!) The “pure” part has a few components to it, specifically PureDetail (multi-level selectable edge enhancement), PureColor (a color-enhancement mode that stretches the projector’s gamut), and PureMotion (affects 24p content transferred 3:2 to 480i, 720p, and 1080i formats).

Edge enhancement can make a difference with lower-resolution analog content, although it could also enhance unwanted compression artifacts from digital SD video sources. I’d avoid using this control at all with 720p, 1080i, and 1080p sources. I’d also leave PureColor off and stick to matching the color space in which the TV show or movie was encoded. (As you’ll see shortly, the HD8200 does a good job already matching up to the ITU BT.709 HD color space.)

PureMotion may be the most useful gadget of the three, particularly when correcting for 24p “judder.”  If you’ve never seen a judder-correction processor at work, it can be a revelation as the “film look” gives way to a live video feel. Is this right or wrong? Well, some folks like it, and some purists don’t. You’ll have to experiment on your own to see which settings work for you.

As far as aspect ratios go, the HD8200 lets you select among 4:3, 16:9, Native (no image scaling at all), or LBX – short for “letterbox.” LBX mode lets you watch CinemaScope movies on a 2.35:1 screen with a companion anamorphic lens. According to the owner’s manual, LBX mode is also suitable for a “…non-16×9 letterbox source.”

Additional image tweaks include Overscan (eliminates noise and digital sync from appearing on certain TV channels), Edge Mask (basically a digital zoom function and not a left/right/top/bottom masking system), Vertical Image Shift (digital), and digital keystone correction.

My advice is to stay away from any digital image shift functions and instead use the H and V offset controls, large thumbwheels that are mounted under the lens along with the manual zoom adjustment. You’ll be able to shift images horizontally by ±15% and vertically by ±50%, which is quite a wide range for a single-chip DLP projector.

One last image adjustment bears mention. It’s called SuperWide, and requires the use of a 2.0:1 aspect ratio projection screen. With SuperWide on, both 16:9 and 2.35:1 programs will be displayed without any black bars. Of course, there is a slight amount of anamorphic stretching and compression in effect to pull this off, and that may go against your “purist” instincts.

There are a couple of useful tools in the operations menu. Not much mention is made of it, but the HD8200 has a two-position auto irising system to lower black levels, based on the average brightness of individual scenes. If you are familiar with auto iris systems, you know that they reduce brightness as well as deepen black levels, so I’d experiment with this setting to see if you can live with the results.

The other useful tool is Screen Trigger B, which can be configured to activate an external anamorphic lens assembly when 2.35:1 movies are being displayed. It can also be set to activate in 4:3, 16:9, Native, or LBX modes, although the utility of those selections isn’t as obvious to me as the anamorphic lens trigger.

Figure 3. The HD8200’s gamma performance was most consistent in Standard gamma mode.

Figure 4. Once above 20 IRE, the HD8200 tracked an incredibly tight grayscale.

ON THE TEST BENCH

So much for menus and features! How did the HD8200 do under fire? Not, bad, although there are a few areas where this projector could use further improvement.

I calibrated the HD8200 to light up a new, 92-inch Da-Lite JKP Affinity front screen (gain = .9) at a distance of 12 feet. After going through the menu to make sure all contrast, white level, and black level enhancements were switched off and that the auto iris was disabled, I adjusted the projector for best dynamic range and most accurate color rendering, using an AccuPel HDG4000 pattern generator and ColorFacts 7.5 software, plus a Minolta CL-200 colorimeter.

After calibration, I measured brightness at 364 ANSI lumens in Cinema mode. Readings in Bright, Photo, and Reference modes were 478, 468, and 449 ANSI lumens, respectively. Note that these were all taken with the projector’s lamp operating in standard mode – switching to bright mode results in a boost in lumens of about 15%.

Brightness uniformity calculated to 91% to the average corner, and 76% to the worst corner. These are excellent numbers for any single-chip DLP projector, some models of which have exhibited a 50% fall-off to the worst corner and noticeable hot spots in my tests.

Contrast measurements were comparable to some of the better 3LCD long-throw projectors I’ve tested, clocking at 559:1 ANSI (average) and 873:1 peak in Cinema mode. Black levels on this projector are higher than the best 3LCD and LCoS models – not substantially, but you can see a difference with low-light program material. The auto iris, disabled for this test, does improve blacks when active but also brings down white levels a corresponding amount.

