Gamma Match Adjusments

[tecnicoloco]

Hi All:
I need some help with tuning a Sirio 4 Element Beam,is configure Horizontal.
Anyway,I went to SE page and they have the Diagram or Plans to Modify a Regular Maco 104C into a Freeband Design for 27.555Mhz. (optimize) for this operation frecuency,base on a Maco104C.
Well,I bought a Sirio 4 Element,I change the original design over to this design,but could not tune the antenna???( boom and element sizes)
I loss my Antenna Analizer(Drop from the Tower)not long ago,and I'm triying to do this with a regular SWR Meter.
I never have any problems before with 4 or 5 beams that I asemble in the past,but this one is giving me a hard time.
I would really apreciate any input on how to adjust the gamma match properlly,to tune this antenna.
Should I move the top bar first all the way out??
Should I move the bottom bar(Capacitor) all the way out??
I tried the original size for this antenna,but could not get it to work,then I start moving things around in the gamma match but only tune on 28.000 down to 1.1.1 swr.

will really apreciate your help.
Tecnicoloco
73's

 

[Master Chief]

Your driven element is too short. Lengthen both sides about 2" each at a time and readjust for lowest SWR. If you see that 2" only moved you a couple kilocycles, move them 4", etc.

The next problem is that your spacing and reflector/director lengths will not be optimum. It will work however.

The article on SE takes a specific antenna with KNOWN tubing diameters and lengths. Unless your Sirio beam is identical, your results will not be the same.

 

[tecnicoloco]

Hi Master Chief:
Thanks for your reply,honestly I was hoping to hear from you in this matter.
There are a little diferences betewen the Maco 104C and the Sirio SY4.

1.-The Boom in the Maco is 2" OD.
The Boom in the Sirio is 1 1/2" OD.

2.-The Element spacing is follow to the specs from SE.

3.-The Only diference from the Maco is:they use 5/8" & 1/2" OD for the elements,only 2 sizes,and the Sirio use 3 diferent sizes: 5/8",1/2" and 1/4" OD. the last piece of the element is 5" Inches in every element made out of the 1/4" OD.

4.-The Gamma Match Lenght on the Maco is 24" away from the Boom,the Sirio is 26 5/8",this numbers are for Factory on both antennas.

Comment:
While waiting for reply,hints,sugestions or ideas,I been moving the top bar away from the Boom Passing the 24" and the 26 5/8" and I can see the SWR is around,2.1.1 @ 27.500, 1.5.1 @ 27.700 and getting lower @ higher frec. 28.000 1.1.1

If you have any more ideas or hints,they are very welcome.


Thanks again for your help Master Chief
Tecnicoloco
73's

 

[DXman]

Around what Freq are you shooting for?

 

[tecnicoloco]

Hi DXMan:
I'm triying to adjust this antenna on 27.555Mhz. for Center Frecuency.
I follow Master Chief Advise and lenght the Driven Element 2" Inches,and really help,now I wonder how this change will afect the performance of this antenna.
I mean the Transmision Pattern??
The antenna when down to 1.2.1 on 27.700 and 1.3.1 on 27.550 Mhz.
Also,I wonder if I gonna have to increase the size off each element?? like Reflector,and Directors too??

Thanks for your help
Tecnicoloco
73's.

 

[DXman]

Well tecnicoloco,
Your pattern is going to depend mostly on the spacing of the elements and there lengths. It will be very hard to know what it is untill you were to run your measurements into antenna modeling program.

But with the match that you have now on your operating freq, I would think it should work fairly good. Just use it for awhile and see how it works.

Whooops - I see you are using the one from the SE site. Should work good as long as the elements are the same size in dia.
Yikes...I see Master Chief already said that!

Ok...I am done.

 

[DXman]

Tecnicoloco,
Here is program that you can mess around for setting your beam. Just click on the Qy4 logo.
Quickyagi4

 

[Master Chief]

The antenna when down to 1.2.1 on 27.700 and 1.3.1 on 27.550 Mhz. Also, I wonder if I gonna have to increase the size off each element?? Like Reflector, and Directors too??

Go out another inch per side (you did go 2" on BOTH sides, right?!). Then, adjust the shorting bar, followed by the inner tube until you find the lowest SWR. This takes care of the driven element.

Next is to experiment with the driven and the reflector. As a start, you can extend them the same amount as the driven (3" per side) and see if that gives you any increase in performance.

Lastly, you can adjust the spacing between the elements. What you will learn is that making spacing changes + or - a few inches will show no + or - in performance. Sure things will change a bit, but without a field strength meter, you would be hard pressed to see any changes.

If I had exact tubing lengths and exposed area dimensions, I could model the antenna for you, but its really not worth the effort as you seem to be pretty close now.

 

[tecnicoloco]

Hi Master Chief:
I dunno what happen but I missed your reply.
Thanks for the offer to model the antenna,I finally nail this antenna,I think that is working excellent now.
My biggest mistake was not to follow the tapper diameter of the elements,I borrow the ground plane radials and tip from a broken Maco V-5/8 as a source of 1/2"inch pipe and and extra 12 foot pipe that I have from before,then I start cutting the 5/8" OD tubing to design lenght and the 1/2" OD,after asemble all the elements,the antenna start to tune a lot better.
I got 1.1.1 swr at my target frecuency and good match over 600Khz.,also the field strenght meter shows an increase of 18% in the front lobe.
The lesson learned was to follow close atention to tapper diameters or your R,Z and x will be off.
Now I'm hook on EzNec and other modeling programs,very interesting subjects.
Thanks again Master Chief for your support and help.

http://img435.imageshack.us/img435/24/imag0006sf2.jpg

de vy 73 Tecnicoloco

 

[Robalo]

you have pm. sr.