DB-8 Redesign - Hacked CM4221HD Outperforms it?

[Ibra]

Ok i received mine it's a 2009 but im lost at step 2 : Attach combining bars to the binding posts on the antenna (bow tie) elements. I just would like to see how it is since on the picture it's not very clear since i would like to know if the element go in between the nut screw and the bolt or under the bolt ?

[stampeder]

Dealers have been informing some of our members that the 2009 model of the DB-8 is different than the previous model. If you have any hard data, facts, figures, specifications, rumours, gossip, comments, photos, links, or other info about a new 2009 DB-8 please let us know.

I cannot post the retail link to the Antennas Direct site but here is a snippet about the redesigned DB-8:

DB8 Multidirectional HDTV Antenna

New DB8 Redesigned for 2009 - Now 22% higher net gain!

* More efficient
* Higher Gain
* Enhanced High VHF performance
* Optimized for post 2009 DTV frequencies
* More secure signal connections

Intended for people at great distances from the transmitters, the DB8 is our most powerful multi-directional HD antenna. In fact, its 15.8 dB gain make it one of the most powerful multi-directional antennas available.

The bow tie design of the DB8 uses triangular elements instead of rods to greatly increase the bandwidth allowing it to cover the entire UHF band. Additionally, the mesh reflector of the bowtie is more efficient than a rod reflector, is lower in weight, and provides less wind resistance for greater performance and durability.

This DB8 is the ideal antenna for use in locations that can pull long range signals from various directions and offers an attractive alternative to using a directional antenna mounted on a rotator.

* Range: Up to 70 miles or more
* Impedance 300/75 ohm
* Works up to 70 miles or more from transmitters
* Very flexible aiming characteristics
* Weatherproof construction
* High gain across entire UHF band (UHF channels 14-69)
* Max Gain 15.8 dB
* Dimensions 29" H x 42" W x 4" Deep
* Weight: 10 pounds
* Lifetime Warranty

And here is a PDF of the installation instructions: http://www.antennasdirect.com/pdf/db8_assembly.pdf

[stampeder]

Ken Nist comments on the DB-8 here (not sure if he means the 2009 model though... ?) along with the new CM4228HD:

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

[300ohm]

the DB8 is our most powerful multi-directional HD antenna.

MULTI-DIRECTIONAL ????

This DB8 is the ideal antenna for use in locations that can pull long range signals from various directions and offers an attractive alternative to using a directional antenna mounted on a rotator.

1. The DB8 comes with:
• 2 reflectors
• 2 sets of bow tie elements
• Combiner bars with 75 ohm transformer
• 4 sets of bolts with aluminum sleeves
• 2 cross braces
• 2 Mast clamps

Hmm, wheres the rest of the stuff ??

[sunnydays]

Gosh, I am all confused now, I thought Mr Nist commented that the "new" DB8 is worst off than the old DB8? I am still waiting for the new antennacraft 4500.

[300ohm]

The thing is, John E. Ross, of Antennas Direct, JER on this forum, is heavily involved in smart antenna design. (hes probably the best in the world at that) Thats why I think stuff is missing from the above. Unless he has the smart antenna stuff hidden inside of those cross bars somehow, heh. Or is this another case of the marketing dept gone wild ? Nothing in the installation/assembly sheets indicates multi-directionality parts (or even an adjustment to the spacing between the bays, which by changing them, can produce different angle lobes. The spacing between the bays is static in the installation/assembly sheets)

[dohcacr]

This is my experience with a antennas direct db8 that I purchased this week. I have a technical background but I'm a novice when it comes to antennas. I purchased a db4 antenna from solidsignal about 2 months ago and I was very pleased with the reception. The antenna was installed on a 6' mast on the peak of my house roof and directed to 136 degrees. I was able to get by with 25' of RG6. The antenna location is 34.26387-85.03220. After June 12th, I was receiving 23 digital stations(up to 55 miles distant) from Atlanta and the North Georgia area. My only displeasure was that I was barely pulling in channel 30, and I can't tolerate missing Nova. Since I was getting some signal on 30, I figured that a upgrade to a db8 would allow me to pull in channel 30 with good quality.