Using the factory settings, I measured gamma response in Video mode at 1.82. That’s too shallow for video, and in fact the upper end of the grayscale was starting to flatten out at 80 IRE. Ironically, the projector’s Graphics gamma (measured at 2.21) was closer to ideal for video, except that this setting was also starting to flatline at 80 IRE.

Using a calibrated setting, I found the best gamma response (2.29) using the Standard gamma setting, resulting in a consistent climb out of black and not clipping at the high end. I also found this gamma curve provided me with the most consistent grayscale track, as seen in Figure 3.

Figure 4 shows the resulting grayscale track from 20 to 100 IRE. Maintaining a stable, consistent color of gray is a consistent attribute of the best DLP projectors, since the imaging devices have no inherent color bias. As you can see, the measured color temperature was consistent, varying by just 140 degrees in User mode and by 229 degrees in Cinema mode. That’s reference-grade performance!

I mentioned the HD8200’s color gamut earlier. As seen in Figure 5, it’s enough to cover 100% of the BT.709 standard, although the green and red pints are oversaturated and the cyan and magenta coordinates are shifted towards blue. Color management tools would help clean these up – the percentage of coordinate shift required isn’t enormous.

Figure 5. The projector’s color gamut is large enough to cover BT.709. Color management tools would lock it in even closer.

IMAGE QUALITY

For this part of the test, I cued up a few Blu-ray discs on OPPO’s new BDP-83 player. The BBC’s Planet Earth has some great scenes for evaluating dynamic range, specifically Ice Worlds and Oceans Deep. Ice Worlds has clips with lots of different shades of “white,” something that will reveal subtle changes in color temperature and whether any white clipping is going on.

Image contrast and detail was excellent with these clips, although it appeared that blacks and low grays could have been deeper. Color saturation appeared normal, particularly with close-ups of monkeys, leopards, and eagles that were captured with the sun at a low angle. That could have resulted in exaggerated reds and warm tones, but it didn’t.

My next test was with the director’s cut of Ghost Rider, an exceptionally detailed and contrasty transfer on Blu-ray. This is a great BD to test out dynamic range performance, particularly with the nighttime confrontation between the police and the Rider as he roars up and down the Longhorn Insurance Company skyscraper, spewing orange flames in his wake. (Come to think of it, there’s a lot of blue and orange shading in this film…wonder if the director or DP was a Syracuse or Florida graduate?)

The earlier scene where Johnny Blaze leaps over six helicopters on his motorcycle has some great punchy reds, oranges, and yellows. Flesh tones in these scenes could have easily been overpowered, but weren’t. At times, I thought I saw an ever-so-slight slight magenta tint to flesh tones, but that may just have been the transfer as I also observed this watching the same clip on a 50” Panasonic plasma monitor.

Once again, it seemed like the blacks weren’t quite deep enough, particularly in the final confrontation in the abandoned church between Wes Bentley and Nicolas Cage. Turning on the auto iris circuit pushed blacks down a lot more, but didn’t help shadow detail. I could have enhanced black levels to recover the detail, but would have lost the clean gamma curve I originally plotted.

The HD8200’s PureMotion processor sure does work! You can apply a high level of processing and basically eliminate all 24p film judder from any movie, making it look more like live 60 Hz video. So I repeat – is that good, or bad? Some viewers will no doubt love it; others will surely rail against it. As for myself, a little bit of judder reduction is nice, but I don’t go for the “video look” when watching a movie.

That Pixelworks processor does an excellent job with interlaced content. The HD8200 had no trouble whatsoever with the video and film resolution loss tests from the Realta Blu-ray disc. However, I should mention that a quick test of frequency response, using a 1080p luminance multiburst pattern, showed some filling at 37.5 MHz. That would result in the loss of very fine picture detail, and it’s another thing Optoma may want to look at.

CONCLUSIONS

Optoma’s HD8200 does indeed break new ground and should help single-chip DLP technology recover much of the ground it has lost to 3LCD and LCoS projectors. The projector delivers sharp, contrasty images with good color saturation and great dynamic range, albeit with slightly higher black levels than the best LCoS/LCD designs.

