Area 51 for Antenna Modelers & Builders (See Post #1) - Page 76 - Canadian TV, Computing and Home Theatre Forums

300ohm · 2011-12-13, 08:46 PM

Since I saw the dimensions of the AC turnstile clone, model FMSS, 53" long and 8" high, I made a model of it.
Interesting to note that the turnstiles, while having a 100 degree plus beamwidth front and back, still have nulls.

Code:

CM Antenna Craft FMSS Turnstile Clone
CM AGT = 1.0 (0 db) at 98 mhz,   Autoseg = 21
CE
GW	1	9	0	1.09	-1	0	26.5	-1	0.1875
GW	2	9	0	-1.09	-1	0	-26.5	-1	0.1875
GW	3	1	0	-26.5	-1	0	-26.5	-4	0.1875
GW	4	1	0	26.5	-1	0	26.5	-4	0.1875
GW	5	19	0	26.5	-4	0	-26.5	-4	0.1875
GW	6	9	-1.09	0	1	-26.5	0	1	0.1875
GW	7	9	1.09	0	1	26.5	0	1	0.1875
GW	8	1	26.5	0	1	26.5	0	4	0.1875
GW	9	1	-26.5	0	1	-26.5	0	4	0.1875
GW	10	19	-26.5	0	4	26.5	0	4	0.1875
GW	11	1	-1.09	0	1	1.09	0	1	0.1875
GW	12	1	0	-1.09	-1	0	1.09	-1	0.14
GS	0	0	0.0254		' All in in.
GE	0
EK
TL	11	1	12	1	450	0
LD	5	0	0	0	2.49e7	0
EX	0	12	1	0	1	0
GN	-1
FR	0	1	0	0	98	0

holl_ands · 2011-12-14, 12:57 PM

FM "Omni" Antennas:

Certainly NOT an Omni-directional antenna pattern....
Looks like a typical bi-directional pattern, except rotated with deep nulls at 45-deg.
Note that pattern is same whether Horizontal, Vertical or Total Gain.

Antennacraft Spec Sheet for FMSS doesn't say very much:
http://www.antennacraft.com/pdfs/FMSS.pdf

However, the FMSS Manual shows a "9-in Intercoupler" (Twinlead) that is
wrapped around the mount (so element to element distance is a bit less than 9-in):
http://www.antennacraft.com/Manuals/FMSS_Manual.pdf

Adding this phasing harness to the model may improve the antenna pattern,
even though it isn't even close to a 1/4-wavelength (30-in, 90-degrees):
http://electriciantraining.tpub.com/.../14182_211.htm
http://www.cebik.com/content/a10/wire/turns.html [Cebik's website requires FREE Registration]

BTW: Most on-line info re Turnstile Antennas pertains to their use for Satcom, with
a ground plane, exploiting the overhead (presumably circularly polarized) coverage.

holl_ands · 2011-12-14, 01:56 PM

FM "Omni" Antennas continued:

FYI: Winegard HD-6010 is a similar FM Turnstile...except NOT Folded...NOT Omni...
and they don't want to talk about SWR:
http://www.winegard.com/kbase/upload/HD-6010.pdf
http://www.winegard.com/kbase/upload/1450463.pdf
Hmmm....spec sheet says 10-in Height...so Element spacing might be about 9-in
and interconnecting feedline might be 11-13-in???

Antiference (U.K.), Triax (U.K.) & others below make FM Omni Antennas where
a single Folded Dipole is bent into nearly a complete circle...or HOOP:
http://www.antiference.co.uk/sitefil...0%20Aerial.jpg
http://www.antiference.co.uk/sitefil...%20Radio_0.pdf
http://www.triax.co.uk/Products/Aeri...20Aerials.aspx [Somewhat better picture in their catalog.]

FWIW: Bruce Carter cites a 1978 Audio Magazine series of articles by Michael J. Salvatti:
http://www.mindspring.com/~brucec/fmant.htm
Note that a single Folded Dipole bent into an "S" shape MIGHT have an Omni pattern.
Dipole (Poland) still makes this type of FM antenna...but fortuitously mounts it VERTICALLY
(for Vertical as well as Horizontal polarization coverage):
http://www.dipolnet.com/estore-antennas-fm,4346.htm
Click on image for full specs. Also note HOOP (Horiz only) and HOOP+WHIP (H+V) Omnis.

Fracarro is the only one who actually publishes an Azimuthal Gain chart for the "S"...but NOT Hoop:
http://www.fracarro.co.uk/index.php?...87&&Itemid=262 [Yup, it's OMNI.]

And Televes appears to be the only one who publishes Azimuthal Gain chart for the HOOP:
http://www.televes.com/en/content/dra-1201gif [Yup, it's OMNI.]
http://www.televes.com/en/node/2314

Have fun and don't forget to check Horizontal, Vertical and Total antenna patterns....

300ohm · 2011-12-14, 02:03 PM

Quote:

Antennacraft Spec Sheet for FMSS doesn't say very much:

Hmm, Solid Signal had it listed as 53", which I used above, while the spec sheet says 55".

Quote:

However, the FMSS Manual shows a "9-in Intercoupler" (Twinlead) that is wrapped around the mount (so element to element distance is a bit less than 9-in):

In the model above I used a 2" 450 ohm TL line, so it should be adjusted to 9". It does look like 450 ohm lead in the manual drawing/picture.

holl_ands · 2011-12-14, 08:00 PM

FM Double-Hoop Omni Antenna:

First cut at a 4nec2 model for the Double-Hoop Omni Antenna, which
may be a few tenths of an inch larger diameter than SOME manu' specs
and I'm guessing at the size of the "Open Space" opposite the Feedpoint.

It's DEFINITELY AN OMNI (-1.6 to +1.3 dBi) with high SWR (7-15) and
only responds to Horizontally polarized signals. [Rescaling slightly LARGER
would be a better "fit"...and/or maybe a larger "Open Space"...still tweaking]:

Code:

