Antennacraft U8000 Hardware Hacks

[holl_ands]

I've run many "optimization" runs on a lot of antenna models....half-an-inch
one way or another is barely perceptible....

[300ohm]

With the help of envirogeek for the pictures and dimensions of the U8000 phasing lines, heres a closer to real life model of the U8000.

Raw Gain:


Note:
At the 470 mhz end of the scale, add about .3 dBi. At the 806 mhz end of the scale, subtract about .12 dBi. The middle of the scale doesnt need to be adjusted.

SWR:


NEC file:

CM AntennaCraft U8000 NEC model, Closer to Real Life 
CM Modeled by 300 ohm, measured by octopod, phasing line help from envirogeek
CM BowLen=8.0", BowSep=8.0", Reflector to Element Sep=4.00" (AWG9 Elements/Phase Lines)
CM 9 Refl. Rods, 20-in long.  Autoseg(21), AGT=1.0 at 585 mhz.
CM AGT= .93 (-0.3 db) at 470 mhz, AGT= 1.03 (.12 db) at 806 mhz
CM FeedSep=2.0"  on individual U4000's
CE
GW	1	3	0	-9.125	4	0	-8.4178932	4.70710678	0.05721178
GW	2	13	0	-8.4178932	4.70710678	0	-1.7620476	6.875	0.05721178
GW	3	3	0	-9.125	4	0	-8.4178933	3.29289331	0.05721178
GW	4	13	0	-8.4178933	3.29289331	0	-1.7620476	1.125	0.05721178
GW	5	3	0	-11.125	4	0	-11.832107	4.70710709	0.05721178
GW	6	13	0	-11.832107	4.70710709	0	-18.487952	6.875	0.05721178
GW	7	3	0	-11.125	4	0	-11.832107	3.29289331	0.05721178
GW	8	13	0	-11.832107	3.29289331	0	-18.487952	1.125	0.05721178
GW	9	3	0	-9.125	12	0	-8.4178932	12.7071068	0.05721178
GW	10	13	0	-8.4178932	12.7071068	0	-1.7620476	14.875	0.05721178
GW	11	3	0	-9.125	12	0	-8.4178933	11.2928933	0.05721178
GW	12	13	0	-8.4178933	11.2928933	0	-1.7620476	9.125	0.05721178
GW	13	3	0	-11.125	12	0	-11.832107	12.7071071	0.05721178
GW	14	13	0	-11.832107	12.7071071	0	-18.487952	14.875	0.05721178
GW	15	3	0	-11.125	12	0	-11.832107	11.2928933	0.05721178
GW	16	13	0	-11.832107	11.2928933	0	-18.487952	9.125	0.05721178
GW	17	3	0	-9.125	-12	0	-8.4178932	-11.292893	0.05721178
GW	18	13	0	-8.4178932	-11.292893	0	-1.7620476	-9.125	0.05721178
GW	19	3	0	-9.125	-12	0	-8.4178933	-12.707107	0.05721178
GW	20	13	0	-8.4178933	-12.707107	0	-1.7620476	-14.875	0.05721178
GW	21	3	0	-11.125	-12	0	-11.832107	-11.292893	0.05721178
GW	22	13	0	-11.832107	-11.292893	0	-18.487952	-9.125	0.05721178
GW	23	3	0	-11.125	-12	0	-11.832107	-12.707107	0.05721178
GW	24	13	0	-11.832107	-12.707107	0	-18.487952	-14.875	0.05721178
GW	25	3	0	-9.125	-4	0	-8.4178932	-3.2928932	0.05721178
GW	26	13	0	-8.4178932	-3.2928932	0	-1.7620476	-1.125	0.05721178
GW	27	3	0	-9.125	-4	0	-8.4178933	-4.7071067	0.05721178
GW	28	13	0	-8.4178933	-4.7071067	0	-1.7620476	-6.875	0.05721178
GW	29	3	0	-11.125	-4	0	-11.832107	-3.2928929	0.05721178
GW	30	13	0	-11.832107	-3.2928929	0	-18.487952	-1.125	0.05721178
GW	31	3	0	-11.125	-4	0	-11.832107	-4.7071067	0.05721178
GW	32	13	0	-11.832107	-4.7071067	0	-18.487952	-6.875	0.05721178
GW	33	7	0	-11.125	4	0	-11.125	0	0.05721178
GW	34	7	0	-11.125	0	0	-11.125	-4	0.05721178
GW	35	7	0	-9.125	4	0	-9.125	0	0.05721178
GW	36	7	0	-9.125	0	0	-9.125	-4	0.05721178
GW	38	33	-4	-20.125	15.5	-4	-0.125	15.5	0.1875
GW	39	33	-4	-20.125	11.5	-4	-0.125	11.5	0.1875
GW	40	33	-4	-20.125	7.75	-4	-0.125	7.75	0.1875
