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Bob,

Here ya go.

I sent this to Master Chief via email earlier, then remembered my password.

Been following the thread Bob85 started on WWDX.

I, too, for three years, have argued that it's a modified slot antenna, and have NEVER seen the patent. I didn't even know the patent existed!

HOWEVER, I, HAVE MODELED IT!

It has max gain at 34.3 degrees, 8.23 dBi (referenced over REAL ground, and antenna GROUND mounted. You can skew the results ANY way you want by just changing lengths. You also HAVE to Balun feed this type of antenna, coil of coax works fine, 6 to 7 1/2 turns for 15 mtrs on up. JUST ENSURE ITS SOLENOID WOUND, NOT BUNCHED UP!!!) . At 27 mhz. 14.4+494 ohms. 14 ohms resistive, 494 ohms of inductive reactance... Hence the necessity for the cap (gamma match).

At 12-14 degrees, the Avanti Sigma antenna gives 2.7dBi of gain as well.

Calling it a J-Pole is complete, and udder bullshit. A J-Pole is called a J-Pole because of the configuration of the matching network. This is antenna 101, and can be verified by looking up a J Pole and a Slot and comparing them in either the ARRL Antenna Handbook, or almost ANY of Orr's manuals. The "designer" that called it a J-Pole should have been ignored at that point, simply because of the fact that the J portion is the matching network. Had the Avanti BEEN a JPole style antenna, no gamma match. The quarter wave stub will match almost ANYTHING to ANYTHING!!! Hence the reason we use them at V/UHF for matching our linears. You can match from 1 ohm to a megohm with a quarter wave stub (I mean, a "J Pole"). Incidentally, for more 'backing up' of my statements, search zeppelin antenna, not the end fed crap we hams use today, but the original zeps... They used the "J" style match, but didn't call it a J Pole because it didn't stand on it's end, resembling a pole... They trailed out.

You can also google Jagi or any other variant of the "J" matching method.

The slot, BTW, is common at microwave freqs... . UHF as well.

CB Ground Plane antenna. 4 Radials, all 1 meter long (each side, so a total of a bit over 6 feet... Didn't really matter if I made them longer in any type of near field (model-able) crap.

Antenna height 3M over real ground, default ground setup (typical of > 50 percent of earth, according to my modelling software)

Max Gain, 2.53 dBi at 41.8 degrees. 64+163, so 64 ohms with 164 ohms of inductance.
At 13 and 14 degrees, you have 1.8dBi of gain as well...

So, that's what I get, using a NEC2 style engine. Feel free to post the results, I forgot my password and associated email addy on that site.....

You CAN really screw up the Sigma's pattern by NOT balun feeding it. I can take it to a negative gain antenna by playing with feedline lengths, etc.... Source the voltage / current AT the feedpoint, and the proof is in the model.

I haven't even tried to increase (optimize) the gain.... My software allows for optimization on anything, f/b, gain, swr, impedance, whatever you want.

I'm using one of my Sigma's as my radiator for 160-10 now... Have it fed at the base, mounted at the 2nd story balcony. Using a marine tuna at the base, and a single ground rod (constantly soaked, NICE loamy soil, can't really ask for better), and I do OK. 1.2 swr ANYWHERE, butthe RF voltage is a bit high on 160!!!

Anyway, as I said, feel free to post the results. I DID model the antennas, and the sigma, properly installed will blow nearly ANYTHING else out of the water. Modelled as a sigma (I DID use a triangular "ring" for the top in my model. I can't do circles, each point becomes a new wire, but I did try using all different shapes, triangle, square, octagon, etc... And it didn't change the models nearly 1 bit... All within a dB. The problem with the sigma is this (and this is ANY antenna): The installer and installation!

Penetrator and nearly ANY style of groundplane that uses a decent matching system, the feedling currents will be decoupled by the ground radials. At least, in theory, this is how it works. HOWEVER, you WILL get some decoupling from them regardless, making the installation of a GP style antenna almost idiot proof.

The Sigma, you actually have to know what your doing, and install it as a system. A nice feedline choke, W2DU style balun, or nearly any other method of decoupling (qw sleeve, etc) will make a Sigma sit up and dance.

I compared my Sigma IV to a Radio Shack ground plane for a year up on the mountain in ******. All tuned MFJ, blah blah blah. The Sigma, for LOS comms, was the HANDS DOWN winner. The Radio Shack ground plane would eat it for lunch, however, when it came down to getting over a particular mountain, and after modelling them both, I can see why..... The Sigma had ALL it's RF below a particular point..... The RS ground plane was a LOT shorter, and had some interesting patterns.

