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Is the Sigma IV really a J-Pole?

yes, my mistake. i was simply using the 5/8 example to demonstrate the difference between the physical measurements versus the relevant electrical lengths when balancing reactances to establish resonance is used in antenna design. we need to become less concerned with the physical length and more so with the electrical length when in regard to actual antenna operating wavelength / performance.
 
Exactly! Electrical length is everything! Taking a Maco beam and changing the element lengths and overlaps WILL also change the electrical length of the element!

As you pointed out, the imports used smaller diameter tubing (I use that term loosely) and therefore the electrical length was different.

For those who don't understand what I'm saying, hear this:

A 18' piece of 14ga wire is electrically SHORTER than an 18' piece of 1" tubing! Physically they are the same length, but electrically they are completely different due to their diameter.

If a yagi used 1" tubing for all its elements, it would be physically shorter than an antenna that used 1", 7/8", 3/4", 5/8", 1/2" stepped elements. Beacause the diameter of the element tapers down in size, you have to make it physically longer in order to make it electrically the correct length. Cool huh!

To really illustrate it, if you made a quad using 16 guage wire, and a quad using 10 guage wire, the loops using the 10 guage wire would be physically shorter (but not by much! I only use this to illustrate a point).
 
one of my points exactly. a larger diameter (total surface area) conductor presents far higher levels of inductance than a top vertical element which tapers more quickly thereby requiring it to be much longer to achieve the required cancellation of any and all (or equal amounts) capacitive reactance in the system.
 
after having said all of that, electrically speaking these antennas, sigmaIV, lw150, lw101, (a typo) saliut 27, the vector, etc. are modified, endfed 3/4 wave ground planes. the patent does an excellent job of explaining the advantages of the upswept radial system which was the primary "current art" stated as the basic goal of the design, that coupled with the ability to restore some of the gain lost by a straightforward 3/4 wave design.
 
An lot has gone on since you answered my questions MC. You state:
I was scrolling back and forth while trying to respond to your questions. I hope I answered them all!
Click to expand...

You answered just fine MC, except that I did not suggest that maybe you had a new feeder design for the I-10K, I asked if you or Jay had tried feeding the Sigma IV in a different way or maybe tried using the trombone feeder idea in the Sigma IV.

I will have to look into that Bird field strength meter.

Thanks.
 
Yes I said it badly, but I meant that Jay's feeder, the trombone feeder is unique and great. That is what I meant. My question was had you or he, they tried feeding an old Sigma with such a device?

Thanks for the link to the FS meter.

I just talked to Eddie Chicconi and I am waiting for him to get back about the trip to the desert. It would be great if he could make that deal. I really think his idea and design there has some real possibilities as well and I would love to go heads up with him using my Starduster that just today even got better with an additional mode that I made.

I was going to put up Eddie's .50_11M, but I ran into a problem with some loose screws. We are getting that fixed and Eddie is also going to send me a new coil he has designed for this one an maybe a new base element with a new insulator to adjust the reactance in the antenna better.

He is a great fellow to do business with. Just wished he was not so busy.

Thanks MC.
 

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