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

388778 Views 939 Replies 87 Participants Last post by Scorpio_333, Nov 13, 2020

300ohm

· #2 · Mar 9, 2010

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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nikiml

Discussion Starter · #3 · Mar 9, 2010

The curved top hat NAROD may eliminate that.

Are talking about smoothing (arc-ing) the bents on the narods?

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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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Xauto

· #6 · Mar 10, 2010

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. http://www.digitalhome.ca/forum/showpost.php?p=968772&postcount=269

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nikiml

Discussion Starter · #7 · Mar 10, 2010

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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nikiml

Discussion Starter · #8 · Mar 10, 2010

which makes me think that I should try this

Code:

     ___________
    /           \
___/             \___

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300ohm

· #9 · Mar 10, 2010

Had all parameters open for the optimizer and it turned it to:

Wow, the optimizer did a number on that, heh.

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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nikiml

Discussion Starter · #10 · Mar 10, 2010

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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nikiml

Discussion Starter · #11 · Mar 10, 2010

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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300ohm

· #12 · Mar 10, 2010

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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majortom

· #13 · May 24, 2010

-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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300ohm

· #14 · May 24, 2010

Those are off center NAROD reflectors.

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majortom

· #15 · May 24, 2010

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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300ohm

· #16 · May 24, 2010

He has 2 Top Hat type NARODs and 3 NAROD reflectors.

NAROD stands for Not A Reflector Or Director and its an unconnected wire floating in space.

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stampeder

· #17 · May 24, 2010

majortom, you can see the major events in the evolution of the GH designs starting in Post #1 of this thread:

http://www.digitalhome.ca/forum/showthread.php?t=81982

It helps people to understand the terminology better.

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nikiml

Discussion Starter · #18 · Jun 2, 2010 (Edited by Moderator)

GH8 with top hat narods and 3 narod reflectors

Here is another model with good vhf-hi gain.
This one is based on the jed's GH8.
And again the jed's parameters are not modified,
the antenna is equivelent to the Jed's GH8 but has narods and
narod reflectors added.

Here is the model:

Code:

CM model segmentation is derived from autosegmentation 22 at 800Mhz	
CM for VHF AGT of 1 set the radius multiplier of the souce wire to 1
CM 
CE
SY radius=0.003175
SY hat_rad=0.003175	'0.0010265
SY l1=0.314
SY g1=0.018
SY z1=0.083
SY l2=0.340
SY g2=0.0305
SY z2=0.258
SY l3=0.417
SY g3=0.0425
SY z3=0.439
SY l4=0.302
SY g4=.054
SY z4=0.620
SY l5=0.270
SY g5=4e-3
SY z5=0.592
SY x=-0.081
SY a1=0.193
SY a2=0.193
SY a3=0.183
SY b=0.121
SY feed=0.0725
SY a1ma2=a1-a2
SY a1pa2=a1+a2
SY a1ma2pa3=a1ma2+a3
SY a1pa2pa3=a1pa2+a3
SY n_top_l=0.214173
SY n_b_l=0.120877
SY n_z_sp=0.012
SY n_h=0.048478
SY n_b_z=a1pa2pa3*.7071+n_z_sp+hat_rad-radius
SY n_top_z=n_b_z+n_h
SY n_b_ystart=-n_top_l	'-feed-0.70711*a1ma2pa3-n_b_ysp
SY n_b_yend=n_b_ystart-n_b_l
SY n_back=-0.29961
SY n_refl_size=0.406309
SY n_refl_z=0.43301
SY n_refl_size1=0.479869
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	21	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	37	x	g1	z1	x	l1+g1	z1	radius
GW	6	41	x	g2	z2	x	l2+g2	z2	radius
GW	7	49	x	g3	z3	x	l3+g3	z3	radius
GW	8	35	x	g4	z4	x	l4+g4	z4	radius
GW	11	7	0	-n_top_l	n_top_z	0	n_b_ystart	n_b_z	hat_rad
GW	14	15	0	n_b_ystart	n_b_z	0	n_b_yend	n_b_z	hat_rad
GX	20	010
GW	10	51	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	17	0	-feed	0	0	feed	0	radius*.8675
GW	16	113	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	9	0	1			
FR	0	0	0	0	800	0
RP	0	60	73	1001	0	0	3	5		
EN