--Toll_Free

edited for spelling error

<blockquote data-quote="Toll_Free" data-source="post: 145753" data-attributes="member: 1736">Bob,Here ya go.I sent this to Master Chief via email earlier, then remembered my password.Been following the thread Bob85 started on WWDX.&nbsp;I, too, for three years, have argued that it&#039;s a modified slot antenna, and have NEVER seen the patent.&nbsp; I didn&#039;t even know the patent existed!&nbsp;HOWEVER, I, HAVE MODELED IT!&nbsp;It has max gain at 34.3 degrees, 8.23 dBi (referenced over REAL ground, and antenna GROUND mounted.&nbsp; You can skew the results ANY way you want by just changing lengths.&nbsp; You also HAVE to Balun feed this type of antenna, coil of coax works fine, 6 to 7 1/2 turns for 15 mtrs on up.&nbsp; JUST ENSURE ITS SOLENOID WOUND, NOT BUNCHED UP!!!) .&nbsp; At 27 mhz.&nbsp; 14.4+494 ohms.&nbsp; 14 ohms resistive, 494 ohms of inductive reactance... Hence the necessity for the cap (gamma match).&nbsp;At 12-14 degrees, the Avanti Sigma antenna gives 2.7dBi of gain as well.&nbsp;Calling it a J-Pole is complete, and udder bullshit.&nbsp; A J-Pole is called a J-Pole because of the configuration of the matching network.&nbsp; This is antenna 101, and can be verified by looking up a J Pole and a Slot and comparing them in either the ARRL Antenna Handbook, or almost ANY of Orr&#039;s manuals.&nbsp; The &quot;designer&quot; that called it a J-Pole should have been ignored at that point, simply because of the fact that the J portion is the matching network.&nbsp; Had the Avanti BEEN a JPole style antenna, no gamma match.&nbsp; The quarter wave stub will match almost ANYTHING to ANYTHING!!!&nbsp; Hence the reason we use them at V/UHF for matching our linears.&nbsp; You can match from 1 ohm to a megohm with a quarter wave stub (I mean, a &quot;J Pole&quot;).&nbsp; Incidentally, for more &#039;backing up&#039; of my statements, search zeppelin antenna, not the end fed crap we hams use today, but the original zeps...&nbsp; They used the &quot;J&quot; style match, but didn&#039;t call it a J Pole because it didn&#039;t stand on it&#039;s end, resembling a pole...&nbsp; They trailed out.&nbsp;You can also google Jagi or any other variant of the &quot;J&quot; matching method.&nbsp;The slot, BTW, is common at microwave freqs... . UHF as well.&nbsp;CB Ground Plane antenna.&nbsp; 4 Radials, all 1 meter long (each side, so a total of a bit over 6 feet...&nbsp; Didn&#039;t really matter if I made them longer in any type of near field (model-able) crap.&nbsp;Antenna height 3M over real ground, default ground setup (typical of &gt; 50 percent of earth, according to my modelling software)&nbsp;&nbsp;Max Gain, 2.53 dBi at 41.8 degrees.&nbsp; 64+163, so 64 ohms with 164 ohms of inductance.At 13 and 14 degrees, you have 1.8dBi of gain as well...&nbsp;So, that&#039;s what I get, using a NEC2 style engine.&nbsp; Feel free to post the results, I forgot my password and associated email addy on that site.....&nbsp;You CAN really screw up the Sigma&#039;s pattern by NOT balun feeding it.&nbsp; I can take it to a negative gain antenna by playing with feedline lengths, etc....&nbsp; Source the voltage / current AT the feedpoint, and the proof is in the model.&nbsp;I haven&#039;t even tried to increase (optimize) the gain....&nbsp; My software allows for optimization on anything, f/b, gain, swr, impedance, whatever you want.&nbsp;I&#039;m using one of my Sigma&#039;s as my radiator for 160-10 now...&nbsp; Have it fed at the base, mounted at the 2nd story balcony.&nbsp; Using a marine tuna at the base, and a single ground rod (constantly soaked, NICE loamy soil, can&#039;t really ask for better), and I do OK.&nbsp; 1.2 swr ANYWHERE, butthe RF voltage is a bit high on 160!!!&nbsp;Anyway, as I said, feel free to post the results.&nbsp; I DID model the antennas, and the sigma, properly installed will blow nearly ANYTHING else out of the water.&nbsp; Modelled as a sigma (I DID use a triangular &quot;ring&quot; for the top in my model.&nbsp; I can&#039;t do circles, each point becomes a new wire, but I did try using all different shapes, triangle, square, octagon, etc...&nbsp; And it didn&#039;t change the models nearly 1 bit...&nbsp; All within a dB.&nbsp; The problem with the sigma is this (and this is ANY antenna):&nbsp; The installer and installation!&nbsp;Penetrator and nearly ANY style of groundplane that uses a decent matching system, the feedling currents will be decoupled by the ground radials.&nbsp; At least, in theory, this is how it works.&nbsp; HOWEVER, you WILL get some decoupling from them regardless, making the installation of a GP style antenna almost idiot proof.&nbsp;The Sigma, you actually have to know what your doing, and install it as a system.&nbsp; A nice feedline choke, W2DU style balun, or nearly any other method of decoupling (qw sleeve, etc) will make a Sigma sit up and dance.&nbsp;I compared my Sigma IV to a Radio Shack ground plane for a year up on the mountain in ******.&nbsp; All tuned MFJ, blah blah blah.&nbsp; The Sigma, for LOS comms, was the HANDS DOWN winner.&nbsp; The Radio Shack ground plane would eat it for lunch, however, when it came down to getting over a particular mountain, and after modelling them both, I can see why.....&nbsp; The Sigma had ALL it&#039;s RF below a particular point.....&nbsp; The RS ground plane was a LOT shorter, and had some interesting patterns.&nbsp;--Toll_Freeedited for spelling error</blockquote>

