"Top Hat" GH with NARODs for VHF-HI: Major GH Improvement
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Nice job Pelo1968, I'm in an apartment too but have an overhang preventing a similar set up, I've got a GH10 that rocks but I'm planning an FF8 build for spring, will post pics once done.
I also have to cleae the balcony roof. If yoi look closely you will see the antenna is hagging at the end on an horisontal pole, it's 4 feet long. There is also a crossbar the antanna is tied to either and of the crossbar from the botton with strings. As tge stibgs are diagonal the keep the antenna from wobling in the wind.
how to handle distance lost to bending radius
I know I've read this somewhere but I can't find the relevant posts now. I built the element from the gh10 with the 1/4 6061 aluminum (which, by the way you can straighten after bending but that is another story). I bent it using the 2 to 3 x diameter bend radius. This means that the corners of the bends end up slightly short of the model, which uses a right angle. This means that if you use the feed point gap in the model the elements actually end up narrower.
I found that I didn't receive the station at channel 14 which I expected to, which I'm wondering is as a result of the altered geometry vs the model. Can anyone provide a way of determining the effect of the difference vs model?.
I know I've read this somewhere but I can't find the relevant posts now. I built the element from the gh10 with the 1/4 6061 aluminum (which, by the way you can straighten after bending but that is another story). I bent it using the 2 to 3 x diameter bend radius. This means that the corners of the bends end up slightly short of the model, which uses a right angle. This means that if you use the feed point gap in the model the elements actually end up narrower.
I found that I didn't receive the station at channel 14 which I expected to, which I'm wondering is as a result of the altered geometry vs the model. Can anyone provide a way of determining the effect of the difference vs model?.
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788 Posts
If you are talking about differences of 6 mm or so in the driven element I wouldn't worry about it based on my real experience with a GH10. The dimensions that can really ruin reception are the distances between reflector rods and the gap between tophat and driven element.
P.S. RF14, WUTV is very problematic for a lot of Torontonians for many reasons, Co-channel interference from rf 15 in Hamilton (CHCH) and the radiation pattern WUTV uses.
http://www.rabbitears.info/pattern.php?request=ant_pat&ant_id=76608&rotation=0&erp=1000
P.S. RF14, WUTV is very problematic for a lot of Torontonians for many reasons, Co-channel interference from rf 15 in Hamilton (CHCH) and the radiation pattern WUTV uses.
http://www.rabbitears.info/pattern.php?request=ant_pat&ant_id=76608&rotation=0&erp=1000
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504 Posts
Nice addition nikiml with the tophats. Strong front and rear VHF. Nicely done.
Depends on which of several DOZEN versions you're looking for. This particular thread started with the DBG10 and DBG10n adds "NARODS" to improve Hi-VHF Band coverage. Click on desired model and it will show you an interactive Model:
nikiml's Antenna pages - DBGH for UHF
nikiml's Antenna pages - GH with tilt hat NARODs for UHF/VHF-hi
The "latest" DBGH16n is found in nikiml's Post #924 by clicking on "here":
http://clients.teksavvy.com/~nickm/dbgh_n_uV/dbgh16n.html
nikiml's Antenna pages - DBGH for UHF
nikiml's Antenna pages - GH with tilt hat NARODs for UHF/VHF-hi
The "latest" DBGH16n is found in nikiml's Post #924 by clicking on "here":
http://clients.teksavvy.com/~nickm/dbgh_n_uV/dbgh16n.html
You should post your tvfool report to get better recommendations.
to add another link to holl_ands's :
nikiml's Antenna pages - GH with NARODs and 3 NAROD reflectors for UHF/VHF-hi
to add another link to holl_ands's :
nikiml's Antenna pages - GH with NARODs and 3 NAROD reflectors for UHF/VHF-hi
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504 Posts
And a DBGH16n is also up there. Somebody has been busy.
It's been ages since I was on the site to get help with my CM4228. Good grief, so much has happened !
I'm finally fed up with trying to attenuate the signals from the CN tower and Hamilton exactly at the CM4228 side lobes which often drown out the signals from Buffalo/Jamestown.
After a quick look at the past year or 5, I'd like to build a Gray-Hoverman because it appears that the reception pattern might be superior to the CM4228 for my needs.
