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Discussion Starter #1
Quick question.

Browsing these forums I get the impression that the "billboard" or "grid" UHF aerials (bowtie with reflector e.g. Channel Master 4221, Winegard 4400, etc.) are vastly more popular in Canada than UHF Yagis.

Whereas they are quite unusual over here in Europe, for example almost everyone in the UK has a Yagi instead. Some people in strong signal areas use log periodics. But grid aerials? They were marketed as "anti ghosting" aerials years ago, but I think I have only personally seen 2 or 3 grid installs in my life.

Yagis have higher gain, and have lower wind loading, and are very cheap. So why are grid aerials so popular in Canada?

-rapido
 

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I think it boils down to gain vs complexity. The more elements a Yagi has to get gain, the more complex it is to make. much easier to put up a reflector screen. At lower frequencies, the reflector becomes too big to be practical
 

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Broadside antennas perform better for me than yagi / LPDA styles mostly because I have trees in front of the antenna. I dont have ghosting or multipath problems.

Also a 16 to 17 dbi uhf yagi is going to be narrow band and pretty long. A DBGH of 16 to 17 dbi covers channels 14 to 51 nicely and has a better center of gravity.

If you have the ghosting or multipath problems, a yagi could be better. In severe cases, you could enclose a yagi in a cage.
 

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Geography

First let's be clear that we are discussing UHF-only antennas, as it is clear that the experimental bowtie reflector antennas for VHF channels were colossal and therefore never popularized. :)

The previous posts are correct, so I'm clarifying that the main reason that bowtie reflector antennas are so popular and successful in North America and Australia (where they are known as "phased array panel" antennas) is geography: chiefly due to the effects of great distances on transmitted TV signals. In Europe the distance to transmitters is rarely if ever as great as that which we commonly face here and Down Under, and the spread of transmitter sites in Europe is not as wide as we commonly see here. An online aiming tool like TVFool would tend to generate quite boring results in most of Europe.

A Yagi-Uda at comparatively short range with a single aiming point is simple, effective, and small, but at typical ranges seen in North America and Australia the relative size and complexity of Yagi-Uda antennas grows and grows. Thus, products like the excellent AD 91XG Yagi-Uda for deep to deepest fringe reception are monstrously large, complex, and quite finicky to aim compared to the much smaller and simpler Yagi-Udas commonly seen on European rooftops.

Comparisons going back many decades in long range reception scenarios show that the 4-bay and 8-bay bowtie reflector antennas exhibit much better capture of scatter from deep fringe signals and are easier to aim for such long distance results. Similarly, the Gray-Hoverman antenna (and others derived from the Chiereix) are vertical, reflector-using antennas that exhibit wider reception patterns than the afore-mentioned 91XG. For a variety of reception issues one can choose which of the different designs suits their situation best.

Hopefully that helps to clarify things. Please see Posts #3 and #5 in the OTA FAQ for more info on the differences.
 

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In Europe the distance to transmitters is rarely if ever as great as that which we commonly face here and Down Under, and the spread of transmitter sites in Europe is not as wide as we commonly see here.
Good point, and retransmitters are more common in Europe than here.

The Facarro modified double bi-quad broadside antenna seems to be popular on Italian rooftops, from the pictures mlord posted.
 

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rapido: In addition to the positive points you make of Yagi antennas, I prefer the fact that they occupy less vertical space on my tower mast. This leaves room for the installation of other antennae, such as a good VHF.
 

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Discussion Starter #7
Many thanks for all your replies.

I have to agree that a simple medium-gain Yagi is probably sufficient for the vast majority of installations in the UK. But of course we do have locations where terrestrial reception is difficult even with a high gain model.

Nonetheless, narrow bandwidth has always been a very useful feature of a Yagi, as the analogue channels were planned to be grouped for each transmitter. So I am to understand there is no call for grouped Yagis in Canada due to having a spread of received stations across the UHF?