GW	41	33	-4	-20.125	3.875	-4	-0.125	3.875	0.1875
GW	42	33	-4	-20.125	-3.875	-4	-0.125	-3.875	0.1875
GW	43	33	-4	-20.125	-7.75	-4	-0.125	-7.75	0.1875
GW	44	33	-4	-20.125	-11.5	-4	-0.125	-11.5	0.1875
GW	45	33	-4	-20.125	-15.5	-4	-0.125	-15.5	0.1875
GW	46	33	-4	-20.125	0	-4	-0.125	0	0.1875
GW	47	5	0	-11.125	12	0.3072	-10.625	9.33333333	0.05721178
GW	48	5	0.3072	-10.625	9.33333333	0.3072	-9.625	6.66666667	0.05721178
GW	49	5	0.3072	-9.625	6.66666667	0	-9.125	4	0.05721178
GW	50	5	0	-9.125	12	-0.3072	-9.625	9.33333333	0.05721178
GW	51	5	-0.3072	-9.625	9.33333333	-0.3072	-10.625	6.66666667	0.05721178
GW	52	5	-0.3072	-10.625	6.66666667	0	-11.125	4	0.05721178
GW	53	5	0	-9.125	-4	-0.3072	-9.625	-6.6666667	0.05721178
GW	54	5	-0.3072	-9.625	-6.6666667	-0.3072	-10.625	-9.3333333	0.05721178
GW	55	5	-0.3072	-10.625	-9.3333333	0	-11.125	-12	0.05721178
GW	56	5	0	-11.125	-4	0.3072	-10.625	-6.6666667	0.05721178
GW	57	5	0.3072	-10.625	-6.6666667	0.3072	-9.625	-9.3333333	0.05721178
GW	58	5	0.3072	-9.625	-9.3333333	0	-9.125	-12	0.05721178
GW	59	3	0	11.125	4	0	11.8321068	4.70710678	0.05721178
GW	60	13	0	11.8321068	4.70710678	0	18.4879524	6.875	0.05721178
GW	61	3	0	11.125	4	0	11.8321067	3.29289331	0.05721178
GW	62	13	0	11.8321067	3.29289331	0	18.4879524	1.125	0.05721178
GW	63	3	0	9.125	4	0	8.4178933	4.70710709	0.05721178
GW	64	13	0	8.4178933	4.70710709	0	1.7620476	6.875	0.05721178
GW	65	3	0	9.125	4	0	8.4178933	3.29289331	0.05721178
GW	66	13	0	8.4178933	3.29289331	0	1.7620476	1.125	0.05721178
GW	67	3	0	11.125	12	0	11.8321068	12.7071068	0.05721178
GW	68	13	0	11.8321068	12.7071068	0	18.4879524	14.875	0.05721178
GW	69	3	0	11.125	12	0	11.8321067	11.2928933	0.05721178
GW	70	13	0	11.8321067	11.2928933	0	18.4879524	9.125	0.05721178
GW	71	3	0	9.125	12	0	8.4178933	12.7071071	0.05721178
GW	72	13	0	8.4178933	12.7071071	0	1.7620476	14.875	0.05721178
GW	73	3	0	9.125	12	0	8.4178933	11.2928933	0.05721178
GW	74	13	0	8.4178933	11.2928933	0	1.7620476	9.125	0.05721178
GW	75	3	0	11.125	-12	0	11.8321068	-11.292893	0.05721178
GW	76	13	0	11.8321068	-11.292893	0	18.4879524	-9.125	0.05721178
GW	77	3	0	11.125	-12	0	11.8321067	-12.707107	0.05721178
GW	78	13	0	11.8321067	-12.707107	0	18.4879524	-14.875	0.05721178
GW	79	3	0	9.125	-12	0	8.4178933	-11.292893	0.05721178
GW	80	13	0	8.4178933	-11.292893	0	1.7620476	-9.125	0.05721178
GW	81	3	0	9.125	-12	0	8.4178933	-12.707107	0.05721178
GW	82	13	0	8.4178933	-12.707107	0	1.7620476	-14.875	0.05721178
GW	83	3	0	11.125	-4	0	11.8321068	-3.2928932	0.05721178
GW	84	13	0	11.8321068	-3.2928932	0	18.4879524	-1.125	0.05721178
GW	85	3	0	11.125	-4	0	11.8321067	-4.7071067	0.05721178
GW	86	13	0	11.8321067	-4.7071067	0	18.4879524	-6.875	0.05721178
GW	87	3	0	9.125	-4	0	8.4178933	-3.2928929	0.05721178
GW	88	13	0	8.4178933	-3.2928929	0	1.7620476	-1.125	0.05721178
GW	89	3	0	9.125	-4	0	8.4178933	-4.7071067	0.05721178
GW	90	13	0	8.4178933	-4.7071067	0	1.7620476	-6.875	0.05721178
GW	91	7	0	9.125	4	0	9.125	0	0.05721178
GW	92	7	0	9.125	0	0	9.125	-4	0.05721178
GW	93	7	0	11.125	4	0	11.125	0	0.05721178
GW	94	7	0	11.125	0	0	11.125	-4	0.05721178
GW	96	33	-4	0.125	15.5	-4	20.125	15.5	0.1875