Improving black levels could simply be a matter of refining the optical path to cut down on refracted light, and also using a projection lens with improved coatings. The auto iris is certainly fast, but not fast enough on some scenes – you’re better off leaving it disengaged more often than not. I do recommend using a gray screen with the HD8200 for best results, particularly if there is light reflecting around your theater environment.

But my hat’s off to Optoma for building in mechanical lens shift and a longer zoom lens at this price point. I would have a hard time justifying spending more money for any other single-chip DLP projector after seeing the HD8200 in action. Down the road, how about adding multi-level RGBW gamma correction and color management tools to the menu? Now, that would be a hot product!

Optoma HD8200 Home Theater Projector
MSRP: $4,999

Specifications:


Dimensions: 14.6” W x 7.6” H x 19.2” D (projector)
Weight: 18.5 lbs. (projector)
Imaging Device: 1x .65” DarkChip3 1920×1080 DMD
Lamp: 220W UHP
Lens: 1.49 – 2.0:1 manual zoom/focus
Inputs: 1x each composite/S-video, 1x RCA YPbPr, 15p VGA, 2x HDMI 1.3

Signal compatibility: 480i/p, 720p, 1080i, 1080p24/60, VGA-SXGA+, WXGA, HD

Available from:

Optoma Technology Inc.
715 Sycamore Drive
Milpitas, CA 95035
408-383-3700
http://www.optomausa.com/

Product Review: Kramer ProScale VP-729 Presentation Switcher/Scaler (June 2009)

It wasn’t all that many years ago that the idea of a seamless presentation switcher was nothing more than fantasy. Back in the late 1990s, the farthest anyone had come with switching and mixing video signals was to combine the functions of basic line doublers and quadruplers with a couple of frame buffers, resulting in a product with five- and six-figure price tags.

But Moore’s Law prevailed, as it always does. Today, it’s possible to buy a presentation switcher for less than $2,000 that works better than those early line-doubling models. That’s good news for anyone who has a modest AV facility, but wants to switch between video and computer sources as smoothly and elegantly as staging companies do.

Kramer Electronics, one of the fastest-growing companies in the Pro AV marketplace, specializes in feature-rich but affordable video and audio interfaces. Their earlier efforts at presentation switching have been met with favorable reviews by a myriad of end-users. It was only a matter of time before a product like the VP-729 made its curtain call, combining HQV-quality video signal processing with Ethernet connectivity and a very attractive price – just $1,595 MSRP.

Figure 1. Front view of Kramer’s ProScale VP-729 presentation switcher.

OUT OF THE BOX

The VP-729 is surprisingly compact, measuring just 1RU in height. It’s finished in the usual Kramer blue-gray, sporting nine input selection buttons, three additional function buttons, and eight smaller buttons for accessing the menu and other functions, including navigation. A separate power switch is on the far left, along with an IR control sensor.

There are nine inputs on the rear of the VP-729, four of which can be configured to accommodate multiple analog video formats. In addition, there’s a USB 2.0 jack on the front panel that does double duty as a JPEG still image reader and a port for uploading firmware updates.

Each of the four analog video inputs consists of three RCA jacks and will accept composite, S-video, and component (YPbPr) video signals up to a maximum resolution of 1920x1080p 50/60. Note that you’ll need a special adapter cable to connect S-video to the VP-729. Kramer hasn’t included DIN-style S-video jacks on this switcher, but given how few people use that signal format anymore, it may be a non-issue.

The next two inputs are standard 15-pin VGA jacks, labeled “UXGA 1&2” on the front and back panels. These connectors will accept just about any RGBS/RGBHV signal format all the way to 1920×1200 resolution with a 60Hz frame rate. You can also create a custom configuration in the Advanced menu to work with even higher image resolutions.

The last two inputs are HDMI 1.3 types. Like more and more companies in the pro AV channel, Kramer has opted to replace DVI connections with HDMI, ostensibly because they take up less room, and can also carry digital audio – a real handy thing to have in a switcher. The connectors are fully HDCP-compliant, which might throw up a red flag in terms of being able to switch sources smoothly. (Not a problem, as you’ll see shortly.)

Figure 2. You’ll have enough connectors for just about any conference room or classroom installation.

Kramer has provided two video outputs. The first is another HDMI 1.3 jack, while the second is a 15-pin VGA connector. (You can drive both at the same time.) The VGA jack can work as a conventional RGBHV connection, or be configured to transport YPbPr signals on three of its pins.

