Original Gray-Hoverman Generation 2 Thread (Now Closed)

[300ohm]

I think the bundles are like $12 for (12) 32" pickets.

39 inch lengths I think. My Lowes carries it. Its inside where the fancy post caps are sold. Only problem, no couplings, tees or ells for it so you have to make your own. I would couple them with a square piece of wood that fits perfectly inside. It nice stiff stuff.

And with a round mast, it's incredibly difficult to get the three front holes

Yeah, with the round pvc pipe, its actually more accurate not to use a drill press to drill all the way thru. (any tiny wobbling/movement messes it up) Mark a line on both sides of the pipe (easy if on a flat surface, just run a sharp pencil along it) exactly 180 degrees apart. Then measure the same distances from the same end. And just drill thru one side at a time.

It does seem to work, probably about as well as the dual PR-8800 array higher up.

Yep, looking at Ken Nists graphs, the SBGH GH10 should out perform the PR-8800 from channel 17 on up. The dual PR-8800 is still a db better at channel 14. Of course, with the DBGH GH19 even that little advantage is gone, heh.

[300ohm]

Heres the DBGH GH19 Net Gain chart:



And the SWR chart:

[Autofils]

I had mentioned in a previous post that I could post a nec file model for a DBGH-Horizontal GH20 design, so if you want to contribute to the model work on this, feel free to experiment.

This model is based on the parameters of the GH10 UHF-Mid design (h=0.163).
This model has just one variable 'BS' which is the spacing between the feed-gaps of the two arrays (center to center).
The min value for BS in this model is 1.09m, there is no limit on the max value, other than practical values for building the antenna. Do not use BS value less than 1.09 !!

The use of the SY card ( ie variable 'BS' ) will allow you to experiment with 4nec2's optimizer functions.

I have not designed any phasing line, simply because I currently don't have the free time; hence this model uses current source drivers at the feedpoint of each array. Using this approach and running the sweep optimizer at 610Mhz, the optimal BS spacing is 1.35 meters. Based on this value, the overall dimensions for the DBGH-Horizontal GH20 would be 94"w x 58"h.

To complete this design, you need to interconnect the two arrays with either a phasing-line (not yet designed) or by using 75 ohm coax interconnection with two baluns (300-75 ohm) and a combiner, just like some commercial antennas do.

I'm hoping the 300ohm, can take this file and add his phasing-line design.
I'm sure this forum would certainly welcome modeling efforts by anyone that has the time and some knowledge of phasing-line design.

Raw Gain and SWR plots, using the two current sources:





