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In rabbit73's results it does show a freq shift [leveling effect] and a slight overall improvement, but is it due to the feed point centering or is it that the balun spacers moved the feed point further outward from the face of the wisker elements?
I think it is because of the centering, rather than moving the balun further out. The balun on the stock design touches more than one point on the strips, so the contact point is not definite. The spacers make the contact point definite at the center between the two inner bays.

I retained the shape of the strips in order to be able to repeat measurements on the stock design if needed, and intend to (if I have time) substitue straight strips which I believe will work just as well.

The gain curve of a well designed 4-bay antenna rises slowly from the low end to the high end. This is because the elements and bay spacings become a greater percentage of a wavelength. My test results with the spacers seem to imply that. Without the spacers, there is an unexpected gain increase at the midchannels, which might be helpful to some viewers.

In any case, the modifications found so far improve the performance of the stock 4221HD, and make it much better than the original 4221.
 

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Hello, balm.

I see that you are very active doing antenna experiments at a new location.

Nice work indeed.
Thank you for your kind words. Maybe after the holiday season, if I have any more useful ideas, I might post them.
 

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Discussion Starter · #304 ·
Yep, like I suspected.

If you move the balun connection point down, closer to the lower two bays, the main lobe pattern points UP and vice versa.

I took a reflectorless CM4221a (not the HD, but it will be the same) and moved the connection point down 2 inches from centered. At 470mhz, the main lobe pointed upwards 10 degrees (when centered it was 0 degrees). At 585mhz, the main lobe pointed upwards only 5 degrees. At 698mhz, it was back to 10 degrees upwards.
Purposely off-setting the balun lower could be a useful trick for someone living in a low lying area;)
 

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Purposely off-setting the balun lower could be a useful trick for someone living in a low lying area
Yep, thats what Im thinking, and the beam bending is adjustable. A small motorized device could take the place of a pricey mast tilter.

Unmotorized, manually, fine tuning adjustment up/down could be done with alligator clips on the ends of a balun.
 

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Has anyone tried hacking a CM4221HD into an optimized M4, say 9.5x9

Im wondering if its even possible, or worth the effort

It would involve moving the inner bays inwards by .5" each, and moving the outer bays out by .5" each....then changing out or lengthening all the bow-ties, and then the flat bars wouldnt match the phase lines of an M4 either....this I assume would be basically rebuilding the whole antenna...?
 

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hack "reversal"

Hi All,

I have a pair of stacked/hacked (balun flip, caps, removed, balun with plastic spacers), and had reasonable results with aimed between TO and Buffalo (results in the Brantford reception thread).

I have had issues with signal "quality" on some VHF stations (10.1, for example), and some of the UHF Buffalo stations I receive which I had attributed to multipath issues. The issue was widely fluctuating signal quality (varying 40-50% at times). I had tried angling the antenna, which didn't help.

Yesterday, on a hunch, I removed the stock, spaced, CM baluns and used some cheap GE baluns I purchased to replace them.

The result was a stablization of the previous varying signal quality levels on all of my problematic stations. I also regained CFTO (9.1), which for me had been unobtainable the last month an 1/2 or so. I could not gauge if I lost any signal strength, as probably an hour or so passed over the time it took to make the change, and conditions do change going from afternoon to evening.

Possibly there was a faulty CM balun on one of the two 4221HD's, or perhaps there are other issues with the CM baluns that affect fringe reception (high signal loss). I have read other posts which suggest the CM balun is well designed, but this change has made a big difference for my installation.

Regards,
 

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has anyone modeled combining 2 x 4221HD's horizontally...

I tried this, and the gain in UHF appears very high (at 15 dbi - before deducting combiner loss), and VHF-Hi gain doesn't seem to make sense. It also appears much better that the 4228HD :confused:

I put the 2 - 4221HDs tip to tip on reflector rods

AGT is very difficult to adjust for 1.
 

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Except for the low-freq drop off, I get 15-17 dBi for New CM4228HD with "perfect" combining,
i.e. Lossless RF Combiner Mod:
http://imageevent.com/holl_ands/multibay/8bayrefl/cm4228hdmod
Also note Excellent Hi-VHF performance, except on lower channels...

Yup...adjusting AGT=1.0 can be very difficult with some antennas....esp multibay+reflector...
Hunt around for "good" combination of number of segments in SOURCE and AUTOSEG(??) value.

And when all else fails, think out of the box and try something DIFFERENT in the model, such
as getting rid of the bowtie apexes by defining a small triangle at the apex, subdivide the outer
vertical wire in the triangle into three wires and attach bowties to the inner two nodes, thereby
avoiding the SHARP ANGLE Warning problem, as done here for SIX Whisker Bowtie example:
http://www.digitalhome.ca/forum/showthread.php?p=971480
Read down a couple posts for the 4nec2 file....and a physical manifestation....
 

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yes, using your 4228HD model, I had 11-16 dbi, NET, from 470-680 Mhz, before combiner loss.

with 2 x 4221HDs combined, I get 15-17 dbi, NET, from 470-680 Mhz, before combine loss - AGT is under control on UHF

I will check again, but that seems to be overestimating possible gain on UHF

On VHF-HI, I didnt fix AGT yet...

thanks for the tips

EDIT: well, my "hunting" has ended, at least for a while...the best AGT adjustment was +2 across VHF-HI...it seems impossible
 

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using your 4228HD model, I had 11-16 dbi, NET, from 470-680 Mhz, before combiner loss.

with 2 x 4221HDs combined, I get 15-17 dbi, NET, from 470-680 Mhz, before combine loss
Maybe not surprising as the 4228HD may not have the optimized horizontal distance between bays.
 