CM FM Omni Double Hoop, Open Space=5segs~2.5-in, 4nec2 by holl_ands, 14Dec2011
CM Diameter=20-in, Separation=2-in, 125 segments per full Hoop, Feedpoint Gap=2segs~1-in.
CM 3/8-in Diameter Aluminum Elements.
CE
SY Rsrc=0.22	' SOURCE Wire Radius, Adjust for AGT=1.0: Rsrc=0.22 at 98 MHz.
' GW	1	1	-10		0		-1	-9.9873697	-0.5024433	-1	0.1875 ' GAP
GW	2	1	-9.9873697	-0.5024433	-1	-9.9495102	-1.0036173	-1	0.1875
GW	3	1	-9.9495102	-1.0036173	-1	-9.8865173	-1.5022559	-1	0.1875
GW	4	1	-9.8865173	-1.5022559	-1	-9.7985504	-1.9971		-1	0.1875
GW	5	1	-9.7985504	-1.9971		-1	-9.6858315	-2.4868988	-1	0.1875
GW	6	1	-9.6858315	-2.4868988	-1	-9.5486453	-2.9704157	-1	0.1875
GW	7	1	-9.5486453	-2.9704157	-1	-9.3873386	-3.4464291	-1	0.1875
GW	8	1	-9.3873386	-3.4464291	-1	-9.2023185	-3.9137366	-1	0.1875
GW	9	1	-9.2023185	-3.9137366	-1	-8.9940524	-4.3711575	-1	0.1875
GW	10	1	-8.9940524	-4.3711575	-1	-8.7630669	-4.8175366	-1	0.1875
GW	11	1	-8.7630669	-4.8175366	-1	-8.5099449	-5.2517465	-1	0.1875
GW	12	1	-8.5099449	-5.2517465	-1	-8.235326	-5.6726894	-1	0.1875
GW	13	1	-8.235326	-5.6726894	-1	-7.9399039	-6.0793031	-1	0.1875
GW	14	1	-7.9399039	-6.0793031	-1	-7.6244252	-6.4705594	-1	0.1875
GW	15	1	-7.6244252	-6.4705594	-1	-7.2896862	-6.8454709	-1	0.1875
GW	16	1	-7.2896862	-6.8454709	-1	-6.9365331	-7.2030902	-1	0.1875
GW	17	1	-6.9365331	-7.2030902	-1	-6.5658575	-7.5425138	-1	0.1875
GW	18	1	-6.5658575	-7.5425138	-1	-6.1785961	-7.8628843	-1	0.1875
GW	19	1	-6.1785961	-7.8628843	-1	-5.7757272	-8.1633925	-1	0.1875
GW	20	1	-5.7757272	-8.1633925	-1	-5.3582681	-8.4432791	-1	0.1875
GW	21	1	-5.3582681	-8.4432791	-1	-4.9272732	-8.7018374	-1	0.1875
GW	22	1	-4.9272732	-8.7018374	-1	-4.4838323	-8.9384142	-1	0.1875
GW	23	1	-4.4838323	-8.9384142	-1	-4.0290642	-9.1524118	-1	0.1875
GW	24	1	-4.0290642	-9.1524118	-1	-3.5641189	-9.3432894	-1	0.1875
GW	25	1	-3.5641189	-9.3432894	-1	-3.0901701	-9.5105654	-1	0.1875
GW	26	1	-3.0901701	-9.5105654	-1	-2.608415	-9.6538165	-1	0.1875
GW	27	1	-2.608415	-9.6538165	-1	-2.1200713	-9.7726811	-1	0.1875
GW	28	1	-2.1200713	-9.7726811	-1	-1.6263717	-9.8668594	-1	0.1875
GW	29	1	-1.6263717	-9.8668594	-1	-1.1285638	-9.936113	-1	0.1875
GW	30	1	-1.1285638	-9.936113	-1	-0.6279051	-9.9802673	-1	0.1875
GW	31	1	-0.6279051	-9.9802673	-1	-0.1256602	-9.9992106	-1	0.1875
GW	32	1	-0.1256602	-9.9992106	-1	0.37690197	-9.9928949	-1	0.1875
GW	33	1	0.37690197	-9.9928949	-1	0.87851181	-9.9613362	-1	0.1875
GW	34	1	0.87851181	-9.9613362	-1	1.37790276	-9.9046142	-1	0.1875
GW	35	1	1.37790276	-9.9046142	-1	1.87381299	-9.8228724	-1	0.1875
GW	36	1	1.87381299	-9.8228724	-1	2.36499016	-9.7163173	-1	0.1875
GW	37	1	2.36499016	-9.7163173	-1	2.85019252	-9.5852177	-1	0.1875
GW	38	1	2.85019252	-9.5852177	-1	3.32819528	-9.4299055	-1	0.1875
GW	39	1	3.32819528	-9.4299055	-1	3.79779094	-9.250772	-1	0.1875
GW	40	1	3.79779094	-9.250772	-1	4.25779291	-9.0482705	-1	0.1875
GW	41	1	4.25779291	-9.0482705	-1	4.70703937	-8.8229122	-1	0.1875
GW	42	1	4.70703937	-8.8229122	-1	5.14439528	-8.5752665	-1	0.1875
GW	43	1	5.14439528	-8.5752665	-1	5.5687563	-8.3059591	-1	0.1875
GW	44	1	5.5687563	-8.3059591	-1	5.97905		-8.0156697	-1	0.1875
GW	45	1	5.97905		-8.0156697	-1	6.37423976	-7.7051323	-1	0.1875
GW	46	1	6.37423976	-7.7051323	-1	6.75332795	-7.3751311	-1	0.1875
GW	47	1	6.75332795	-7.3751311	-1	7.11535669	-7.0264996	-1	0.1875
GW	48	1	7.11535669	-7.0264996	-1	7.45941142	-6.6601185	-1	0.1875
GW	49	1	7.45941142	-6.6601185	-1	7.78462283	-6.2769138	-1	0.1875
GW	50	1	7.78462283	-6.2769138	-1	8.09017008	-5.8778524	-1	0.1875
GW	51	1	8.09017008	-5.8778524	-1	8.37528031	-5.4639433	-1	0.1875
GW	52	1	8.37528031	-5.4639433	-1	8.63923425	-5.0362319	-1	0.1875
GW	53	1	8.63923425	-5.0362319	-1	8.88136457	-4.5957984	-1	0.1875
GW	54	1	8.88136457	-4.5957984	-1	9.10105984	-4.1437559	-1	0.1875
GW	55	1	9.10105984	-4.1437559	-1	9.29776496	-3.6812457	-1	0.1875
GW	56	1	9.29776496	-3.6812457	-1	9.47098307	-3.2094362	-1	0.1875
GW	57	1	9.47098307	-3.2094362	-1	9.62027677	-2.7295193	-1	0.1875
GW	58	1	9.62027677	-2.7295193	-1	9.7452689	-2.2427075	-1	0.1875
GW	59	1	9.7452689	-2.2427075	-1	9.84564331	-1.7502307	-1	0.1875
GW	60	1	9.84564331	-1.7502307	-1	9.92114685	-1.2533323	-1	0.1875
' GW	61	1	9.92114685	-1.2533323	-1	9.97158898	-0.7532681	-1	0.1875 ' OPEN
' GW	62	1	9.97158898	-0.7532681	-1	9.99684173	-0.2513008	-1	0.1875 ' OPEN
' GW	63	1	9.99684173	-0.2513008	-1	9.99684173	0.25130079	-1	0.1875 ' OPEN
' GW	64	1	9.99684173	0.25130079	-1	9.97158898	0.75326811	-1	0.1875 ' OPEN
' GW	65	1	9.97158898	0.75326811	-1	9.92114685	1.25333228	-1	0.1875 ' OPEN
GW	66	1	9.92114685	1.25333228	-1	9.84564331	1.75023071	-1	0.1875
GW	67	1	9.84564331	1.75023071	-1	9.7452689	2.24270748	-1	0.1875
GW	68	1	9.7452689	2.24270748	-1	9.62027677	2.72951929	-1	0.1875
GW	69	1	9.62027677	2.72951929	-1	9.47098307	3.20943622	-1	0.1875
GW	70	1	9.47098307	3.20943622	-1	9.29776496	3.68124567	-1	0.1875
GW	71	1	9.29776496	3.68124567	-1	9.10105984	4.14375591	-1	0.1875
GW	72	1	9.10105984	4.14375591	-1	8.88136457	4.59579843	-1	0.1875
GW	73	1	8.88136457	4.59579843	-1	8.63923425	5.03623189	-1	0.1875
GW	74	1	8.63923425	5.03623189	-1	8.37528031	5.46394331	-1	0.1875
GW	75	1	8.37528031	5.46394331	-1	8.09017008	5.87785236	-1	0.1875
GW	76	1	8.09017008	5.87785236	-1	7.78462283	6.27691378	-1	0.1875
GW	77	1	7.78462283	6.27691378	-1	7.45941142	6.6601185	-1	0.1875
GW	78	1	7.45941142	6.6601185	-1	7.11535669	7.02649961	-1	0.1875
GW	79	1	7.11535669	7.02649961	-1	6.75332795	7.3751311	-1	0.1875
GW	80	1	6.75332795	7.3751311	-1	6.37423976	7.70513228	-1	0.1875
GW	81	1	6.37423976	7.70513228	-1	5.97905		8.01566969	-1	0.1875