GW	97	33	-4	0.125	11.5	-4	20.125	11.5	0.1875
GW	98	33	-4	0.125	7.75	-4	20.125	7.75	0.1875
GW	99	33	-4	0.125	3.875	-4	20.125	3.875	0.1875
GW	100	33	-4	0.125	-3.875	-4	20.125	-3.875	0.1875
GW	101	33	-4	0.125	-7.75	-4	20.125	-7.75	0.1875
GW	102	33	-4	0.125	-11.5	-4	20.125	-11.5	0.1875
GW	103	33	-4	0.125	-15.5	-4	20.125	-15.5	0.1875
GW	104	33	-4	0.125	0	-4	20.125	0	0.1875
GW	105	5	0	9.125	12	0.3072	9.625	9.33333333	0.05721178
GW	106	5	0.3072	9.625	9.33333333	0.3072	10.625	6.66666667	0.05721178
GW	107	5	0.3072	10.625	6.66666667	0	11.125	4	0.05721178
GW	108	5	0	11.125	12	-0.3072	10.625	9.33333333	0.05721178
GW	109	5	-0.3072	10.625	9.33333333	-0.3072	9.625	6.66666667	0.05721178
GW	110	5	-0.3072	9.625	6.66666667	0	9.125	4	0.05721178
GW	111	5	0	11.125	-4	-0.3072	10.625	-6.6666667	0.05721178
GW	112	5	-0.3072	10.625	-6.6666667	-0.3072	9.625	-9.3333333	0.05721178
GW	113	5	-0.3072	9.625	-9.3333333	0	9.125	-12	0.05721178
GW	114	5	0	9.125	-4	0.3072	9.625	-6.6666667	0.05721178
GW	115	5	0.3072	9.625	-6.6666667	0.3072	10.625	-9.3333333	0.05721178
GW	116	5	0.3072	10.625	-9.3333333	0	11.125	-12	0.05721178
GW	1000	5	-1.5	-1.25	-14.75	-1.4999995	1.25	-14.75	0.045371
GW	1003	1	-1.4999995	1.25	-14.75	-1.25	1.25	-14.75	0.05721178
GW	1004	1	-1.5	-1.25	-14.75	-1.25	-1.25	-14.75	0.05721178
GW	1005	3	0	11.125	0	-0.9999998	11.1250086	0	0.05721178
GW	1006	3	0	9.12499824	0	-0.9999	9.10978141	0	0.05721178
GW	1007	3	0	-9.125	0	-1	-9.125	0	0.05721178
GW	1008	3	0	-11.125	0	-1	-11.125	0	0.05721178
GW	1009	9	-1	-11.125	0	-1.1369963	-8.4139905	-4.049356	0.05721178
GW	1011	9	-1.3627339	-3.9610055	-10.70065	-1.5	-1.2500002	-14.75	0.05721178
GW	1012	13	-1.511996	-8.413995	-4.04935	-1.737734	-3.961005	-10.70065	0.0572118
GW	1014	1	-1.511996	-8.413995	-4.04935	-1.136996	-8.41399	-4.049356	0.0572118
GW	1015	1	-1.737734	-3.961005	-10.70065	-1.362734	-3.961005	-10.70065	0.0572118
GW	1016	9	-1	-9.125	0	-1.1369963	-6.4139905	-4.049356	0.05721178
GW	1017	9	-1.5	-1.5215514	-10.739498	-1.4999995	1.25	-14.75	0.05721178
GW	1018	13	-1.481954	-6.266946	-4.047133	-1.738806	-1.806844	-10.69254	0.0572118
GW	1019	1	-1.481954	-6.266946	-4.047133	-1.136996	-6.41399	-4.049356	0.0572118
GW	1020	1	-1.738806	-1.806844	-10.69254	-1.5	-1.521551	-10.7395	0.0572118
GW	1038	9	-0.9999	9.10978141	0	-1.1699612	6.31694603	-3.9920945	0.05721178
GW	1040	9	-1.1823972	1.55442342	-10.762988	-1.25	-1.25	-14.75	0.05721178
GW	1041	13	-1.437782	6.16597	-4.206811	-1.557289	1.5596016	-10.75563	0.0572118
GW	1042	1	-1.169961	6.316946	-3.992095	-1.437782	6.16597	-4.206811	0.0572118
GW	1043	1	-1.182397	1.5544234	-10.76299	-1.557289	1.5596016	-10.75563	0.0572118
GW	1044	9	-1	11.125009	0	-1.067962	8.413188	-4.050555	0.0572118
GW	1046	9	-1.1819999	3.96181678	-10.699438	-1.25	1.25	-14.75	0.05721178
GW	1047	13	-1.442925	8.4161204	-4.046175	-1.557	3.9618117	-10.69945	0.0572118
GW	1048	1	-1.067962	8.413188	-4.050555	-1.442925	8.4161204	-4.046175	0.0572118
GW	1049	1	-1.182	3.9618168	-10.69944	-1.557	3.9618117	-10.69945	0.0572118
GS	0	0	0.0254		' All in in.
GE	0
EK
LD	5	0	0	0	3.77e7	0
EX	0	1000	3	0	1	0
GN	-1
FR	0	1	0	0	470	0
RP 0 1 73 1510 90 0 1 5 0 0