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yes, also maybe because its a much wider reflector than the 4228HD

the 2 x 4221HDs are 23.6" apart, the 4228HD is 20" between bays

heres the nec file for VHF:

Code:
CM 2 x CM4221HD combined 8-Bay W 16 Reflector Rods, VHF-HI, 26 dec 2011
CE
GW	1	3	6.25	-0.59	0	6.25	0.59	0	0.15748031
GW	2	1	6.25	0.59	0	5.75	0.59	0	0.0815
GW	3	1	6.25	-0.59	0	5.75	-0.59	0	0.0815
GW	4	5	4.25	8.2404314	6.89	4.25	0.59	4.92	0.0815
GW	5	5	4.25	8.2404314	2.95	4.25	0.59	4.92	0.0815
GW	6	5	4.25	-0.59	4.92	4.25	-8.240431	6.89	0.0815
GW	7	5	4.25	-0.59	4.92	4.25	-8.240431	2.95	0.0815
GW	8	5	4.25	8.2404314	-6.89	4.25	0.59	-4.92	0.0815
GW	9	5	4.25	8.2404314	-2.95	4.25	0.59	-4.92	0.0815
GW	10	5	4.25	-0.59	-4.92	4.25	-8.240431	-6.89	0.0815
GW	11	5	4.25	-0.59	-4.92	4.25	-8.240431	-2.95	0.0815
GW	12	5	4.25	8.2404314	15.35	4.25	0.59	13.38	0.0815
GW	13	5	4.25	8.2404314	11.41	4.25	0.59	13.38	0.0815
GW	14	5	4.25	-0.59	13.38	4.25	-8.240431	15.35	0.0815
GW	15	5	4.25	-0.59	13.38	4.25	-8.240431	11.41	0.0815
GW	16	5	4.25	8.2404314	-15.35	4.25	0.59	-13.38	0.0815
GW	17	5	4.25	8.2404314	-11.41	4.25	0.59	-13.38	0.0815
GW	18	5	4.25	-0.59	-13.38	4.25	-8.240431	-15.35	0.0815
GW	19	5	4.25	-0.59	-13.38	4.25	-8.240431	-11.41	0.0815
GW	20	1	4.25	0.59	13.38	4.25	0.59	12.38	0.0595
GW	21	1	4.25	-0.59	13.38	4.25	-0.59	12.38	0.0595
GW	22	3	4.25	0.59	10.38	4.25	0.59	4.92	0.0595
GW	23	3	4.25	-0.59	10.38	4.25	-0.59	4.92	0.0595
GW	24	1	4.25	-0.59	10.38	4.65	0	11.38	0.0595
GW	25	1	4.25	0.59	12.38	4.65	0	11.38	0.0595
GW	26	1	4.25	0.59	10.38	3.85	0	11.38	0.0595
GW	27	1	4.25	-0.59	12.38	3.85	0	11.38	0.0595
GW	28	1	4.25	0.59	-13.38	4.25	0.59	-12.38	0.0595
GW	29	1	4.25	-0.59	-13.38	4.25	-0.59	-12.38	0.0595
GW	30	3	4.25	0.59	-10.38	4.25	0.59	-4.92	0.0595
GW	31	3	4.25	-0.59	-10.38	4.25	-0.59	-4.92	0.0595
GW	32	1	4.25	-0.59	-10.38	4.65	0	-11.38	0.0595
GW	33	1	4.25	0.59	-12.38	4.65	0	-11.38	0.0595
GW	34	1	4.25	0.59	-10.38	3.85	0	-11.38	0.0595
GW	35	1	4.25	-0.59	-12.38	3.85	0	-11.38	0.0595
GW	36	1	4.25	0.59	4.92	4.25	0.59	3.92	0.1875
GW	37	1	4.25	-0.59	4.92	4.25	-0.59	3.92	0.1875
GW	38	1	4.25	0.59	-4.92	4.25	0.59	-3.92	0.1875
GW	39	1	4.25	-0.59	-4.92	4.25	-0.59	-3.92	0.1875
GW	40	3	4.25	0.59	3.92	5.75	0.59	2.5	0.1875
GW	41	3	4.25	-0.59	3.92	5.75	-0.59	2.5	0.1875
GW	42	3	4.25	0.59	-3.92	5.75	0.59	-2.5	0.1875
GW	43	3	4.25	-0.59	-3.92	5.75	-0.59	-2.5	0.1875
GW	44	3	5.75	0.59	0	5.75	0.59	2.5	0.1875
GW	45	3	5.75	-0.59	0	5.75	-0.59	2.5	0.1875
GW	46	3	5.75	0.59	0	5.75	0.59	-2.5	0.1875
GW	47	3	5.75	-0.59	0	5.75	-0.59	-2.5	0.1875
GW	70	7	0	-11.8	2	0	0	2	0.0965
GW	71	7	0	0	2	0	11.8	2	0.0965
GW	72	7	0	-11.8	3.93	0	0	3.93	0.0965
GW	73	7	0	0	3.93	0	11.8	3.93	0.0965
GW	74	7	0	-11.8	5.86	0	0	5.86	0.0965
GW	75	7	0	0	5.86	0	11.8	5.86	0.0965
GW	76	7	0	-11.8	7.79	0	0	7.79	0.0965
GW	77	7	0	0	7.79	0	11.8	7.79	0.0965
GW	78	7	0	-11.8	9.72	0	0	9.72	0.0965
GW	79	7	0	0	9.72	0	11.8	9.72	0.0965
GW	80	7	0	-11.8	11.65	0	0	11.65	0.0965
GW	81	7	0	0	11.65	0	11.8	11.65	0.0965
