GH with NARODs for VHF-HI & UHF

[300ohm]

The space from rod to reflector is 10". The main reflector (Al.-foil 42X30 with hour glass slit 1" center and 3.125"at the ends) space is 15" from the elements.

Thats interesting, the main reflector is in back of the NAROD reflector. That should hurt your uhf performance in that direction, not being at the best 100mm Reflector to Element spacing.

Also, is the peak Vhf performance in the right direction ? (0 degrees meaning in the direction of the station, 180 degrees meaning away from it)

[Xauto]

Yes The elements are South and the NOROD reflector and the main reflector are North. Ch.11,13,24,30 are all South of me. I have mixed and matched things. The reflector spacing from whisker type 4 bay(VHF-HI) and your 10" space. This did help, but it did subtract from Ch.32. By the way the stubs are straight not fractal.

[TexasTV]

Hello 300ohm et al,

This is my first post on this forum. I found this forum in November 2008 and have been reading many of the threads, because I am interested in building my own SBGH antenna, like the one in the top of the first post in this thread. I have a few questions though, so here they are.

1) Can the driven elements, reflectors, NARODs and NAROD reflectors all be made from the same diameter wire?

In my case I was thinking AWG #6 Solid Copper Wire.

2) In the VHF-HI band where I live there are 4 channels: 8, 10, 11, 13. I must have 11(CBS), and 13(ABC) and would like to have 8(PBS). I'm indifferent about 10. If I receive it, great. If not, ok.

What should the length of the NAROD and NAROD reflectors be to accomplish this?

3) During my search for information on antennas, I read somewhere on the Internet about orienting an antenna slightly above the horizon to improve reception. I believe this was done with a Quadruple Bow Tie antenna.

Is there any benefit to doing something similar with a GH antenna, and if so, how many degrees above horizon should I tilt it?

[300ohm]

1) Yes, 6 gauge copper wire will work fine for all the metal pieces. Just measure center of wire to center of wire. Using copper for the reflectors is pricey overkill though, so you may want to consider aluminum or hollow galvanized steel tubing for the reflectors.

2) Are they all in the same direction ? Is channel 8 or channel 13 weaker ?

3) Tilting is always done by experimentation. It varies by location and even by time of day. Most DXers who tilt use a tilting rotor.

[300ohm]

For the channel range peaking at channels 8,9,10 and a good VHF-HI overall compromise, the NAROD and NAROD reflector length is 30.25 inches and the NAROD to NAROD reflector distance is 11.5 inches. As you can see from the 3 different models (VHF-HI low, middle and high range) it doesnt take much to distort the gain range.

CH Raw Gain dBi SWR
-- ------------ ---
07 09.04 2.81
08 11.70 2.80
09 11.50 3.32
10 11.10 2.92
11 10.70 2.48
12 10.30 2.37
13 09.99 2.66



And the NEC File:
JED, the elements,NARODs and the voltage source wire on this model are all 10 gauge. A small .1 dBi AGT adjustment needs to be added to the calculated result for VHF-HI, and .06 dBi needs to be subtracted from UHF. (Its adjusted in the above VHF-HI figures, but not the UHF chart) So according to Cebriks guidelines, all looks good. Except of course the tiny balun wires, but that applies to all models, including Ken Nists. Keep in mind, we're modeling antennas in "free space" environment at the antenna terminals. What happens after that on the way to the tuner (and including the tuner) can vary greatly with each installation, location and TV set.

