Thanks Ben. Waiting for completion of your work and posting of results. 73, abcd.Good evening!
No thanks needed - I'm new to EZNEC and this was a great opportunity to learn some of its features. Up until buying EZNEC, I had been evaluating my ADS-B antennas in the same fashion as you have been doing - maximum range evaluation. Here at my house, plane traffic varies greatly from day to day, so to get a good comparison between antennas, I've got to set up an antenna and let it run for a week or so before being confident I can compare the results. It appears that your location has a *lot* more airplane traffic, so you may not have to wait as long to have repeatable, comparable results. With EZNEC, I plan to model the designs, tweak the model, then do the maximum range comparison as the final test.
I'll be happy to share my tweaks, but I want to do two things before I do that. First, I need to double-check my model, as I think I may have an error in how I created the model of the stub itself. In my model, instead of keeping the stub length constant and moving the connection of the coax on the stub, I connected the coax at the end of the stub and varied the length of the stub. While the end result is still good, it may or may not represent the design you have presented. Second, I want to create a drawing of the antenna with the tweaks. While I think I can describe the tweaks in words without an issue, a picture will really make things clear. I would also like to show the antenna patterns predicted by EZNEC, as this antenna has a very directional response in elevation that I believe is very favorable for ADS-B reception. I may not be able to do this until this weekend, unless things are work calm down a little bit.
I'll be happy to model the shorted stub Franklin with 10mm spacing. If I'm looking at the diagrams correctly, the dimensions between the 10mm open stub version and the 10mm closed stub version are the same, with the only difference being the closed end to the stub. I will double-check this before I finish the models.
I am indeed an amateur radio operator, callsign KD5BYB.
thanks much and 73,