GW	82	7	0	-11.8	13.58	0	0	13.58	0.0965
GW	83	7	0	0	13.58	0	11.8	13.58	0.0965
GW	84	7	0	-11.8	15.51	0	0	15.51	0.0965
GW	85	7	0	0	15.51	0	11.8	15.51	0.0965
GW	86	7	0	-11.8	-2	0	0	-2	0.0965
GW	87	7	0	0	-2	0	11.8	-2	0.0965
GW	88	7	0	-11.8	-3.93	0	0	-3.93	0.0965
GW	89	7	0	0	-3.93	0	11.8	-3.93	0.0965
GW	90	7	0	-11.8	-5.86	0	0	-5.86	0.0965
GW	91	7	0	0	-5.86	0	11.8	-5.86	0.0965
GW	92	7	0	-11.8	-7.79	0	0	-7.79	0.0965
GW	93	7	0	0	-7.79	0	11.8	-7.79	0.0965
GW	94	7	0	-11.8	-9.72	0	0	-9.72	0.0965
GW	95	7	0	0	-9.72	0	11.8	-9.72	0.0965
GW	96	7	0	-11.8	-11.65	0	0	-11.65	0.0965
GW	97	7	0	0	-11.65	0	11.8	-11.65	0.0965
GW	98	7	0	-11.8	-13.58	0	0	-13.58	0.0965
GW	99	7	0	0	-13.58	0	11.8	-13.58	0.0965
GW	100	7	0	-11.8	-15.51	0	0	-15.51	0.0965
GW	101	7	0	0	-15.51	0	11.8	-15.51	0.0965
GW	102	1	0	0	2	0	0	3.93	0.0965
GW	103	1	0	0	3.93	0	0	5.86	0.0965
GW	104	1	0	0	5.86	0	0	7.79	0.0965
GW	105	1	0	0	7.79	0	0	9.72	0.0965
GW	106	1	0	0	9.72	0	0	11.65	0.0965
GW	107	1	0	0	11.65	0	0	13.58	0.0965
GW	108	1	0	0	13.58	0	0	15.51	0.0965
GW	109	1	0	0	-2	0	0	-3.93	0.0965
GW	110	1	0	0	-3.93	0	0	-5.86	0.0965
GW	111	1	0	0	-5.86	0	0	-7.79	0.0965
GW	112	1	0	0	-7.79	0	0	-9.72	0.0965
GW	113	1	0	0	-9.72	0	0	-11.65	0.0965
GW	114	1	0	0	-11.65	0	0	-13.58	0.0965
GW	115	1	0	0	-13.58	0	0	-15.51	0.0965
GW	116	3	0	0	2	0	0	-2	0.0965
GW	117	3	6.25	-24.19	0	6.25	-23.01	0	0.15748031
GW	118	1	6.25	-23.01	0	5.75	-23.01	0	0.0815
GW	119	1	6.25	-24.19	0	5.75	-24.19	0	0.0815
GW	120	5	4.25	-15.359569	6.89	4.25	-23.01	4.92	0.0815
GW	121	5	4.25	-15.359569	2.95	4.25	-23.01	4.92	0.0815
GW	122	5	4.25	-24.19	4.92	4.25	-31.840431	6.89	0.0815
GW	123	5	4.25	-24.19	4.92	4.25	-31.840431	2.95	0.0815
GW	124	5	4.25	-15.359569	-6.89	4.25	-23.01	-4.92	0.0815
GW	125	5	4.25	-15.359569	-2.95	4.25	-23.01	-4.92	0.0815
GW	126	5	4.25	-24.19	-4.92	4.25	-31.840431	-6.89	0.0815
GW	127	5	4.25	-24.19	-4.92	4.25	-31.840431	-2.95	0.0815
GW	128	5	4.25	-15.359569	15.35	4.25	-23.01	13.38	0.0815
GW	129	5	4.25	-15.359569	11.41	4.25	-23.01	13.38	0.0815
GW	130	5	4.25	-24.19	13.38	4.25	-31.840431	15.35	0.0815
GW	131	5	4.25	-24.19	13.38	4.25	-31.840431	11.41	0.0815
GW	132	5	4.25	-15.359569	-15.35	4.25	-23.01	-13.38	0.0815
GW	133	5	4.25	-15.359569	-11.41	4.25	-23.01	-13.38	0.0815
GW	134	5	4.25	-24.19	-13.38	4.25	-31.840431	-15.35	0.0815
GW	135	5	4.25	-24.19	-13.38	4.25	-31.840431	-11.41	0.0815
GW	136	1	4.25	-23.01	13.38	4.25	-23.01	12.38	0.0595
GW	137	1	4.25	-24.19	13.38	4.25	-24.19	12.38	0.0595
GW	138	3	4.25	-23.01	10.38	4.25	-23.01	4.92	0.0595
GW	139	3	4.25	-24.19	10.38	4.25	-24.19	4.92	0.0595
GW	140	1	4.25	-24.19	10.38	4.65	-23.6	11.38	0.0595
GW	141	1	4.25	-23.01	12.38	4.65	-23.6	11.38	0.0595
GW	142	1	4.25	-23.01	10.38	3.85	-23.6	11.38	0.0595
GW	143	1	4.25	-24.19	12.38	3.85	-23.6	11.38	0.0595
GW	144	1	4.25	-23.01	-13.38	4.25	-23.01	-12.38	0.0595
GW	145	1	4.25	-24.19	-13.38	4.25	-24.19	-12.38	0.0595
GW	146	3	4.25	-23.01	-10.38	4.25	-23.01	-4.92	0.0595
GW	147	3	4.25	-24.19	-10.38	4.25	-24.19	-4.92	0.0595
