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Discussion Starter #1
Just curious, if you have two perpendicular loops, wouldn't that take it from a bidirectional to an omnidirectional?

I'm just going from my basic understanding of wireless transmissions, so please let me know if there's some fundamental reason why this wouldn't work...

My rationale is: loops react to the perpendicular component of the magnetic field going through them. If you have one loop perpendicular to the first, then as the source (test) signal moves from perpendicular to parallel on the first, it will be moving from parallel to perpendicular, which should mean that a signal would never drop below .707*full perpendicular strength?
 

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if you have two perpendicular loops, wouldn't that take it from a bidirectional to an omnidirectional?
Yes, if used with a ground plane (like a whip antenna that uses a ground plane). There are commercial versions sold. IIRC, the gain on them is less than a simple dipole, ie less than 2.15 dBi.

The problem with the double perpendicular loops used as stand alone TV antennas like single loops discussed here is the matter of the feed-point location. Depending on where you locate the feed-point on the double perpendicular loop, the pattern changes, making it non-omnidirectional.

Heres a NEC file for a 23.5" vhf-hi double perpendicular loop, if someone wants to play with it.

CM 23.5 inch double perpendicular loop
CM AGT = 1.0 at 195mhz, Auto Segmentation = 21
CE
GW 1210 7 0 -11.75 0 0 -11.493228 -2.4429528 0.125
GW 1211 7 0 -11.493228 -2.4429528 0 -10.734173 -4.7791732 0.125
GW 1212 7 0 -10.734173 -4.7791732 0 -9.5059449 -6.9064961 0.125
GW 1213 7 0 -9.5059449 -6.9064961 0 -7.8622835 -8.7319685 0.125
GW 1214 7 0 -7.8622835 -8.7319685 0 -5.875 -10.175787 0.125
GW 1215 7 0 -5.875 -10.175787 0 -3.6309449 -11.174921 0.125
GW 1216 7 0 -3.6309449 -11.174921 0 -1.2282283 -11.68563 0.125
GW 1233 7 0 -1.2282283 11.6856299 0 -3.6309449 11.1749213 0.125
GW 1234 7 0 -3.6309449 11.1749213 0 -5.875 10.1757874 0.125
GW 1235 7 0 -5.875 10.1757874 0 -7.8622835 8.7319685 0.125
GW 1236 7 0 -7.8622835 8.7319685 0 -9.5059449 6.90649606 0.125
GW 1237 7 0 -9.5059449 6.90649606 0 -10.734173 4.77917323 0.125
GW 1238 7 0 -10.734173 4.77917323 0 -11.493228 2.44295276 0.125
GW 1239 7 0 -11.493228 2.44295276 0 -11.75 0 0.125
GW 1240 3 0 -1.2282283 11.6856299 0 0 11.75 0.125
GW 1242 7 -11.75 0 0 -11.493228 0 -2.4429528 0.125
GW 1243 7 -11.493228 0 -2.4429528 -10.734173 0 -4.7791732 0.125
GW 1244 7 -10.734173 0 -4.7791732 -9.5059449 0 -6.9064961 0.125
GW 1245 7 -9.5059449 0 -6.9064961 -7.8622835 0 -8.7319685 0.125
GW 1246 7 -7.8622835 0 -8.7319685 -5.875 0 -10.175787 0.125
GW 1247 7 -5.875 0 -10.175787 -3.6309449 0 -11.174921 0.125
GW 1248 7 -3.6309449 0 -11.174921 -1.2282283 0 -11.68563 0.125
