Gary,

I wrote some code to automate the optimization of the quad for my
goals - but my code only deals with element length, so I am hoping
that I don't need to add more code to manipulate the value of the load
too.

-Scott, WU2X


On Dec 14, 5:23*pm, wrote:
On Dec 14, 11:16 am, Scott M wrote:

Hi - I am trying to play around with modeling a loaded 40 meter
cubical quad. To start I made a single loop the size I wanted (about
2/3 full size) - I then looked at the impedance on 7.1Mhz. I added a
load (inductance) to bring the loop to resonance on 7.1Mhz. I then
created some parasitic elements - a director and reflector. I used the
same value load for these elements. Now, can I just adjust the lengths
of the wires to tune the feedpoint impedance and directivity and leave
the value of the load alone? Or is there some reason I will need to
adjust those values too? I placed the load opposite the feedpoint,
FYI.

-Scott, WU2X

Hi Scott, *Seems to me since this is a quad that your goal is maximum
gain or F/B. *As such, I would adjust the loads and element spacing
keeping the element lengths constant, until you have the current
distribution in the elements optimum for your goal. *Then check the
source impedance, and if it is not too bad, devise a way to match.
Suggest that instead of a single load opposite the source, use two
loads, should help with current distribution. *Good luck.

Gary N4AST

On Dec 14, 10:03�pm, Scott M wrote:
Gary,

I wrote some code to automate the optimization of the quad for my
goals - but my code only deals with element length, so I am hoping
that I don't need to add more code to manipulate the value of the load
too.

-Scott, WU2X
- Show quoted text -

OK, for modelling purposes, you can keep the load constant, and vary
the element lengths. From a practical standpoint, if you have this
beast up in the air, tuning is easier with a tapped inductor.

Other factors that will effect the gain and F/B are the element
spacing, and how high you can get the thing. Practically, these are
not things you can change easily.

I just did a quick 2 element 66% (reflector) quad in a diamond
configuration with 17' spacing on EZNEC, and got a 10.25 dbi gain at
35 degrees. F/B about 13 db. Feedpoint impedance was 44+j0 with a
678pf shunt capacitor. The element lengths were the same on both,
varied loads to get max gain and best match. The center of the
diamond was 50' up.

Gary N4AST