GW	148	1	4.25	-24.19	-10.38	4.65	-23.6	-11.38	0.0595
GW	149	1	4.25	-23.01	-12.38	4.65	-23.6	-11.38	0.0595
GW	150	1	4.25	-23.01	-10.38	3.85	-23.6	-11.38	0.0595
GW	151	1	4.25	-24.19	-12.38	3.85	-23.6	-11.38	0.0595
GW	152	1	4.25	-23.01	4.92	4.25	-23.01	3.92	0.1875
GW	153	1	4.25	-24.19	4.92	4.25	-24.19	3.92	0.1875
GW	154	1	4.25	-23.01	-4.92	4.25	-23.01	-3.92	0.1875
GW	155	1	4.25	-24.19	-4.92	4.25	-24.19	-3.92	0.1875
GW	156	3	4.25	-23.01	3.92	5.75	-23.01	2.5	0.1875
GW	157	3	4.25	-24.19	3.92	5.75	-24.19	2.5	0.1875
GW	158	3	4.25	-23.01	-3.92	5.75	-23.01	-2.5	0.1875
GW	159	3	4.25	-24.19	-3.92	5.75	-24.19	-2.5	0.1875
GW	160	3	5.75	-23.01	0	5.75	-23.01	2.5	0.1875
GW	161	3	5.75	-24.19	0	5.75	-24.19	2.5	0.1875
GW	162	3	5.75	-23.01	0	5.75	-23.01	-2.5	0.1875
GW	163	3	5.75	-24.19	0	5.75	-24.19	-2.5	0.1875
GW	164	7	0	-35.4	2	0	-23.6	2	0.0965
GW	165	7	0	-23.6	2	0	-11.8	2	0.0965
GW	166	7	0	-35.4	3.93	0	-23.6	3.93	0.0965
GW	167	7	0	-23.6	3.93	0	-11.8	3.93	0.0965
GW	168	7	0	-35.4	5.86	0	-23.6	5.86	0.0965
GW	169	7	0	-23.6	5.86	0	-11.8	5.86	0.0965
GW	170	7	0	-35.4	7.79	0	-23.6	7.79	0.0965
GW	171	7	0	-23.6	7.79	0	-11.8	7.79	0.0965
GW	172	7	0	-35.4	9.72	0	-23.6	9.72	0.0965
GW	173	7	0	-23.6	9.72	0	-11.8	9.72	0.0965
GW	174	7	0	-35.4	11.65	0	-23.6	11.65	0.0965
GW	175	7	0	-23.6	11.65	0	-11.8	11.65	0.0965
GW	176	7	0	-35.4	13.58	0	-23.6	13.58	0.0965
GW	177	7	0	-23.6	13.58	0	-11.8	13.58	0.0965
GW	178	7	0	-35.4	15.51	0	-23.6	15.51	0.0965
GW	179	7	0	-23.6	15.51	0	-11.8	15.51	0.0965
GW	180	7	0	-35.4	-2	0	-23.6	-2	0.0965
GW	181	7	0	-23.6	-2	0	-11.8	-2	0.0965
GW	182	7	0	-35.4	-3.93	0	-23.6	-3.93	0.0965
GW	183	7	0	-23.6	-3.93	0	-11.8	-3.93	0.0965
GW	184	7	0	-35.4	-5.86	0	-23.6	-5.86	0.0965
GW	185	7	0	-23.6	-5.86	0	-11.8	-5.86	0.0965
GW	186	7	0	-35.4	-7.79	0	-23.6	-7.79	0.0965
GW	187	7	0	-23.6	-7.79	0	-11.8	-7.79	0.0965
GW	188	7	0	-35.4	-9.72	0	-23.6	-9.72	0.0965
GW	189	7	0	-23.6	-9.72	0	-11.8	-9.72	0.0965
GW	190	7	0	-35.4	-11.65	0	-23.6	-11.65	0.0965
GW	191	7	0	-23.6	-11.65	0	-11.8	-11.65	0.0965
GW	192	7	0	-35.4	-13.58	0	-23.6	-13.58	0.0965
GW	193	7	0	-23.6	-13.58	0	-11.8	-13.58	0.0965
GW	194	7	0	-35.4	-15.51	0	-23.6	-15.51	0.0965
GW	195	7	0	-23.6	-15.51	0	-11.8	-15.51	0.0965
GW	196	1	0	-23.6	2	0	-23.6	3.93	0.0965
GW	197	1	0	-23.6	3.93	0	-23.6	5.86	0.0965
GW	198	1	0	-23.6	5.86	0	-23.6	7.79	0.0965
GW	199	1	0	-23.6	7.79	0	-23.6	9.72	0.0965
GW	200	1	0	-23.6	9.72	0	-23.6	11.65	0.0965
GW	201	1	0	-23.6	11.65	0	-23.6	13.58	0.0965
GW	202	1	0	-23.6	13.58	0	-23.6	15.51	0.0965
GW	203	1	0	-23.6	-2	0	-23.6	-3.93	0.0965
GW	204	1	0	-23.6	-3.93	0	-23.6	-5.86	0.0965
GW	205	1	0	-23.6	-5.86	0	-23.6	-7.79	0.0965
GW	206	1	0	-23.6	-7.79	0	-23.6	-9.72	0.0965
GW	207	1	0	-23.6	-9.72	0	-23.6	-11.65	0.0965
GW	208	1	0	-23.6	-11.65	0	-23.6	-13.58	0.0965
GW	209	1	0	-23.6	-13.58	0	-23.6	-15.51	0.0965
GW	210	3	0	-23.6	2	0	-23.6	-2	0.0965
GS	0	0	0.0254		' All in in.
GE	0
EK
LD	5	0	0	0	1.67e7	0
EX	0	1	2	0	1	0
EX	0	117	2	0	1	0
GN	-1
FR	0	8	0	0	174	6
RP	0	1	73	1510	90	0	1	5	0	0
 