There are several ways you can have audio follow video around during switching. Separate stereo RCA jack are provided for each of the four analog video inputs, while a pair of 1/8” mini phone jacks are used to interface PC audio. Embedded audio through the HDMI jacks moves around just as easily, and you can enable/disable the embedded audio stream from the menu.

For audio output, Kramer has included one additional pair of RCA jacks for an analog connection, plus a coaxial SPDIF output. And of course, the HDMI output jack also carries switched audio from any source. The connector complement is topped off with a standard DB9 RS232 port for remote control, plus an Ethernet jack for TCP/IP operation.

REMOTE AND MENUS

The supplied remote control was too busy for me with 30 buttons of similar size and color. (The Power and Menu buttons are red; all others are white.) But the upside is that you’ll have direct access to any input and generally fast navigation when making adjustments.

In addition to discrete up/down/left/right buttons for navigation, you’ll also find eight buttons at the bottom of the remote for designating the picture-in-picture (PiP) source signal. I would have left these behind a cover – it’s not likely that the settings will be changed all that frequently.

Additional buttons operate the switcher’s Freeze Image mode, let you switch to a blank screen, capture a JPEG image to be used as a screen-saver or boot-up screen, save and recall image settings, and mute audio. You can also push and hold the RESET button to restore the VP-729 back to its default output resolution of 1024×768 (XGA), just in case you accidentally configure a non-supported output signal. (Like that’s never happened before, right?)

When it comes to menus and adjustments, you’ll be in hog heaven. Kramer has included just about every adjustment you could imagine, taking full advantage of the IDT HQV video processor. Not only does that mean top-notch de-interlacing and 3:2 motion correction, but it also places image warping and rotation tweaks at your fingertips. These are extremely handy settings when you are mounting a projector off-center or at a severe angle to the screen.

The Input menu lets you configure the four universal video jack sets to accept composite, S-video, or component signals. You can also set the video standard (NTSC, NTSC 4.43, PAL, SECAM or Auto modes), fine-tune the horizontal and vertical image position for RGB signals, and play with frequency and phase to clean up clock errors. There’s also an Auto Image button for fast setup.

The Picture menu is where you’ll make basic image adjustments, along with five steps of output gamma, film/video mode (for detection of 2:2 and 3:2 frame cadences), and three kinds of noise reduction – temporal, mosquito, and block. Surprisingly, these adjustments are grayed-out when viewing content through an HDMI connection, which is where they’d be most needed, as mosquito and block noise are the results of digital image compression.

Kramer has also provided multiple steps of detail, luma transition, and chroma transition enhancement. I’d suggest staying away from these tweaks completely, except with low-resolution composite video such as those you’d see from ½” and ¾” videotape formats. Otherwise, you’ll find up with some weird ringing and edge artifacts around higher-resolution video signals. (Repeat to yourself – HDTV does NOT need edge enhancement…)

The Output menu is where you’ll configure the VGA and HDMI output ports. For your convenience, Kramer has provided 28 pre-programmed settings that start at 640×480 (VGA) and top out at 1680×1050 (UXGA+). Among those choices, you’ll also find eight standard component/HDMI video formats, including 1080p/60, or you can simply set the native HDMI input format to be the output format. (According to Kramer’s technical staff, the VP-729 can actually scale all input signals up to 1920×1200 (WUXGA) resolution, using the Custom menu settings.)

The HDMI output connector can be toggled to operate in full HDMI mode with embedded audio, or in basic DVI mode (video only). Five different aspect ratios are also at your fingertips, including Standard, Letterbox, Anamorphic (stretch), Virtual Wide, and Native (pass-through). A Custom option is also included for your imagination.

The Output menu also gives you access to some of the goodies packed within the HQV processor, including the ability to pan and zoom images horizontally and vertically, or to digitally zoom the entire image from 100 to 450%.

There’s also a Picture In Picture menu where you define PiP mode (overlay, side-by-side, or split screen), choose the Pip source and window size, set the horizontal and vertical position of the PiP window, and turn on or off a colored frame around the window’s edge, with red, green, or blue being the choices.

