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"Top Hat" GH with NARODs for VHF-HI: Major GH Improvement

397K views 939 replies 87 participants last post by  Scorpio_333 
#1 ·
this is a modification of the JED's GH10 (rev2),
with bent NARODs and 3 narod reflectors.

Chart:


Numerical gain data (VHF-hi):
Code:
Ch		7	8	9	10	11	12	13
swr		1.63	1.69	2.24	2.2	1.84	1.34	1.17
Net Gain	9.06	9.33	8.9	8.78	8.83	8.81	8.29
Numerical gain data (UHF):
Code:
Ch		14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48	49	50	51	52	53	54
swr		1.22	1.27	1.36	1.45	1.52	1.55	1.47	1.38	1.35	1.35	1.36	1.37	1.38	1.38	1.39	1.39	1.4	1.4	1.41	1.42	1.44	1.48	1.53	1.57	1.6	1.62	1.64	1.67	1.69	1.72	1.75	1.78	1.8	1.83	1.85	1.87	1.91	1.95	2.01	2.09	2.18
Net Gain	13.59	13.9	14.14	14.29	14.35	14.33	14.43	14.59	14.65	14.66	14.65	14.61	14.58	14.55	14.51	14.5	14.49	14.47	14.43	14.38	14.27	14.13	14.05	14.1	14.27	14.46	14.61	14.76	14.88	14.99	15.11	15.22	15.32	15.41	15.47	15.47	15.39	15.18	14.86	14.39	13.74
nec code
Code:
CE
SY radius=0.003175
SY hat_rad=0.003175	'0.0010265
SY l1=0.381
SY g1=0.019
SY z1=0.037
SY l2=0.280
SY g2=0.009
SY z2=0.137
SY l3=0.556
SY g3=0.0055
SY z3=0.262
SY l4=0.511
SY g4=4e-3
SY z4=0.414
SY l5=0.270
SY g5=4e-3
SY z5=0.592
SY x=-0.081
SY a1=0.196
SY a2=0.192
SY a3=0.190
SY b=0.120
SY feed=0.0548348
SY a1ma2=a1-a2
SY a1pa2=a1+a2
SY a1ma2pa3=a1ma2+a3
SY a1pa2pa3=a1pa2+a3
SY n_l=0.449369
SY n_top_l=0.223443
SY n_b_l=(n_l - n_top_l)/2
SY n_z_sp=0.012
SY n_h=0.04795
SY n_b_z=a1pa2pa3*.7071+n_z_sp+hat_rad-radius
SY n_top_z=n_b_z+n_h
SY n_back=-0.25325
SY n_refl_size=0.404294
SY n_refl_z=0.367714
SY n_refl_size1=0.447082
GW	1	23	0	-feed	0	0	-feed-0.70711*a1	0.70711*a1	radius
GW	2	23	0	-feed-0.70711*a1	0.70711*a1	0	-feed-0.70711*a1ma2	0.70711*a1pa2	radius
GW	3	23	0	-feed-0.70711*a1ma2	0.70711*a1pa2	0	-feed-0.70711*a1ma2pa3	0.70711*a1pa2pa3	radius
GW	4	15	0	-feed-0.70711*a1ma2pa3	0.70711*a1pa2pa3	0	-feed-0.70711*a1ma2pa3-b	0.70711*a1pa2pa3	radius
GW	5	45	x	g1	z1	x	l1+g1	z1	radius
GW	6	33	x	g2	z2	x	l2+g2	z2	radius
GW	7	65	x	g3	z3	x	l3+g3	z3	radius
GW	8	61	x	g4	z4	x	l4+g4	z4	radius
GW	8	33	x	g5	z5	x	l5+g5	z5	radius
GW	13	7	0	-n_top_l	n_top_z	0	-n_top_l	n_b_z	hat_rad
GW	14	13	0	-n_top_l	n_b_z	0	-n_top_l-n_b_l	n_b_z	hat_rad
GX	20	010
GW	10	53	0	n_top_l	n_top_z	0	-n_top_l	n_top_z	hat_rad
GW	15	95	n_back	-n_refl_size	n_refl_z	n_back	n_refl_size	n_refl_z	radius
GX	40	001
GW	100	13	0	-feed	0	0	feed	0	radius*.8675
GW	16	105	n_back	-n_refl_size1	0	n_back	n_refl_size1	0	radius
GE	0
LD	5	0	0	0	24900000
GN	-1
EK
EX	0	100	7	0	1			
FR	0	0	0	0	800	0
RP	0	60	73	1001	0	0	3	5		
EN
 
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1
#608 ·
I wanted to use 6 ga cause I have a bunch left over from the build. I will probably just solder the balun connection. Or will pound the 6 ga flat at the end and drill a hole and bolt it.
Yeah, you could do it that way.
Still trying to not use bolts at this point but for ease of construction might.
From a practical standpoint, you wouldnt want to do soldering way up high in the air, so brass bolts (with copper) are almost a necessity.

Since the balun is behind the reflectors will it matter if it is horizontal or vertical? I assumed the only reason it mattered in other builds was that it was near the reflector to driven area and influenced the signal that way. Just my guessing here as I really don't know too much about signal propagation inside the reflector area.
The best way to handle that is testing and tweaking the position of the balun when installed, but before permanently tying it up. Depending on position, some channels will do a bit better and others a bit worse, so tweak for your weakest must have channels.
 