DBGH-Hor GH20 Nec File



CM ************************************************************ *****************************
CM * 2nd Generation Gray-Hoverman UHF Antenna Design by Autofils (22Aug 08) *
CM * ============================================================ =========== *
CM * *
CM * GH20 Horizontal DBGH Collinear Rod reflectors *
CM * *
CM * Variable 'BS' is the distance between arrays (center to center) *
CM * Note : Min value of "BS' = 1.09 meters *
CM * *
CM ************************************************************ *****************************
CE
SY BS=1.35 'BS=center to center distance between arrays (meters)
GW 1 7 0 -0.0475 0 0 0.0475 0 2.8e-3
GW 2 17 0 0.0475 0 0 0.2105 0.163 3.5e-3
GW 3 17 0 0.2105 0.163 0 0.0475 0.326 3.5e-3
GW 4 17 0 0.0475 0.326 0 0.2105 0.489 3.5e-3
GW 5 7 0 0.2105 0.489 0 0.3045 0.489 3.5e-3
GW 6 17 0 0.0475 0 0 0.2105 -0.163 3.5e-3
GW 7 17 0 0.2105 -0.163 0 0.0475 -0.326 3.5e-3
GW 8 17 0 0.0475 -0.326 0 0.2105 -0.489 3.5e-3
GW 9 7 0 0.2105 -0.489 0 0.3045 -0.489 3.5e-3
GW 10 17 0 -0.0475 0 0 -0.2105 0.163 3.5e-3
GW 11 17 0 -0.2105 0.163 0 -0.0475 0.326 3.5e-3
GW 12 17 0 -0.0475 0.326 0 -0.2105 0.489 3.5e-3
GW 13 7 0 -0.2105 0.489 0 -0.3045 0.489 3.5e-3
GW 14 17 0 -0.0475 0 0 -0.2105 -0.163 3.5e-3
GW 15 17 0 -0.2105 -0.163 0 -0.0475 -0.326 3.5e-3
GW 16 17 0 -0.0475 -0.326 0 -0.2105 -0.489 3.5e-3
GW 17 7 0 -0.2105 -0.489 0 -0.3045 -0.489 3.5e-3
GW 18 17 -0.094 0.252 -0.7335 -0.094 0.025 -0.7335 3.5e-3
GW 19 17 -0.094 -0.252 -0.7335 -0.094 -0.025 -0.7335 3.5e-3
GW 22 28 -0.094 0.395 -0.5705 -0.094 0.025 -0.5705 3.5e-3
GW 23 28 -0.094 -0.395 -0.5705 -0.094 -0.025 -0.5705 3.5e-3
GW 30 37 -0.094 0.52 -0.4075 -0.094 0.025 -0.4075 3.5e-3
GW 31 37 -0.094 -0.52 -0.4075 -0.094 -0.025 -0.4075 3.5e-3
GW 38 20 -0.094 0.293 -0.2445 -0.094 0.025 -0.2445 3.5e-3
GW 39 20 -0.094 -0.293 -0.2445 -0.094 -0.025 -0.2445 3.5e-3
GW 46 29 -0.094 0.417 -0.0815 -0.094 0.025 -0.0815 3.5e-3
GW 47 29 -0.094 -0.417 -0.0815 -0.094 -0.025 -0.0815 3.5e-3
GW 52 29 -0.094 0.417 0.0815 -0.094 0.025 0.0815 3.5e-3
GW 53 29 -0.094 -0.417 0.0815 -0.094 -0.025 0.0815 3.5e-3
GW 60 17 -0.094 0.293 0.2445 -0.094 0.025 0.2445 3.5e-3
GW 61 17 -0.094 -0.293 0.2445 -0.094 -0.025 0.2445 3.5e-3
GW 68 28 -0.094 0.52 0.4075 -0.094 0.025 0.4075 3.5e-3
GW 69 28 -0.094 -0.52 0.4075 -0.094 -0.025 0.4075 3.5e-3
GW 76 37 -0.094 0.395 0.5705 -0.094 0.025 0.5705 3.5e-3
