St. Louis-based antennas maker Antennas Direct announced its new, ultra-efficient, compact, digital TV antenna, ClearStream2, will arrive June 30. Orders are being taken now.

ClearStream2 is Antennas Direct's latest model of digital TV antennas, which are optimized specifically for the 2009 digital conversion.

The first DTV antenna created with...

Read Bulletin

That's the most BS I've read in a single press release in quite some time.

A single bow tie? 50 miles?

I thought this might stir up discussion.

We should expect to see more of this from Antenna manufacturers as we inch closer to the Feb cut-off, and beyond.

Perhaps we can put together an FAQ here in the forum and publish it as an article to clear up the FUD?

- Shane

Its not a bowtie antenna, its a dual tapered loop antenna. Nearly the same gain as a 4 bay bowtie, but with better VSWR.

The performance claims are not outrageous. There is still plenty of efficiency to be wrung out of antennas.

Well thanks for the input... would love to hear from Ken on this one...

rich644 wrote:
The performance claims are not outrageous.

Maybe not, but comments like

optimized specifically for the 2009 digital conversion.

are bogus. There is nothing magical happening to UHF/VHF broadcasts or reception next year. Any working UHF/VHF antenna will continue to work next year.

rich644 wrote:Its not a bowtie antenna, its a dual tapered loop antenna. Nearly the same gain as a 4 bay bowtie, but with better VSWR.

We would love to see some performance data rather than marketing hype.

http://www.hdtvprimer.com/ANTENNAS/types.html

Bogus claim #1: That this antenna performs like antennas five times larger. (This claim is on the maker’s website.) This could be true only if the comparison antenna was for another band.

Bogus claim #2: That this antenna is made for digital signals. In truth there are no differences between analog and digital antennas.

Antenna designs tend to follow the rule-of-thumb “The gain-bandwidth product is always constant”. For example, moving the DB2’s dipoles closer to the screen can increase the gain, but it reduces the range of frequencies for which it is a good antenna. There are many other examples where such a tradeoff must be made in selecting antenna dimensions.

What this means for Feb 17, 2009 is that the reduced band size (all channels above 51 are to be abandoned) is an opportunity for slightly higher gain antennas, plus a need to re-center the antennas around the new band limits. I believe all antenna makers who want to remain competitive will adjust the dimensions of their antennas accordingly.

From its picture I would guess the ClearStream’s performance is between the DB2 and the DB4. The claimed 10 dBi gain figure supports that. I see no reason why it couldn’t be a very good antenna for that niche. But I will not know for sure until I simulate it, and that is not on my short list of things to do.

AntennasDirect seems to be trying very hard to convince people that there is a difference between analog and digital antennas. I view that as deceptive and not helpful. But since the difference between that argument and the bandsize argument is too subtle for many buyers, I would stop short of calling it dishonest. -Ken

As I own the company, I may be able to provide some insight into the Clearstream series.

While the PR folks may have gotten carried away, there is technical merit to the new Clearstreams. We chose tapered circular loops for its potential to increase bandwidth performance over the uniform circular loop and fan dipoles. (bowties) This choice was motivated by a recent paper that analyzed the electromagnetic dual (tapered circular slot) of this geometry for application in ultra-wide band / short pulse applications. We have expanded upon this and adapted these theories to create new geometries targeting the core DTV frequencies. We are betting heavily on the new tapered loop elements, and will be releasing two more designs in the coming months based on this research: a single loop (Clearstream 1) and a quad loop (Clearstream 4).

Short version;
It’s not a miracle antenna but it is a breakthrough. It is has nearly the directivity as our larger bowtie designs, but with significant improvements in efficiency. It can have equivalent range, in a much smaller form factor, more aesthetic appearance and with better high VHF performance.

Longer version:
Fan dipole antennas (Bowties) are very effective radiators, it has taken us over two 1/2 years, thousands of simulations and dozens of prototypes before we could find something that could beat them. Losing 100 MHz of bandwidth was a blessing to the element designers. Only having to concentrate on 470 -698 MHz opened up some new avenues.