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Yeah, there are wide swings in the AGT figure over the vhf-hi range. In cases like that, I like to calculate channel by channel and add or subtract the AGT (db) figure. And do the Net Gain also channel by channel.
 

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2,421 Posts
AGT bracketed values are RED, so I thought that meant the model needs to be corrected more, before even considering using the values to correct the gain :confused:

so in this case, 2 x 4221HDs is useless in term of net VHF-Hi gain, wheras the 4228HD is excellent.

EDIT: to get the AGT to work the reflectors needs to be separated (not touching, say by 1"), then AGT is corrected and a little gain is lost on lo UHF....I think

EDIT: OR the outer reflector rods of each unit, need to be made a single, continuous rods in the model, going from center of one unit to center of the other...


heres the file for 1" separation between reflector rods, NET gain is more than 14-17 dbi from 470 Mhz to 680 Mhz, Hi VHF-HI is mediocre, but decent at 213 Mhz - if the models are correct this means it beats any other 8-bay, hacked or not, and its cheaper also - of course more work is involved in supporting the combination structure

Code:
CM 2 x CM4221HD combined 8-Bay W 16 Reflector Rods, VHF-HI, 26 dec 2011, 1" separation between ref rods
CE
GW	1	1	6.25	-0.59	0	6.25	0.59	0	0.11811024
GW	2	1	6.25	0.59	0	5.75	0.59	0	0.0815
GW	3	1	6.25	-0.59	0	5.75	-0.59	0	0.0815
GW	4	5	4.25	8.2404314	6.89	4.25	0.59	4.92	0.0815
GW	5	5	4.25	8.2404314	2.95	4.25	0.59	4.92	0.0815
GW	6	5	4.25	-0.59	4.92	4.25	-8.240431	6.89	0.0815
GW	7	5	4.25	-0.59	4.92	4.25	-8.240431	2.95	0.0815
GW	8	5	4.25	8.2404314	-6.89	4.25	0.59	-4.92	0.0815
GW	9	5	4.25	8.2404314	-2.95	4.25	0.59	-4.92	0.0815
GW	10	5	4.25	-0.59	-4.92	4.25	-8.240431	-6.89	0.0815
GW	11	5	4.25	-0.59	-4.92	4.25	-8.240431	-2.95	0.0815
GW	12	5	4.25	8.2404314	15.35	4.25	0.59	13.38	0.0815
GW	13	5	4.25	8.2404314	11.41	4.25	0.59	13.38	0.0815
GW	14	5	4.25	-0.59	13.38	4.25	-8.240431	15.35	0.0815
GW	15	5	4.25	-0.59	13.38	4.25	-8.240431	11.41	0.0815
GW	16	5	4.25	8.2404314	-15.35	4.25	0.59	-13.38	0.0815
GW	17	5	4.25	8.2404314	-11.41	4.25	0.59	-13.38	0.0815
GW	18	5	4.25	-0.59	-13.38	4.25	-8.240431	-15.35	0.0815
GW	19	5	4.25	-0.59	-13.38	4.25	-8.240431	-11.41	0.0815
GW	20	1	4.25	0.59	13.38	4.25	0.59	12.38	0.0595
GW	21	1	4.25	-0.59	13.38	4.25	-0.59	12.38	0.0595
GW	22	6	4.25	0.59	10.38	4.25	0.59	4.92	0.0595
GW	23	6	4.25	-0.59	10.38	4.25	-0.59	4.92	0.0595
GW	24	1	4.25	-0.59	10.38	4.65	0	11.38	0.0595
GW	25	1	4.25	0.59	12.38	4.65	0	11.38	0.0595
GW	26	1	4.25	0.59	10.38	3.85	0	11.38	0.0595
GW	27	1	4.25	-0.59	12.38	3.85	0	11.38	0.0595
GW	28	1	4.25	0.59	-13.38	4.25	0.59	-12.38	0.0595
GW	29	1	4.25	-0.59	-13.38	4.25	-0.59	-12.38	0.0595
GW	30	6	4.25	0.59	-10.38	4.25	0.59	-4.92	0.0595
GW	31	6	4.25	-0.59	-10.38	4.25	-0.59	-4.92	0.0595
GW	32	1	4.25	-0.59	-10.38	4.65	0	-11.38	0.0595
GW	33	1	4.25	0.59	-12.38	4.65	0	-11.38	0.0595
GW	34	1	4.25	0.59	-10.38	3.85	0	-11.38	0.0595
GW	35	1	4.25	-0.59	-12.38	3.85	0	-11.38	0.0595
GW	36	1	4.25	0.59	4.92	4.25	0.59	3.92	0.1875
GW	37	1	4.25	-0.59	4.92	4.25	-0.59	3.92	0.1875
GW	38	1	4.25	0.59	-4.92	4.25	0.59	-3.92	0.1875
GW	39	1	4.25	-0.59	-4.92	4.25	-0.59	-3.92	0.1875
GW	40	3	4.25	0.59	3.92	5.75	0.59	2.5	0.1875