GW 77 37 -0.094 -0.395 0.5705 -0.094 -0.025 0.5705 3.5e-3
GW 80 20 -0.094 0.252 0.7335 -0.094 0.025 0.7335 3.5e-3
GW 81 20 -0.094 -0.252 0.7335 -0.094 -0.025 0.7335 3.5e-3
GW 82 7 0 -0.0475+BS 0 0 0.0475+BS 0 2.8e-3
GW 83 17 0 0.0475+BS 0 0 0.2105+BS 0.163 3.5e-3
GW 84 17 0 0.2105+BS 0.163 0 0.0475+BS 0.326 3.5e-3
GW 85 17 0 0.0475+BS 0.326 0 0.2105+BS 0.489 3.5e-3
GW 86 7 0 0.2105+BS 0.489 0 0.3045+BS 0.489 3.5e-3
GW 87 17 0 0.0475+BS 0 0 0.2105+BS -0.163 3.5e-3
GW 88 17 0 0.2105+BS -0.163 0 0.0475+BS -0.326 3.5e-3
GW 89 17 0 0.0475+BS -0.326 0 0.2105+BS -0.489 3.5e-3
GW 90 7 0 0.2105+BS -0.489 0 0.3045+BS -0.489 3.5e-3
GW 91 17 0 -0.0475+BS 0 0 -0.2105+BS 0.163 3.5e-3
GW 92 17 0 -0.2105+BS 0.163 0 -0.0475+BS 0.326 3.5e-3
GW 93 17 0 -0.0475+BS 0.326 0 -0.2105+BS 0.489 3.5e-3
GW 94 7 0 -0.2105+BS 0.489 0 -0.3045+BS 0.489 3.5e-3
GW 95 17 0 -0.0475+BS 0 0 -0.2105+BS -0.163 3.5e-3
GW 96 17 0 -0.2105+BS -0.163 0 -0.0475+BS -0.326 3.5e-3
GW 97 17 0 -0.0475+BS -0.326 0 -0.2105+BS -0.489 3.5e-3
GW 98 7 0 -0.2105+BS -0.489 0 -0.3045+BS -0.489 3.5e-3
GW 99 17 -0.094 0.252+BS -0.7335 -0.094 0.025+BS -0.7335 3.5e-3
GW 100 17 -0.094 -0.252+BS -0.7335 -0.094 -0.025+BS -0.7335 3.5e-3
GW 101 28 -0.094 0.395+BS -0.5705 -0.094 0.025+BS -0.5705 3.5e-3
GW 102 28 -0.094 -0.395+BS -0.5705 -0.094 -0.025+BS -0.5705 3.5e-3
GW 103 37 -0.094 0.52+BS -0.4075 -0.094 0.025+BS -0.4075 3.5e-3
GW 104 37 -0.094 -0.52+BS -0.4075 -0.094 -0.025+BS -0.4075 3.5e-3
GW 105 20 -0.094 0.293+BS -0.2445 -0.094 0.025+BS -0.2445 3.5e-3
GW 106 20 -0.094 -0.293+BS -0.2445 -0.094 -0.025+BS -0.2445 3.5e-3
GW 107 29 -0.094 0.417+BS -0.0815 -0.094 0.025+BS -0.0815 3.5e-3
GW 108 29 -0.094 -0.417+BS -0.0815 -0.094 -0.025+BS -0.0815 3.5e-3
GW 109 29 -0.094 0.417+BS 0.0815 -0.094 0.025+BS 0.0815 3.5e-3
GW 110 29 -0.094 -0.417+BS 0.0815 -0.094 -0.025+BS 0.0815 3.5e-3
GW 111 20 -0.094 0.293+BS 0.2445 -0.094 0.025+BS 0.2445 3.5e-3
GW 112 20 -0.094 -0.293+BS 0.2445 -0.094 -0.025+BS 0.2445 3.5e-3
GW 113 37 -0.094 0.52+BS 0.4075 -0.094 0.025+BS 0.4075 3.5e-3
GW 114 37 -0.094 -0.52+BS 0.4075 -0.094 -0.025+BS 0.4075 3.5e-3
GW 115 28 -0.094 0.395+BS 0.5705 -0.094 0.025+BS 0.5705 3.5e-3
GW 116 28 -0.094 -0.395+BS 0.5705 -0.094 -0.025+BS 0.5705 3.5e-3
GW 117 17 -0.094 0.252+BS 0.7335 -0.094 0.025+BS 0.7335 3.5e-3
GW 118 17 -0.094 -0.252+BS 0.7335 -0.094 -0.025+BS 0.7335 3.5e-3
GE 0
LD 5 0 0 0 24900000
GN -1
EK
EX 6 1 4 0 1 0
EX 6 82 4 00 1 0
FR 0 0 0 0 585 0
EN

