Modified M103 TO A M104

[LightFoot]

Hi,
I just modified my M103c to a M104C by ordering the 6 foot extension boom and an extra director. Total length is now 17 foot boom at 1 1/2 diameter boom. No problem there. No sagging of boom or elements. I have her matched pretty well. I was wondering can someone please advise me if you can model this on a program for optimum performance. I'm using LMR400 coax and elements are 5/8" and 1/2" aluminum tubing telescoping into each other. Frequency preferred would be at center CB . Thanks and best regards to you all from the coast of San Francisco................

[Spiderleggs]

Yes, I had some old programs that took into account element spacing, diameter of elements and boom, frequency input etc, and would display a graph as to what your signal would look like. By changing numbers you it would change the radiation pattern among other things.

[LightFoot]

Hello spiderleggs,
Thank you for responding to my post. Ive heard soo much about modeling and wanted to see if i can achieve better results from my M104 Horizontal or just leave well enough alone. I know there are free programs out there but feel kind of Leary about using them. Can you input my info if you still have the program and advise me what is the best overall performance or should i just leave it alone. You know the old saying that goes if it aint broke don't fix it, Hahaha, Thanks and best regards to you................

[Double D]

I have a number of 4 element designs i'll post the numbers for one.

[LightFoot]

Thanks Double D. Just wondering what the difference is between the way I have her and the new way. Looking forward to it. Sincerely appreciate your time and effort. Best regards and wishes from us on the coast of San Francisco.......

[Double D]

Here you go:

[Please login or register to view this link]

[Double D]

Some details:

Free Space Gain: 8.6 DBi 6.45 DBd
Gain 36 feet over average ground: 13.8 DBi
Front to Back: 23 DB
2 to 1 Bandwidth: 1760 KHz
Center Frequency: 27.205

['Doc]

And the biggy with all that is deciding which particular aspect that you want to make 'better'. They all are interrelated, meaning if you increase one aspect of performance, other aspects will be decreased to some extent.
One example of that is forward gain and F/B ratio or rejection off the back of the antenna. If you increase one, the other decreases. As that forward gain increases, the antenna changes from a unidirectional antenna to a bidirectional one. Just changing the 'shape' of the radiation pattern. There are limits.
You can 'optimize' almost anything to some extent. The 'trick' is deciding what aspect you want to make better at the expense of something else. The observable differences get smaller as the optimization gets better. When you can't tell any differences from a change, quit, you're about as close as is practical.
- 'Doc

[LightFoot]

Just want to say thank you Double D For Inputing the specs and Doc for your words of wisdom . I'm sure it took time to input all this. Just 1 more thing please so with these new measurements what am I gaining over the traditional specs of a Maco 4. Or is it just a better over all balance of more foward gain and more F/B. Best wishes and Regards From the Coast of San Francisco...................

[LightFoot]

Doc your right. Guess you cant have it all. Must sacrifice something to gain something. Must be the nature of this beast. Best wishes to you.....................LightFoot with the wave.....................

[Double D]

Just want to say thank you Double D For Inputing the specs and Doc for your words of wisdom . I'm sure it took time to input all this. Just 1 more thing please so with these new measurements what am I gaining over the traditional specs of a Maco 4. Or is it just a better over all balance of more foward gain and more F/B. Best wishes and Regards From the Coast of San Francisco...................

I optimized for bandwidth and Front to Back over the 11 meter band which tends to yield a cleaner pattern.

[LightFoot]

Thanks Double D. Well Put..............Thank you again..............................

[Double D]

No problem... If you use my specs, let me know how it works out for you.

[LightFoot]

Hi Double D. Definitely will be going up perhaps Thursday. I have that day off. I wish i could of observed the difference of before and after on your program. Just curious to what the stock version compares to the Modeled version. Some Programs shows it all in 3d. I'm sure your results will yield a better over all Performance. I promise to post results.........

[Double D]

I have modeled the entire M series of maco yagis and believe me they do need optimization. As for the difference between my optimized version and the stock version, my version has greater bandwidth and F/B while the stock version has slightly more forward gain.

[LightFoot]

Definitely prefer the optimized bandwidth and f/b ratio with a cleaner pattern than a slightly forward gain. Thank you Double D. Cant wait to implement the Optimized Specs to my stock M104. You must be using some nice programs. Ive got a few of the free ones offered but I'm betting on your specs.................

[LightFoot]

Double D I hope you see this. But with the Measurements you gave me this is what I came up with. Please direct me if Im off.

Reflector would be a total of 18 ft 5 1/2 inch
Driven element total is 17 ft 4 1/4 inch
1 st director is 17 ft 1 1/2 inch
2 nd director is 15 ft 6 inches.

Please can you give me the break down better on the spacing. like 5 ft 3-9/64 would be closer to what?
3 FT 8- 29/64 '' '' '' '' '' ?
8 FT 0-27/64. '' '' '' '' '' ?


Thanks again and hope to hear from you once more..................

[Double D]

Okay for clarity i'm disregarding the fractions:

Reflector total length: 18 ft 5 in
Driven total length: 17 ft 4 in
Director 1 total length: 17 ft 1 in
Director 2 total length: 15 ft 5 in

Spacing between Reflector and Driven: 5 ft 3 in
Spacing between Driven and Director 1: 3 ft 8 in
Spacing between Director 1 and Director 2: 8 ft 0 in

I hope this clears it up for you.

[LightFoot]

Man your the best. I was racking my head. Best wishes to you.

[Double D]

10-4