GH with NARODs for VHF-HI & UHF

[300ohm]

Success !!! I got the Vhf-Hi gain going the right way with the colinear rod reflector models and with more gain to boot ! (This does not apply to the mesh models, for obvious reasons.)

Using the basic original SBGH gen1 colinear rod plans (with 10ga elements, 3/8 inch reflectors), I placed additional 28 inch, 3/8 inch reflectors 10 inches behind the 28 inch 10 ga NARODs that are 1/2 inch above the stubs. Oddly, using a larger reflector than the driven element, typical in most TV antenna designs, decreased performance, as did a smaller reflector.

The effective bandwidth for Vhf-Hi is somewhat limited to about 4 channels. I tweaked for channels 10 to 13, so if channels 7 to 9 are needed, adjustments have to be made.

The use of the NARODs levels out and dips the gain curve similiar to the SBGH JED Gold Standard model, so the original SBGH gen1 model is so far the best to use in this case so as to not exacerbate the dip further.

VHF-HI

CH Raw Gain SWR
-- -------- -----
07 5.56 dBi 62.3 (7.93 dBi at 180 degrees)
08 6.27 dBi 23.0 (8.02 dBi at 180 degrees)
09 8.07 dBi 5.67
10 9.66 dBi 2.37
11 9.81 dBi 3.7
12 9.26 dBi 3.58
13 8.66 dBi 3.16

Channel 10 pattern :



3D Picture :



UHF Raw Gain Chart :



UHF SWR :



NEC file :

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	29	0	-14	15.5	0	0	15.5	0.0511811
GW	142	29	0	0	15.5	0	14	15.5	0.0511811
GW	139	29	0	-14	-15.5	0	0	-15.5	0.0511811
GW	143	29	0	0	-15.5	0	14	-15.5	0.0511811
GW	144	23	-10	14	15.5	-10	-14	15.5	0.1875
GW	145	23	-10	14	-15.5	-10	-14	-15.5	0.1875
GW	146	3	0	-1.7322835	0	0	1.73228346	0	0.01
GS	0	0	0.0254		' All in in.
GE	0
EK
EX	0	146	2	0	1	0
GN	-1
FR	0	38	0	0	473	6
RP 0 1 10 1510 90. 0. 0. 20. 0. 0.

See development background in this thread: http://www.digitalhome.ca/forum/showthread.php?t=98619

[Xauto]

I like it. Two reflectors. Is the 10" max? My starting points would have been 9" or 11.25".

[300ohm]

Yeah, for channels 10 to 13. For channels 7 to 9, it would be a little more.

[300ohm]

And as expected, a nice healthy increase in gain with the DBGH version. This puts it near the top of the VHF-Hi antenna gain chart for the design range of channels 10 to 13, and still at the top of the UHF range, per HDPrimer.com.
The dimensions of this DBGH are a compact 28 inches wide by 66 inches high by 10 inches deep.



CH Raw Gain dBi SWR
-- ------------ ---
07 06.82 12.5 (8.71 dBi at 180 degrees)
08 07.63 3.94 (7.96 dBi at 180 degrees)
09 08.74 1.77
10 11.6 1.65
11 11.8 2.35
12 11.3 2.16
13 10.8 1.89

3D picture of DBGH :



UHF Raw Gain and SWR of this DBGH :



And the NEC file :

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	29	0	-14	15.5	0	0	15.5	0.0511811
GW	142	29	0	0	15.5	0	14	15.5	0.0511811
GW	139	29	0	-14	-15.5	0	0	-15.5	0.0511811
GW	143	29	0	0	-15.5	0	14	-15.5	0.0511811
GW	144	23	-10	14	15.5	-10	-14	15.5	0.1875
GW	145	23	-10	14	-15.5	-10	-14	-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	29	0	-14	50.5	0	0	50.5	0.0511811
GW	176	29	0	0	50.5	0	14	50.5	0.0511811
GW	177	29	0	-14	19.5	0	0	19.5	0.0511811
GW	178	29	0	0	19.5	0	14	19.5	0.0511811
GW	179	23	-10	14	50.5	-10	-14	50.5	0.1875
GW	180	23	-10	14	19.5	-10	-14	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.

[stampeder]

Wow, congratulations!

That's one heck of an excellent post-transition broadband TV antenna (VHF-HI channels 7-13 with UHF channels 14-51)

Great work, and we all appreciate it!

[stampeder]

Out of curiosity, is there any hope of FM Radio gain, or does it drop off before reaching those lower frequencies?

[300ohm]

Probably not, if you want VHF-Hi TV too. Ill see when I calculate the dimensions for the channel 7 to 9 range.

I can see building this DBGH using wulleebullee's 1st build douple pipe pvc method with some mods. I would put some painted pex tubing pieces in the middle to straighten and keep the gap on the uhf reflector rods. Then I would use my snap on pvc tees to hold the NARODs and the NAROD reflectors.

[Xauto]

I'm now using your VHF-HI bracket rods (NAROD) with Al.-foil reflector at 15" now all I have to do is add reflector rods in between. Off to scavenge material. It is now 6:30. Up date. Do not tell my wife. I removed a slat from the venetian blinds. At 5 foot cut in half it made the bracket rod reflector. On analog Ch. 11 improved greatly (did not know there was an 11). Digital UHF had side effects(same as with bracket rods only), but what was lost was greatly made up for in VHF-hi.