CE
GW	30	15	0	1.73228346	0	0	6.73228346	5	0.05094856
GW	31	15	0	1.73228346	10	0	6.73228346	5	0.05094856
GW	32	15	0	1.73228346	10	0	6.73228346	15	0.05094856
GW	34	15	0	-1.7322835	0	0	-6.7322835	5	0.05094856
GW	35	15	0	-1.7322835	10	0	-6.7322835	5	0.05094856
GW	36	15	0	-1.7322835	10	0	-6.7322835	15	0.05094856
GW	38	15	0	1.73228346	0	0	6.73228346	-5	0.05094856
GW	39	15	0	1.73228346	-10	0	6.73228346	-5	0.05094856
GW	40	15	0	1.73228346	-10	0	6.73228346	-15	0.05094856
GW	42	15	0	-1.7322835	0	0	-6.7322835	-5	0.05094856
GW	43	15	0	-1.7322835	-10	0	-6.7322835	-5	0.05094856
GW	44	15	0	-1.7322835	-10	0	-6.7322835	-15	0.05094856
GW	79	25	-4.1338583	-0.3937008	15	-4.1338583	-12.440945	15	0.1875
GW	80	25	-4.1338583	0.39370079	15	-4.1338583	12.4409449	15	0.1875
GW	81	25	-4.1338583	0.39370079	-15	-4.1338583	12.4409449	-15	0.1875
GW	82	25	-4.1338583	-0.3937008	-15	-4.1338583	-12.440945	-15	0.1875
GW	84	25	-4.1338583	0.39370079	2.5	-4.1338583	12.007874	2.5	0.1875
GW	85	25	-4.1338583	-0.3937008	2.5	-4.1338583	-12.007874	2.5	0.1875
GW	86	25	-4.1338583	0.39370079	7.5	-4.1338583	12.4409449	7.5	0.1875
GW	87	25	-4.1338583	-0.3937008	7.5	-4.1338583	-12.440945	7.5	0.1875
GW	88	25	-4.1338583	0.39370079	-2.5	-4.1338583	12.007874	-2.5	0.1875
GW	89	25	-4.1338583	-0.3937008	-2.5	-4.1338583	-12.007874	-2.5	0.1875
GW	90	25	-4.1338583	0.39370079	-7.5	-4.1338583	12.4409449	-7.5	0.1875
GW	91	25	-4.1338583	-0.3937008	-7.5	-4.1338583	-12.440945	-7.5	0.1875
GW	103	13	0	6.73228346	15	0	12.3228346	15	0.05094856
GW	104	13	0	-6.7322835	15	0	-12.322835	15	0.05094856
GW	106	13	0	6.73228346	-15	0	12.3228346	-15	0.05094856
GW	107	13	0	-6.7322835	-15	0	-12.322835	-15	0.05094856
GW	138	13	0	-15.125	15.5	0	0	15.5	0.0511811
GW	142	13	0	0	15.5	0	15.125	15.5	0.0511811
GW	139	13	0	-15.125	-15.5	0	0	-15.5	0.0511811
GW	143	13	0	0	-15.5	0	15.125	-15.5	0.0511811
GW	144	25	-11.5	15.125	15.5	-11.5	-15.125	15.5	0.1875
GW	145	25	-11.5	15.125	-15.5	-11.5	-15.125	-15.5	0.1875
GW	147	15	0	1.73228346	35	0	6.73228346	40	0.05094856
GW	148	15	0	1.73228346	45	0	6.73228346	40	0.05094856
GW	149	15	0	1.73228346	45	0	6.73228346	50	0.05094856
GW	150	15	0	-1.7322835	35	0	-6.7322835	40	0.05094856
GW	151	15	0	-1.7322835	45	0	-6.7322835	40	0.05094856
GW	152	15	0	-1.7322835	45	0	-6.7322835	50	0.05094856
GW	153	15	0	1.73228346	35	0	6.73228346	30	0.05094856
GW	154	15	0	1.73228346	25	0	6.73228346	30	0.05094856
GW	155	15	0	1.73228346	25	0	6.73228346	20	0.05094856
GW	156	15	0	-1.7322835	35	0	-6.7322835	30	0.05094856
GW	157	15	0	-1.7322835	25	0	-6.7322835	30	0.05094856
GW	158	15	0	-1.7322835	25	0	-6.7322835	20	0.05094856
GW	159	25	-4.1338583	-0.3937008	50	-4.1338583	-12.440945	50	0.1875
GW	160	25	-4.1338583	0.39370079	50	-4.1338583	12.4409449	50	0.1875
GW	161	25	-4.1338583	0.39370079	20	-4.1338583	12.4409449	20	0.1875
GW	162	25	-4.1338583	-0.3937008	20	-4.1338583	-12.440945	20	0.1875
GW	163	25	-4.1338583	0.39370079	37.5	-4.1338583	12.007874	37.5	0.1875
GW	164	25	-4.1338583	-0.3937008	37.5	-4.1338583	-12.007874	37.5	0.1875
GW	165	25	-4.1338583	0.39370079	42.5	-4.1338583	12.4409449	42.5	0.1875
GW	166	25	-4.1338583	-0.3937008	42.5	-4.1338583	-12.440945	42.5	0.1875
GW	167	25	-4.1338583	0.39370079	32.5	-4.1338583	12.007874	32.5	0.1875
GW	168	25	-4.1338583	-0.3937008	32.5	-4.1338583	-12.007874	32.5	0.1875
GW	169	25	-4.1338583	0.39370079	27.5	-4.1338583	12.4409449	27.5	0.1875
GW	170	25	-4.1338583	-0.3937008	27.5	-4.1338583	-12.440945	27.5	0.1875
GW	171	13	0	6.73228346	50	0	12.3228346	50	0.05094856
GW	172	13	0	-6.7322835	50	0	-12.322835	50	0.05094856
GW	173	13	0	6.73228346	20	0	12.3228346	20	0.05094856
GW	174	13	0	-6.7322835	20	0	-12.322835	20	0.05094856
GW	175	13	0	-15.125	50.5	0	0	50.5	0.0511811
GW	176	13	0	0	50.5	0	15.125	50.5	0.0511811
GW	177	13	0	-15.125	19.5	0	0	19.5	0.0511811
GW	178	13	0	0	19.5	0	15.125	19.5	0.0511811
GW	179	25	-11.5	15.125	50.5	-11.5	-15.125	50.5	0.1875
GW	180	25	-11.5	15.125	19.5	-11.5	-15.125	19.5	0.1875
GW	181	15	1	-1	35	1	-1	17.5	0.05094856
GW	182	15	1	1	35	1	1	17.5	0.05094856
GW	183	15	1	-1	0	1	-1	17.5	0.05094856
GW	184	15	1	1	0	1	1	17.5	0.05094856
GW	185	3	1	-1	17.5	1	1	17.5	0.05094856
GW	186	1	0	1.73228346	35	1	1	35	0.05094856
GW	187	1	0	-1.7322835	35	1	-1	35	0.05094856
GW	188	1	0	-1.7322835	0	1	-1	0	0.05094856
GW	189	1	0	1.73228346	0	1	1	0	0.05094856
GS	0	0	0.0254		' All in in.
GE	0
EK
EX	0	185	2	0	1	0
GN	-1
FR	0	38	0	0	473	6
RP 0 1 10 1510 90. 0. 0. 20. 0. 0.