I ordered a d8 from solidsignal, installed it on a 10' mast, directed it to 136 degrees, and tweaked the direction for maximum signal. Now I'm only picking up 18 digital channels. I have no detectable signal from channel 30, and have completely dropped channel 69, and numerous others that I don't care much about. Theoretically I should have seen a 2.5 db increase in signal strength with the installation of the db8 antenna. I have checked and double checked the installation, including the pointing of the antenna, and the best reception I receive with the db8 , is 5 channels down from what I receive with the db4. I've been trying to contact SolidSignal all day today, via their phone support and fourms, without success. They claimed they would return my call within 1 hour, and as of now it's been 6 hours. I'm starting to wonder if the poor reception is the result of the balun problem I've been reading about on the web. I assume this is the new 2009 db8. The box does not indicate that it is anything but a db8 antenna.

[300ohm]

After June 12th, I was receiving 23 digital stations(up to 55 miles distant) from Atlanta and the North Georgia area. My only displeasure was that I was barely pulling in channel 30, and I can't tolerate missing Nova. Since I was getting some signal on 30, I figured that a upgrade to a db8 would allow me to pull in channel 30 with good quality.

Dont panic. A lot of stations are going to be on lower power for the next few weeks or so while they update their new systems. You could call the station to see if they are one of them.

It does sound like a bad balun on the DB8.

[dohcacr]

I'm comparing the reception of the db8 and the db4 within the same 6 hour period. The reception of the db8 is definitely inferior to the db4, and I'd guess also that the problem is the balun.

I did finally get through to Solid Signal, and they are going to send me a replacement. I'll update this thread with the results.

[neilkaz]

For my first post here, I have to thank all for a wonderful forum!!

Dohcacr, I hope the new DB8 they send you will be an improvement over the DB4. If it isn't, perhaps the production version of the new DB8 has some fatal flaws with the balun or feed lines from the two DB4's. What works perfectly in the engineering lab and on the antenna test range, doesn't always come out of production the same.

A few things you may want to try to improve your PBS reception. 1) Raise the DB4 a few feet and see if things improve. 2) Vertical stack two DB4's and raise if needed. (Guying will likely be a must). 3) Consider the DIY route. 4) Add an amp.

Anyhow I am rolling on the floor laughing at some of the nonsense at the Solid Signal site with regards to Antenna's Direct antennas.

They seem to have no clue what the actual beamwidths the bowtie series DB antennas are and calling a narrow beamed antenna like the DB8 (http://www.hdtvprimer.com/antennas/DB8.html) multidirectional is a bad joke!

It is also funny to see them spec the C2 and the C4 (two dual loops arrayed side by side) as the same 70 degree beamwidth, which most certainly isn't the real life case.

http://www.hdtvprimer.com/antennas/DB8.html says that Ken's modelling of the DB8 gives a more narrow beamwidth than the corresponding CM4228HD. This makes perfect sense when one looks at the pictures of the two antennas and also the patterns. The DB8 appears to have more spacing between the horizonantally arrayed DB4 pairs than the CM4228 does between it's 4 bay pairs. This results in a more narrow beamwidth but with higher sidelobes as shown in the patterns.

One also wonders, when and if, being a US company, A-D/Terrestrial Digital will see if they can add a half dB or more improvement to their older UHF antennas by optimizing for RF 14-51 and forgetting about the higher channels.

... neilkaz ...

[M.Satterfield]

My only displeasure was that I was barely pulling in channel 30, and I can't tolerate missing Nova. Since I was getting some signal on 30, I figured that a upgrade to a db8 would allow me to pull in channel 30 with good quality.