[300ohm]

For the channel range 7 to 9, the best NAROD and NAROD reflector length is 31.5 inches, and the best NAROD to NAROD reflector distance is 12.5 inches. NAROD to stub distance is still 1/2 inch for the best compromise between gain and SWR. (FM gain is still less than rabbit ears)
Ill optimize for channel 9 next, which may be a good overall vhf-hi general compromise.

DBGH (channel 7 optimized) VHF-Hi raw gain and SWR:

CH Raw Gain dBi SWR
-- ------------ ---
07 11.48 3.38
08 11.23 3.71
09 10.85 3.21
10 10.46 2.71
11 10.17 2.56
12 09.83 2.82
13 09.53 3.45

DBGH (channel 7 optimized) UHF gain and SWR :

[j3d]

Originally Posted by 300ohm

Using the basic original SBGH gen1 colinear rod plans (with 10ga
elements, 3/8 inch reflectors), I placed additional 28 inch, 3/8 inch
reflectors 10 inches behind the 28 inch 10 ga NARODs that are 1/2 inch
above the stubs. Oddly, using a larger reflector than the driven
element, typical in most TV antenna designs, decreased performance, as
did a smaller reflector.

Hi 300ohm.

I have a question about your model. It seems that in order to bring
the AGT value down near 1.0, you decreased the radius of the
horizontal excited element from about 0.05 inches to 0.01 inches. It is
unclear to me how this affects the validity of the model. I have read
many times that NEC-2 cannot properly handle models where wires of
dissimilar diameters are connected together. For example, the late L.
B. Cebik (a widely respected antenna modeler) wrote:

Second, the coax wire, with a diameter of 6.35 mm, differs from the
1-mm diameter of the dipole wires, creating an angular junction of
wires with dissimilar diameters. NEC has a known limitation in such
cases, and the error is greater in NEC-2 than NEC-4.

(taken from http://www.antennex.com/w4rnl/col0606/amod100.html)

For this reason, I would be interested in seeing a version that does not suffer from this
limitation.

Finally, I admire your dedication to this project and appreciate
your willingness to help others. You are a real asset to this forum.

Thanks,
--John

[Xauto]

The analog NM from TVFool Ch.11=0.2 pic.-good,Ch.13=-1.7 pic.-fair,Ch.24=-4.3 pic.-fair,Ch30=-8.2 pic.-poor. Ch. that I did not try before.

[300ohm]

Xauto, what exact dimensions, lengths diameters and spacings, are you using for the NAROD and NAROD reflector ?

[300ohm]

I have a question about your model. It seems that in order to bring
the AGT value down near 1.0, you decreased the radius of the
horizontal excited element from about 0.05 inches to 0.01 inches. It is
unclear to me how this affects the validity of the model. I have read
many times that NEC-2 cannot properly handle models where wires of
dissimilar diameters are connected together. For example, the late L.
B. Cebik (a widely respected antenna modeler) wrote:


Quote:
Second, the coax wire, with a diameter of 6.35 mm, differs from the
1-mm diameter of the dipole wires, creating an angular junction of
wires with dissimilar diameters. NEC has a known limitation in such
cases, and the error is greater in NEC-2 than NEC-4.

(taken from http://www.antennex.com/w4rnl/col0606/amod100.html)

For this reason, I would be interested in seeing a version that does not suffer from this
limitation.

Thanks JED, good point and an interesting read. Like Cebrik concludes :

The situation does demonstrate that modeling is not an end in itself. In many situations, the results of modeling require experimental confirmation, if only to show that a model either is or is not a model of the situation under analysis.

I probably wont be making a real antenna for a few months. Maybe by then we can tweak for some more gain, or at least get rid of that dip, heh. Xauto's experimentation seems to be in line with the model.

Ill redo the wire sizes and segmentation on the model to see if I still get the same results.

Second, the coax wire, with a diameter of 6.35 mm, differs from the
1-mm diameter of the dipole wires, creating an angular junction of
wires with dissimilar diameters.

Does he state coax and the dipole wires backwards ? Anyway, I get his point. Most of baluns Ive taken apart I estimate use 24 or 30 gauge wire around the ferrite core. In a lot of cases, the balun attaches to a 3/8 inch aluminum diameter rod. Big diameter difference, but the models seem to be reasonably accurate. Also, in that Cebriks example above, he seems to imply NEC2 UNDERSTATES the dBi gain. Hope thats true, heh.

Also, what are your thoughts on the NAROD ??

[stampeder]

I want to compliment Xauto for doing the empirical testing side of this new design. Its one thing to see the computer model work that 300ohm has done, but to have Xauto try it out physically in almost real time is invaluable!

[Xauto]

The slat from the venetian blinds is 29.5"by 1" by 1/64". The concave side is to the rods. The rods(NOROD) are the telescoping rods off of rabbit ears. They are make up of 8" piece tube in tube(largest OD 3/8 to 1/16 rod). Adjusted to 29.5". 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. The elements is a fractal so the NOROD's are 34.5" center to center.