"Top Hat" GH with NARODs for VHF-HI: Major GH Improvement - Canadian TV, Computing and Home Theatre Forums

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post #1 of 936 (permalink) Old 2010-03-09, 11:12 AM Thread Starter
 
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Thumbs up "Top Hat" GH with NARODs for VHF-HI: Major GH Improvement

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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post #2 of 936 (permalink) Old 2010-03-09, 01:28 PM
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That does produce excellent vhf-hi gains for a SBGH. The square top hat NAROD still has that annoying dip in the gain curve from CH 32 - 36. The curved top hat NAROD may eliminate that.

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post #3 of 936 (permalink) Old 2010-03-09, 02:31 PM Thread Starter
 
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Quote:
The curved top hat NAROD may eliminate that.
Are talking about smoothing (arc-ing) the bents on the narods?
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post #4 of 936 (permalink) Old 2010-03-09, 05:21 PM
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Yep, like this General Purpose ch 7 - 13 Top Hat NAROD :



Might need to be adjusted a little for JEDs GH10 model. (maybe the curves not needed but just a double backing over the stub ?) Xauto and Ramkat worked on it in Area 51.

NEC file with two of them:

Code:
CE
GW	1000	7	0	68	16	0	77.5	16	0.05721178
GW	1001	1	0	77.5	16	0	77.75	15.75	0.05721178
GW	1002	1	0	77.75	15.75	0	77.75	15.25	0.05721178
GW	1003	1	0	77.75	15.25	0	77.5	15	0.05721178
GW	1004	1	0	77.5	15	0	76	15	0.05721178
GW	1005	1	0	76	15	0	75.75	14.75	0.05721178
GW	1006	1	0	75.75	14.75	0	75.75	14.25	0.05721178
GW	1007	1	0	75.75	14.25	0	76	14	0.05721178
GW	1008	3	0	80.125	14	0	76	14	0.05721178
GW	1009	7	0	68	16	0	58.5	16	0.05721178
GW	1010	1	0	58.5	16	0	58.25	15.75	0.05721178
GW	1011	1	0	58.25	15.75	0	58.25	15.25	0.05721178
GW	1012	1	0	58.25	15.25	0	58.5	15	0.05721178
GW	1013	1	0	58.5	15	0	60	15	0.05721178
GW	1014	1	0	60	15	0	60.25	14.75	0.05721178
GW	1015	1	0	60.25	14.75	0	60.25	14.37	0.05721178
GW	1016	1	0	60.25	14.37	0	60	14	0.05721178
GW	1017	3	0	60	14	0	55.875	14	0.05721178
GW	1018	7	0	68	-19	0	77.5	-19	0.05721178
GW	1019	1	0	77.5	-19	0	77.75	-18.75	0.05721178
GW	1020	1	0	77.75	-18.75	0	77.75	-18.25	0.05721178
GW	1021	1	0	77.75	-18.25	0	77.5	-18	0.05721178
GW	1022	1	0	77.5	-18	0	76	-18	0.05721178
GW	1023	1	0	76	-18	0	75.75	-17.75	0.05721178
GW	1024	1	0	75.75	-17.75	0	75.75	-17.25	0.05721178
GW	1025	1	0	75.75	-17.25	0	76	-17	0.05721178
GW	1026	3	0	80.125	-17	0	76	-17	0.05721178
GW	1027	7	0	68	-19	0	58.5	-19	0.05721178
GW	1028	1	0	58.5	-19	0	58.25	-18.75	0.05721178
GW	1029	1	0	58.25	-18.75	0	58.25	-18.25	0.05721178
GW	1030	1	0	58.25	-18.25	0	58.5	-18	0.05721178
GW	1031	1	0	58.5	-18	0	60	-18	0.05721178
GW	1032	1	0	60	-18	0	60.25	-17.75	0.05721178
GW	1033	1	0	60.25	-17.75	0	60.25	-17.25	0.05721178
GW	1034	1	0	60.25	-17.25	0	60	-17	0.05721178
GW	1035	3	0	60	-17	0	55.875	-17	0.05721178
GS	0	0	0.0254		' All in in.
GE	0
EK
EX	0	18	3	0	1	0
GN	-1
FR	0	1	0	0	473	0
RP 0 1 10 1510 90. 0. 0. 20. 0. 0.