Many models claim high peak gains; the Clearstreams have nearly even gain across the targeted band. The values for the C2 are between 9.7 and 10.1 dBi across the whole core UHF band. It also has very flexible aiming characteristics. ClearStream2 simulations predict a 1/2 power (i.e. -3dB) beam width of approximately 70 degrees. Remarkably, this value is nearly constant across the whole post 2009 UHF DTV band. We have also been able to squeeze some modest gains at 174-216 MHz, which should give reasonable performance at High VHF

Almost all the published specifications for antenna comparisons is focused on directivity (since that number is always larger) with less attention on the other links of the chain. While the directivity may be a little lower compared to our bowties, the amount of signal that actually makes it to the cable can be equivalent or even higher. Field testing is showing the Clearstreams to have an effective range comparable to our Bowtie antennas nearly twice their size and combination antennas several times their size.


Importance of efficiency:

The key to the electrically small antennas is its efficiency. The Efficiency of an antenna tells us how much of the power makes it to the cable. In all antennas, a portion of the energy is wasted. For most antennas, mismatch loss is the single largest factor in determining the efficiency of the antenna.

At its optimum frequency, the mismatch loss for the ClearStream2 is very low - about .1 dB or less. At the band edges, it may creep up to about .75 dB- worst case.

Losses can also occur in the balun. For ferrite core baluns used for most Television antennas, the losses there can be from about 0.8 dB at Channel 4 to about 1.2 dB at Channel 44. Some improvements have been made here as well. The PCB baluns on the Clearstream models are lower loss, about 0.5 dB.

There are fundamental limits on bandwidth & efficiency for electrically small antennas , we thought the Clearstream designs was surely pushing those limits, but recently we have discovered there is a possibility to reduce the size of the antennas still further (while maintaining performance), and we hope to have an announcement by the end of the year.



To address some of the other issues;

Trust me; lots of people are struggling with traditional designs

Most of the Antennas Direct customers have previously purchased another type of antenna - and have failed. We have a large body of experience to draw from and have learned a lot about what has the highest likelihood to work in the field. While it’s correct that antennas can’t tell the difference between analog or digital, there are definitely certain models which have higher DTV batting averages than others. (I know because I have to refund their money when it doesn’t work) We speak to thousands of people struggling with reception issues every year. After a while, common themes start to emerge. I can assure you not all antennas are equally suited for DTV. You may hear lots of anecdotes from people insisting all that’s needed is a good set of rabbit ears. And it’s true that there are people who can shove a coat hanger into the back of the TV and get a lock on their digital channels, but a percentage will require something a little more tailored for DTV reception, and that’s the purpose, of this Clearstream effort.

I hope you find this helpful

Richard

PR claims are nothing new. In the 60's I worked for an antenna manufacturer and we stamped the cartons of our antennas with "Approved for Color", even though the same antennas had been sold for ten years for black-and-white TV reception.

For purists it is worth noting that the magnitude of the "gain-bandwith product" (which is constant) of an "electricaly small antenna" will always be less than that of a full size (compared to wavelength) design.

Therefore, if you want the best, accept the size (and bandwith limitation) of, say, a single channel Yagi. Everything less is a compromise. But we all live with compromises.l

rschneider wrote:While it’s correct that antennas can’t tell the difference between analog or digital, there are definitely certain models which have higher DTV batting averages than others. (I know because I have to refund their money when it doesn’t work) We speak to thousands of people struggling with reception issues every year. After a while, common themes start to emerge. I can assure you not all antennas are equally suited for DTV.

Richard - thanks for posting, and yes - the PR folks got carried away here. Then again, so have all the rest of them so you're certainly not alone in that respect.

What makes an antenna good or bad for DTV has to do with the channels currently being used for DTV which, in most cases for most people, are new. How many current DTV viewers were watching analog UHF channels previously? Not many, that's for sure.

The simple point is this - any antenna that provides excellent reception of ATSC channel 39 (e.g.) would provide the exact same excellent reception of NTSC channel 39 and vice versa. However, in reality what happens is that the viewer goes from NTSC channel 2 to ATSC channel 39 for the same local station, thus the need for a different type of antenna.

If it has performance advantages then say that, but the "optimized for DTV" crap needs to stop (everywhere)!

I appreciate that this isn't turning into a flame war.

About some of the marketing hype. When we started in 2003 I was just going to focus on home theater enthusiasts like myself. I assumed that most people were familiar with the basics of OTA and the frequencies where the digital stations were broadcasting.