[DTV Student]

Hi Folks,

mlord... I am totally impressed with your fabrication techniques. Your work is very professional looking. Way to go!!!

300ohm and autofils... I copied 300ohm's NEC file for the "Double Bay Gray Hoverman GH19 Parabola Kicker". I tried to do a frequency sweep of it and got a message from 4NEC2 that reminded me of something that autofils mentioned a few weeks ago, i.e. the need to be able to process more than 1500 antenna segments. The "Double Bay Gray Hoverman GH19 Parabola Kicker" had 1597 segments. I downloaded both sets of extensions for the 4NEC2 modeling software (Nec2dXS_FB.zip and Nec2dXS_VM.zip), unpacked them, copied only the nec2dxs3k0.exe from the FB set to my C:\4nec2\exe directory and re-ran the frequency sweep with no problems. For some time now, I have been having problems analyzing simple antennas with rectangular reflector grids for probably the very same reason. Grids really add a lot of segments. So, I often set up my grid to have say "20 Vertical X 1 Horizontal" sections and reduced the number of segements in each major element of the grid. That worked and it ran pretty fast, but being able to model with more than 1500 segments is helpful. Thanks autofils and 300ohm.

Oh yes... a few days ago, I looked at some earlier work posted by autofils on the second generation Gray Hoverman. It had to do with optimizing the antenna for the lower UHF frequencies. In my area there are digital tv channels that run the scale from actual channel 19 to 51. This a good opportunity to see if I can model a compromise to autofils' great work. So, I have been experimenting with modifying the dimensions of just the active driver portion of the Gray Hoverman antenna. I am thinking I can sort of zoom in on a good compromise for the driver assembly then add a reflector later.

I plan to keep the general shape of the Gray Hoveman antenna and to vary the length of the zig zag elements and the stubs. This is really a modeling problem, so I will move over to the "Modeling" thread to detail my little modeling experiment. Anybody interested in modeling, please take a look from time to time.

Your comments and suggestions are appreciated.

Thank you,
DTV Student

[300ohm]

In my area there are digital tv channels that run the scale from actual channel 19 to 51. This a good opportunity to see if I can model a compromise to autofils' great work.

Channels 19 to 51 ? Take a look at the DBGH Gen 1 gain graphs and youre just about there. All you would want to do is shift the curve to the left about 1 channel (6mhz). Increase the element lengths a little in the model from the original 7 inches, and add a hair to the stubs, while keeping the spacings (except for the feed gap, see the feed gap analysis) and the 90 degree and 135 degree angles the same. Then you may want to try putting my curved reflector behind it and bending the ends of the element corners out an inch forward. Have fun !


Actually IIRC, there is an even easier way to shift the curve 1 channel to the left on a DBGH. Just increase the feed point to feed point spacing between the two SBGH's an inch or two. But dont just take my word for it, model it !

[hungt1999]

I finally built this DBGH antenna using chickenwire as a reflector at the back. I live in Laval and installed this antenna in my attic.

Initially when I connected this antenna, almost all channels gave 0% reading on the signal meter. I was pretty discouraged until I accidentally loosen a connection, then I started to some channel coming in. I then started suspecting maybe the signal is too strong and saturated the tuner?

Is-that possible that too strong a signal can provide 0% reading on the TV signal meter? I am not using any amplifier of any kind on the set-up.

I then used a splitter and then some channels started coming in. I ended up using 3 splitters in a cascade configuration. Each split gives about 3.5 dB attenuation so my total attenuation is about 10.5 dB. I have now all the channels that I used to have with my 8-bay bowtie but the signal is not stable, I am experiencing frequent drop-out and freezing.

What is the best way of attenuating the signal? Should I go buy more of those splitters and keep cascading them?

[300ohm]

What is the best way of attenuating the signal? Should I go buy more of those splitters and keep cascading them?

Autofils posted a link to inexpensive attenuators only a couple of pages back. Cheaper and better than more splitters, heh.

I finally built this DBGH antenna using chickenwire as a reflector at the back.

An easy solution is to split your DoubleBayGrayHoverman into its original two halves, unless you meant SingleBayGrayHoverman ?

Using this approach and running the sweep optimizer at 610Mhz, the optimal BS spacing is 1.35 meters.

Autofils,
I thought you and mlord were most concerned with channel 23 (524-530mhz) ? Just using my rough guideline formula (not optimized, just black magic) of 2X the wavelength spacing distance (1.145 meters), I get 18.38 dbi RG versus 18.34 dbi RG at the 1.35 meter distance. Of couse, the top RG at 605mhz suffers going from 18.74 dbi down to 18.62 dbi, but thats one of the design trade-offs that sometimes has to be made. In other words, the choice is, do you want the highest possible gain overall even if it falls on a useless or strong station, or do you want the highest possible gain on the specific weak channel youre trying to get, heh.

Based on this value, the overall dimensions for the DBGH-Horizontal GH20 would be 94"w x 58"h.