TVFOOL: TV Fool
Postal Code M6R2C5, 35' above ground level
I've read the "info for DIYers" and the "Introduction to the Gray-Hoverman" but I'm more confused as I read more
Questions:
- it seems that the older versions of the GH used a grid reflector of various forms but the more recent versions all use rod reflectors. To make the project simpler, are there any "current" designs that use a "solid" reflector?
- with my limited technical knowledge, I think the whole essence of the active element(s) is to be the length that would resonate centered within the desired frequency range. When bending the zigzag, is the length of each "zig" more important than the tip to tip length ?
I've just got back to antenna stuff.... be gentle.
I'm finally fed up with trying to attenuate the signals from the CN tower and Hamilton exactly at the CM4228 side lobes which often drown out the signals from Buffalo/Jamestown.
After a quick look at the past year or 5, I'd like to build a Gray-Hoverman because it appears that the reception pattern might be superior to the CM4228 for my needs.
TVFOOL: TV Fool
Postal Code M6R2C5, 35' above ground level
I've read the "info for DIYers" and the "Introduction to the Gray-Hoverman" but I'm more confused as I read more
Questions:
- it seems that the older versions of the GH used a grid reflector of various forms but the more recent versions all use rod reflectors. To make the project simpler, are there any "current" designs that use a "solid" reflector?
- with my limited technical knowledge, I think the whole essence of the active element(s) is to be the length that would resonate centered within the desired frequency range. When bending the zigzag, is the length of each "zig" more important than the tip to tip length ?
I've just got back to antenna stuff.... be gentle.
I modeled a bunch of nikiml's GH* elements with "chicken wire" reflectors. They all worked remarkably well. The only drawback is that using reflector rods reshapes the gain curve to make it flatter and more even across the range of frequencies while using a screen doesn't allow for that so the gain curve looks more like the originals.
I've also modeled building I.e. a gh10 and only putting in 4,6,8 reflectors. That works quite well too, so you could build simple to start and add rods if necessary. I don't have the models at hand but I could dig them out if necessary.
I've also modeled building I.e. a gh10 and only putting in 4,6,8 reflectors. That works quite well too, so you could build simple to start and add rods if necessary. I don't have the models at hand but I could dig them out if necessary.
Tried optimizing GH6n3 for the repacked UHF/VHF frequencies.
Below are the html view and the nec code for the result.
html view
Below are the html view and the nec code for the result.
html view
Code:
CM GH6n3 optimized by nikiml
CM UHF net gain 14.2dbi VHF-hi net gain 9.85
CM covered by GPL v3 or later (http://www.gnu.org/licenses/gpl.txt)
CM see http://www.digitalhome.ca/forum/showpost.php?p=907404&postcount=2
CMD--OPT -s(470,6,24) -t(14.2,14.4) -s(174,6,8) -t(9.5,9) -n4 -a10 -r restart.log -L
CMD--OPT -F .2*ave_max_gain_diff+.8*ave_gain_diff
CMD--EVAL -s(174,6,8) -s(470,6,24) -a10
CM
CM Score -0.397421
CE
SY radius=0.003175
SY narod_surf_spacing=0.006
SY narod_spacing=0.012
SY feed=0.03776106' 0.02, 0.07
SY b=0.121252' 0.075, 0.25
SY a1=0.1945679' 0.07, 0.22
SY _G3=0.06374546' 0.006, 0.1
SY a2=a1+feed-_G3'this is to avoid self intersection since _G3 is to be > radius+2.5mm
SY a3=0.1321573' 0.07, 0.22
SY x=-0.07477662' -0.1, -0.06
SY g1=0.04301694' 0.002, 0.045
SY g2=0.04430498' 0.002, 0.045
SY g3=0.006236525' 0.002, 0.045
SY l1=0.3144561' 0.1, 0.6
SY l2=0.4490271' 0.1, 0.65
SY l3=0.5567192' 0.1, 0.65
SY n_h=0.08642624' 0.05, 0.14
SY n_f_dx=0
SY n_top_dy=-0.03529455' -0.06, 0.04