GW	82	1	5.97905		8.01566969	-1	5.5687563	8.30595906	-1	0.1875
GW	83	1	5.5687563	8.30595906	-1	5.14439528	8.57526654	-1	0.1875
GW	84	1	5.14439528	8.57526654	-1	4.70703937	8.8229122	-1	0.1875
GW	85	1	4.70703937	8.8229122	-1	4.25779291	9.04827047	-1	0.1875
GW	86	1	4.25779291	9.04827047	-1	3.79779094	9.25077205	-1	0.1875
GW	87	1	3.79779094	9.25077205	-1	3.32819528	9.42990551	-1	0.1875
GW	88	1	3.32819528	9.42990551	-1	2.85019252	9.58521772	-1	0.1875
GW	89	1	2.85019252	9.58521772	-1	2.36499016	9.71631732	-1	0.1875
GW	90	1	2.36499016	9.71631732	-1	1.87381299	9.82287244	-1	0.1875
GW	91	1	1.87381299	9.82287244	-1	1.37790276	9.90461417	-1	0.1875
GW	92	1	1.37790276	9.90461417	-1	0.87851181	9.96133622	-1	0.1875
GW	93	1	0.87851181	9.96133622	-1	0.37690197	9.99289488	-1	0.1875
GW	94	1	0.37690197	9.99289488	-1	-0.1256602	9.99921063	-1	0.1875
GW	95	1	-0.1256602	9.99921063	-1	-0.6279051	9.98026732	-1	0.1875
GW	96	1	-0.6279051	9.98026732	-1	-1.1285638	9.93611299	-1	0.1875
GW	97	1	-1.1285638	9.93611299	-1	-1.6263717	9.86685945	-1	0.1875
GW	98	1	-1.6263717	9.86685945	-1	-2.1200713	9.7726811	-1	0.1875
GW	99	1	-2.1200713	9.7726811	-1	-2.608415	9.65381654	-1	0.1875
GW	100	1	-2.608415	9.65381654	-1	-3.0901701	9.51056535	-1	0.1875
GW	101	1	-3.0901701	9.51056535	-1	-3.5641189	9.34328937	-1	0.1875
GW	102	1	-3.5641189	9.34328937	-1	-4.0290642	9.15241181	-1	0.1875
GW	103	1	-4.0290642	9.15241181	-1	-4.4838323	8.93841417	-1	0.1875
GW	104	1	-4.4838323	8.93841417	-1	-4.9272732	8.7018374	-1	0.1875
GW	105	1	-4.9272732	8.7018374	-1	-5.3582681	8.44327913	-1	0.1875
GW	106	1	-5.3582681	8.44327913	-1	-5.7757272	8.16339252	-1	0.1875
GW	107	1	-5.7757272	8.16339252	-1	-6.1785961	7.86288425	-1	0.1875
GW	108	1	-6.1785961	7.86288425	-1	-6.5658575	7.54251378	-1	0.1875
GW	109	1	-6.5658575	7.54251378	-1	-6.9365331	7.20309016	-1	0.1875
GW	110	1	-6.9365331	7.20309016	-1	-7.2896862	6.84547087	-1	0.1875
GW	111	1	-7.2896862	6.84547087	-1	-7.6244252	6.47055945	-1	0.1875
GW	112	1	-7.6244252	6.47055945	-1	-7.9399039	6.07930315	-1	0.1875
GW	113	1	-7.9399039	6.07930315	-1	-8.235326	5.67268937	-1	0.1875
GW	114	1	-8.235326	5.67268937	-1	-8.5099449	5.25174646	-1	0.1875
GW	115	1	-8.5099449	5.25174646	-1	-8.7630669	4.81753661	-1	0.1875
GW	116	1	-8.7630669	4.81753661	-1	-8.9940524	4.37115748	-1	0.1875
GW	117	1	-8.9940524	4.37115748	-1	-9.2023185	3.91373661	-1	0.1875
GW	118	1	-9.2023185	3.91373661	-1	-9.3873386	3.44642913	-1	0.1875
GW	119	1	-9.3873386	3.44642913	-1	-9.5486453	2.97041575	-1	0.1875
GW	120	1	-9.5486453	2.97041575	-1	-9.6858315	2.48689882	-1	0.1875
GW	121	1	-9.6858315	2.48689882	-1	-9.7985504	1.9971		-1	0.1875
GW	122	1	-9.7985504	1.9971		-1	-9.8865173	1.50225591	-1	0.1875
GW	123	1	-9.8865173	1.50225591	-1	-9.9495102	1.00361732	-1	0.1875
GW	124	1	-9.9495102	1.00361732	-1	-9.9873697	0.50244331	-1	0.1875
' GW	125	1	-9.9873697	0.50244331	-1	-10		0		-1	0.1875 ' GAP
GW	126	1	-10		0		1	-9.9873697	0.50244331	1	0.1875
GW	127	1	-9.9873697	-0.5024433	1	-9.9495102	-1.0036173	1	0.1875
GW	128	1	-9.9495102	-1.0036173	1	-9.8865173	-1.5022559	1	0.1875
GW	129	1	-9.8865173	-1.5022559	1	-9.7985504	-1.9971		1	0.1875
GW	130	1	-9.7985504	-1.9971		1	-9.6858315	-2.4868988	1	0.1875
GW	131	1	-9.6858315	-2.4868988	1	-9.5486453	-2.9704157	1	0.1875
GW	132	1	-9.5486453	-2.9704157	1	-9.3873386	-3.4464291	1	0.1875
GW	133	1	-9.3873386	-3.4464291	1	-9.2023185	-3.9137366	1	0.1875
GW	134	1	-9.2023185	-3.9137366	1	-8.9940524	-4.3711575	1	0.1875
GW	135	1	-8.9940524	-4.3711575	1	-8.7630669	-4.8175366	1	0.1875
GW	136	1	-8.7630669	-4.8175366	1	-8.5099449	-5.2517465	1	0.1875
GW	137	1	-8.5099449	-5.2517465	1	-8.235326	-5.6726894	1	0.1875
GW	138	1	-8.235326	-5.6726894	1	-7.9399039	-6.0793031	1	0.1875
GW	139	1	-7.9399039	-6.0793031	1	-7.6244252	-6.4705594	1	0.1875
GW	140	1	-7.6244252	-6.4705594	1	-7.2896862	-6.8454709	1	0.1875
GW	141	1	-7.2896862	-6.8454709	1	-6.9365331	-7.2030902	1	0.1875
GW	142	1	-6.9365331	-7.2030902	1	-6.5658575	-7.5425138	1	0.1875
GW	143	1	-6.5658575	-7.5425138	1	-6.1785961	-7.8628843	1	0.1875
GW	144	1	-6.1785961	-7.8628843	1	-5.7757272	-8.1633925	1	0.1875
GW	145	1	-5.7757272	-8.1633925	1	-5.3582681	-8.4432791	1	0.1875
GW	146	1	-5.3582681	-8.4432791	1	-4.9272732	-8.7018374	1	0.1875
GW	147	1	-4.9272732	-8.7018374	1	-4.4838323	-8.9384142	1	0.1875
GW	148	1	-4.4838323	-8.9384142	1	-4.0290642	-9.1524118	1	0.1875
GW	149	1	-4.0290642	-9.1524118	1	-3.5641189	-9.3432894	1	0.1875
GW	150	1	-3.5641189	-9.3432894	1	-3.0901701	-9.5105654	1	0.1875
GW	151	1	-3.0901701	-9.5105654	1	-2.608415	-9.6538165	1	0.1875
GW	152	1	-2.608415	-9.6538165	1	-2.1200713	-9.7726811	1	0.1875
GW	153	1	-2.1200713	-9.7726811	1	-1.6263717	-9.8668594	1	0.1875
GW	154	1	-1.6263717	-9.8668594	1	-1.1285638	-9.936113	1	0.1875
GW	155	1	-1.1285638	-9.936113	1	-0.6279051	-9.9802673	1	0.1875
GW	156	1	-0.6279051	-9.9802673	1	-0.1256602	-9.9992106	1	0.1875
GW	157	1	-0.1256602	-9.9992106	1	0.37690197	-9.9928949	1	0.1875
GW	158	1	0.37690197	-9.9928949	1	0.87851181	-9.9613362	1	0.1875
GW	159	1	0.87851181	-9.9613362	1	1.37790276	-9.9046142	1	0.1875
GW	160	1	1.37790276	-9.9046142	1	1.87381299	-9.8228724	1	0.1875
GW	161	1	1.87381299	-9.8228724	1	2.36499016	-9.7163173	1	0.1875
GW	162	1	2.36499016	-9.7163173	1	2.85019252	-9.5852177	1	0.1875
GW	163	1	2.85019252	-9.5852177	1	3.32819528	-9.4299055	1	0.1875
GW	164	1	3.32819528	-9.4299055	1	3.79779094	-9.250772	1	0.1875
GW	165	1	3.79779094	-9.250772	1	4.25779291	-9.0482705	1	0.1875
GW	166	1	4.25779291	-9.0482705	1	4.70703937	-8.8229122	1	0.1875
GW	167	1	4.70703937	-8.8229122	1	5.14439528	-8.5752665	1	0.1875