I am familar with this same area as I was born and raised there (I am from Dahlonega)! Why not try to get channel 8 for PBS? They are now on VHF-8. Where I lived, we always got better results with VHF reception due to all those pine needles on the pine trees zapping UHF! You may want to consider a VHF-Hi antenna to get RF channels 8 and 10-->WGTV-8.1 and WXIA-11.1 respectively.

BTW, this is what I am putting on my Mama's roof so she can get digital tv from Atlanta:



HTH

Mike

[300ohm]

and I'd guess also that the problem is the balun.

Heres a picture of the DB8 balun from Ken Nists Temporary page. Its a 200 to 75 ohm balun :



It looks pretty durable, relative to most baluns. Maybe something else is breaking or bad soldering ?

[M.Satterfield]

Possible cold solder joint. Re-melt them all and see if that helps.

HTH.

Mike

[cfraser]

Originally Posted by M.Satterfield

BTW, this is what I am putting on my Mama's roof so she can get digital tv from Atlanta:
Mike

Very nice-looking job!

[hieronymous]

dohcacr,

I suspect there is something to 300ohm's suggestion that your problem with channel 30(Real 21) may be due to them not transmitting on full power yet. I'm in Alpharetta myself, just under 21 miles north of the transmitter, and have the same problem with terrible signal and frequent dropouts on WPBA 30 only. I've scanned the web but haven't found anything confirming this yet. This is the only channel showing green or yellow for me in tvfool that I have trouble picking up, regardless of how I orient my antenna.

Initially I thought the problem was the build quality of my diy DB-4 knockoff(my first attempt, built last Friday night, and not a thing of beauty by any stretch) having a problem with that particular frequency. Then I realized looking at tvfool that there were several other channels rather nearby in frequency that I was picking up with no problem, such as 46(Real 19) and 17(Real 20). That's when it occurred to me that they might not be at full power yet.

By the way, after hacking this thing together on Friday, I am more than pleasantly surprised at the results I'm getting, especially since I know from reading here and elsewhere that the specs. I used were sub-optimal to say the least.

9+ months ago when I had only done a little casual reading here and elsewhere, and watched one of the now much maligned youtube videos, I had stumbled across some wire doll stands in a little dollar store that was going out of business. Just google "wire doll stand" if you want to see what I mean. They're basically a piece of 1/8"(8 to 9 guage I think?) diameter wire shaped into a "V" at the bottom with a circular shape at the top. I immediately thought antenna when I saw them and used a tape measure in the store and saw that if I clipped off the top portion they made perfect pre-bent 7" V's, which at the time I thought was plenty long enough. I'm not sure if they're steel or aluminum, but from their weight I would guess the latter. Anway I picked up 8 of them for probably $1.50 or so and have had them laying around. Well when I got around to reading up on diy antennas again 2-3 weeks ago just before the transition, I learned that 7" was unlikely to cut it and had pretty much decided to scrap them.

What changed my mind was that I was over at lumenlab where a user named will1384 had purchased a DB-8. Before assembling it he took some nice pictures and detailed measurements and posted them there. I was stunned to learn that it used whiskers just under 7" and roughly the same length gap between whiskers. I decided that instead of scrapping these I'd use it for practice and build a 7 X 7 bowtie just to see what results I got, and to finally try out my Zenith CECB box which I had never even unpacked since I bought it 9 months ago. The results are so good, I'm going to have to manufacture excuses to experiment with other builds. I haven't even tried adding a reflector yet.

My biggest surprise is that I'm having no problem at all picking up 8(Real 8) or 11(Real 10) which is where I really expected sub-par results. They're coming in as strong as the others according to the Zenith. Obviously I'm in a good location since in theory this antenna should be doing next to nothing for me at those frequencies. All in all I'm picking up a total of about 30 (virtual) channels, some of which I'm surprised are not even available on my basic cable with Comcast(for example 3, that's right 3 Korean language channels, lol).