GH with NARODs for VHF-HI & UHF

[tvmonkey]

Im a bit confused. Which plans are the best to use? I am looking at this thread, but see 2-3 different kinds of antennas posted in the pictures. I like the look of the curved antenna, is this a good one?

http://www.digitalhome.ca/forum/showthread.php?t=95898

[PoppaDigital]

I thought the Oroginsl DBGH had only 1 set of coliner reflectors at the stack joint insread of the 2 shown, 11 pair total. I 've got an unfinished carboard & coathanger project with 11 pair in place that I plan to convert.

[Cottager]

What would happen if you ganged two SBGHs horizontally with the mesh reflectors touching? Would it result in any VHF-high gain? What would happen to UHF gain?

I am asking since this is how the CM4228 achieves VHF-high gain.

The following is a quote from HDTVprimer:
"This antenna (CM4228) is advertised solely as a UHF antenna. But, as many people have discovered, it has strong gain for VHF-high, especially channel 9-13. What gives it this ability is the continuous screen. Other 8-bays have a reflector that is not continuous across the right and left halves. Those antennas have little usefulness for VHF channels.
The continuous screen is not simply a reflector for these channels, but rather it becomes the primary radiating element. As a result, radiation out the back is very strong, nearly bi-directional for some channels."

If there is the possibily of VHF-high gain, is anyone interested in modelling it?

[300ohm]

What would happen if you ganged two SBGHs horizontally with the mesh reflectors touching? Would it result in any VHF-high gain? What would happen to UHF gain?

I am asking since this is how the CM4228 achieves VHF-high gain.

Nope, the GH behaves differently than the bowties. The NARODs are the only way found so far to give positive VHF-Hi net gain.

[holl_ands]

Using 4nec2, I calculated performance charts for 300ohm's DBGH (with 28 NARODs):
http://imageevent.com/holl_ands/grayhoverman

I used the Combo Hi-VHF & UHF capability to investigate what happens if insulated
AWG10 wire is used instead of Bare wire....it wasn't very pretty....(NARODS were left Bare).

FYI: In NEC, fol. Loading card adds 24 mil PVC coating on top of AWG10 for each GW#:
LD 7 GW# 0 0 4.5 0.075
Repeat as necessary for all affected wires....

[mlord]

Originally Posted by PoppaDigital

I thought the Oroginsl DBGH had only 1 set of coliner reflectors at the stack joint insread of the 2 shown, 11 pair total.

That is correct. The link tvmonkey posted does not show an original DBGH.

-ml

[300ohm]

holl_ands,

I need to clarify my terminology for you. The NARODS are only the 4 wires directly above the stubs. (I have them split into 2 pieces each on the model to investate the effects of slanting them). The term NAROD stands for Not A Reflector Or Director. I coined the term because I dont know what else to call them. NARODS are interesting little animals. They are having some kind of a drastic capacitance or current effect on the GH driven elements.

The rest of the wires are reflectors or driven elements. (the wires 10 or so inches behind the NARODs could be called NAROD reflectors). So in the model you link to, there are only 4 NARODs and 4 NAROD reflectors, installed on DBGH gen 1 co-linear rod 12 pair model.

The vhf-hi bandwidth is narrow, hence the need for 3 different models. And if youll notice, the max vhf-hi forward gain can flip direction 180 degrees on some of the off channels.

From my actual builds in the past (other designs) Ive always noticed that bare wire performs better, so Im not surprised by your results. Bare wire also gives the antenna more of an antenna look, instead of a bunch of (different colored in my case) house wire thrown together, heh.

[Xauto]

I have added vertical wires (alligator clips with 18 gauge) to NARODS (29.5"). This makes a loop around the driven element. It seems to reduce analog ghosts on the weak Ch. (NM -8). I'm running gen. 2 GH fractal with Al.-foil reflector (15") and NARODS reflectors at 11.5" spacing.