#609 ·
Hi All:

Quick question about how to properly measure your starting 1/4" diameter rod/wire length for the active elements and NARODs. If the length of all sections of an active element in a GH10n3 with NARODs totals 56-1/4", do you cut that specific length of rod/wire first and then form the bends (because the total length of the rod/wire is the important part) or do you just start bending each section of the element to its individual proper length (not caring about the overall length of rod/wire used, but knowing that the overall length of rod/wire used for the element will end up being longer than 56-1/4" because the bends use up some of the overall length)?

Thanks!
 
#612 ·
do you cut that specific length of rod/wire first and then form the bends (because the total length of the rod/wire is the important part) or do you just start bending each section of the element to its individual proper length (not caring about the overall length of rod/wire used,
I did measure, bend, measure from the center of the bend, bend, measure from the center, bend and so on. That way the part of the wire 'consumed' by the bending doesn't accumulate.

jf
 
#614 ·
I hope this request is appropriate to post here. I came across the GH design (a big thanks to all the contributors) while researching OTA antennas, wanting to finally ditch cable/dish.

Antenna will go in a townhouse top loft, indoors if possible (immediately behind a sliding glass door which faces our Mt. Wilson antenna farm at 325 deg perfectly). Due to the indoor location I am most interested in the physically smaller GHn2 lineup, but before building thought I would post my TV fool to see if the smaller designs have any hope of working for me:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=361688726e6ed5

Opinions/advice most welcomed. Moving up to a GN4n and or outside remains a possibility if needed.
 
#619 ·
Antenna will go in a townhouse top loft, indoors if possible (immediately behind a sliding glass door which faces our Mt. Wilson antenna farm at 325 deg perfectly). Due to the indoor location I am most interested in the physically smaller GHn2 lineup, but before building thought I would post my TV fool to see if the smaller designs have any hope of working for me:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=361688726e6ed5

Opinions/advice most welcomed. Moving up to a GN4n and or outside remains a possibility if needed.
You TVFOOL shows 2 edge for almost every signal. This isn't looking good. On my location, I couldn't get anything below +10dB of NM even in the attic. When I moved outside, I got everything solid, even some channel that are so low that they are not shown in my tvfool... and I still get them today. So whatever plans you do, build it cheap and fast to test if it works inside, then put it outside just to check it the result is better and I guess you'll want to build something sturdy to go outside pretty fast.

jf
 
#616 ·
In considering wrapping Al tape around fiberglass rods for the main reflectors and NAROD reflectors for a GH10n3, I understand that the 5/16" diameter fiberglass rods are considerably stiffer than the 1/4" ones. Does switching to the 5/16" size significantly affect performance, or would the overall dimensions of the antenna need to be changed? Could you still use 1/4" Al rod for the driven elements with the 5/16" main reflectors and NAROD reflectors, or would that just throw everything out of whack?
 
#623 ·
Thanks thats a big help. It looks like your site has dimensions for a few varieties. I've already added numbers to the n3 variant. Now I just need to figure out a frame to hold it all!

Are the green rods in the bg intended to replace the mesh I have seen in photos of other designs?

...Mike
 
#624 ·
Now I just need to figure out a frame to hold it all!
Most build nikiml's models using a "H" or ladder type pvc frame. The grey pvc pipe is much cheaper than the white and is UV resistant to boot. You will still have to use white pvc fittings though because of the unavailability of grey fittings.

Are the green rods in the bg intended to replace the mesh I have seen in photos of other designs?
Yes, there are two basic types of GH reflectors, the rod models and the mesh/solid surface models. The mesh/solid surface reflector models cant receive vhf-hi as of yet, only the rod reflector models can.
 
#625 ·
Great, I'll try to whip something up, pipe-wise. I'll just have to remember to hold off on final assembly until I get it through the attic doorway!

One last question: is there a difference in the wire material/diameter between the zigzag part and the reflector part? Or can I make all the metal parts from the same wire?

Oh, and will any old balun work? Or is there a preferred model?

...Mike
 
#626 ·
All of the models I've posted were optimized for 1/4 inch aluminum wire for all elements.

Small deviations in the wire thickness should be ok. For example I have checked the performance with 5/16 inch for the reflectors and it was very close.

Any balun covering both the UHF and the VHF-hi spectrums should work.
but of course some baluns are made better than others...
 
#628 ·
Good tip on the flexible copper tubing...I found that in the plumbing department. The straightening trick with the dril won't work with tubing though...I'll have to roll it or something.

I found this

http://www.instructables.com/id/GH10n3-Gray-Hoverman-TV-Antenna/

but no cutting diagrams, which is a real shame as that seems like a sturdy way to do it. Guess I'll hack around and see what I come up with. Sure missing my workroom right now.

We have an industrial wreckers in town, I think I may swing by there tomorrow to see what I find. Maybe they have old antennas or scram aluminum.

...Mike
 
#632 ·
Nikiml,

Something Ive been meaning to ask but always forgot.

On your GH optimizations, did you ever take into consideration the X axis position of the NAROD ? IE, like having the NAROD in front of or in back of the stubs ?

Ive only done some small testing of that.
 
#635 ·
Another Dumb? Question

Now that the weather is better I have been thinking about some modifications to my GH6.

One thing that I question is why not take the top hat narod off my GH6 and leave the GH6 without the tophat and top hat refectors and dedicate my GH6to UHF reception. Without the tophat UHF reception would be better yes?

Now with the tophat off would it make sense to use the tophat and tophat reflectors for a dedicated separate VHF antenna and then later combine the separate UHF signal from the GH6 and the separate VHF signal from the tophat antenna?

Maybe I am being fooled by the fact that without the tophat my GH6 really doesn't pick up VHF signals for me. But with the tophat it does so the tophat design is great at picking up VHF. If so am I wrong to think that using the tophat as a separate VHF antenna it would be even better?
 
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