Compared to what it could be, ie post #65, the phasing lines kill the potential performance.

The U4000, however is an excellent deal for the money at $27.50.

[Mark_OB1]

300ohms, re: Posting 65:

> Ill post the charts of what is theoretically possible by ganging up two U4000s in their present positions of the U8000 (which actually looks good because no serious lobes are produced). Ill do this by eliminating the phasing lines and putting 2 excitation sources into the NEC file. <

Is there some reason that the F/B graphs are all flatlined at 0? That would imply that it was done w/o reflectors, but the NEC file shows the rods are defined there.

> From the above results, you have to subtract estimated losses from the 2 baluns and the 2 way splitter. <

It seems like splitter/combiner losses would negate most of the gains. Would it not be possible to redesign the phasing harness for better performance instead? The existing harness actually looked rather clever to me, though apparently it did seriously degrade the end result.

[300ohm]

Is there some reason that the F/B graphs are all flatlined at 0? That would imply that it was done w/o reflectors, but the NEC file shows the rods are defined there.

Yes, there is a reason. Those were run with Total Gain calculating option, which produces no F/B or F/R results. And being lazy, I capture the whole active window for posting instead of just capturing the relevant area, heh. If you want, I can rerun with the Horizontal (or Vertical) Gain option showing F/B and F/R. Which chart do you want me to rerun ?