[d510d180]

holl_hands, you wrote:
LD 7 GW# 0 0 4.5 0.075

Is your nec file mistakenly back in meters?
See the GS instruction, if you have any.
The nec files of 300ohms earlier are in inches and show a GS scale of 0.0254.

I set a DB4 model to add the
LD 7 0 0 0 4.5 0.075
(GW# of 0 means all wires)
and when I clicked on a wire, the popup box showed me I had 75mm of coating!

So be sure you have the right units.
In a metric file, (no GS scale), I have
LD 7 0 0 0 4.5 0.001905

that is 1.905 mm outer radius.
The simulation show no noticeable change. Coating has no visible effect.
Sorry.

[300ohm]

The simulation show no noticeable change. Coating has no visible effect.

Im still gonna use bare wire, heh.

[300ohm]

have added vertical wires (alligator clips with 18 gauge) to NARODS (29.5"). This makes a loop around the driven element. It seems to reduce analog ghosts on the weak Ch. (NM -8). I'm running gen. 2 GH fractal with Al.-foil reflector (15") and NARODS reflectors at 11.5" spacing.

Quick modeling shows that should give you about .25 to 1.5 dBi less gain with a higher SWR, so net gain would be even less. I didnt see hardly any change in the radiation pattern either, so I cant explain less ghosts. Ghosts are tricky and can be caused by many things, even the placement of the coax and balun.

[Xauto]

Thanks for the quick modeling. I just cann't get the kid out of me. On weak analog I just have to play. Have not add Al.-foil banners to the stub yet!

[holl_ands]

Originally Posted by d510d180

holl_hands, you wrote:
LD 7 GW# 0 0 4.5 0.075

Is your nec file mistakenly back in meters?
See the GS instruction, if you have any.
The nec files of 300ohms earlier are in inches and show a GS scale of 0.0254.

I set a DB4 model to add the
LD 7 0 0 0 4.5 0.075
(GW# of 0 means all wires)
and when I clicked on a wire, the popup box showed me I had 75mm of coating!

So be sure you have the right units.
In a metric file, (no GS scale), I have
LD 7 0 0 0 4.5 0.001905

that is 1.905 mm outer radius.
The simulation show no noticeable change. Coating has no visible effect.
Sorry.

Thanks for pointing out my error....that's the second time I've fallen into the "GS Trap".
Anything BELOW the GS Card has to be in meters. And GS Card doesn't directly apply to SY Cards...

I updated all of the UHF and Hi-VHF runs:
http://imageevent.com/holl_ands/grayhoverman

Adding 45mil PVC insulation coating (e.g. THW AWG10 house wire), caused significant
impact above Ch47 to both Raw Gain and additional Net Gain Loss due to increasing SWR.

I was surprised to see impacts to Ch7 and adjacent out-of-band region.
Although it did not adversely impact the DBGH design, it could impact other designs.

[holl_ands]

Here's the 4nec2 file for Insulated AWG10 in DBGH with 28 (Bare) Reflector RODS:
[I was also tempted to round off excessive precision...cuz it clutters up the listing.]
[I hope 300ohm is happy with "Reflector RODS" instead of "NARODS".....]
[So are GW42-49 crosswires the "NARODS"???]