GW 1249 7 -1.2282283 0 11.6856299 -3.6309449 0 11.1749213 0.125
GW 1250 7 -3.6309449 0 11.1749213 -5.875 0 10.1757874 0.125
GW 1251 7 -5.875 0 10.1757874 -7.8622835 0 8.7319685 0.125
GW 1252 7 -7.8622835 0 8.7319685 -9.5059449 0 6.90649606 0.125
GW 1253 7 -9.5059449 0 6.90649606 -10.734173 0 4.77917323 0.125
GW 1254 7 -10.734173 0 4.77917323 -11.493228 0 2.44295276 0.125
GW 1255 7 -11.493228 0 2.44295276 -11.75 0 0 0.125
GW 1256 3 -1.2282283 0 11.6856299 0 0 11.75 0.125
GW 1258 7 0 11.75 4.371e-15 0 11.493228 -2.4429528 0.125
GW 1259 7 0 11.493228 -2.4429528 0 10.7341728 -4.7791732 0.125
GW 1260 7 0 10.7341728 -4.7791732 0 9.50594488 -6.9064961 0.125
GW 1261 7 0 9.50594488 -6.9064961 0 7.86228346 -8.7319685 0.125
GW 1262 7 0 7.86228346 -8.7319685 0 5.875 -10.175787 0.125
GW 1263 7 0 5.875 -10.175787 0 3.63094488 -11.174921 0.125
GW 1264 7 0 3.63094488 -11.174921 0 1.22822835 -11.68563 0.125
GW 1265 7 0 1.22822835 11.6856299 0 3.63094488 11.1749213 0.125
GW 1266 7 0 3.63094488 11.1749213 0 5.875 10.1757874 0.125
GW 1267 7 0 5.875 10.1757874 0 7.86228346 8.7319685 0.125
GW 1268 7 0 7.86228346 8.7319685 0 9.50594488 6.90649606 0.125
GW 1269 7 0 9.50594488 6.90649606 0 10.7341728 4.77917323 0.125
GW 1270 7 0 10.7341728 4.77917323 0 11.493228 2.44295276 0.125
GW 1271 7 0 11.493228 2.44295276 0 11.75 4.371e-15 0.125
GW 1272 3 0 1.22822835 11.6856299 0 0 11.75 0.125
GW 1274 7 11.75 0 0 11.493228 0 -2.4429528 0.125
GW 1275 7 11.493228 0 -2.4429528 10.7341728 0 -4.7791732 0.125
GW 1276 7 10.7341728 0 -4.7791732 9.50594488 0 -6.9064961 0.125
GW 1277 7 9.50594488 0 -6.9064961 7.86228346 0 -8.7319685 0.125
GW 1278 7 7.86228346 0 -8.7319685 5.875 0 -10.175787 0.125
GW 1279 7 5.875 0 -10.175787 3.63094488 0 -11.174921 0.125
GW 1280 7 3.63094488 0 -11.174921 1.22822835 0 -11.68563 0.125
GW 1281 7 1.22822835 0 11.6856299 3.63094488 0 11.1749213 0.125
GW 1282 7 3.63094488 0 11.1749213 5.875 0 10.1757874 0.125
GW 1283 7 5.875 0 10.1757874 7.86228346 0 8.7319685 0.125
GW 1284 7 7.86228346 0 8.7319685 9.50594488 0 6.90649606 0.125
GW 1285 7 9.50594488 0 6.90649606 10.7341728 0 4.77917323 0.125
GW 1286 7 10.7341728 0 4.77917323 11.493228 0 2.44295276 0.125
GW 1287 7 11.493228 0 2.44295276 11.75 0 0 0.125
GW 1288 3 1.22822835 0 11.6856299 0 0 11.75 0.125
GW 1289 7 0 -1.2282283 -11.68563 0 1.22822835 -11.68563 0.125
GS 0 0 0.0254 ' All in in.
GE 0
EK
EX 0 1289 1 00 1 0
LD 5 0 0 0 58000000
GN -1
FR 0 1 0 0 638 0
 

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if someone wants to play with it.
I couldnt resist playing with it some more, so I came up with a ball loop that is omni-directional. The 300 ohm feed-point is in the center of the ball.
It has a Raw gain of 1.98 dBi with a SWR of 6.46, giving less than -1 dBi Net gain. It could be tweaked for less SWR. Or since the impedance is so high, it could be quad stacked ?? Squished down for more horizontal gain ?? Project for another day, heh.