In the Czech Republic I saw a few "bowtie reflector" (to use the preferred term here!) aerials, seemingly with directors sticking out of the bowties...(?).

-rapido
 

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Many thanks for all your replies.

I have to agree that a simple medium-gain Yagi is probably sufficient for the vast majority of installations in the UK. But of course we do have locations where terrestrial reception is difficult even with a high gain model.

Nonetheless, narrow bandwidth has always been a very useful feature of a Yagi, as the analogue channels were planned to be grouped for each transmitter. So I am to understand there is no call for grouped Yagis in Canada due to having a spread of received stations across the UHF?

In the Czech Republic I saw a few "bowtie reflector" (to use the preferred term here!) aerials, seemingly with directors sticking out of the bowties...(?).

-rapido
You are correct, there is no attempt to group broadcast stations by frequency like there is in the UK. Until recently in Canada, neither was there even a requirement to co-locate transmitters. (Industry Canada, the government department in charge of Spectrum Management, now expresses a preference for tower-sharing, but that arose out of the prolferation of cell towers, and was not really directed at broadcaters.)

That said, co-location of broadcast transmitters has always been more prevalent in Canada than in the US, where even if stations are on the same mountain, they often use(d) different towers. That is slowly changing.
 

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My preliminary investigations into adding directors to the bowties seem to indicate there isn't a real gain to be added, especially with the added build complexity.
 

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^^^^
Perhaps they're for "marketing gain". People will buy stuff simply because it looks impressive, whether it does anything or not.
 

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No idea how that antenna in Post #8 models out, but I'd be interested to see. I don't know if those yagi-like elements are even connected to the bowties but I do know that they are not necessary according to antenna theory.

Bowtie whiskers are meant to represent the upper and lower edges of an imaginary cone extending outwards from the connection point to the tip of the whiskers. The effect is similar to actually using a cone of copper sheeting, but using whiskers is much easier to build and adjust, with better wind tolerance. Adding anything to the bowtie construct means disrupting that virtual cone and therefore its reception capabilities.
 

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Discussion Starter #14
Yes, pretty much like on that wholesale link. I did take a photo when I was there, but it is too indistinct. So here's a couple of links:

http://www.digizone.cz/clanky/anteny-a-antenni-soustavy-pro-prijem-digitalni-televize/

http://www.ansat-tn.sk/shop/index.php?main_page=product_info&cPath=16_56&products_id=268

A high gain wideband model would be of interest to me, as there are a few UK transmitters which will transmit across the UHF bands after the digital switchover. Yagi widebands are available here, but of course have lower gain below 600MHz, whereas a flatter gain curve would be preferred.

-rapido
 

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Here's another very impressive chi'tenna designed for marketing to the unknowing;
http://www.alibaba.com/product-gs/322682194/Yagi_outdoor_tv_antenna_model_SNY/showimage.html

The same bowtie with the same fake directors plus a great big lower bowtie :p

That oversized lower element may help keep the birds off the upper bowtie, but otherwise it looks pretty unbalanced and most likely useless in the real world of reception.
 

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My preliminary investigations into adding directors to the bowties seem to indicate there isn't a real gain to be added, especially with the added build complexity.
Yep, I played around with bowtie directors too. I found the best director for a bowtie is another bowtie, and you need a mess of them for significance.

Those tiny couple of 2" or 3" wire directors in front of a bowtie could maybe, just maybe, help old channel 83 gain a tiny bit, heh.
 

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There are several reasons at play as to why 4-Bay and 8-Bay Bowtie antennas have been
popular in the U.S. and Canada.

1. Up until DTV transition in the U.S. (Jun2009) and still in Canada (Aug2011), the new DTV
stations are almost always found in the UHF Band. Hence there was no "NEED" for HI-VHF
(or VHF) performance in most new antennas. So small, UHF-only, was "good enough for now"...