CM Hi-VHF & UHF Gray-Hoverman with 28 Reflector RODs - EZNEC by 300ohm on 16Jan2009
CM Insulation on ALL AWG10 Wires (Vert. Zig-Zags & Feedline). Renumbered GWs. - 31Jan2009
CM To apply to ONLY Vertical Zig-Zags, comment out "LD 7" Card on GW33-49 - by holl_ands
CE
SY Rwire=0.05094856 ' Wire radius (in inches) for vertical Zig-Zags
SY Rwtoo=0.0511811 ' Wire radius (in inches) for Top_Mid_Mid_Bottom Crosswires
SY Rod=0.1875 ' Wire radius (in inches) for Rear and Middle Reflector RODs
' Two Vertical Zig-Zags
GW 1 15 0 1.73228346 0 0 6.73228346 5 Rwire
GW 2 15 0 1.73228346 10 0 6.73228346 5 Rwire
GW 3 15 0 1.73228346 10 0 6.73228346 15 Rwire
GW 4 15 0 -1.7322835 0 0 -6.7322835 5 Rwire
GW 5 15 0 -1.7322835 10 0 -6.7322835 5 Rwire
GW 6 15 0 -1.7322835 10 0 -6.7322835 15 Rwire
GW 7 15 0 1.73228346 0 0 6.73228346 -5 Rwire
GW 8 15 0 1.73228346 -10 0 6.73228346 -5 Rwire
GW 9 15 0 1.73228346 -10 0 6.73228346 -15 Rwire
GW 10 15 0 -1.7322835 0 0 -6.7322835 -5 Rwire
GW 11 15 0 -1.7322835 -10 0 -6.7322835 -5 Rwire
GW 12 15 0 -1.7322835 -10 0 -6.7322835 -15 Rwire
GW 13 15 0 1.73228346 35 0 6.73228346 40 Rwire
GW 14 15 0 1.73228346 45 0 6.73228346 40 Rwire
GW 15 15 0 1.73228346 45 0 6.73228346 50 Rwire
GW 16 15 0 -1.7322835 35 0 -6.7322835 40 Rwire
GW 17 15 0 -1.7322835 45 0 -6.7322835 40 Rwire
GW 18 15 0 -1.7322835 45 0 -6.7322835 50 Rwire
GW 19 15 0 1.73228346 35 0 6.73228346 30 Rwire
GW 20 15 0 1.73228346 25 0 6.73228346 30 Rwire
GW 21 15 0 1.73228346 25 0 6.73228346 20 Rwire
GW 22 15 0 -1.7322835 35 0 -6.7322835 30 Rwire
GW 23 15 0 -1.7322835 25 0 -6.7322835 30 Rwire
GW 24 15 0 -1.7322835 25 0 -6.7322835 20 Rwire
' Spurs off the Vertical Zig-Zags
GW 25 13 0 6.73228346 15 0 12.3228346 15 Rwire
GW 26 13 0 -6.7322835 15 0 -12.322835 15 Rwire
GW 27 13 0 6.73228346 -15 0 12.3228346 -15 Rwire
GW 28 13 0 -6.7322835 -15 0 -12.322835 -15 Rwire
GW 29 13 0 6.73228346 50 0 12.3228346 50 Rwire
GW 30 13 0 -6.7322835 50 0 -12.322835 50 Rwire
GW 31 13 0 6.73228346 20 0 12.3228346 20 Rwire
GW 32 13 0 -6.7322835 20 0 -12.322835 20 Rwire
' Feedline and Simulated SOURCE (GW41)
GW 33 1 0 1.73228346 35 1 1 35 Rwire
GW 34 1 0 -1.7322835 35 1 -1 35 Rwire
GW 35 1 0 -1.7322835 0 1 -1 0 Rwire
GW 36 1 0 1.73228346 0 1 1 0 Rwire
GW 37 15 1 -1 35 1 -1 17.5 Rwire
GW 38 15 1 1 35 1 1 17.5 Rwire
GW 39 15 1 -1 0 1 -1 17.5 Rwire
GW 40 15 1 1 0 1 1 17.5 Rwire
GW 41 3 1 -1 17.5 1 1 17.5 Rwire
' Top, Mid, Mid & Bottom Crosswires
GW 42 13 0 -15.125 15.5 0 0 15.5 Rwtoo
GW 43 13 0 0 15.5 0 15.125 15.5 Rwtoo
GW 44 13 0 -15.125 -15.5 0 0 -15.5 Rwtoo
GW 45 13 0 0 -15.5 0 15.125 -15.5 Rwtoo
GW 46 13 0 -15.125 50.5 0 0 50.5 Rwtoo
GW 47 13 0 0 50.5 0 15.125 50.5 Rwtoo
GW 48 13 0 -15.125 19.5 0 0 19.5 Rwtoo
GW 49 13 0 0 19.5 0 15.125 19.5 Rwtoo
' 28 Rear and Middle Reflector RODS (3/8-inch O.D.)
GW 50 25 -4.1338583 -0.3937008 15 -4.1338583 -12.440945 15 Rod
GW 51 25 -4.1338583 0.39370079 15 -4.1338583 12.4409449 15 Rod
GW 52 25 -4.1338583 0.39370079 -15 -4.1338583 12.4409449 -15 Rod
GW 53 25 -4.1338583 -0.3937008 -15 -4.1338583 -12.440945 -15 Rod
GW 54 25 -4.1338583 0.39370079 2.5 -4.1338583 12.007874 2.5 Rod