GW	41	3	4.25	-0.59	3.92	5.75	-0.59	2.5	0.1875
GW	42	3	4.25	0.59	-3.92	5.75	0.59	-2.5	0.1875
GW	43	3	4.25	-0.59	-3.92	5.75	-0.59	-2.5	0.1875
GW	44	3	5.75	0.59	0	5.75	0.59	2.5	0.1875
GW	45	3	5.75	-0.59	0	5.75	-0.59	2.5	0.1875
GW	46	3	5.75	0.59	0	5.75	0.59	-2.5	0.1875
GW	47	3	5.75	-0.59	0	5.75	-0.59	-2.5	0.1875
GW	70	5	0	-11.8	2	0	0	2	0.0965
GW	71	5	0	0	2	0	11.8	2	0.0965
GW	72	5	0	-11.8	3.93	0	0	3.93	0.0965
GW	73	5	0	0	3.93	0	11.8	3.93	0.0965
GW	74	5	0	-11.8	5.86	0	0	5.86	0.0965
GW	75	5	0	0	5.86	0	11.8	5.86	0.0965
GW	76	5	0	-11.8	7.79	0	0	7.79	0.0965
GW	77	5	0	0	7.79	0	11.8	7.79	0.0965
GW	78	5	0	-11.8	9.72	0	0	9.72	0.0965
GW	79	5	0	0	9.72	0	11.8	9.72	0.0965
GW	80	5	0	-11.8	11.65	0	0	11.65	0.0965
GW	81	5	0	0	11.65	0	11.8	11.65	0.0965
GW	82	5	0	-11.8	13.58	0	0	13.58	0.0965
GW	83	5	0	0	13.58	0	11.8	13.58	0.0965
GW	84	5	0	-11.8	15.51	0	0	15.51	0.0965
GW	85	5	0	0	15.51	0	11.8	15.51	0.0965
GW	86	5	0	-11.8	-2	0	0	-2	0.0965
GW	87	5	0	0	-2	0	11.8	-2	0.0965
GW	88	5	0	-11.8	-3.93	0	0	-3.93	0.0965
GW	89	5	0	0	-3.93	0	11.8	-3.93	0.0965
GW	90	5	0	-11.8	-5.86	0	0	-5.86	0.0965
GW	91	5	0	0	-5.86	0	11.8	-5.86	0.0965
GW	92	5	0	-11.8	-7.79	0	0	-7.79	0.0965
GW	93	5	0	0	-7.79	0	11.8	-7.79	0.0965
GW	94	5	0	-11.8	-9.72	0	0	-9.72	0.0965
GW	95	5	0	0	-9.72	0	11.8	-9.72	0.0965
GW	96	5	0	-11.8	-11.65	0	0	-11.65	0.0965
GW	97	5	0	0	-11.65	0	11.8	-11.65	0.0965
GW	98	5	0	-11.8	-13.58	0	0	-13.58	0.0965
GW	99	5	0	0	-13.58	0	11.8	-13.58	0.0965
GW	100	5	0	-11.8	-15.51	0	0	-15.51	0.0965
GW	101	5	0	0	-15.51	0	11.8	-15.51	0.0965
GW	102	1	0	0	2	0	0	3.93	0.0965
GW	103	1	0	0	3.93	0	0	5.86	0.0965
GW	104	1	0	0	5.86	0	0	7.79	0.0965
GW	105	1	0	0	7.79	0	0	9.72	0.0965
GW	106	1	0	0	9.72	0	0	11.65	0.0965
GW	107	1	0	0	11.65	0	0	13.58	0.0965
GW	108	1	0	0	13.58	0	0	15.51	0.0965
GW	109	1	0	0	-2	0	0	-3.93	0.0965
GW	110	1	0	0	-3.93	0	0	-5.86	0.0965
GW	111	1	0	0	-5.86	0	0	-7.79	0.0965
GW	112	1	0	0	-7.79	0	0	-9.72	0.0965
GW	113	1	0	0	-9.72	0	0	-11.65	0.0965
GW	114	1	0	0	-11.65	0	0	-13.58	0.0965
GW	115	1	0	0	-13.58	0	0	-15.51	0.0965
GW	116	3	0	0	2	0	0	-2	0.0965
GW	117	1	6.25	-25.19	0	6.25	-24.01	0	0.11811024
GW	118	1	6.25	-24.01	0	5.75	-24.01	0	0.0815
GW	119	1	6.25	-25.19	0	5.75	-25.19	0	0.0815
GW	120	5	4.25	-16.359569	6.89	4.25	-24.01	4.92	0.0815
GW	121	5	4.25	-16.359569	2.95	4.25	-24.01	4.92	0.0815
GW	122	5	4.25	-25.19	4.92	4.25	-32.840431	6.89	0.0815
GW	123	5	4.25	-25.19	4.92	4.25	-32.840431	2.95	0.0815
GW	124	5	4.25	-16.359569	-6.89	4.25	-24.01	-4.92	0.0815
GW	125	5	4.25	-16.359569	-2.95	4.25	-24.01	-4.92	0.0815
GW	126	5	4.25	-25.19	-4.92	4.25	-32.840431	-6.89	0.0815
GW	127	5	4.25	-25.19	-4.92	4.25	-32.840431	-2.95	0.0815
GW	128	5	4.25	-16.359569	15.35	4.25	-24.01	13.38	0.0815
GW	129	5	4.25	-16.359569	11.41	4.25	-24.01	13.38	0.0815
GW	130	5	4.25	-25.19	13.38	4.25	-32.840431	15.35	0.0815
GW	131	5	4.25	-25.19	13.38	4.25	-32.840431	11.41	0.0815
GW	132	5	4.25	-16.359569	-15.35	4.25	-24.01	-13.38	0.0815
GW	133	5	4.25	-16.359569	-11.41	4.25	-24.01	-13.38	0.0815
GW	134	5	4.25	-25.19	-13.38	4.25	-32.840431	-15.35	0.0815
GW	135	5	4.25	-25.19	-13.38	4.25	-32.840431	-11.41	0.0815
GW	136	1	4.25	-24.01	13.38	4.25	-24.01	12.38	0.0595
GW	137	1	4.25	-25.19	13.38	4.25	-25.19	12.38	0.0595
GW	138	6	4.25	-24.01	10.38	4.25	-24.01	4.92	0.0595
GW	139	6	4.25	-25.19	10.38	4.25	-25.19	4.92	0.0595
GW	140	1	4.25	-25.19	10.38	4.65	-24.6	11.38	0.0595