1.145 knocks 8 inches off the width, another design consideration.

[Walter Dnes]

This may be a stupid question, but here goes... what happens if you take a single bay 4-reflector (SBGH4) and replace the 4 reflectors with a wide strip of aluminum foil? This would obviously be an indoors-only design.

[300ohm]

take a single bay 4-reflector (SBGH4) and replace the 4 reflectors with a wide strip of aluminum foil?

It would no longer be called a SBGH4, it would be a mesh reflector of infinite mesh. As such, the best reflector size would be about 44 inches by 60 inches with a 1 inch vertical gap between the right and left sides.

[Autofils]

Originally Posted by 300ohm

Autofils,
I thought you and mlord were most concerned with channel 23 (524-530mhz) ? Just using my rough guideline formula (not optimized, just black magic) of 2X the wavelength spacing distance (1.145 meters), I get 18.38 dbi RG versus 18.34 dbi RG at the 1.35 meter distance. Of couse, the top RG at 605mhz suffers going from 18.74 dbi down to 18.62 dbi, but thats one of the design trade-offs that sometimes has to be made. In other words, the choice is, do you want the highest possible gain overall even if it falls on a useless or strong station, or do you want the highest possible gain on the specific weak channel youre trying to get, heh.


1.145 knocks 8 inches off the width, another design consideration.

300ohm,

The GH10 was originally designed for our local desire to receive OTA digital channels 23 and 38 from upper NY state, and indeed the model results show high gain for those channels with a SBGH GH10.

MLord has made two GH10's and was looking for guidance on spacing between two GH10's in a horizontal config, so I put together the DBGH-Hor GH20 model to provide that guidance. Since I don't have much free time to complete the DBGH-Hor GH20 design with a phasing-line, I also posted this GH20 DBGH model which could be used for phasing-line investigations by other modelers. It was also an opportunity for me to provide another of my "mini- 4nec2 tutorials" ...optimizer functions in 4nec2.

This GH20 model allows running 4nec2 sweep optimizer for variations in the Bay-Spacing (BS) parameter.

When I run the sweep optimizer on this GH20 model for 527Mhz (Ch23) and
617 (Ch38), the max RawGain/ min SWR occurs at:

=================================================
Freq ....... BS ..............RawGain (dBi) ................. SWR
=================================================

527 ........ 1.38m ............ 18.61 ....................... 1.1673
617 .........1.35m ............ 18.66 ....................... 1.5115

=================================================

Here is a capture of the 4nec2 Sweep optimizer results for BS over the range 1.2 to 1.5(m) for 527Mhz.

SweepOpt Results for BS at 527Mhz




If you haven't yet used the optimizer function, give it a try.
It is a very POWERFUL tool !!
All you need to run the optimizer is to model the variable that you wish to optimize in a SY card.

300ohm:
I'd really appreciate if you could take my DBGH GH20 model and add your "best phasing-line design" for Ch 23/38.... thanks

[DTV Student]

Hi Folks,

300ohm recently posted:

Last night I stumbled upon by accident a little known/unintended feature of 4nec2 that makes it very useful for importing data into a spreadsheet. The feature is really designed/intended for the wGNUplot program, but the exported data it produces works fine for other programs too. Once the data is into a spreadsheet, the amount of calculation and graphing that can be done on it is endless, heh.

After running the frequency sweep as normal, the gain, swr and impedence charts are produced. There is an option of plot then available on that screen. Click on it and choose what you want outputted to a plot file. Since I dont have wGNUplot.exe installed, it gives an error message, but it still creates a text file called plot.txt. It lies about where it exports the plot.txt file in the message, the actual file is in the C:\4nec2\plot directory. This must be renamed before running another plot option or it will be over-written with the new data. A simple copy and paste from the plot.txt file to my Open Office Calc spreadsheet program formats the data as pretty as you please, complete with column headings, heh. Should work just as fine in MS Excel or any other spreadsheet program. This feature is very very useful and saves many hours for calculating net gain if you have a lot of frequencies to deal with.

Yeah!!!