GW	168	1	5.14439528	-8.5752665	1	5.5687563	-8.3059591	1	0.1875
GW	169	1	5.5687563	-8.3059591	1	5.97905		-8.0156697	1	0.1875
GW	170	1	5.97905		-8.0156697	1	6.37423976	-7.7051323	1	0.1875
GW	171	1	6.37423976	-7.7051323	1	6.75332795	-7.3751311	1	0.1875
GW	172	1	6.75332795	-7.3751311	1	7.11535669	-7.0264996	1	0.1875
GW	173	1	7.11535669	-7.0264996	1	7.45941142	-6.6601185	1	0.1875
GW	174	1	7.45941142	-6.6601185	1	7.78462283	-6.2769138	1	0.1875
GW	175	1	7.78462283	-6.2769138	1	8.09017008	-5.8778524	1	0.1875
GW	176	1	8.09017008	-5.8778524	1	8.37528031	-5.4639433	1	0.1875
GW	177	1	8.37528031	-5.4639433	1	8.63923425	-5.0362319	1	0.1875
GW	178	1	8.63923425	-5.0362319	1	8.88136457	-4.5957984	1	0.1875
GW	179	1	8.88136457	-4.5957984	1	9.10105984	-4.1437559	1	0.1875
GW	180	1	9.10105984	-4.1437559	1	9.29776496	-3.6812457	1	0.1875
GW	181	1	9.29776496	-3.6812457	1	9.47098307	-3.2094362	1	0.1875
GW	182	1	9.47098307	-3.2094362	1	9.62027677	-2.7295193	1	0.1875
GW	183	1	9.62027677	-2.7295193	1	9.7452689	-2.2427075	1	0.1875
GW	184	1	9.7452689	-2.2427075	1	9.84564331	-1.7502307	1	0.1875
GW	185	1	9.84564331	-1.7502307	1	9.92114685	-1.2533323	1	0.1875
' GW	186	1	9.92114685	-1.2533323	1	9.97158898	-0.7532681	1	0.1875 ' OPEN
' GW	187	1	9.97158898	-0.7532681	1	9.99684173	-0.2513008	1	0.1875 ' OPEN
' GW	188	1	9.99684173	-0.2513008	1	9.99684173	0.25130079	1	0.1875 ' OPEN
' GW	189	1	9.99684173	0.25130079	1	9.97158898	0.75326811	1	0.1875 ' OPEN
' GW	190	1	9.97158898	0.75326811	1	9.92114685	1.25333228	1	0.1875 ' OPEN
GW	191	1	9.92114685	1.25333228	1	9.84564331	1.75023071	1	0.1875
GW	192	1	9.84564331	1.75023071	1	9.7452689	2.24270748	1	0.1875
GW	193	1	9.7452689	2.24270748	1	9.62027677	2.72951929	1	0.1875
GW	194	1	9.62027677	2.72951929	1	9.47098307	3.20943622	1	0.1875
GW	195	1	9.47098307	3.20943622	1	9.29776496	3.68124567	1	0.1875
GW	196	1	9.29776496	3.68124567	1	9.10105984	4.14375591	1	0.1875
GW	197	1	9.10105984	4.14375591	1	8.88136457	4.59579843	1	0.1875
GW	198	1	8.88136457	4.59579843	1	8.63923425	5.03623189	1	0.1875
GW	199	1	8.63923425	5.03623189	1	8.37528031	5.46394331	1	0.1875
GW	200	1	8.37528031	5.46394331	1	8.09017008	5.87785236	1	0.1875
GW	201	1	8.09017008	5.87785236	1	7.78462283	6.27691378	1	0.1875
GW	202	1	7.78462283	6.27691378	1	7.45941142	6.6601185	1	0.1875
GW	203	1	7.45941142	6.6601185	1	7.11535669	7.02649961	1	0.1875
GW	204	1	7.11535669	7.02649961	1	6.75332795	7.3751311	1	0.1875
GW	205	1	6.75332795	7.3751311	1	6.37423976	7.70513228	1	0.1875
GW	206	1	6.37423976	7.70513228	1	5.97905		8.01566969	1	0.1875
GW	207	1	5.97905		8.01566969	1	5.5687563	8.30595906	1	0.1875
GW	208	1	5.5687563	8.30595906	1	5.14439528	8.57526654	1	0.1875
GW	209	1	5.14439528	8.57526654	1	4.70703937	8.8229122	1	0.1875
GW	210	1	4.70703937	8.8229122	1	4.25779291	9.04827047	1	0.1875
GW	211	1	4.25779291	9.04827047	1	3.79779094	9.25077205	1	0.1875
GW	212	1	3.79779094	9.25077205	1	3.32819528	9.42990551	1	0.1875
GW	213	1	3.32819528	9.42990551	1	2.85019252	9.58521772	1	0.1875
GW	214	1	2.85019252	9.58521772	1	2.36499016	9.71631732	1	0.1875
GW	215	1	2.36499016	9.71631732	1	1.87381299	9.82287244	1	0.1875
GW	216	1	1.87381299	9.82287244	1	1.37790276	9.90461417	1	0.1875
GW	217	1	1.37790276	9.90461417	1	0.87851181	9.96133622	1	0.1875
GW	218	1	0.87851181	9.96133622	1	0.37690197	9.99289488	1	0.1875
GW	219	1	0.37690197	9.99289488	1	-0.1256602	9.99921063	1	0.1875
GW	220	1	-0.1256602	9.99921063	1	-0.6279051	9.98026732	1	0.1875
GW	221	1	-0.6279051	9.98026732	1	-1.1285638	9.93611299	1	0.1875
GW	222	1	-1.1285638	9.93611299	1	-1.6263717	9.86685945	1	0.1875
GW	223	1	-1.6263717	9.86685945	1	-2.1200713	9.7726811	1	0.1875
GW	224	1	-2.1200713	9.7726811	1	-2.608415	9.65381654	1	0.1875
GW	225	1	-2.608415	9.65381654	1	-3.0901701	9.51056535	1	0.1875
GW	226	1	-3.0901701	9.51056535	1	-3.5641189	9.34328937	1	0.1875
GW	227	1	-3.5641189	9.34328937	1	-4.0290642	9.15241181	1	0.1875
GW	228	1	-4.0290642	9.15241181	1	-4.4838323	8.93841417	1	0.1875
GW	229	1	-4.4838323	8.93841417	1	-4.9272732	8.7018374	1	0.1875
GW	230	1	-4.9272732	8.7018374	1	-5.3582681	8.44327913	1	0.1875
GW	231	1	-5.3582681	8.44327913	1	-5.7757272	8.16339252	1	0.1875
GW	232	1	-5.7757272	8.16339252	1	-6.1785961	7.86288425	1	0.1875
GW	233	1	-6.1785961	7.86288425	1	-6.5658575	7.54251378	1	0.1875
GW	234	1	-6.5658575	7.54251378	1	-6.9365331	7.20309016	1	0.1875
GW	235	1	-6.9365331	7.20309016	1	-7.2896862	6.84547087	1	0.1875
GW	236	1	-7.2896862	6.84547087	1	-7.6244252	6.47055945	1	0.1875
GW	237	1	-7.6244252	6.47055945	1	-7.9399039	6.07930315	1	0.1875
GW	238	1	-7.9399039	6.07930315	1	-8.235326	5.67268937	1	0.1875
GW	239	1	-8.235326	5.67268937	1	-8.5099449	5.25174646	1	0.1875
GW	240	1	-8.5099449	5.25174646	1	-8.7630669	4.81753661	1	0.1875
GW	241	1	-8.7630669	4.81753661	1	-8.9940524	4.37115748	1	0.1875
GW	242	1	-8.9940524	4.37115748	1	-9.2023185	3.91373661	1	0.1875
GW	243	1	-9.2023185	3.91373661	1	-9.3873386	3.44642913	1	0.1875
GW	244	1	-9.3873386	3.44642913	1	-9.5486453	2.97041575	1	0.1875
GW	245	1	-9.5486453	2.97041575	1	-9.6858315	2.48689882	1	0.1875
GW	246	1	-9.6858315	2.48689882	1	-9.7985504	1.9971		1	0.1875
GW	247	1	-9.7985504	1.9971		1	-9.8865173	1.50225591	1	0.1875
GW	248	1	-9.8865173	1.50225591	1	-9.9495102	1.00361732	1	0.1875
GW	249	1	-9.9495102	1.00361732	1	-9.9873697	0.50244331	1	0.1875
GW	250	1	-9.9873697	-0.5024433	1	-10		0		1	0.1875
GW	251	5	9.92114685	-1.2533323	-1	9.92114685	-1.2533323	1	0.1875 ' Connect
GW	252	5	9.92114685	1.25333228	-1	9.92114685	1.25333228	1	0.1875 ' Connect
GW	253	1	-9.9873697	-0.5024433	-1	-9.9873697	0.50244331	-1	Rsrc   ' SOURCE
GS	0	0	0.0254		' All in inches.