Picture:


Nec file:
Code:
CM 23.5 inch ball loop
CM AGT = 1.0 at 195mhz, Auto Segmentation = 21
CE
GW	1210	7	0	-11.75	0	0	-11.493228	-2.4429528	0.125
GW	1211	7	0	-11.493228	-2.4429528	0	-10.734173	-4.7791732	0.125
GW	1212	7	0	-10.734173	-4.7791732	0	-9.5059449	-6.9064961	0.125
GW	1213	7	0	-9.5059449	-6.9064961	0	-7.8622835	-8.7319685	0.125
GW	1214	7	0	-7.8622835	-8.7319685	0	-5.875	-10.175787	0.125
GW	1215	7	0	-5.875	-10.175787	0	-3.6309449	-11.174921	0.125
GW	1216	7	0	-3.6309449	-11.174921	0	-1.2282283	-11.68563	0.125
GW	1233	7	0	-1.2282283	11.6856299	0	-3.6309449	11.1749213	0.125
GW	1234	7	0	-3.6309449	11.1749213	0	-5.875	10.1757874	0.125
GW	1235	7	0	-5.875	10.1757874	0	-7.8622835	8.7319685	0.125
GW	1236	7	0	-7.8622835	8.7319685	0	-9.5059449	6.90649606	0.125
GW	1237	7	0	-9.5059449	6.90649606	0	-10.734173	4.77917323	0.125
GW	1238	7	0	-10.734173	4.77917323	0	-11.493228	2.44295276	0.125
GW	1239	7	0	-11.493228	2.44295276	0	-11.75	0	0.125
GW	1240	3	0	-1.2282283	11.6856299	0	0	11.75	0.125
GW	1242	7	-11.75	0	0	-11.493228	0	-2.4429528	0.125
GW	1243	7	-11.493228	0	-2.4429528	-10.734173	0	-4.7791732	0.125
GW	1244	7	-10.734173	0	-4.7791732	-9.5059449	0	-6.9064961	0.125
GW	1245	7	-9.5059449	0	-6.9064961	-7.8622835	0	-8.7319685	0.125
GW	1246	7	-7.8622835	0	-8.7319685	-5.875	0	-10.175787	0.125
GW	1247	7	-5.875	0	-10.175787	-3.6309449	0	-11.174921	0.125
GW	1248	7	-3.6309449	0	-11.174921	-1.2282283	0	-11.68563	0.125
GW	1249	7	-1.2282283	0	11.6856299	-3.6309449	0	11.1749213	0.125
GW	1250	7	-3.6309449	0	11.1749213	-5.875	0	10.1757874	0.125
GW	1251	7	-5.875	0	10.1757874	-7.8622835	0	8.7319685	0.125
GW	1252	7	-7.8622835	0	8.7319685	-9.5059449	0	6.90649606	0.125
GW	1253	7	-9.5059449	0	6.90649606	-10.734173	0	4.77917323	0.125
GW	1254	7	-10.734173	0	4.77917323	-11.493228	0	2.44295276	0.125
GW	1255	7	-11.493228	0	2.44295276	-11.75	0	0	0.125
GW	1256	3	-1.2282283	0	11.6856299	0	0	11.75	0.125
GW	1258	7	0	11.75	4.371e-15	0	11.493228	-2.4429528	0.125
GW	1259	7	0	11.493228	-2.4429528	0	10.7341728	-4.7791732	0.125
GW	1260	7	0	10.7341728	-4.7791732	0	9.50594488	-6.9064961	0.125
GW	1261	7	0	9.50594488	-6.9064961	0	7.86228346	-8.7319685	0.125
GW	1262	7	0	7.86228346	-8.7319685	0	5.875	-10.175787	0.125
GW	1263	7	0	5.875	-10.175787	0	3.63094488	-11.174921	0.125
GW	1264	7	0	3.63094488	-11.174921	0	1.22822835	-11.68563	0.125
GW	1265	7	0	1.22822835	11.6856299	0	3.63094488	11.1749213	0.125
GW	1266	7	0	3.63094488	11.1749213	0	5.875	10.1757874	0.125
GW	1267	7	0	5.875	10.1757874	0	7.86228346	8.7319685	0.125
GW	1268	7	0	7.86228346	8.7319685	0	9.50594488	6.90649606	0.125
GW	1269	7	0	9.50594488	6.90649606	0	10.7341728	4.77917323	0.125
GW	1270	7	0	10.7341728	4.77917323	0	11.493228	2.44295276	0.125
GW	1271	7	0	11.493228	2.44295276	0	11.75	4.371e-15	0.125