[Spin]

Hello, 300ohm,
I am a new member and but I have been going over the postings for the last year. I was just wondering if you have made any progress on the DBGH GH10 CURVED MESH plans since the middle of the year and or have you abandoned that concept. I am also curious about the spacing of the 2 bays. Do you think that the NAROD concept will work for the curved mesh antenna?
By the way, wonderful research!

[TexasTV]

Accordng to tvfool.com, all of my Channels are between 25.3 miles and 26.3 miles away and between 288° and 291° from True North, except one really close one, Channel 15, which is at 104° from True North and 9.3 miles away.

In respect to your question, Channel 8 is at -39dBm, while Channel 13 is at -38.7dBm. They are both 25.3 miles away and at 291° from True North.

[300ohm]

In respect to your question, Channel 8 is at -39dBm, while Channel 13 is at -38.7dBm. They are both 25.3 miles away and at 291° from True North.

Since theyre both strong, the middle choice would suit you, NAROD and NAROD lengths at 30.25 inches and NAROD to NAROD reflectors spacing of 11.5 inches.

You should be able to pick up channel 15 on the back side no problem.

[TexasTV]

11.5 inches is center to center spacing between the NAROD and NAROD reflectors, correct?

[300ohm]

I was just wondering if you have made any progress on the DBGH GH10 CURVED MESH plans since the middle of the year and or have you abandoned that concept.

Not really, Im using the SBGH GH10 Curved Mesh as my garage antenna.The SBGH GH10 Curved Mesh is a big antenna at 4 ft wide by 5 ft high. The DBGH GH10 Curved Mesh would be about 4 ft wide by 11 ft high and overkill for me.

I am also curious about the spacing of the 2 bays.

That follows my rule of thumb for all DBGHs, 2 times the wavelength of the desired peaking channel minus 2 %, feedpoint to feedpoint spacing. For the 89mm feedpoint gap, a 2 inch (50mm) phasing line gap, 1 inch (25mm) in front of the elements works fine. Keep the phasing lines perfectly parallel, using plastic spacers if necessary.

Do you think that the NAROD concept will work for the curved mesh antenna?

Nope, unfortunately the mesh messes up the gain and gain direction. I havent found a way around that yet and still perserve the great uhf gain.

[300ohm]

11.5 inches is center to center spacing between the NAROD and NAROD reflectors, correct?

Yes, thats correct.

[TexasTV]

I'm planning on building a SBGH 6 using effects build as a guide, except I'm going to have to find a way to add the NARODs and NAROD reflectors to his build.