In the Audio menu, you can toggle between analog and SPDIF (digital) audio inputs and fiddle with input and output volume, bass, treble, balance, and loudness. Kramer has thoughtfully included a user-programmable digital audio delay line, which will help clear up lip-sync errors on large flat panel HDTVs or even fix a problem with digital TV broadcasts. The maximum delay is 340 milliseconds, or you can simply leave it set to Dynamic, which corrects automatically for the video processing chain inside the VP729.

Other menus include Geometry, where you can go crazy with image warping and keystone correction settings; Setup, where you can define and save image profiles in a maximum of eight memory locations, plus lock in frame rates, and Info, where you’ll see a static display of input and output signal information and firmware versions.

Hidden in the Setup menu is the previously mentioned ADVANCED sub-menu. This menu lets you download and store a custom logo from a USB drive, capture a displayed image to internal memory for use as a screen saver or boot-up screen, lock the front panel buttons or save your locked configuration, and define the FREEZE button function to operate alone, or pair it with the audio muting function.

This is also the place to input your own timing rates and create a custom output resolution. Caution – you’ll need to know several image parameters to do so without screwing things up. Otherwise, just stick with the factory definitions.

IN OPERATION

I decided to test the VP-729 with Pioneer’s PRO-111FD 50-inch plasma TV, connecting composite, component, and HDMI outputs from Aurora Multimedia’s V-Tune Pro HDTV tuner. I also hooked up component video signals from an AccuPel HDG-2000 test pattern generator and an Extron VTG-300 pattern generator. A second HDMI signal came from Toshiba’s HD-A2 HD DVD player. (Both HDMI inputs to the VP-729 carried embedded digital audio.)

The VP-729 recognizes input signals very quickly, especially HDMI sources. I selected 1080p/60 output resolution through the HDMI output to drive the Pioneer, after applying a software/firmware update from Kramer’s tech wizards Chris and Tom Kopin. This update from a USB flash drive ensured embedded HDMI audio was always recognized and transported smoothly through the switcher.

In my tests, all analog video sources switched between themselves with a smooth fade-down/fade-up sequence. Kramer calls this process Fade-Thru-Black™ switching, and it works by muting the input audio, then fading the selected video/PC signal to black. Next, a sync/audio switch is made, with the new video/PC source fading up. Audio follows shortly afterwards.

It took two seconds to make a complete analog video transition, with audio active in about three seconds. Switching from analog video to an HDMI source took slightly longer for video, but audio isn’t restored in this mode until nearly five seconds have gone by.

Unlike analog video sources, HDMI signals do not fade up. Instead, they “cut,” which may be a limitation of dealing with HDCP-compliant signals. Switching from analog video to an RGB signal also results in the latter “cutting” onto the screen, not a smooth fade up.

HDMI/HDMI transitions were as fast as analog video, with audio recovering after four seconds. The slowest transition was from analog component to HDMI video. It took about 2.5 seconds for the video to switch and nearly six seconds to hear audio.

During my tests, I lost the HDMI signal from the HD-A2 player completely after about 15 minutes. The player was looping one of the Realta HQV test patterns when I lost sync, and it could only be restored by powering down both the VP-729 and the HD-A2, then re-booting everything. The culprit might have been an older version of HDMI running on the HD-A2, which only has 1080i/30 output capability.

Video image quality was excellent with all inputs. The VP-729 passed both the Video Resolution and Film Resolution loss tests from the Realta HD DVD test disc with flying colors, along with the 3:2 sequence, rotating bars, mixed film and video titles, and variable cadences from the standard Realta HQV DVD.

The K-Storm scaler handles standard-definition video with ease. Expect some softness from sources like composite and S-video, which you can sharpen up using a variety of detail, luma, and chroma edge enhancements. But leave these off when working with HD video signals, which should not need any enhancement.

I’d like to see Kramer open up access to the three noise-reduction processors when switching HDMI signals. Mosquito and block noise artifacts are digital in origin and always the result of excessive video compression, something that digital video often suffers from when it originates from terrestrial, cable, or satellite broadcast systems.

CONCLUSIONS

Kramer’s VP-729 is a winner. It’s just the ticket for affordable seamless switching and scaling. Given HDMI’s inexorable creep into the pro AV market (whether you want it or not), it’s good to see manufacturers responding quickly with compatible interfaces. And a pro install these days is likely to include a few consumer signal sources, like set-top boxes and Blu-ray and upscaling DVD players.