GW	141	1	4.25	-24.01	12.38	4.65	-24.6	11.38	0.0595
GW	142	1	4.25	-24.01	10.38	3.85	-24.6	11.38	0.0595
GW	143	1	4.25	-25.19	12.38	3.85	-24.6	11.38	0.0595
GW	144	1	4.25	-24.01	-13.38	4.25	-24.01	-12.38	0.0595
GW	145	1	4.25	-25.19	-13.38	4.25	-25.19	-12.38	0.0595
GW	146	6	4.25	-24.01	-10.38	4.25	-24.01	-4.92	0.0595
GW	147	6	4.25	-25.19	-10.38	4.25	-25.19	-4.92	0.0595
GW	148	1	4.25	-25.19	-10.38	4.65	-24.6	-11.38	0.0595
GW	149	1	4.25	-24.01	-12.38	4.65	-24.6	-11.38	0.0595
GW	150	1	4.25	-24.01	-10.38	3.85	-24.6	-11.38	0.0595
GW	151	1	4.25	-25.19	-12.38	3.85	-24.6	-11.38	0.0595
GW	152	1	4.25	-24.01	4.92	4.25	-24.01	3.92	0.1875
GW	153	1	4.25	-25.19	4.92	4.25	-25.19	3.92	0.1875
GW	154	1	4.25	-24.01	-4.92	4.25	-24.01	-3.92	0.1875
GW	155	1	4.25	-25.19	-4.92	4.25	-25.19	-3.92	0.1875
GW	156	3	4.25	-24.01	3.92	5.75	-24.01	2.5	0.1875
GW	157	3	4.25	-25.19	3.92	5.75	-25.19	2.5	0.1875
GW	158	3	4.25	-24.01	-3.92	5.75	-24.01	-2.5	0.1875
GW	159	3	4.25	-25.19	-3.92	5.75	-25.19	-2.5	0.1875
GW	160	3	5.75	-24.01	0	5.75	-24.01	2.5	0.1875
GW	161	3	5.75	-25.19	0	5.75	-25.19	2.5	0.1875
GW	162	3	5.75	-24.01	0	5.75	-24.01	-2.5	0.1875
GW	163	3	5.75	-25.19	0	5.75	-25.19	-2.5	0.1875
GW	164	5	0	-36.4	2	0	-24.6	2	0.0965
GW	165	5	0	-24.6	2	0	-12.8	2	0.0965
GW	166	5	0	-36.4	3.93	0	-24.6	3.93	0.0965
GW	167	5	0	-24.6	3.93	0	-12.8	3.93	0.0965
GW	168	5	0	-36.4	5.86	0	-24.6	5.86	0.0965
GW	169	5	0	-24.6	5.86	0	-12.8	5.86	0.0965
GW	170	5	0	-36.4	7.79	0	-24.6	7.79	0.0965
GW	171	5	0	-24.6	7.79	0	-12.8	7.79	0.0965
GW	172	5	0	-36.4	9.72	0	-24.6	9.72	0.0965
GW	173	5	0	-24.6	9.72	0	-12.8	9.72	0.0965
GW	174	5	0	-36.4	11.65	0	-24.6	11.65	0.0965
GW	175	5	0	-24.6	11.65	0	-12.8	11.65	0.0965
GW	176	5	0	-36.4	13.58	0	-24.6	13.58	0.0965
GW	177	5	0	-24.6	13.58	0	-12.8	13.58	0.0965
GW	178	5	0	-36.4	15.51	0	-24.6	15.51	0.0965
GW	179	5	0	-24.6	15.51	0	-12.8	15.51	0.0965
GW	180	5	0	-36.4	-2	0	-24.6	-2	0.0965
GW	181	5	0	-24.6	-2	0	-12.8	-2	0.0965
GW	182	5	0	-36.4	-3.93	0	-24.6	-3.93	0.0965
GW	183	5	0	-24.6	-3.93	0	-12.8	-3.93	0.0965
GW	184	5	0	-36.4	-5.86	0	-24.6	-5.86	0.0965
GW	185	5	0	-24.6	-5.86	0	-12.8	-5.86	0.0965
GW	186	5	0	-36.4	-7.79	0	-24.6	-7.79	0.0965
GW	187	5	0	-24.6	-7.79	0	-12.8	-7.79	0.0965
GW	188	5	0	-36.4	-9.72	0	-24.6	-9.72	0.0965
GW	189	5	0	-24.6	-9.72	0	-12.8	-9.72	0.0965
GW	190	5	0	-36.4	-11.65	0	-24.6	-11.65	0.0965
GW	191	5	0	-24.6	-11.65	0	-12.8	-11.65	0.0965
GW	192	5	0	-36.4	-13.58	0	-24.6	-13.58	0.0965
GW	193	5	0	-24.6	-13.58	0	-12.8	-13.58	0.0965
GW	194	5	0	-36.4	-15.51	0	-24.6	-15.51	0.0965
GW	195	5	0	-24.6	-15.51	0	-12.8	-15.51	0.0965
GW	196	1	0	-24.6	2	0	-24.6	3.93	0.0965
GW	197	1	0	-24.6	3.93	0	-24.6	5.86	0.0965
GW	198	1	0	-24.6	5.86	0	-24.6	7.79	0.0965
GW	199	1	0	-24.6	7.79	0	-24.6	9.72	0.0965
GW	200	1	0	-24.6	9.72	0	-24.6	11.65	0.0965
GW	201	1	0	-24.6	11.65	0	-24.6	13.58	0.0965
GW	202	1	0	-24.6	13.58	0	-24.6	15.51	0.0965
GW	203	1	0	-24.6	-2	0	-24.6	-3.93	0.0965
GW	204	1	0	-24.6	-3.93	0	-24.6	-5.86	0.0965
GW	205	1	0	-24.6	-5.86	0	-24.6	-7.79	0.0965
GW	206	1	0	-24.6	-7.79	0	-24.6	-9.72	0.0965
GW	207	1	0	-24.6	-9.72	0	-24.6	-11.65	0.0965
GW	208	1	0	-24.6	-11.65	0	-24.6	-13.58	0.0965
GW	209	1	0	-24.6	-13.58	0	-24.6	-15.51	0.0965
GW	210	3	0	-24.6	2	0	-24.6	-2	0.0965
GS	0	0	0.0254		' All in in.
GE	0
EK
LD	5	0	0	0	1.67e7	0
EX	0	1	1	0	1	0
EX	0	117	1	0	1	0
GN	-1
'FR	0	8	0	0	174	6
FR	0	36	0	0	470	6
RP 0 1 73 1510 90 0 1 5 0 0
 