Our first version of the DB2, the package said: "UHF antenna - Channels 14 -69" Imagine my surprise when we had scores of complaints from irate people that wanted an "HDTV" antenna not a UHF antenna. Some customers were insistent that their channels were on 5.1 or 2.1. Dozens actually refused delivery of their antenna. The experience cost us thousands of dollars. I finally got tired of arguing with people and changed the box to read HDTV antenna, we kept "UHF antenna" but in smaller type. Was that deceptive? I don't think so; the customer got a reliable antenna, our rates of returns dropped by 70% and we both avoided some confusion and aggravation.

2009 will make matters even more confusing for customers. Many of the station engineers I have spoken with are planning on keeping their current VHF channel identifiers (2.1, 4.1 5.1 etc...) after the 2009 shut off. This will create even more confusion in the marketplace when people (mistakenly) seek antennas which are suited for low VHF. Can you understand why I'm keeping "HDTV" antenna on the boxes?

The antennas are optimized for 470 -700 MHz, should we say that instead? Does the general population know what that frequency represents? I admit I have to walk a line here. If all of my customers were educated as the readers on the forum, all I would need to do is post the specs on the box and let the market & word of mouth do the rest.

To make matters worse, we had a buyer from a “big box” discount chain asking why they should stock the Clearstream 1 with “only” 8 dB when they already have a “55 dB” antenna currently on their sales floor for half the price. (BTW, here is a picture of an actual 50 dB antenna: http://www.gb.nrao.edu/ )

Testing has shown these new models will be a little more reliable (for most) on the post 2009 DTV frequencies than our older models. Additionally, if the designs are smaller then they are more likely to go on the roof rather than the attic. (Roofing materials can attenuate UHF signals 30 -90%) Bottom line I want people to be successful. If OTA can be as reliable as the pay TV services, then I believe it will eventually become the new basic cable.

I’m getting hammered from both ends; from the forum posters who think anything we say is bullsh!t, and from the purchasing agents who demur because we don’t hype enough. When both groups are equally disdainful, I know I found the right balance.

Richard- The flaw in your reasoning is that the VHF channels are not going away, the day of the combo antenna is not over, and some of your customers are going to be angry with you on Feb 17 because their “HDTV” antenna cannot get all the stations. Only 7 Missouri stations will stay in VHF after Feb 17, but in other states the fraction is much larger. Calling a 470-700 MHz antenna an HDTV antenna is simply not accurate. There is no alternative to properly educating the buyer.

Listening to your sales people is beneficial in the short run, but protecting your reputation is more important in the long run. I look forward to the day when AntennasDirect has a full line of VHF antennas, and so will be less tempted to sell people the wrong antenna. -Ken

I guess I didn't make it clear, one of the primary reasons we are migrating to the Clearstreams was to improve our capabilities on high VHF. Trust me, I have the list, We are very aware that 24% of the DTV stations will be on the high VHF band, post 2009 (about 400 stations). The necessity to cover both bands was why we started this project in the first place.

While it won't have the same range as on UHF, The Clearstream 2 offers modest performance of about 3.7 - 4.4 dB between 174 -216 MHz. (less than the VHF performance of our larger combination antennas) The single hardest part of the entire effort was trying to cover both bands with one design while not compromising the UHF performance.

While there have been some recent improvements, Bowties can have a problem with pattern & impedance. Specifically at high VHF, additionally, the reason for the decreased high VHF performance of bowtie antennas is the result of the phase reversal on the transmission line connecting each pair of dipoles. At high frequencies this phase reversal is necessary to compensate for the added distance between the feed point and the outer pair of fan dipoles. At lower frequencies however the phase reversal results in over compensation causing the signals received by the outer dipoles to cancel the signals received by the inner dipoles. The cleaner structure in the Clearstream tapered loop elements to the feedpoint as well as some cunning engineering has resulted in much improved high VHF performance. We have made no attempt to cover low VHF however, since we have not found a way to incorporate low VHF capabilities without severe penalties to the UHF performance.


For existing UHF antenna owners, this fall we will be releasing the Clearstream 5, a high VHF only design bundled with a UHF/VHF diplexer. (We'll unveil it at CEDIA) It will have directivity of about 9.5 dBi between 174- 216 MHz, and will have a form of 20"x 24" x 6" - about the same size as a DB4. The majority of the Clearstream owners however should be fine without the need for a supplemental antenna to cover High VHF.


( just FYI, we have offered the V10, High VHF/UHF antenna for about 4 years)