I’m not sure what caused the signal dropout from my HD DVD player, but Kramer has been pretty good about diagnosing these glitches and promptly issuing firmware updates. I’d suggest checking to see if you have the latest firmware before you purchase one of these. If not, the updates are easy enough to load from USB flash drives.

Kramer Electronics

ProScale VP-729 Presentation Switcher/Scaler

MSRP: $1,595

Specifications:

Dimensions: 19” W x 9.3” D x 1RU

Weight: 6.6 lbs

Video Inputs: 4x C/YC/YPbPr universal, 2x 15p VGA, 2x HDMI 1.3

Video Outputs: 1x HDMI 1.3, 1x 15p VGA

Audio Inputs: 4x RCA Stereo, 2x 1/8” mini, 2x HDMI

Audio Outputs: 1x Stereo RCA, 1x coaxial SPDIF, HDMI

Control: DB9 RS232, Ethernet

Supported input resolutions: VGA-UXGA+, WXGA, 480i/p, 576i/p, 720p, 1080i, and custom

Output resolutions: VGA-UXGA+, WXGA, WUXGA (1920×1200), 480p, 576p, 720p 50/60, 1080i 50/60, 1080p 50/60, custom

Available from:

Kramer Electronics USA

96 Route 173 West, Suite 1
Hampton, NJ 08827

(888) 275-6311

www.kramerus.com

HDTV Tech Talk: I’ve Got The Low-Band DTV Blues (June 2009)

One of the more interesting stories that has developed following D-Day (June 12) is the trouble that viewers are having in several large markets with low-band TV channels – specifically, channel 6, which is now digital in Albany, NY; Philadelphia, PA, New Haven, CT, and five other TV markets.

There have also been reports of difficulty with stations on channel 7, most notably WLS in Chicago and WABC in New York City. The situation there is quite different, but we’ll take a quick look at it at the end of this article.

THE OP-ED SECTION

First off, let it be said that the FCC’s decision to retain channels 2 through 6 in the DTV channel core was ill advised. These are some of the oldest TV channels in existence and used to be the prime spots for a TV station, since they were the lowest channel numbers on tuners.

But the frequencies in which these channels are located – specifically, from 55 MHz to about 88 MHz, give or take several kilohertz – have long been plagued with impulse noise, such as you’d get from noisy fluorescent lamp ballast, brush motors, or any electronic equipment that creates inductive voltage spikes.

To make matters worse, seasonal signal propagation enhancement, caused by sporadic ionization of the ionosphere’s E-layer, can cause signals on these frequencies to hop across the country and create co-channel interference many thousands of miles away. Ham radio operators like myself refer to this summertime phenomenon as “E-skip,” for short.

Here’s another reason why channels 2 through 6 should have been retired: They require very large antennas for efficient reception. A full-wave loop antenna for channel 2 (56 MHz) would measure 5.4 meters in length, or about 17.5 feet! (Contrast that with a full-wave loop for UHF channel 42, which would be about 18 inches around.)

This makes it problematic to design an indoor antenna with any kind of gain, short of adding an internal amplifier. Unless that amplifier’s design is bullet-proof (and for normal Radio Shack prices, it usually isn’t), the antenna system will be overwhelmed with noise and interference from other nearby RF signals, such as FM radio stations.

THE CHANNEL SIX CONUNDRUM

But that’s water under the bridge now, and 40 stations have decided to stay put on this not-so-valuable real estate. As a result, I’m getting quite a few emails about some bizarre low-band VHF reception issues.

My favorite so far is from a television station monitoring service, whose rooftop channel 5 antenna in West Virginia is being routinely wiped out every day by fluorescent lights in the Ace Hardware below, during normal store hours. (Not impossible to fix, but it will take some detective work.)

Getting back to my home market of Philadelphia, there are plenty of problems with reception of WPVI’s digital signal on channel 6. And it became evident pretty quickly that WPVI was having these problems just 24 hours after shutting down their analog signal on channel 6.

Subsequently, WPVI and CBS affiliate WRGB in Schenectady, NY (also on channel 6, and also experiencing reception issues) applied to the FCC for an emergency authorization to go to higher power.

According to  a news story in the June 22 issue of Broadcasting and Cable magazine, “…The FCC granted the station (WPVI) a special temporary authority (STA) to boost its transmission power on Ch. 6 from the relatively low 7.5 kilowatts (kW) to 30.6 kW, the maximum power for the northeastern “Zone 1” region of the U.S.”