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3,397 Posts
Horizontally-Stacked CM4221's with RF Combiner:

I initially checked balm's 4nec2 file (post #313) and found No Errors, but many segment Warnings.
AGT was slightly off in the Original: UHF AGT=0.99 (-0.1 dB), Hi-VHF AGT=0.93 (-0.3 dB).

Inspecting the file, I uncovered what I think is an unintended Wire Radius for the
Inner Feedline Radius (GW36-47 & GW152-163), which I changed from 0.1875-in
to 0.0595, matching what was used for the Outer Feedline Radius (GW20-35 & GW136-151).
All of the Segment Warnings went away...and still NO Errors.

After inserting my usual FR/RP Card Set, I added the variable SYmbol Rsrc to adjust AGT=1.0.
There was no significant change to either UHF Raw Gain or SWR compared to original:
UHF Raw Gain=14.1 dBi (470 MHz), 17.7 dBi (698 MHz) & 18.3 dBi (806 MHz), SWR<2.8.

To investigate whether the very short 0.5-in "Simulated Balun" wires connecting the SOURCE
wire to the antenna were causing any problems, I lengthened them to 2.0-in. No significant
effect on Raw Gain, but SWR at 470 MHz increased a bit to 2.9.

I then eliminated the "Simulated Balun" entirely, connecting the SOURCE directly between the
Feedlines (as is the usual practice with Multi-Bay antennas). No significant change wrt Original.

Finally, since the Original appears to have used Autoseg=6 (a bit small), I did Autoseg=11.
Raw Gain increased a bit: UHF Raw Gain=14.1 (470 MHz), 17.8 (698 MHz) & 18.4 dBi (806 MHz)
and SWR remained < 2.8. This is the final 4nec2 file I ran to obtain results posted here:
http://imageevent.com/holl_ands/multibay/8bayrefl/horizstackcm4221hd

The 4nec2 File and Hi-VHF results were also uploaded. Hi-VHF was about as problematic
as the CM4228HD, with very irregular Gain across most channels (degrades DTV) and
Excessive SWR on all but Ch11 & Ch12.

Since the 4nec2 file tolerated these several different variations, I BELIEVE that these are
TRUE results and not some sort of calculation engine fluke.

The challenge now is to find an Interconnection Harness that doesn't lose as much as
the 0.5 to 2.0+ dB loss in a typical RF Combiner, see www.antennahacks.com

It would also be of interest to sweep the bowties forward (probably 1 to 2-in) and
try wider separation between the Bays and/or additional Reflector Rods to see if either
the UHF Raw Gain, Forward Sidelobes or Hi-VHF Performance can be improved.....
 

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holl_ands, thanks for fixing that file ...looks like I was overestimating low UHF, and underestimating mid-high UHF...

still, pretty decent results

as for the wire configurations and wire radii (not at the balun), I believe I used the same data as in you model of the 4221HD (unchanged radii) ;)

I just took 2 of the 4221HDs as they were, and made the screens touch

it looks like your using separated reflector screens, similar to what I did in post #315



another idea might be to reduce tine separation to 2"



BTW, I CANNOT run your new 4211HD combined model...I get parser, constant, token errors, then I have to crash the program to get out...I thought it had to do with the quote/spacer markers, but after removing all comments, I have the same problem

EDIT: OK, tags #90 to #95 (reflector rods) got mangled out of position, and the radii got truncated to zero, in the opening of the file (I guess) - anyway I fixed it in my file

thanks
 

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Although the uploaded file LOOKS good...and still LOOKS good when downloaded,
I have the same problem with GW90-95...maybe there are some hidden control char's???
Whatever it is, the NEW NEC EDITOR immediately recognizes that something is messed up.

I manually replaced all TABs with SPACEs and uploaded again....now it's fixed....I hope...

Looking back on my CM4221HD 4nec2 model, I see what you mean about the Inner
Feedlines being a much fatter 3/8-in, cuz it's simulating the FLAT BANDS going to the Balun.
Guess it doesn't really make much difference.....I'll fix the file tomorrow & repost results.
 

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I'm not sure if the EXACT detail of the "bumped out" Rabbit73 balun modification was modeled, or more importantly if it made any difference in the model results as compared to JUST the balun flip mod ? just curious.

Thanks
 

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Is there a reliable way of simply extending the CM4221HD whiskers to 9" long. I put an ALMOST perfectly fitting 3/16" aluminum tubing over the ends but I have not yet figured a way to fasten it solidly to the whiskers (its not quite tight enough to hold on its own)

So maybe some sort of glue that withstands outdoors ???, but then I assumed it would change the surface area properties and affect the antenna performance ...???
 
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