holl_ands · 2011-12-14, 08:01 PM

The rest of the above 4nec2 file:

Code:

GE	0
EK
LD	5	0	0	0	3.77e7	0	' Aluminum
EX	0	253	1	0	1	0	' Simulated SOURCE on GW253
GN	-1
' FR Freq Sweep choices in order of increasing calculation time (fm holl_ands):
' FR 0 0 0 0 198 0		' Fixed Freq
' FR 0 0 0 0 590 0		' Fixed Freq
' FR 0 29 0 0 470 12		' Freq Sweep 470-806 every 12 MHz - OLD UHF BAND
' FR 0 34 0 0 410 12		' Freq Sweep 410-806 every 12 MHz - Even Wider Sweep
' FR 0 39 0 0 470 6		' Freq Sweep 470-698 every 6 MHz - PREFERRED FOR UHF
' FR 0 77 0 0 470 3		' Freq Sweep 470-698 every 3 MHz
' FR 0 153 0 0 470 1.5		' Freq Sweep 470-698 every 1.5 MHz
' FR 0 71 0 0 300 10		' Freq Sweep 300-1000 every 10 MHz - WIDEBAND SWEEP
' FR Hi-VHF choices:
' FR 0 15 0 0 174 3		' Freq Sweep 174-216 every 3 MHz
' FR 0 29 0 0 174 1.5		' Freq Sweep 174-216 every 1.5 MHz - PREFERRED
' FR 0 43 0 0 174 1		' Freq Sweep 174-216 every 1 MHz - Hi-Rez
' FR 0 26 0 0 150 6		' Freq Sweep 150-300 every 6 MHz - WIDEBAND SWEEP
' FR Lo-VHF choices:
FR 0 22 0 9 87 1   		' Frequency Sweep every 1 MHz for 87-108 MHz - FM Band
' FR 0 19 0 0 54 3		' Frequency Sweep every 3 MHz for Ch2-6 + FM
' FR 0 28 0 0 54 6		' Wide Freq Sweep every 6 MHz for Ch2-13
' FR 0 35 0 0 54 1		' Frequency Sweep every 1 MHz for Ch2-6
' FR 0 36 0 0 75 1		' Frequency Sweep every 1 MHz for Ch5 + Ch6 + FM
' FR 0 41 0 0 75 2		' Frequency Sweep every 2 MHz for 75-115 MHz
' FR 0 64 0 0 54 12		' Super Wide Freq Sweep 54-810 every 12 MHz
' RP choices in order of increasing calculation time:
' RP 0 1 1 1510 90 90 1 1 0 0		' 1D Gain toward 0-deg Azimuth - SIDE GAIN
' RP 0 1 1 1510 90 0 1 1 0 0		' 1D Gain toward 90-deg Azimuth - FORWARD GAIN
' RP 0 1 1 1510 90 180 1 1 0 0		' 1D Gain toward 270-deg Azimuth - REVERSE GAIN
' RP 0 1 37 1510 90 0 1 5 0 0 		' 2D (Left only) Azimuthal Gain Slice
RP 0 1 73 1510 90 0 1 5 0 0 		' 2D Azimuthal Gain Slice - PREFERRED
' RP 0 73 1 1510 90 0 5 1 0 0 		' 2D Elevation Gain Slice
' RP 0 73 73 1510 90 0 5 5 0 0 		' 3D Lower Hemisphere reveals antenna (Fixed Freq)
' RP 0 285 73 1510 90 0 5 5 0 0		' 3D Full Coverage obscures antenna (Fixed Freq)
EN

