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Awhile back, ADTech said that NEWER 91XG used a Printed Circuit Board (PCB) balun which uses unequal stripline delays to form the equivalent of a Coax Balun, which ONLY works on UHF Band and severely attenuates Hi-VHF. You probably could figure out a way to replace the PCB Balun....perhaps ADTech can help...

OLDER 91XG's used the usual Transformer Balun which doesn't have this problem, so it should be about as fol. 4nec2 model calculates:
http://imageevent.com/holl_ands/yagis/91xg
Note that there is more Gain to the REAR than Forward....but on Ch13 it's a tossup vs CM4221HD...

Compare to CM4221HD that uses the usual Transformer Balun:
http://imageevent.com/holl_ands/multibay/4bayrefl/uhfnewcm4221hd
Note that there is ALWAYS usable Gain FORWARD, but on LOWER channels Gain is HIGHER to the REAR.

Extending CM4221 Overall Width of Reflector Rods from 23.6-in to "about" 30-ish inches will IMPROVE Hi-VHF Max Gain numbers, esp on Ch13....by ensuring that it is always directed FORWARD....

I'll work on calculating Hi-VHF Gain improvements to determine "best" lengths for CM4221HD after I finish up a similar investigation on the mclapp M4 with a FLAT Reflector made from either Screen Grid or multiple Reflector Rods that I'll be publishing "soonish" (finalizing Charts for Screen Grid Reflector right now).

Here is the larger M4 with three different sizes of FLAT Screen Grid Reflector Rods...CM4221 should be similar:
http://imageevent.com/holl_ands/multibay/4bayrefl/m49590gridrefl
 

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Thanks Holl_ands. Your answers are always very thorough and appreciated. Not exactly the answer I was hoping for though. What if I went for the DB8 or DB8e? How do they compare to the cm4221hd for vhf-hi? Thanks again.
 

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You'll have to direct your question to ADTech, esp whether either antenna uses their new "PCB - Printed circuit Board" type Balun which severely degrades SWR amd attenuates Hi-VHF. I haven't seen anyone post detailed dimensions for either antenna from which a 4nec2 model can be constructed and A-D does NOT cite any Hi-VHF performance for either antenna.
 

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Bark64, why not combine the dipole from a C2 VHF Reflector Assembly (just remove the reflector mesh, as is is only for use with a C2 and use the included mounting bracket) with whatever UHF antenna you choose. It will have more gain than any of them and can be properly aimed towards CKCO.
 

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CPA 19

Does AD or anyone else here KNOW what the noise figure of the CPA-19 is around 647 Mhz, Ch. 43....thanks

the specs say UHF - 2 dbs
 

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Project,


Nice find, your quick...thanks

So thats what I wanted to know, its at LEAST 2 dbs....

No offense to AD, but that means I have still more than 2 dbs room for improvement in my system depending what amplifier, and configuration I decide to experiment further with...
 

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When you're on the ragged, bleeding edge of reception, a 1 or 2 dB improvement in system NF isn't going to move you very far as a simple change in weather can wipe out the improvement.

You'd really do best investing is a spectrum analyzer. For about $200 or so on ebay, you can get one and avoid spinning your wheels.
 

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I understand what you say, but I also disagree somewhat, the goal is NOT 100 % reliability, but improved reception ;)

So far, not every move, but several moves I have made in my COMPLEX set-up has lead towards some measure of improvement in reliability, plus I like to experiment....obviously for the strong channels its the opposite, almost nothing I do can kill them, so there is no challenge there.

Im not against the SA, but as you say since conditions change so much where I am, I would not even rely on the SA to govern what changes to make

I agree 1 db here, & there doesnt change anything, but heres my philosophy, improve the amp by 2 dbs, add another boom section, improve 1 db, remove UVSJ, improve another .7 db, improve tuner, another 1 db, etc, etc...adds up, even if this comes into play only on the moderate days, will make it watchable on those days
 

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Where I live I have 4 VHF-hi stations. So I decided to add the $20 C2v VHF kit to the DB4e. I used the existing holes and supplied hardware. It works quite well allowing me to receive those 4 stations that I had dropouts before. I did not notice any degradation on the UHF stations, so I'm a happy camper.





Just wanted to say thank you for the info on building a "DB4e-V."

In my situation, I need to pull in signals from channels 5, 11, 27, and 38. The C2-V I tried initially was marginal on the channel 27. So, I purchased a DB4e and a VHF reflector kit for the C2 and transferred the dipole to the DB4e.

It's working like a charm!
 

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Hi gawellman,

This "DB4eV" seems to be quite the hit, great UHF performance and the two simple dipoles seem to add quite the boost on VHF. Seems like everyone is doing this mod now...