SY n_b_taper=0.0445677' 0, 0.1
SY n_top=_G3+a3+n_top_dy- n_b_taper/2'hat head size
SY n_f=x + n_f_dx'so the hat does not tilt behind the reflectors
SY narod_top = a1+a2+a3+narod_spacing+n_h'want to put 3 reflectors between z=very_small and z=narod_top +/- very_small, 1 reflectors around narod_top and 1 above it
SY dz3=0.1409803' 0.017, 0.15
SY above_below=-1
SY sign = abs(above_below)/above_below' may fail at 0
SY z3 = sign*dz3+narod_top
SY dz = z3/5
SY dz1=1.72834' 0.2, 2
SY z1 = (1+(dz1-1))*dz
SY dz2=1.733665' 0.2, 2
SY z2 = (3+(dz2-1))*dz
SY ay1=feed+a1
SY ay2=feed+a1-a2
SY ay3=feed+a1-a2+a3
SY ay4=feed+a1-a2+a3+b
SY az2=a1+a2
SY az3=a1+a2+a3
SY n_b_z=az3+narod_spacing
SY n_b_y1=n_top+n_b_taper
SY n_b_y2=n_b_y1+b
SY n_z_coef=0.7314852' 0.5, 1.4
SY n_zsz=0.4049281' 0.3, 0.55
SY n_0sz=0.4701482' 0.3, 0.6
SY n_x_diff=0.2752484' 0.15, 0.4
SY n_x = x-n_x_diff
SY n_z = narod_top*n_z_coef
GW 1 15 0 feed 0 0 ay1 a1 radius'#00f
GW 2 13 0 ay1 a1 0 ay2 az2 radius'#00f
GW 3 9 0 ay2 az2 0 ay3 az3 radius'#00f
GW 4 7 0 ay3 az3 0 ay4 az3 radius'#00f
GW 5 17 x g1 z1 x l1+g1 z1 radius'#0f0
GW 6 23 x g2 z2 x l2+g2 z2 radius'#0f0
GW 7 29 x g3 z3 x l3+g3 z3 radius'#0f0
GW 11 7 n_f n_top n_b_z+n_h 0 n_b_y1 n_b_z radius'#000
GW 12 7 0 n_b_y1 n_b_z 0 n_b_y2 n_b_z radius'#000
GX 20 010
GW 13 15 n_f -n_top n_b_z+n_h n_f n_top n_b_z+n_h radius'#000
GW 15 43 n_x -n_zsz n_z n_x n_zsz n_z radius'#D00
GX 40 001
GW 16 51 n_x -n_0sz 0 n_x n_0sz 0 radius'#D00
GW 100 5 0 -feed 0 0 feed 0 radius*.8675'#f40
GE 0
LD 5 0 0 0 24900000
GN -1
EK
EX 0 100 3 0 1
FR 0 0 0 0 800 0
EN
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9 Posts
Hi Nikiml
Been using my GH6n3 antenna for about 8 years I think and it's performed quite well but the recent repack is probably causing certain channels to pixelate, even the strong ones. I'm wondering if your modifications will bring changes to the element and narod spacing. Also if an LTE filter would help because of the strong signals now being used that disrupt antenna performance.
Thanks,
Scorpio333
The antenna from my previous post still has good gain above 608 Mhz, and so if it is interference that is causing the problem, it probably wont help. Not sure about the filter.
On the other hand, after 8 years, have you checked the connections for corrosion?
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9 Posts
Thanks for your reply. This past summer, I "de-oxidized" (sanded clean) the antenna copper elements, replaced the old balun that had wires as the twin lead with a "Channel Master type" that has 2 small washers at the end of the twin lead. I did this in the hope of having a better "electrical connection" to get the maximum gain possible, and I think I succeeded in some way. You can say I "refurbished" an old trusted antenna that has performed well throughout the many years of service (a big thanks to your expert calculating skills and know-how, we couldn't have done it without you).
I'm no expert in these matters, but my question is, would it be possible to redesign (I suppose with new dimensions, added or removed narods, etc.) the GH6n3 in such a way as to knock out as much gain above the 608 Mhz frequency spectrum (now being used for 4G or 5G frequencies) and in so doing improve the gain between the useful remaining VHF-hi 7 to UHF 36 (all the while keeping the existing antenna's height and width)?
I'm no expert in these matters, but my question is, would it be possible to redesign (I suppose with new dimensions, added or removed narods, etc.) the GH6n3 in such a way as to knock out as much gain above the 608 Mhz frequency spectrum (now being used for 4G or 5G frequencies) and in so doing improve the gain between the useful remaining VHF-hi 7 to UHF 36 (all the while keeping the existing antenna's height and width)?
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