300ohm · 2011-12-14, 10:40 PM

Thats interesting. The single 3D pattern is a double facing eyeball, heh. I like that its only 20" in diameter. It doesnt seem to be a 300ohm antenna as expected as the SWR is high at 300.

I stacked it at 8 inches apart same as the FMSS, rotated the bottom element 180 degrees and the gain increased, and the vertical pattern is on a diagonal while the horizontal pattern remains round, which is nice.

NEC file:

http://www.wuala.com/300ohm/Document...0_stacked.nec/

holl_ands · 2011-12-24, 10:14 AM

IN SEARCH OF THE "BEST" OMNI FOR FM BAND: [May rescale to other Bands.]

Fol. Table compares nine different OMNI (many are Quasi-OMNI) Antennas.
Full analysis with charts and graphs and descriptions can be found here:
http://imageevent.com/holl_ands/omni

Code:

FM WORST/BEST Gain (dBi, all angles & freqs):    HORIZONTAL      VERTICAL          TOTAL        SWR

a) FM Monopole Whip (Vert. Pol.):                     0        +1.5 to +1.6    +1.5 to +1.6    3-4.5 (75-ohms)
b) FM Vertical Folded Dipoles (Vert. Pol.):           0        -1.7 to +2.6    -1.7 to +2.6    1-2.0 (300-ohms)

c) FM Turnstile (Horiz. Pol.):                  -13 to +1.4         0          -13 to +1.4     3.5-1.5 (300-ohms)
d) FM Double-Hoop (Horiz. Pol.):                -2.1 to +1.3        0          -2.1 to +1.3    6-11 (300-ohms)

e) FM Double-Hoop with Vertical Whip:           -3.7 to +1.2   -53 to -4.6     -3.2 to +1.9    5.1-7.1 (300-ohms)
f) FM Double-Hoop + Vertical-Dipole Outside:    -12 to +1.0    -13 to +1.9     -1.9 to +2.1    1-5 (75-ohms)
g) FM Double-Hoop + Vertical-FD Outside:        -3.9 to +1.2   -22 to -1.4     -2.3 to +1.8    6.4-6.8 (300-ohms)
h) FM Double-Hoop + Vertical-Dipole In Center:  -5.9 to +0.9   -9.4 to +1.5    -1.2 to +2.4    2.6-6 (300-ohms)
i) FM Double-Hoop + Vertical-FD In Center:      -5.2 to +0.8   -10 to +1.2     -1.8 to +2.3    2.2-7.2 (300-ohms)

To Print the above: Select ALL characters, Paste into NOTEPAD, Change
SETUP to Landscape and then PRINT.

Vertically Polarized (ONLY) signals:
Vertical Folded Dipole (VFD) had slightly higher Gain FORWARD and much
better SWR than the Vertical Monopole Whip. VFD Gain was within +/- 2.2 dB
across all angles and frequencies with excellent SWR between 1 and 2.
VFD is a truly Superior OMNI Antenna (for Vert. Pol. ONLY).

Horizontally Polarized (ONLY) signals:
Double-Hoop (DH) Gain was within +/- 1.5 dB across all angles and
frequencies, but SWR of 6-11 was quite high. However, it was clearly
superior to the Turnstile (Crossed Folded Dipoles), which had
very deep Gain holes away from the Bi-Directional lobes....both of
which changed angles as the frequency changed.
Perhaps there is something that can be done to reduce the DH's SWR????

As the Double-Hoop (DH) Opening (opposite the Feedpoint) gets smaller,
Gain increases slightly, but at the expense of higher SWR. I picked an Opening of
3.5-in as being the "best" compromise, rather than 2.5-in in post#1130 above.

Vertically & Polarized signals:
Double-Hoop + Vertical-Dipole-In-Center barely edged out the
Double-Hoop + Vertical-Folded Dipole-In-Center.
Horizontal Gain for the "worst case" angle and frequency was -5.2 and -5.9 dBi,
with "worst case" Vertical Gain being -9.4 and -10 dBi respectively.
Clearly we haven't yet found the ideal Dual Polarization OMNI....

The other three candidates had higher or much higher "worst case" Vertical Gain
and one even had a "worst case" Horizontal Gain of -12 dBi (with 75-ohm impedance).

There are a few more candidates for which I have not yet run 4nec2 analyses.....

300ohm · 2011-12-24, 11:11 AM

Quote:

a) FM Monopole Whip (Vert. Pol.):

I picked up a Jensen FM25 whip for almost nothing at a thrift store which Ill take apart to model after the holidays. The variable gain preamp specs claimed are 0 - 26 db with a NF of less than 3.

It has a 8ft mini coax run from the whip to the receiver end with a 300 to 75 ohm balun at the receiver end. I always thought whips were balanced to ground, so wouldnt a 75 ohm whip used in this way technically need two baluns, one 1:1 at the antenna end to go from balanced to unbalanced, and one 4:1 at the receiver end for 300 ohm input ?

holl_ands · 2011-12-24, 11:22 AM

Quote:

Originally Posted by 300ohm

I picked up a Jensen FM25 whip for almost nothing at a thrift store which Ill take apart to model after the holidays. The variable gain preamp specs claimed are 0 - 26 db with a NF of less than 3.

It has a 8ft mini coax run from the whip to the receiver end with a 300 to 75 ohm balun at the receiver end. I always thought whips were balanced to ground, so wouldnt a 75 ohm whip used in this way technically need two baluns, one 1:1 at the antenna end to go from balanced to unbalanced, and one 4:1 at the receiver end for 300 ohm input ?