Figure 1. WPVI’s DTV signal on VHF channel 6, seen at 1:00 PM on June 12. Each of the sharp, rounded signals to its immediate right are FM radio stations.

WPVI’s original digital signal on June 12 at 1 PM, as seen in Figure 1, wasn’t too shabby to begin with, and I could receive it quite easily on both my rooftop and attic antenna systems. It also came in nicely near the southwest wall of my house, on both floors, while using Eviant’s T7 Card portable digital TV set.

But there are always devils in the details, and you can see them quite clearly immediately to the right of WPVI’s flat-topped 8VSB carrier. Those numerous rounded peaks are FM broadcast stations, the closest of which is on 88.5 MHz (WXPN). Almost immediately adjacent is WRTI’s FM operation on 90.1, followed by WHYY on 90.9, etc.

So, what’s the problem? Those FM stations are co-located at the Roxborough TV tower farm, NW of Center City. And they present very strong signals that can slip through the filters in NITA converter boxes, resulting in interference to the channel 6 signal. What’s more, FM and TV signals mixing in converter box receivers will produce sum and difference frequencies that wind up right in a portion of the channel 6 spectrum.

So what’s likely happening is that closer-in TV viewers, who probably don’t have really long rabbit ears (a full-wave loop @ 85 MHz measures 3.53 meters, or 11.6 feet) are trying to pull in a signal that’s competing with strong, adjacent-channel signals from FM  broadcasters. Toss in the usual elevated noise floor from arc lamps, power transformers, air conditioning compressors, and refrigerator motors, and you have a sticky wicket indeed!

Figure 2. WPVI’s “boosted” DTV signal, as seen at 9:45 AM on June 22. It’s about 6 dB stronger than before.

Figure 3. This wide view of the TV spectrum from channel 2 to channel 13 shows how strong WPVI’s new signal is, compared to WBPH-9 and WHYY-12 (far right).

WPVI’s Special Temporary Authorization (STA) from the FCC definitely resulted in a stronger signal, as seen in Figure 2. And Figure 3, which shows a wider view of all low-band and high-band VHF channels, plus the FM band, reveals that WPVI’s broadcast is now the strongest TV signal coming out of Philadelphia. (Notice the comparatively weaker signal from WHYY-12, the 8VSB carrier to the far right.) But is WPVI even strong enough now?

In both of my spectrum analyzer screen grabs, you may notice that the FM radio station carriers get progressively weaker as the frequency increases. That’s because I’m using an FM trap to try and attenuate them. But that filter simply isn’t sharp enough to subdue WXPN, WRTY, and WHYY without also affecting the strength of WPVI’s signal.

Only precision signal filters with multiple poles and what we call “Hi-Q” sharp filter skirts can solve this problem. Except that filters like that are VERY expensive to manufacture, and not something you’d put into a $59 converter box or a $500 TV set.

The adjacent channel overload problem is compounded by the use of circular signal polarization from FM stations. This is done among other reasons so that their broadcast signals remain moderately stable in as your drive around in your car. But that’s no help to the home TV viewer, who may try to no avail to weaken the FM signals by positioning their TV antenna horizontally or vertically.

Figure 4. A spectral view of WRGB-6 in Schenectady, NY, also “up against it” with multiple strong FM stations in close proximity.

In case you think this is just a “big city” problem, look at Figure 4, which shows the FM carrier immediately upstream from WRGB-6 in Schenectady. Same problem – multiple strong FM stations that can play havoc with converter boxes and integrated TV sets are located immediately adjacent to WRGB’s 8VSB carrier. And similar complaints about lost reception are coming into the chief engineer’s office up there.

OK, SO WHAT DO WE DO NOW?

Unfortunately, there isn’t any “one size fits all” fix to this problem. But there are some things that may work.

Inline signal attenuators: First of all, ATSC signals will come through at very low carrier-to-noise ratios, where analog NTSC signals won’t. It stands to reason that viewers close to the TV antenna farms have more than enough signal to begin with, so the counter-intuitive approach is to add attenuators inline with the antenna leads.

This will result in a weaker signal on channel 6, but will also drag down the levels of FM stations, too. Toss in an inexpensive FM notch filter, and at some point the TV receiver or converter box may be able to make better sense of the differences between the FM and channel 6 8VSB signals.