GW 55 25 -4.1338583 -0.3937008 2.5 -4.1338583 -12.007874 2.5 Rod
GW 56 25 -4.1338583 0.39370079 7.5 -4.1338583 12.4409449 7.5 Rod
GW 57 25 -4.1338583 -0.3937008 7.5 -4.1338583 -12.440945 7.5 Rod
GW 58 25 -4.1338583 0.39370079 -2.5 -4.1338583 12.007874 -2.5 Rod
GW 59 25 -4.1338583 -0.3937008 -2.5 -4.1338583 -12.007874 -2.5 Rod
GW 60 25 -4.1338583 0.39370079 -7.5 -4.1338583 12.4409449 -7.5 Rod
GW 61 25 -4.1338583 -0.3937008 -7.5 -4.1338583 -12.440945 -7.5 Rod
GW 62 25 -11.5 15.125 15.5 -11.5 -15.125 15.5 Rod
GW 63 25 -11.5 15.125 -15.5 -11.5 -15.125 -15.5 Rod
GW 64 25 -4.1338583 -0.3937008 50 -4.1338583 -12.440945 50 Rod
GW 65 25 -4.1338583 0.39370079 50 -4.1338583 12.4409449 50 Rod
GW 66 25 -4.1338583 0.39370079 20 -4.1338583 12.4409449 20 Rod
GW 67 25 -4.1338583 -0.3937008 20 -4.1338583 -12.440945 20 Rod
GW 68 25 -4.1338583 0.39370079 37.5 -4.1338583 12.007874 37.5 Rod
GW 69 25 -4.1338583 -0.3937008 37.5 -4.1338583 -12.007874 37.5 Rod
GW 70 25 -4.1338583 0.39370079 42.5 -4.1338583 12.4409449 42.5 Rod
GW 71 25 -4.1338583 -0.3937008 42.5 -4.1338583 -12.440945 42.5 Rod
GW 72 25 -4.1338583 0.39370079 32.5 -4.1338583 12.007874 32.5 Rod
GW 73 25 -4.1338583 -0.3937008 32.5 -4.1338583 -12.007874 32.5 Rod
GW 74 25 -4.1338583 0.39370079 27.5 -4.1338583 12.4409449 27.5 Rod
GW 75 25 -4.1338583 -0.3937008 27.5 -4.1338583 -12.440945 27.5 Rod
GW 76 25 -11.5 15.125 50.5 -11.5 -15.125 50.5 Rod
GW 77 25 -11.5 15.125 19.5 -11.5 -15.125 19.5 Rod
GS 0 0 0.0254 ' All in inches
GE 0
EK 0
LD 7 1 0 0 4.5 0.00248 ' Applies 45 mil Dielectric Coating to all AWG10 wires
LD 7 2 0 0 4.5 0.00248
LD 7 3 0 0 4.5 0.00248
LD 7 4 0 0 4.5 0.00248
LD 7 5 0 0 4.5 0.00248
LD 7 6 0 0 4.5 0.00248
LD 7 7 0 0 4.5 0.00248
LD 7 8 0 0 4.5 0.00248
LD 7 9 0 0 4.5 0.00248
LD 7 10 0 0 4.5 0.00248
LD 7 11 0 0 4.5 0.00248
LD 7 12 0 0 4.5 0.00248
LD 7 13 0 0 4.5 0.00248
LD 7 14 0 0 4.5 0.00248
LD 7 15 0 0 4.5 0.00248
LD 7 16 0 0 4.5 0.00248
LD 7 17 0 0 4.5 0.00248
LD 7 18 0 0 4.5 0.00248
LD 7 19 0 0 4.5 0.00248
LD 7 20 0 0 4.5 0.00248
LD 7 21 0 0 4.5 0.00248
LD 7 22 0 0 4.5 0.00248
LD 7 23 0 0 4.5 0.00248
LD 7 24 0 0 4.5 0.00248
LD 7 25 0 0 4.5 0.00248
LD 7 26 0 0 4.5 0.00248
LD 7 27 0 0 4.5 0.00248
LD 7 28 0 0 4.5 0.00248
LD 7 29 0 0 4.5 0.00248
LD 7 30 0 0 4.5 0.00248
LD 7 31 0 0 4.5 0.00248
LD 7 32 0 0 4.5 0.00248
LD 7 33 0 0 4.5 0.00248 ' For Vertical Zig-Zags (only), comment out "LD 7" for GW 33-49
LD 7 34 0 0 4.5 0.00248
LD 7 35 0 0 4.5 0.00248
LD 7 36 0 0 4.5 0.00248
LD 7 37 0 0 4.5 0.00248
LD 7 38 0 0 4.5 0.00248
LD 7 39 0 0 4.5 0.00248
LD 7 40 0 0 4.5 0.00248
LD 7 41 0 0 4.5 0.00248
LD 7 42 0 0 4.5 0.00248
LD 7 43 0 0 4.5 0.00248
LD 7 44 0 0 4.5 0.00248
LD 7 45 0 0 4.5 0.00248
LD 7 46 0 0 4.5 0.00248
LD 7 47 0 0 4.5 0.00248
LD 7 48 0 0 4.5 0.00248
LD 7 49 0 0 4.5 0.00248
EX 0 41 2 00 1 0 ' holl_ands mod: "00" needed by 4nec2
GN -1
' FR 0 56 0 0 473 6 ' Freq Sweep UHF Band from 473-803 MHz
FR 0 37 0 0 168 1.5 ' Freq Sweep Hi-VHF Band from 168-222 MHz
' RP 0 1 10 1510 90. 0. 0. 20. 0. 0. 'Fm 300ohm
RP 0 1 73 1510 90. 0. 1. 5. 0. 0. ' Fm holl_ands
EN ' holl_ands mod: End Card needed by 4nec2