If your FM Receiver (or AVR) has 75-ohm coax input, simply plug in the coax.
If your FM Receiver (esp. antiques) only has 300-ohm twinlead input, use Balun.

300ohm · 2011-12-24, 12:06 PM

Quote:

If your FM Receiver (or AVR) has 75-ohm coax input, simply plug in the coax.
If your FM Receiver (esp. antiques) only has 300-ohm twinlead input, use Balun.

Yep, and the end plug/power injector port is built that way to make using a 75 ohm or 300 ohm connection very easy.

But my in general question is, shouldnt a whip antenna require a 1:1 balun before connecting to the 75 ohm mini coax ?

jbkeh · 2011-12-24, 12:41 PM

Quote:

shouldnt a whip antenna require a 1:1 balun before connecting to the 75 ohm mini coax ?

Isn't the purpose of a balun to match a balanced to unbalanced line? If the whip antenna is already 75 ohm unbalanced, what more is needed? Perhaps the device at the receiver end of the coax would be better called a 1:4 "unbal" for receivers with only 300 ohm balanced input.

But then there is the question - should one "inject" the dc power for the preamp into the receiver....

300ohm · 2011-12-24, 02:42 PM

Quote:

Isn't the purpose of a balun to match a balanced to unbalanced line? If the whip antenna is already 75 ohm unbalanced, what more is needed?

From what I understand, the whip is 75 ohms balanced to ground. Or is it ?
When I asked Arie Voors about how to model a whip antenna connected at the base, he said the other end of the EX wire had to go to a ground plane. Makes sense, I think.

Quote:

But then there is the question - should one "inject" the dc power for the preamp into the receiver....

Its 12 vdc, 150 ma in this case. On the receiver end for FM radios, the input goes into coils and/or is buffered by caps, so its not a direct power injection. TVs and FM radios are made for that.

holl_ands · 2011-12-25, 12:51 PM

Quote:

Originally Posted by jbkeh

Isn't the purpose of a balun to match a balanced to unbalanced line? If the whip antenna is already 75 ohm unbalanced, what more is needed? Perhaps the device at the receiver end of the coax would be better called a 1:4 "unbal" for receivers with only 300 ohm balanced input.

But then there is the question - should one "inject" the dc power for the preamp into the receiver....

There should be NO DC voltage coming out of either the Jensen FM25 or ANY Preamp
Power Insertion Module going towards your HDTV.

====================================================
In post#1133 above I provided a link to various OMNI antenna simulations.
At the bottom is the 14-in Whip antenna (with a 2-in base) that came with my Stick Tuner.
Note that the SWR is Excessive on most frequencies, except near the (high) resonant frequency.
Modeling on a larger Ground Plane helped a bit, but it's far from being a "good" SWR.

At the top, you'll also find results for an FM Monopole Whip OMNI, which includes two,
slightly different 4nec2 models. The first is same as for the 14-in Whip, where the bottom
segment of the Whip is declared to be the SOURCE. The second specifically defines
the a 1-in Wire at the bottom of the Whip to be the SOURCE. Since results were within
a couple tenths, I did not post results charts for the second.

I don't know what is inside the Jensen FM25, but it COULD easily include a 1:1 Balun.
But I would guess that the internal Preamp is PROBABLY direct connected between a
very small ground plane in the base and the bottom of the active (FAT) whip element.
Due to the very short connection (much less than a wavelength), common mode
current problems are negligible, so an internal Balun is quite unnecessary:
http://www.eznec.com/Amateur/Articles/Baluns.pdf

PS: I wouldn't rule out some of these TOO TALL "whips" actually being Vertical Dipoles,
which is either 75-ohms or 300-ohms (Folded), fed in the middle....

Interesting....I'm getting hits from someone in Reims, France......on vacation perhaps????

holl_ands · 2011-12-27, 05:11 PM

IN SEARCH OF THE "BEST" OMNI FOR FM BAND: [May rescale to other Bands.]

I added 4nec2 Analysis for two FM Quasi-Omni "ESS-Curve" type antennas, similar to
Italian Fracarro ANT1200A and Polish Dipol A0222 & A0223:
http://www.fracarro.es/download/prod.../FM_SERIES.pdf
http://photos.imageevent.com/holl_an...%20Antenna.jpg

Although Vertical Polarization pattern was close to Omni-Directional, the Horizontal pattern
was Bi-Directional with deep nulls to the Sides (like a Horizontal Folded Dipole):
http://imageevent.com/holl_ands/omni
http://imageevent.com/holl_ands/omni...sfracarrodipol

Here's an update to the comparison table:

Code:

IN SEARCH OF THE "BEST" OMNI FOR FM BAND:

FM WORST/BEST Gain (dBi, all angles & freqs):    HORIZONTAL      VERTICAL          TOTAL        SWR    (Impedance)

a) FM Monopole Whip (Vert. Pol.):                     0        +1.5 to +1.6    +1.5 to +1.6    3-4.5   (75-ohms)
b) FM Vertical Folded Dipoles (Vert. Pol.):           0        -1.7 to +2.6    -1.7 to +2.6    1-2.0   (300-ohms)

c) FM Turnstile (Horiz. Pol.):                  -13 to +1.4         0          -13 to +1.4     3.5-1.5 (300-ohms)
d) FM Double-Hoop (Horiz. Pol.):                -2.1 to +1.3        0          -2.1 to +1.3    6-11    (300-ohms)

e) FM Double-Hoop with Vertical Whip:           -3.7 to +1.2   -53 to -4.6     -3.2 to +1.9    5.1-7.1 (300-ohms)
f) FM Double-Hoop + Vertical-Dipole Outside:    -12 to +1.0    -13 to +1.9     -1.9 to +2.1    1-5     (75-ohms)
g) FM Double-Hoop + Vertical-FD Outside:        -3.9 to +1.2   -22 to -1.4     -2.3 to +1.8    6.4-6.8 (300-ohms)
h) FM Double-Hoop + Vertical-Dipole In Center:  -5.9 to +0.9   -9.4 to +1.5    -1.2 to +2.4    2.6-6   (300-ohms)
i) FM Double-Hoop + Vertical-FD In Center:      -5.2 to +0.8   -10 to +1.2     -1.8 to +2.3    2.2-7.2 (300-ohms)
j) FM ESS-Curve (similar to Fracarro ANT1200A): -4.4 to -1.4   -34 to +0.1     -4.4 to +2.5    1.3-2.7 (300-ohms)
k) FM ESS-Curve (similar to Dipol A0222+A0223): -5.1 to -1.9   -36 to +0.4     -5.1 to +2.4    1.3-2.5 (300-ohms)

2011-12-14, 10:40 PM	#1132
300ohm Veteran Join Date: Mar 2008 Location: Somewhere in Delaware on the flat side Posts: 7,039	Thats interesting. The single 3D pattern is a double facing eyeball, heh. I like that its only 20" in diameter. It doesnt seem to be a 300ohm antenna as expected as the SWR is high at 300. I stacked it at 8 inches apart same as the FMSS, rotated the bottom element 180 degrees and the gain increased, and the vertical pattern is on a diagonal while the horizontal pattern remains round, which is nice. NEC file: http://www.wuala.com/300ohm/Document...0_stacked.nec/ __________________ My builds/plans (not the latest models) are located here.