I was wondering how I was going to easily plot the frequency vs. total gain curves for the many families of Hoverman Driver Arrays I will be comparing in the "Modeling Software" thread. The information you provided above will save me many hours of manual data entry into an Excel spreadsheet.

300ohm... Thanks for posting this little off the wall item.

Your suggestions and comments are always appreciated,
DTV Student

[jdogmoney]

DTV Student, I'm interested to see what you come up with for the 19-51 range. Are you leaning toward a single or double bay version? I am also looking to cover that range. 300ohm is right in that the gen1 dbgh is about a perfect fit with it's versatile freq range. Also, let's all don't get carried away and think we need a gain in the teens to get good reception. I mean, if you have -100 dbm stations on the low & high end then sure, you'll need high gain. But I've found a gain under 10dbi is plenty sufficient for a -75dbm station.

[stampeder]

Originally Posted by hungt1999

What is the best way of attenuating the signal?

You can buy attenuators where you are in Montreal from Raybel, Addison, or The Source and they are not expensive. They are barrel type, so you just unscrew the coax going into your TV set and put one inline (you'll need a very short length of coax or an adapter to patch it inline).

Also there are variable attenuators on the market that allow you to dial up the perfect amount. You can read about Attenuators in this thread:

http://www.digitalhome.ca/forum/showthread.php?t=42428

[jdogmoney]

Well, I went up on the rooftop today (about 30ft above ground) to try out the ol' sbgh10 at a higher place for a better chance to pick up channels 17 & 18. I got nada. No signal at all, which is what I've always got in the afternoon. So I guess tvfool is right in that I won't see much difference in signal strength unless I install a 230ft tower! Oh, well I doubt I'll try the double bay version for another 2db, since I'm thinking there are bigger factors keeping me from getting those channels.

I'm just interested to know if anyone else is trying to get a channel with similar obstacles as me. Just throw the dbm rating out the window for a moment and look at the other factors, mine are:
1) 230 ft below LOS
2) 91 mi away
3) two-edge path

So I'm basically going to give up on trying to get the Roanoke channels and focus on shoring up the Raleigh stations which are easier to get (roughly the same dbm though) The main ones I want are on the high 600's. So I'm trying to decide whether I should go 2nd gen scaled to 690mhz or 1st gen dbgh.

[300ohm]

mine are:
1) 230 ft below LOS
2) 91 mi away
3) two-edge path

When TVFool says "edge path" they mean youre catching the signal on the bounce. Unfortunately for you, those signals are probably bouncing way over your antenna during the day and no amount of gangs of high gain antenna arrays is going to catch it, unless your mast is way, way higher.

The GH10 was originally designed for our local desire to receive OTA digital channels 23 and 38 from upper NY state, and indeed the model results show high gain for those channels with a SBGH GH10.

So I take it you dont mind giving up a few 10ths of a db on channel 23 for overall max gain at about channel 36 ? So Ill use the 1.35m figure in modeling. Unlike vertical phasing lines, length may make a bigger difference in horizonl ones.

300ohm:
I'd really appreciate if you could take my DBGH GH20 model and add your "best phasing-line design" for Ch 23/38.... thanks

Yeah, thats going to take some time. The horizontal phasing lines dont behave like the vertical ones. (Ive heard that before, heh.) Most likely since because they are horizontal, they are picking up signal and distorting everything. Ive run thru a few tests and the best Ive gotten so far is only 17.27dbi RG tops, which means youre better off with the baluns for now. Or try a coax phasing harness. Velocity Factor of RG6 coax is .75. Google for "Dr Ace's How to Build a Home Brew Coax Harness for Co-Phasing And/Or Stacking Two Antennas"

I going to have to try some radical ideas, but that takes time.

It is a very POWERFUL tool !!

Yep, I used it to refine my black magic spacing formula to : 2X wavelength minus .02 wavelength, heh. I had a feeling it was something like that. (1.12 meters is the best RG spacing for channel 23, at least in terms of compact size unless going out to 1.55 meters) Have you noticed that the Geometry (F3) radiation pattern changes while the sweep is running ? Awesome.