GW	1272	3	0	1.22822835	11.6856299	0	0	11.75	0.125
GW	1274	7	11.75	0	0	11.493228	0	-2.4429528	0.125
GW	1275	7	11.493228	0	-2.4429528	10.7341728	0	-4.7791732	0.125
GW	1276	7	10.7341728	0	-4.7791732	9.50594488	0	-6.9064961	0.125
GW	1277	7	9.50594488	0	-6.9064961	7.86228346	0	-8.7319685	0.125
GW	1278	7	7.86228346	0	-8.7319685	5.875	0	-10.175787	0.125
GW	1279	7	5.875	0	-10.175787	3.63094488	0	-11.174921	0.125
GW	1280	7	3.63094488	0	-11.174921	1.22822835	0	-11.68563	0.125
GW	1281	7	1.22822835	0	11.6856299	3.63094488	0	11.1749213	0.125
GW	1282	7	3.63094488	0	11.1749213	5.875	0	10.1757874	0.125
GW	1283	7	5.875	0	10.1757874	7.86228346	0	8.7319685	0.125
GW	1284	7	7.86228346	0	8.7319685	9.50594488	0	6.90649606	0.125
GW	1285	7	9.50594488	0	6.90649606	10.7341728	0	4.77917323	0.125
GW	1286	7	10.7341728	0	4.77917323	11.493228	0	2.44295276	0.125
GW	1287	7	11.493228	0	2.44295276	11.75	0	0	0.125
GW	1288	3	1.22822835	0	11.6856299	0	0	11.75	0.125
GW	1289	3	0	-1.2282283	-11.68563	0	2.5e-8	-11.68563	0.125
GW	1290	3	0	2.5e-8	-11.68563	0	1.22822835	-11.68563	0.125
GW	1291	3	-1.2282283	0	-11.68563	0	2.5e-8	-11.68563	0.125
GW	1292	3	1.22822835	0	-11.68563	0	2.5e-8	-11.68563	0.125
GW	1293	7	0	0	11.75	0	2.77778e-9	9.14604111	0.125
GW	1294	7	0	2.77778e-9	9.14604111	0	5.55556e-9	6.54208222	0.125
GW	1295	7	0	5.55556e-9	6.54208222	0	8.33333e-9	3.93812333	0.125
GW	1296	7	0	8.33333e-9	3.93812333	0	1.11111e-8	1.33416444	0.125
GW	1297	7	0	1.11111e-8	1.33416444	0	1.38889e-8	-1.2697944	0.15
GW	1298	7	0	1.38889e-8	-1.2697944	0	1.66667e-8	-3.8737533	0.125
GW	1299	7	0	1.66667e-8	-3.8737533	0	1.94444e-8	-6.4777122	0.125
GW	1300	7	0	1.94444e-8	-6.4777122	0	2.22222e-8	-9.0816711	0.125
GW	1301	7	0	2.22222e-8	-9.0816711	0	2.5e-8	-11.68563	0.125
GS	0	0	0.0254		' All in in.
GE	0
EK
LD	5	0	0	0	5.8e7	0
EX	0	1297	4	0	1	0
GN	-1
FR	0	1	0	0	195	0
 

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UHF Ball Crossed Loop:
The vertical feed shown above results in a Vertically Polarized antenna. For Horizontal Polarization,
"roll" it over so the inner feed runs from left to right.

BTW: Raw Gain is about +2.1 dBi in a nearly perfect Omni, but I get SWR (300-ohm) that ranges from
10 to 5.3 (Ch7-13). The Characteristic Impedance is about 1200-ohms, which might require cascading
TWO 4:1 Baluns in series....or something else....to get the SWR down to just under 3 (the best it will do
across the full band).
 

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The Characteristic Impedance is about 1200-ohms, which might require cascading
Yep, stacking would lower it to about 600 ohms and quad stacking should put it in 300 ohm range. Of course, it would be quite large and I have yet to see a TVFool that needed a omni-directional Vhf-Hi antenna.
 
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