2. GoogleEarth maps from Sep2009 illustrate that in the U.S. and Canada, TV/DTV
stations are VERY RARELY found in just one location:
http://imageevent.com/holl_ands/files/dtvlocations
Hence, in many cases an antenna with as much Gain as possible, yet still maintaining
a broad beamwidth is highly desirable....which are Multi-Bay Bowties....and G-H.

Most 4-Bay antennas can also receive strong signals (both UHF & Hi-VHF) from the REAR:
http://www.hdtvprimer.com/antennas/comparing.html

3. COST is also important. I can still buy a 4-Bay antenna for US$ 32, incl. tax & local pickup,
while an 8-Bay will be about twice that, incl. some (problematic) Gain on Hi-VHF Band:
http://imageevent.com/holl_ands/multibay/8bayrefl
About the only Outdoor antennas I've found with higher Gain at those prices are some monster
Ch2-69 antiques the retailers are trying to dump from inventory.....

A big UHF Yagi, like the 91XG and others, might provide a bit more UHF Gain (for those few
people who really NEED it), but at a lot higher price and they'ld STILL need to buy a Hi-VHF....
And with the price of a Hi-VHF Log-Yagi (W-G or A-C) being only about US$ 40-50, separate
UHF and Hi-VHF antennas are less expensive than most combo Yagi antennas....

4. DIY Multi-Bay and Grey-Hoverman Antennas are easy to design and easy to build.
There are very few Yagi designs available that provide equivalent performance.
Yagi designs generated by K7MEM's on-line calculator are very narrowband, and are
not optimized for much of anything, with high SWR and very poor F/B & F/R Ratios.

K6STI's Hi-VHF Optimized 5-Element Yagi (which could be rescaled for UHF) is a good DIY choice,
but only has 7.4-9.3 dBi Gain.

I've analyzed several other, longer, higher Gain Yagi's, but none come close to G-H & MultiBays:
http://imageevent.com/holl_ands/yagis
And, of course, Yagi's make TERRIBLE Hi-VHF antennas.....
Whereas there are several G-H and Super-4-Bay designs optimized for Hi-VHF.
 

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Discussion Starter #18
Maybe the Czech installers just use a load of cheap "Made in China" models... I like the huge bowtie at the bottom of the link ota_canuck posted!

But take a look at this video from over 20 years ago:

http://www.youtube.com/watch?v=GrTP3aYRQN4

At about 1:15, look closely and you can see a couple of bowtie reflector aerials! Even if they were more common then, I suppose most would have been destroyed by our gales and storms in the intervening period.

BTW Antennas Direct 91XG (looking at the pics) seems to use flimsy directors that are used by cheapo "wideband Yagis" that are sold in DIY shops here.

-rapido
 

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Blake continues to sell a model JBB "billboard" UHF antenna in the UK but it looks like a rebranded Chinese 4-bay make:

http://www.blake-uk.com/aerials.aspx

Also I believe at one point Antennas Direct (USA) simply imported Blake UHF yagis and rebranded them for sale in North America, but I could be wrong. Their 91XG and 42XG models sure resemble the Blake JBX models.
 

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Discussion Starter #20
Yes, I see the Billboard on the Blake website, but my local aerial shop doesn't actually stock it (perhaps no call for it from installers?) But they do stock the PU16, which looks quite impressive. Nice gain in the middle of the UHF.

The Antennas Direct 91XG doesn't look much like a Blake JBX to me (which have proper sturdy directors), so I doubt it's anything to do with Blake! It looks more like something Philex would sell (e.g. http://www.philex.com/catalogue/product/?id=12&cat=1025 ), in the loft is okay to install, but outside the elements quickly get deformed by birds... or just fall off eventually in wind.

Holl_ands, your information is very interesting. I wonder why the digital switchover isn't used as an opportunity to rationalise the situation in North America. Transmissions all over the bands from different locations - nightmare!

-rapido
 
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