[d510d180]

Adding 45mil PVC insulation coating (e.g. THW AWG10 house wire), caused significant impact above Ch47 to both Raw Gain and additional Net Gain Loss due to increasing SWR.

I was surprised to see impacts to Ch7 and adjacent out-of-band region.
Although it did not adversely impact the DBGH design, it could impact other designs.

I am not quiet sure why you put 45 mil of PVC on gauge 10; it certainly is not that thick. The gauge 12 is likely correct at 27 mil, but the 10 gauge I have here is berely thicker, but not twice. Nevertheless, even with exagerated thickness of 47 mil of coating of 4.5 relative dielectric constant, I tested your nec file with and without the wire insulation (the only diff between the 2 simulations is that I deleted the LD 7 line, as expected).

I observe a shift to the left of the spectrum response, as expected since the coating does reduce the velocity factor and thus virtually make the wires longer, therefore suitable for lower frequencies.

I did a frequency sweep, from 48MHz to 900MHz by steps of 12 MHz, on the frontal gain (elevation 0, azimuth 90). The non uhf bands already sensitive to marginal antenna attributes are changing the most. The UHF band is pretty similar though.

If the simulations were not taking so long on my crawling PC, would test with 34 mil of coating. Given the DB4 simulation with 27 mil of coating didn't show any noticeable diff, that 2 design in 2 that are not largely influenced by wire coating. See results on
AVS Forum > HDTV > HDTV Technical > How to build a UHF antenna... , Post 1556.

(sorry for lack of url, can't post images or link here...somehow).