ADTech, this review mentions that AD may be coming out with a universal dipole kit that would work on all CS and DBe antennas? Any idea on when it's coming out? It's a bit of a waste to keep scrapping the CS2 reflector....
 

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I have dipoles installed behind the reflector on Db4e , would it make a difference if I installed it between reflectors like in the previous post . I am also curious if installing two dipoles would make significant improvement in reception.
 

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Interdit_450,

The molds are almost done. I I had to guess, I say early to middle of the first quarter for them to be in stock at our warehouse.

Bev fan.

I don't know, I haven't tested the two configurations to see if or how they might be different.

Two dipoles, properly spaced with a proper phasing harness feeding into a diplexer would probably work better although by how much I don't know. We have no plans to do any such project.
 

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AD smart antenna patent finally gets approved?

Is AD actually going to give the CEA-909 smart antennas another go or is this an item from the defunct 2008-2009 smart antenna craze that will never actually see the light of day?

Are there even any receivers that support the CEA-909 "self tuning" feature anymore?
 

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That Smart Antenna article is old. I know of no current development effort since, to our knowledge, there' still not a single TV set maker that's incorporated CEA-909/A/B(?).


BTW, the VHF Retrofit Kit is anticipated around Easter (this year) as a stand-alone product, from what I can see in the production forecasts. We are actually shipping a 3rd Gen C2V to US Walmart and Best Buy stores that uses the new VHF module. It's not even yet on our website although it can be ordered from Customer Service if you know to ask for it. Please keep in mind that we are only able to ship directly to the "Lower 48", though.
 

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The VHF Retrofit Kit mentioned two posts prior has finally arrived and is in stock. It should be added to our web site soon.
 

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91XG Wind Load Area in Sq. Ft.

ADTech,

I recently added a 10 ½’ fence top rail and second 91XG to my tower array. Our 60-70 MPH gusts this week spun the stack & NTE ECG U-106/TB-105 3-Wire rotor w/Thrust bearing from 292 deg. to ~230 deg. I’m considering a new rotor and would like to size the antenna/mast loading. Do you have any information on the 91XG Wind Load Area in Sq. Ft?

I am also turning a Winegard HD6065 10 Element FM Antenna and an Antennacraft Y10 7-13. I’ll contact both manufactures but since nobody seems to publish wind loading data for consumer antennas I don’t hold out much hope. If you know and can throw in their information @ no extra charge I would appreciate it. I’m not looking to build a “Prop Pitch” Antenna Rotator System but definitely want something that won’t turn and keep going out of calibration. The U-106 has way more calibration mileage on it than antenna turning mileage. My old Radio Shack 15-1220 & RCA 10W707 haven’t spun or gone out of calibration in almost 50 years and that includes loading from an 8 element 10 Meter beam!

 

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..nobody seems to publish wind loading data for consumer antennas...
That is indeed the case. We've never measured it and I've never seen it specified for this category antenna here in North America.

With an array that large, I'd suggest looking at a ham-class rotor. I've never dealt with them, but I've seen these folks recommended numerous times: www.rotorservice.com
 

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DB4e to DB8e change worth it?

Hi,

Post for ADTech and all the veterans. Does anyone know of a post on the forum comparing a real world DB4e to DB8e upgrade? (with reliable tested results). I have extensively read all the published AD data sheets which are excellent.

I currently have a DB4e, Winegard J-pole roof mount 25ft AGL. Can't go up higher at present. We are fringe but are getting (to me) impressive results for my location. Several channels like WNED (PBS) Buffalo are mostly there even during humid summer days, but understandably a bit sporadic. TV tuner reports Signal Strength ranges around 58% typically, with 100% Signal Quality on optimal days.

However some times they drop off precipitously (10%-30% Signal Strength) with corresponding image breakup. I am pretty sure a DB8e will not necessarily fix that, but curious if anyone has even approximate before/after Signal Strength comparisons for similar fringe locations, comparing a DB4e with a DB8e, in case it improves it somewhat.

TVFool:
http://www.digitalhome.ca/forum/showthread.php?t=94075 (see Post #1456 and later for the situation)

As mentioned I am very familiar with the data sheets on the AD sites. I am azimuth'd directly at WNED for current max gain with the DB4e. I have CKVR about 100 degrees East, but it is our strongest signal and the DB4e is handling that fine, and I would hope the DB8e even thought a bit more directional would similarly find it.

Any info on Signal Strength "improvements" before/after a DB4e/DB8e switch would be appreciated. I understand this is difficult, since strengths often change by the minute. Hopefully someone has some averages.

Thank you for your help. Very impressed with AD. Just curious if the experts think and upgrade may make and improvement of say 10% in average signal strength in my scenario.

Current:
DB4e > CM7777 > 75' Andrews RG-6 > PSU > 25' RG-6 > LG 47" (no splitters)

Proposed:
Same but with DB8e.

Thank you.
 
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