My SBGH Build & Parts Lis-effects

[j3d]

Originally Posted by 300ohm

For the channel range peaking at channels 8,9,10
and a good VHF-HI overall compromise, the NAROD and NAROD reflector
length is 30.25 inches and the NAROD to NAROD reflector distance is
11.5 inches. As you can see from the 3 different models (VHF-HI low,
middle and high range) it doesnt take much to distort the gain range.

Hi 300ohm,

I have not tested your nec file much, but at first sight it looks good
on VHF-Hi. I did not try to increase the segmentation to look for
convergence. Here are the AGT adjusted values that I computed:

 freq[MHz]        SWR    RawGain    NetGain        F/B
       170    4.92268     8.2644    5.75665       1.31
       176    2.84224    8.74569    7.61121       5.62
       182    2.56054    11.5831    10.6567       8.75
       188    3.33013    11.5018    10.0169      21.06
       194    3.00771    11.1019    9.84691      18.93
       200    2.53878    10.6902       9.78      11.36
       206    2.35895    10.3178    9.54153       7.92
       212    2.58387    9.99473    9.05099       5.71

It also looks good on UHF:

 freq[MHz]        SWR    RawGain    NetGain        F/B
       473    5.68674    15.0137    12.0787      12.61
       479    5.01432    15.2936    12.7326      12.98
       485    4.36631    15.5257     13.354      13.43
       491    3.77206    15.7001    13.9123      13.91
       497    3.25089    15.8462    14.4172      14.44
       503    2.81138    15.9439     14.832      14.95
       509     2.4543    16.0229    15.1756      15.42
       515    2.17549     16.063     15.423       15.8
       521    1.96812    16.0641    15.5756      16.04
       527    1.82396    16.0259    15.6395      16.11
       533    1.73304    15.9477    15.6235      16.03
       539    1.68275    15.8084    15.5176       15.8
       545    1.65832    15.6067    15.3319      15.52
       551    1.64678    15.3524     15.085      15.36
       557    1.64067    15.0864    14.8229      15.47
       563    1.63787    14.8499    14.5882      15.93
       569    1.63866    14.6637    14.4016      16.73
       575    1.64508    14.5284    14.2621      17.81
       581    1.66103    14.4548    14.1782      19.16
       587    1.69111    14.4429    14.1465      20.69
       593    1.73773    14.4927    14.1653      22.17
       599    1.79808    14.6031    14.2346      23.11
       605    1.86645    14.7538    14.3376      22.98
       611    1.93462    14.9437    14.4792      21.91
       617    1.99529    15.1527    14.6446      20.44
       623    2.04268    15.3708    14.8282      18.95
       629    2.07319    15.5787    15.0139      17.57
       635    2.08147    15.7778    15.2069      16.34
       641    2.06526    15.9689    15.4099       15.3
       647    2.02027    16.1227    15.5965      14.41
       653    1.94403    16.2583     15.787       13.7
       659    1.83661    16.3643    15.9691      13.13
       665    1.70051    16.4399    16.1374      12.67
       671    1.54057    16.5137    16.3125      12.31
       677    1.36043    16.5862    16.4837      12.01
       683    1.16936    16.6576     16.631      11.74
       689    1.06377     16.729    16.7248       11.5
       695    1.31742    16.7914    16.7092      11.27

Thanks,
--John

[300ohm]

Here are the AGT adjusted values that I computed:

Yep, looks like about the same figures at slightly different frequencies. Autofils and I generally use the middle of the channel. In VHF though its good to see the tops and the bottoms of the channels too, for example the YA-1713 channel 13 drop off, heh.

[300ohm]

I'm planning on building a SBGH 6 using effects build as a guide, except I'm going to have to find a way to add the NARODs and NAROD reflectors to his build.

Yeah, thats a nice build, almost identical to mlords builds.

For the NAROD to stub holders with #6 wire, you could use small thin stiff pieces of plastic (vynil siding cut to about 1 inch by 1/2 inches pieces comes to mind) with holes drilled in them at 1/2 inch on center, drilled just slightly smaller than the wire diameter (9/64ths drill bit ?) so that they can still be slipped on with a little force. I would say about 4 per NAROD would hold nicely. A dab of Plumbers Goop (basically thick model airplane cement) could be used to permanently hold them, if need be.

For the NAROD reflectors, additional tees and 1/2 inch pvc pieces could be used. My slip on tees would work nicely and allow you to adjust the NAROD reflectors until they are perfectly parallel to the NARODs. Then a small #4 screw can hold the tees etc in place.