It seems like splitter/combiner losses would negate most of the gains. Would it not be possible to redesign the phasing harness for better performance instead? The existing harness actually looked rather clever to me, though apparently it did seriously degrade the end result.

Correctly designed horizontal phasing harnesses, that do a good job across the entire band, are a real bear to design for many reasons. (Vertical phasing harnesses are much easier) Only the old CM4228 did it pretty close to correct. (And no, you just cant take the CM4228 harness and apply it to any ole other 4 bays, it just doesnt work that way heh)

A simpler lower loss solution for horizontally stacked antennas is to use the Winegard SD3700 300ohm to 75ohm outdoor coupler. Its downside is its about $20 - $25.

[balm]

In an earlier post, 300ohm, you modeled very good gain on VHF-HI by connecting the reflector rods, I'm not sure if that was the U8000 as is, or after the phasing line mods (combining 2 separate 4 bays) ?

Could the same increased VHF-HI gain hold true for a similarly modified Winegard HD8800 ? (This would be important for people try)

[300ohm]

In an earlier post, 300ohm, you modeled very good gain on VHF-HI by connecting the reflector rods

Yes, mclapp discovered (in around 2008 postings) that pretty much ANY four bay or 8 bay (but not all 2 bays) bowtie antennas can do vhf-hi with a 32" (maybe as low as 28" on some) to 40" (and more width) connected reflector (using common mesh is the easiest. And inserting 32" to 40" etc rod reflectors in between also works.) Generally, you get about in the area of 6 - 7 dbi in gain on vhf-hi, which is perfectly acceptable to most in the designed designated viewing area. Its not DXing type gain though.

If youre willing to sacrifice some uhf gain for vhf-hi gain, moving the reflector to bowtie distance out to about 13" to 15" helps. Exact distances will have to be modeled per antenna design.

On my tweaked Baltimore closed end bowtie antenna, I got a good 7 dbi vhf-hi gain for ch 11 and 13, and almost 16 dbi channels 38 to 46, reflector to element distance of 14", 40" by 40" curved reflector, 2" X 4" mesh, center mesh 1/2". The modeled gain for channel 38 was the exact same as for my GH10 curved mesh model. And guess what ? Real life testing showed the exact same readings on channel 38 on my Sansonic 300 converter box (has signal strength and signal quality) for both antennas. Amazing, heh.

The wide reflector concept does NOT work for the GH, hence the need for NARODs.

[balm]

That's cool, good to know also. Doesn't the CM4228HD have continuous reflector, this mod on the U8000, or HD8800 would put it well ahead of the CM4228, on VHF-HI, correct ? or am I missing something...

How much worse is the split reflector VHF-HI gain as is, none ?

[300ohm]

Doesn't the CM4228HD have continuous reflector,

Yep.

this mod on the U8000, or HD8800 would put it well ahead of the CM4228, on VHF-HI, correct ? or am I missing something...

Yes, depending on the channel I believe.

How much worse is the split reflector VHF-HI gain as is, none ?

Specifically on that model, I havent run the charts. But on other horizontally stacked bowties, the net gain was negative with a split reflector.

[balm]

OK, so the reflector on the CM4228 interacts differently with the bow-ties, compared to the U8000 design, talking in terms of VHF-HI


Would it be a relatively easy, and reversible mod to backup the reflector on the CM4228, or any of the double bays

[300ohm]

Would it be a relatively easy, and reversible mod to backup the reflector on the CM4228, or any of the double bays

I dont think I understand. If you mean increase the size of the CM4228 reflector, then yes its an easy mod to tweak what vhf-hi channel you want , and then reversible.


But Ive tried to put smaller uhf reflectors in front of larger vhf-hi refectors, spaced at the correct distances, like in the case of loops, with pretty poor results, if thats what you mean.

[envirogeek]

I never did connect the reflector rods on my U8000.

Is there a recommended quick and dirty reversible method?

I was thinking of just reusing some 14 gauge aluminum wire to bridge the gap and wrapping it onto the reflector ends with aluminum foil tape.

If the weather holds next week I might make a last trip up on the roof of the cabin.

[balm]

I adjusted the model on the HD8800 (different antenna) to see if the result would be similar to U8000 for connected reflector rods, and it did NOT help on VHF-HI in this case