[edtrutone]

Check out the New DB4 At Antennas Direct Blog 3x WOw

 

[ProjectSHO89]

The new DB2 and DB4 antennas were announced at CEDIA in last month.

http://www.bigpicturebigsound.com/Antennas-Direct-High-Gain-DB2-HDTV-Antenna.shtml

 

[ADTech]

Semi-parabolic?

The reflector is flat as are the elements. No forward curvature on either.

 

[stampeder]

Thanks for pointing that out - my mistake as I had viewed the following DB-2 image on my smartphone, and from the angle of it as displayed on a small screen it looked distinctly parabolic:

The non-horizontal reflector elements could best be described as "radial" then, since they are not completely vertical. The tips of the bowties match the curve of the radial reflector elements too.

I've changed the thread's title.

 

[byebye_cable]

Can't wait for the Ken Nist review

They'd better have gotten it right!!

 

[ota_canuck]

follow the link in post#2 to see the guy holding the actual antenna. It appears to me that the horizontals are straight horizontally and the verticals are straight vertically, but rather it's the screen that is curved [ ) ]

 

[Jase88]

Yes, I had questioned whether they were indeed parabolic or not, as it's difficult to determine from the sketch.

 

[ADTech]

The positioning of the reflector wires was done for styling reasons (hey, it looks cool!). I can see how it makes a bit of an optical illusion and appears somewhat parabolic.

Based on the most recent simulations I've seen, our design engineer is coming up with around a 2-2.5 dB improvement in raw gain across the 470-700 MHz band for the new versions versus the predecessor model. That means he's seeing almost the same gain on the new DB2 as the old DB4 and on the new DB4 compared to the old DB8. Those simulations show a peak gain of 12.4 dBi on the DB2 at 700 MHZ and 15.55 dBi on the DB4, also at 700 MHz.

Can't wait for the Ken Nist review

They'd better have gotten it right!!

We do the best we can to make a commercially successful product. Since we know we can't please everyone who plays a Monday morning quarterback, we do the best we can given the constraints of the business, a fact often overlooked by the enthusiasts.

I haven't had the chance to do any field testing yet on the prototypes since they just got back from Atlanta and I've been working on some other projects. I may try to do some next week before the weather starts to get much cooler.

 

[ota_canuck]

This claim may be overstated, though interesting: [is this claim just for the 2 bay?]

The improved version of the DB2 HDTV antenna offers nearly twice the gain of its predecessor.

Schneider said that the unit's design allows it to reach into the top of the upper VHF band as well, so if some of the digital channels in your area are being broadcast in what used to be analog channels 7 to 13,

Also, how would these work ganged or stacked?

 

[300ohm]

The non-horizontal reflector elements could best be described as "radial" then, since they are not completely vertical. The tips of the bowties match the curve of the radial reflector elements too.

The antenna does have a very nice look to it, and Im sure thats what they were going for.
Vertical or nearly vertical reflector wires do very little to change the characteristics of a double bay bowtie in a horizontally polarized transmission world.

This claim may be overstated, though interesting: [is this claim just for the 2 bay?]

Quote:
The improved version of the DB2 HDTV antenna offers nearly twice the gain of its predecessor.

Yep. Nearly twice the gain would mean a nearly 3 dbi increase in gain, and I cant see how it can achieve that. The old DB2 was pretty good.

But it does look nice from an aesthetic stand point. I can see where the costs may double from making a custom welded reflector like that.

 

[goforit]

I heard the DB-8 will also be re-jigged, looking forward to it.

 

[byebye_cable]

Why peak on the highest channel...unless there's an immediate drop-off.

 

[mclapp]

Most multi bay bowtie type antennas gain drops off pretty fast past peak.

 

[ProjectSHO89]

Why peak on the highest channel...unless there's an immediate drop-off.

That's a pretty typical behavior for colinear arrays such as the bowtie or for yagi style antennas. If you want them to be broadband, you generally have to accept that gain peaks at the top of the design band and will then drop as a function of lowered frequency. The challenge is to keep them good enough without destroying VSWR (efficiency) which would negate the raw gain improvements.

 

[ADTech]

Also, how would these work ganged or stacked?

Gotta love the enthusiasts! We haven't even made the first production unit and they already want to experiment with it. I suspect that we'll have to wait to find out the answer to that question.

Nearly twice the gain would mean a nearly 3 dbi increase in gain, and I cant see how it can achieve that. The old DB2 was pretty good.

I'd plan on a AVERAGE of 2 dB gain across the 14-51 band. Some frequencies will improve more than others. Keep in mind that the process of rescaling the bowtie antenna does two things: 1) It slides the gain curve "leftward" on gain vs. frequency chart and 2) It causes the antenna to physically grow in size, typically by 20-25%. There aren't any free lunches.

As far as high-VHF is concerned, it will be better than the existing DB2 and DB4 due to the larger sizing of the elements and the reflector. However, these antennas are being designed for peak UHF performance and whatever VHF performance happens to occur will be a bonus. The selected PCB balun is extremely efficient on UHF (0.6 to 0.8 dB insertion loss) but is unkind to VHF frequencies. Since we haven't found a suitable broadband balun that doesn't sacrifice performance on UHF while also offering good performance on VHF, we're using our current UHF balun and focusing on UHF performance. Swapping to the broadband balun used on our C5 would peak VHF performance but would cost almost all of the UHF gain from the redesign. No free lunches, again....

I heard the DB-8 will also be re-jigged, looking forward to it.

You didn't hear that from us. We've only announced the DB2 & DB4...


If you happen to know of a commercially available balun, preferably SMD, that offers flat response from 50 to 700 MHZ with less than 1 dB of insertion loss, I'd sure like to get my hands on some samples.

 

[goforit]

Improving the DB-8

According to RS,


The improved versions of the DB2 ($49.99) and DB4 ($69.99) will be available later this year, with tentative plans for an improved DB8 to follow.

Bring it on.

 

[Jase88]

These are likely designed for up to channel 51 only. Therefore I'd caution Canadians (particularly in Toronto) that they may lose some higher channels until next August 31.

 

[stampeder]

If you happen to know of a commercially available balun, preferably SMD, that offers flat response from 50 to 700 MHZ with less than 1 dB of insertion loss, I'd sure like to get my hands on some samples.

So you guys are after the holy grail too, I see. Here's a huge amount of material from our members regarding baluns:

Baluns (Brands, Designs, Losses, DIY Loops, etc.)

 

[ADTech]

So you guys are after the holy grail too, I see.

Isn't everyone? When you spend tens of thousands of dollars improving or creating a design, you can't afford to squander any performance with a poor balun.

These are likely designed for up to channel 51 only.

Yes, but they don't fall of the face of the earth above that. I have the the prototype DB2 hooked up to a spectrum analyzer and I can see all the local activity on the local cellular bands around 860 MHZ.

with tentative plans

Let's just say it's a fluid situation and leave it at that for the moment...

 

[goforit]

I'll be dreaming...