2011-12-24, 10:14 AM	#1133
holl_ands Veteran Join Date: Nov 2008 Location: San Diego, CA Posts: 1,644	IN SEARCH OF THE "BEST" OMNI FOR FM BAND: [May rescale to other Bands.] Fol. Table compares nine different OMNI (many are Quasi-OMNI) Antennas. Full analysis with charts and graphs and descriptions can be found here: http://imageevent.com/holl_ands/omni Code: FM WORST/BEST Gain (dBi, all angles & freqs): HORIZONTAL VERTICAL TOTAL SWR a) FM Monopole Whip (Vert. Pol.): 0 +1.5 to +1.6 +1.5 to +1.6 3-4.5 (75-ohms) b) FM Vertical Folded Dipoles (Vert. Pol.): 0 -1.7 to +2.6 -1.7 to +2.6 1-2.0 (300-ohms) c) FM Turnstile (Horiz. Pol.): -13 to +1.4 0 -13 to +1.4 3.5-1.5 (300-ohms) d) FM Double-Hoop (Horiz. Pol.): -2.1 to +1.3 0 -2.1 to +1.3 6-11 (300-ohms) e) FM Double-Hoop with Vertical Whip: -3.7 to +1.2 -53 to -4.6 -3.2 to +1.9 5.1-7.1 (300-ohms) f) FM Double-Hoop + Vertical-Dipole Outside: -12 to +1.0 -13 to +1.9 -1.9 to +2.1 1-5 (75-ohms) g) FM Double-Hoop + Vertical-FD Outside: -3.9 to +1.2 -22 to -1.4 -2.3 to +1.8 6.4-6.8 (300-ohms) h) FM Double-Hoop + Vertical-Dipole In Center: -5.9 to +0.9 -9.4 to +1.5 -1.2 to +2.4 2.6-6 (300-ohms) i) FM Double-Hoop + Vertical-FD In Center: -5.2 to +0.8 -10 to +1.2 -1.8 to +2.3 2.2-7.2 (300-ohms) To Print the above: Select ALL characters, Paste into NOTEPAD, Change SETUP to Landscape and then PRINT. Vertically Polarized (ONLY) signals: Vertical Folded Dipole (VFD) had slightly higher Gain FORWARD and much better SWR than the Vertical Monopole Whip. VFD Gain was within +/- 2.2 dB across all angles and frequencies with excellent SWR between 1 and 2. *VFD is a truly Superior OMNI Antenna (for Vert. Pol. ONLY).* Horizontally Polarized (ONLY) signals: Double-Hoop (DH) Gain was within +/- 1.5 dB across all angles and frequencies, but SWR of 6-11 was quite high. However, it was clearly superior to the Turnstile (Crossed Folded Dipoles), which had very deep Gain holes away from the Bi-Directional lobes....both of which changed angles as the frequency changed. *Perhaps there is something that can be done to reduce the DH's SWR????* As the Double-Hoop (DH) Opening (opposite the Feedpoint) gets smaller, Gain increases slightly, but at the expense of higher SWR. I picked an Opening of 3.5-in as being the "best" compromise, rather than 2.5-in in post#1130 above. Vertically & Polarized signals: Double-Hoop + Vertical-Dipole-In-Center barely edged out the Double-Hoop + Vertical-Folded Dipole-In-Center. Horizontal Gain for the "worst case" angle and frequency was -5.2 and -5.9 dBi, with "worst case" Vertical Gain being -9.4 and -10 dBi respectively. *Clearly we haven't yet found the ideal Dual Polarization OMNI....* The other three candidates had higher or much higher "worst case" Vertical Gain and one even had a "worst case" Horizontal Gain of -12 dBi (with 75-ohm impedance). There are a few more candidates for which I have not yet run 4nec2 analyses.....

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

2011-12-14, 12:57 PM	#1127
holl_ands Veteran Join Date: Nov 2008 Location: San Diego, CA Posts: 1,644	FM "Omni" Antennas: Certainly NOT an Omni-directional antenna pattern.... Looks like a typical bi-directional pattern, except rotated with deep nulls at 45-deg. Note that pattern is same whether Horizontal, Vertical or Total Gain. Antennacraft Spec Sheet for FMSS doesn't say very much: http://www.antennacraft.com/pdfs/FMSS.pdf However, the FMSS Manual shows a "9-in Intercoupler" (Twinlead) that is wrapped around the mount (so element to element distance is a bit less than 9-in): http://www.antennacraft.com/Manuals/FMSS_Manual.pdf Adding this phasing harness to the model may improve the antenna pattern, even though it isn't even close to a 1/4-wavelength (30-in, 90-degrees): http://electriciantraining.tpub.com/.../14182_211.htm http://www.cebik.com/content/a10/wire/turns.html [Cebik's website requires FREE Registration] BTW: Most on-line info re Turnstile Antennas pertains to their use for Satcom, with a ground plane, exploiting the overhead (presumably circularly polarized) coverage.

2011-12-14, 01:56 PM	#1128
holl_ands Veteran Join Date: Nov 2008 Location: San Diego, CA Posts: 1,644	FM "Omni" Antennas continued: FYI: Winegard HD-6010 is a similar FM Turnstile...except NOT Folded...NOT Omni... and they don't want to talk about SWR: http://www.winegard.com/kbase/upload/HD-6010.pdf http://www.winegard.com/kbase/upload/1450463.pdf Hmmm....spec sheet says 10-in Height...so Element spacing might be about 9-in and interconnecting feedline might be 11-13-in??? Antiference (U.K.), Triax (U.K.) & others below make FM Omni Antennas where a single Folded Dipole is bent into nearly a complete circle...or HOOP: http://www.antiference.co.uk/sitefil...0%20Aerial.jpg http://www.antiference.co.uk/sitefil...%20Radio_0.pdf http://www.triax.co.uk/Products/Aeri...20Aerials.aspx [Somewhat better picture in their catalog.] FWIW: Bruce Carter cites a 1978 Audio Magazine series of articles by Michael J. Salvatti: http://www.mindspring.com/~brucec/fmant.htm Note that a single Folded Dipole bent into an "S" shape MIGHT have an Omni pattern. Dipole (Poland) still makes this type of FM antenna...but fortuitously mounts it VERTICALLY (for Vertical as well as Horizontal polarization coverage): http://www.dipolnet.com/estore-antennas-fm,4346.htm Click on image for full specs. Also note HOOP (Horiz only) and HOOP+WHIP (H+V) Omnis. Fracarro is the only one who actually publishes an Azimuthal Gain chart for the "S"...but NOT Hoop: http://www.fracarro.co.uk/index.php?...87&&Itemid=262 [Yup, it's OMNI.] And Televes appears to be the only one who publishes Azimuthal Gain chart for the HOOP: http://www.televes.com/en/content/dra-1201gif [Yup, it's OMNI.] http://www.televes.com/en/node/2314 Have fun and don't forget to check Horizontal, Vertical and Total antenna patterns....