Here is the predicted gain/swr:

Code:

Channel		7	8	9	10	11	12	13			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
Raw gain [dBi]	9.71	9.77	9.56	9.33	9.13	8.97	8.85			13.81	13.92	14.01	14.09	14.15	14.22	14.27	14.33	14.38	14.39	14.37	14.32	14.26	14.21	14.18	14.16	14.15	14.15	14.15	14.16	14.17	14.18	14.19	14.2	14.21	14.26	14.33	14.42	14.53	14.64	14.76	14.87	14.98	15.07	15.15	15.2	15.21	15.16	15.03	14.78	14.39
SWR		1.69	1.56	1.82	1.83	1.75	1.68	1.67			1.66	1.44	1.28	1.17	1.1	1.09	1.12	1.16	1.2	1.24	1.28	1.32	1.35	1.38	1.41	1.43	1.46	1.49	1.51	1.54	1.57	1.6	1.63	1.67	1.71	1.75	1.8	1.83	1.86	1.88	1.89	1.9	1.89	1.87	1.84	1.8	1.75	1.69	1.63	1.59	1.59
NetGain[Dbi]	9.42	9.56	9.18	8.94	8.79	8.68	8.57			13.53	13.77	13.94	14.06	14.14	14.21	14.26	14.3	14.34	14.34	14.3	14.24	14.16	14.1	14.05	14.02	14	13.98	13.96	13.96	13.95	13.94	13.93	13.92	13.9	13.92	13.96	14.03	14.12	14.21	14.32	14.43	14.55	14.65	14.75	14.83	14.88	14.87	14.77	14.55	14.16

a graph:

the top hat narod looks like that:

Code:

           -----------a-----------           
           |                     |             a = 0.4283m
           b                     |             b = 0.0485m
           |                     |             c = 0.1209m
-----c-----                       -----------

and it is mounted at 12mm distance form the active element's legs

The narod reflectors:

Code:

           ------------L1------------

                                          L0 = 0.9597m
          -------------L0-------------    L1 = 0.8126m
                                          L1_z = 0.433m
                                          X = 0.3m
           ------------L1------------

X here is the distance between the active element and the narod reflectors plane

and 3d image:

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nikiml

Discussion Starter · #19 · Jun 4, 2010

GH6 with top hat narods and 3 narod reflectors

A Jed's GH6 mod this time.
Again, as the previous two, it can be build from and existing GH6
by adding narods and narod reflectors.

Model:

Code:

CM model segmentation is derived from autosegmentation 22 at 800Mhz	
CM for VHF AGT of 1 set the radius multiplier of the souce wire to 1
CM 
CE
SY radius=0.003175
SY hat_rad=0.003175	'0.0010265
SY l1=0.322
SY g1=0.022
SY z1=0.085
SY l2=0.328
SY g2=0.036
SY z2=0.299
SY l3=0.312
SY g3=0.0495
SY z3=0.590
SY x=-0.075
SY a1=0.184
SY a2=0.205
SY a3=0.171
SY b=0.124
SY feed=0.0755
SY a1ma2=a1-a2
SY a1pa2=a1+a2
SY a1ma2pa3=a1ma2+a3
SY a1pa2pa3=a1pa2+a3
SY n_top_l=0.200532
SY n_b_l=0.128128
SY n_z_sp=9.849e-3
SY n_h=0.054536
SY n_b_z=a1pa2pa3*.7071+n_z_sp+hat_rad-radius
SY n_top_z=n_b_z+n_h
SY n_b_ystart=-n_top_l	'-feed-0.70711*a1ma2pa3-n_b_ysp
SY n_b_yend=n_b_ystart-n_b_l
SY n_back=-0.3055
SY n_back1=-0.3055
SY n_refl_size=0.408133
SY n_refl_z=0.44513
SY n_refl_size1=0.493491
GW	1	23	0	-feed	0	0	-feed-0.70711*a1	0.70711*a1	radius
GW	2	25	0	-feed-0.70711*a1	0.70711*a1	0	-feed-0.70711*a1ma2	0.70711*a1pa2	radius
GW	3	21	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	39	x	g1	z1	x	l1+g1	z1	radius
GW	6	39	x	g2	z2	x	l2+g2	z2	radius
GW	7	37	x	g3	z3	x	l3+g3	z3	radius
GW	11	7	0	-n_top_l	n_top_z	0	n_b_ystart	n_b_z	hat_rad
GW	14	15	0	n_b_ystart	n_b_z	0	n_b_yend	n_b_z	hat_rad
GX	20	010
GW	10	51	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	17	0	-feed	0	0	feed	0	radius*.8675
GW	16	113	n_back1	-n_refl_size1	0	n_back1	n_refl_size1	0	radius
GE	0
LD	5	0	0	0	24900000
GN	-1
EK
EX	0	100	9	0	1			
FR	0	0	0	0	800	0
RP	0	60	73	1001	0	0	3	5		
EN

Predicted gain[dBi]/swr

Code:

Channel	7	8	9	10	11	12	13		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
Raw gain	9.66	9.62	9.38	9.15	8.96	8.81	8.7		13.6	13.68	13.72	13.76	13.78	13.8	13.82	13.84	13.83	13.79	13.72	13.65	13.59	13.56	13.55	13.55	13.57	13.58	13.6	13.61	13.62	13.64	13.65	13.68	13.73	13.8	13.88	13.97	14.06	14.16	14.25	14.35	14.44	14.52	14.59	14.65	14.68	14.68	14.61	14.46	14.21
S W R		1.63	1.26	1.43	1.46	1.46	1.52	1.66		1.45	1.24	1.11	1.06	1.11	1.17	1.21	1.25	1.28	1.31	1.34	1.36	1.38	1.4	1.43	1.46	1.49	1.52	1.55	1.58	1.61	1.64	1.68	1.71	1.74	1.78	1.81	1.83	1.86	1.88	1.89	1.89	1.89	1.88	1.86	1.82	1.77	1.7	1.62	1.52	1.42
Net Gain	9.4	9.56	9.24	9	8.8	8.62	8.42		13.45	13.63	13.71	13.76	13.77	13.77	13.78	13.79	13.76	13.71	13.63	13.55	13.48	13.44	13.41	13.4	13.4	13.39	13.39	13.39	13.38	13.37	13.36	13.37	13.4	13.45	13.5	13.58	13.65	13.74	13.82	13.92	14.01	14.1	14.18	14.27	14.33	14.38	14.36	14.27	14.07

gain/swr graph:

the top hat narod dimensions:

Code:

           -----------a-----------           
           |                     |             a = 0.4011m
           b                     |             b = 0.0545m
           |                     |             c = 0.1281m
-----c-----                       -----------

and it is mounted at 10mm distance form the active element's legs.

The narod reflectors dimensions are:

Code:

           ------------L1------------

                                          L0 = 0.987m
          -------------L0-------------    L1 = 0.816m
                                          L1_z = 0.445m
                                          X = 0.306m
           ------------L1------------

X here is the distance between the active element and the narod reflectors plane

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300ohm

· #20 · Jun 4, 2010

Looks good. One question because of the downward gain pattern, are you optimizing the NARODs just for channel 7 and 8 or for 174 to 216 mhz ?

Also, just to keep all the graphs identical, can you put in the numbers for the original GH6 here :
http://www.digitalhome.ca/ota/superantenna/design.htm
optimizing the original GH6 with your top hat narods and 3 narod reflectors, but use a 89mm feedpoint instead of the 44mm one ?

JEDs GHs suffer from being very tall and large when stacked. With the original GH6, a double bay version should be less than 6 ft tall.

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