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post #5 of 936 (permalink) Old 2010-03-09, 07:32 PM Thread Starter
 
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I started with a top hat narod and ended up with the model above. no curving though.
And although I have not triede all possible configurations i order to be certain, from those that I tried the above gave the best results.
(of cource best is relative)

I can try curving.
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post #6 of 936 (permalink) Old 2010-03-09, 08:12 PM
 
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nikim: This is from area 51. The top hat can be tuned by changing the length of the tips. Check this on out by wildbill. Area 51 for Antenna Modelers & Builders (See Post #1)
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post #7 of 936 (permalink) Old 2010-03-09, 11:13 PM Thread Starter
 
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Well,

I had a top hat narod, like that

Code:
   ___________________
  |___             ___|
______|           |______
Had all parameters open for the optimizer and it turned it to:


Code:
        ___________
    ___|           |___
___|                   |___
So I decided to change it into the simpler to build version above and it looked good to me.
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post #8 of 936 (permalink) Old 2010-03-09, 11:16 PM Thread Starter
 
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which makes me think that I should try this

Code:
     ___________
    /           \
___/             \___
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post #9 of 936 (permalink) Old 2010-03-09, 11:45 PM
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Quote:
Had all parameters open for the optimizer and it turned it to:
Wow, the optimizer did a number on that, heh.



Quote:
which makes me think that I should try this
Yeah, try that. I think the key for getting the gain dip out is to have more wire in the NAROD, yet still having it resonate in the vhf hi range within the element stubs. I was going to try a 1 turn helix loop in the middle, with still enough straight wire over the elements stubs.
On the otherhand, the channel 32 - 38 1 db or so dip in the gain curve isnt going to affect those people who dont have ch 32 - 38 or who have decent ch 32 - 38 signals.

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post #10 of 936 (permalink) Old 2010-03-10, 12:41 AM Thread Starter
 
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Quote:
I think the key for getting the gain dip out is to have more wire in the NAROD, yet still having it resonate in the vhf hi range within the element stubs
well I started with more wire, but the optimizer insisted...
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post #11 of 936 (permalink) Old 2010-03-10, 01:21 AM Thread Starter
 
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I also wanted to put the dip into numbers.
So here is the difference of the net gains between the original JED's GH10 rev 2 and the model in this thread.

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
Diff	0.56	0.43	0.33	0.26	0.24	0.32	0.37	0.29	0.2	0.14	0.11	0.09	0.09	0.1	0.12	0.13	0.15	0.21	0.26	0.37	0.52	0.72	0.86	0.88	0.78	0.66	0.58	0.51	0.46	0.42	0.38	0.33	0.26	0.18	0.12	0.07	0.04	0.08	0.15	0.25	0.39
the maximum difference is at channel 37 and is .88 db
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post #12 of 936 (permalink) Old 2010-03-10, 02:51 AM
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Very nice, thats less difference than what I had expected. I forgot JEDs GH10 gain curve was dipping in the middle anyway. http://www.jedsoft.org/fun/antennas/dtv/gh.html

Your vhf-hi gains do seem to be a good 1 dbi better than the straight NAROD setup, so the extra amount of wire helps.

For people who dont know, 9.33 dBi is super for vhf-hi gain, and puts it in the Winegard YA-1713 (a dedicated ch 7 - 13 antenna) class in terms of Vhf-Hi Net Gain. Net gain for Uhf is also at the top for channels 14 - 51.
http://www.hdtvprimer.com/ANTENNAS/comparing.html

Ive found that NARODs scale up the same way as typical antennas do on stacking, so another 2.5 dBi is possible on a double bay version.

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post #13 of 936 (permalink) Old 2010-05-23, 09:14 PM
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-In the model of post #1, what are the three extra elements behind the usual 10 co-linear rods for?
Don't recall seein them on jed's GH10 model.
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post #14 of 936 (permalink) Old 2010-05-23, 10:41 PM
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Those are off center NAROD reflectors.

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post #15 of 936 (permalink) Old 2010-05-23, 11:18 PM
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OK thanks 300 Ohm, I guess i was under the impression the two top Hats were the NARODs.
So it has 5 NARODs altogether? Nuther dumb question, what does NAROD stand for? I'm assuming it's an acronym for sumthin?
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