Seeing picture is enough.
Self-tapping screws on element joints will rust in a few months. Under a wind elements gonna rattle sooner or later and those screws will fall to the ground. Gamma match to trash, better direct feed with choke balun.
Mike
OK all you antenna gurus out there, I need help. Sirio makes a single element dipole antenna that can be used as either a vertical or horizontal antenna. ( Cheap $60-$99 ea). I plan to use it as a 2 element yagi by adding either a director or reflector. My question is, which would give me more gain if any, adding a reflector or a director? I only want a two element antenna because of space considerations. I plan on using some aluminum tubing that I have for the added element. Also, should I orient the antenna vertical or horizontal for shooting skip. I know that by going horizontal I can reduce the signals somewhat from vertical and vice versa but is one more effective over the other
373, I don't present a solution for the Sirio vertical 1/2 wave, but I did an Eznec model of this Sirio 1/2 wave vertical antenna.
The jest of these models is to improvise the likely need for a good coax choke, better still a balun, and direct feed like Mike is suggesting above in his quote.
If you don't understand the modeling, I will try and explain. The models are over Real Earth and in Free Space. My Free Space model produces an Average Gain Report (AGR) gives the Modeler some ideas for the accuracy in the model. This model shows the model to be within reason to consider the model is technically accurate.
Your results may vary from the model however due to your location. I use Average Earth in these models, but your setup might be over some other type of ground. I talk about this below in more detail.
Over Real Earth I used the tool for Average Earth conditions. Here we can see on the model that there is considerable Common Mode Currents (CMC) on the off-set mast...which I set to 48" inches from the bottom part of the radiator. In this model we can see the current problems on the mast if we don't use a good balun or coax choke.
Models
1. is a model over Real Earth with no means to deal with CMC. Here you can see the ill-effects caused to pattern and gain.
The RED lines in the antenna image show the currents acting very bad for performance.
2. is a model with 2 coaxial type chokes on the mast that basically eliminate all the CMC type bad currents on the mast, thus showing a very nice improvement in gain and maximum gain angle closer to the Earth.
3. is a model with the top section of the mast that was originally located next-to and close to the bottom leg of the dipole. Suppose you elected to use a nice sturdy non-conductive element to support the top part of the radiator instead of using all metal for the mast.
Again, this is all about getting your antenna setup to produce the best balance in the pattern and eliminating the CMC problems like Mike talked about earlier.
If you have any questions...just ask, OK?