[QUOTE="Toll_Free, post: 145753, member: 1736"] Bob, Here ya go. I sent this to Master Chief via email earlier, then remembered my password. Been following the thread Bob85 started on WWDX. I, too, for three years, have argued that it's a modified slot antenna, and have NEVER seen the patent. I didn't even know the patent existed! HOWEVER, I, HAVE MODELED IT! It has max gain at 34.3 degrees, 8.23 dBi (referenced over REAL ground, and antenna GROUND mounted. You can skew the results ANY way you want by just changing lengths. You also HAVE to Balun feed this type of antenna, coil of coax works fine, 6 to 7 1/2 turns for 15 mtrs on up. JUST ENSURE ITS SOLENOID WOUND, NOT BUNCHED UP!!!) . At 27 mhz. 14.4+494 ohms. 14 ohms resistive, 494 ohms of inductive reactance... Hence the necessity for the cap (gamma match). At 12-14 degrees, the Avanti Sigma antenna gives 2.7dBi of gain as well. Calling it a J-Pole is complete, and udder bullshit. A J-Pole is called a J-Pole because of the configuration of the matching network. This is antenna 101, and can be verified by looking up a J Pole and a Slot and comparing them in either the ARRL Antenna Handbook, or almost ANY of Orr's manuals. The "designer" that called it a J-Pole should have been ignored at that point, simply because of the fact that the J portion is the matching network. Had the Avanti BEEN a JPole style antenna, no gamma match. The quarter wave stub will match almost ANYTHING to ANYTHING!!! Hence the reason we use them at V/UHF for matching our linears. You can match from 1 ohm to a megohm with a quarter wave stub (I mean, a "J Pole"). Incidentally, for more 'backing up' of my statements, search zeppelin antenna, not the end fed crap we hams use today, but the original zeps... They used the "J" style match, but didn't call it a J Pole because it didn't stand on it's end, resembling a pole... They trailed out. You can also google Jagi or any other variant of the "J" matching method. The slot, BTW, is common at microwave freqs... . UHF as well. CB Ground Plane antenna. 4 Radials, all 1 meter long (each side, so a total of a bit over 6 feet... Didn't really matter if I made them longer in any type of near field (model-able) crap. Antenna height 3M over real ground, default ground setup (typical of > 50 percent of earth, according to my modelling software) Max Gain, 2.53 dBi at 41.8 degrees. 64+163, so 64 ohms with 164 ohms of inductance. At 13 and 14 degrees, you have 1.8dBi of gain as well... So, that's what I get, using a NEC2 style engine. Feel free to post the results, I forgot my password and associated email addy on that site..... You CAN really screw up the Sigma's pattern by NOT balun feeding it. I can take it to a negative gain antenna by playing with feedline lengths, etc.... Source the voltage / current AT the feedpoint, and the proof is in the model. I haven't even tried to increase (optimize) the gain.... My software allows for optimization on anything, f/b, gain, swr, impedance, whatever you want. I'm using one of my Sigma's as my radiator for 160-10 now... Have it fed at the base, mounted at the 2nd story balcony. Using a marine tuna at the base, and a single ground rod (constantly soaked, NICE loamy soil, can't really ask for better), and I do OK. 1.2 swr ANYWHERE, butthe RF voltage is a bit high on 160!!! Anyway, as I said, feel free to post the results. I DID model the antennas, and the sigma, properly installed will blow nearly ANYTHING else out of the water. Modelled as a sigma (I DID use a triangular "ring" for the top in my model. I can't do circles, each point becomes a new wire, but I did try using all different shapes, triangle, square, octagon, etc... And it didn't change the models nearly 1 bit... All within a dB. The problem with the sigma is this (and this is ANY antenna): The installer and installation! Penetrator and nearly ANY style of groundplane that uses a decent matching system, the feedling currents will be decoupled by the ground radials. At least, in theory, this is how it works. HOWEVER, you WILL get some decoupling from them regardless, making the installation of a GP style antenna almost idiot proof. The Sigma, you actually have to know what your doing, and install it as a system. A nice feedline choke, W2DU style balun, or nearly any other method of decoupling (qw sleeve, etc) will make a Sigma sit up and dance. I compared my Sigma IV to a Radio Shack ground plane for a year up on the mountain in ******. All tuned MFJ, blah blah blah. The Sigma, for LOS comms, was the HANDS DOWN winner. The Radio Shack ground plane would eat it for lunch, however, when it came down to getting over a particular mountain, and after modelling them both, I can see why..... The Sigma had ALL it's RF below a particular point..... The RS ground plane was a LOT shorter, and had some interesting patterns. --Toll_Free edited for spelling error [/QUOTE]

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