Of course, for this to work correctly, the attenuator should only be in the VHF antenna line, because it’s also going to clip signals from every TV station upstream from the filter, including high-band VHF and UHF. The VHF antenna should also be horizontally polarized, and not vertically polarized. That means flattening out those rabbit ears, or using a bar antenna or folded dipole on the roof, or in the attic.

Eliminating noise: Another possible problem is broadband noise, as I mentioned earlier. It’s worth checking out DTV reception problems with as many of your home appliances and lights disconnected as possible, to see if some “hash” isn’t getting into your system and creating interference problems.

Such interference would manifest itself on the FM band (Surprise! FM isn’t completely noise-free) as well. Any offending appliances should be replaced or repaired, because they’re likely creating bigger interference problems with other electronic devices in and nearby your home.

Using the wrong antenna: Of course, in more than a few cases, the problem seems to be one of trying to receive VHF channel 6 with a UHF antenna, which of course is akin to trolling for marlin with a Pocket Fisherman.

Many folks don’t realize that WPVI is now relocated a long ways away from its former position on UHF channel 64 (about 771 MHz), and that the small UHF loop antenna that used to work so well to pick up Jim Gardner and Action News is little more than a piece of decorative aluminum when it comes to watching VHF TV channels.

So what’s needed is a pair of longer rabbit ears, or even better yet, a folded dipole antenna that can be mounted on the side of a house, or in the attic – or even on the roof. The size would be ½ the length of a full-wave loop, or about 5 feet 9 inches. (5 feet is close enough for government work.)

This folded loop can be made out of copper tape, aluminum, or stiff wire – anything conductive. Even refrigerator drain hose (also copper) also works. Simply solder the leads of a 300-ohm coaxial balun to the open ends of the loop and run a piece of RG-6 to it, and you’re in business. Here’s a link to a simple folded dipole design, made from TV ribbon wire (twin lead). It’s scalable to any VHF channel.

Of course, you can also try a pair of conventional rabbit ears, but if you’re close in to the TV station (10 miles or less), stay away from amplified designs. They’ll only make the problem worse. On the other hand, WRGB’s chief engineer reported at least one viewer had complained about losing the signal on his rabbit ears antenna…30+ miles away. In that case, the amplifier is a good idea, but a rooftop or attic antenna is a lot more sensible.

MEANWHILE, BACK AT THE RANCH…

The problems that have been reported with reception of VHF channel 7 in New York City and Chicago appear to be arising from either improper antenna selection, or elevated noise floors, a common problem in cities. VHF signals have a tough time penetrating tall buildings, a task that UHF signal seem to handle with more aplomb.

But once again, a UHF antenna is not even close to resonance at 180 MHz (Channel 7). That’s about 1.67 meters, or 5.5 feet for a full-wave loop antenna. The good news is, everyday rabbit ears will usually do the trick here, but you’ll need to experiment with their polarization to see what works best. Fortunately, there aren’t any pesky FM radio station carriers lurking nearby.

What there IS, however, is lots of broadband noise. Figure 5 shows a spectral view of analog channels 7 through 13 in New York City, about 3.5 miles northeast of the Empire State Building, inside a 3rd-floor apartment where I’ve been researching an indoor TV antenna design.

Figure 5. Here’s a view of the TV spectrum from channel 7 through 13, as seen from the upper reaches of Fifth Avenue in New York City.

Figure 6. Whoops! Adding a preamplifier didn’t make matters better; it made them worse by elevating the noise floor.

So far, so good! But I wanted a little bit more separation between TV carriers and noise for more reliable DTV reception and to feed multiple TVs. So, I tested an inline preamplifier – with disastrous results. Figure 6 shows that the amplifier boosted channels 7 through 13 by almost 20 dB, but also kicked up the noise floor by the same amount – basically accomplishing nothing.

Lesson learned? I’ll have to come up with most of the gain in the antenna system, and try with different combinations of attenuators and preamps to see how I can add some “active” gain to the system without adding more noise and creating a new set of headaches.

I’ll be conducting more tests on channel 6 reception and also high-band VHF stations during the summer to see what practical solutions myself and others can come up with. Look for more coverage of this issue later in the summer. In the meantime, email any questions and observations you may have about “difficult” DTV stations, so we can share them with other readers.