If you like send me either here or via PM (at w8bya at mchsi dot com) any design ideas you have for your antenna and I will model it for you to give you an idea of what to expect. I have the more accurate NEC5 version which I have found to be incredibly accurate esp for very low antennas.As an example let me share this story......some years ago I wanted to try out 630m. I know enough about antennas that for best performance I wanted a vertically polarized radiator. Knowing this I still had a burning desire to try out a 2/3 size inv-v antenna hung off one of my 85' towers. The length of each leg was 300' long with each end about 10' off the ground so when drawn to scale this 600' inv-v was nothing more than a horizontal dipole nearly kissing the ground (in terms of wavelength).
Despite this I still wanted to see how this antenna would perform in real life. I started modeling the antenna to see just how bad things were going to be. Since it was electrically short I used a large inductor in the center, at the feedpoint, to resonate the antenna exactly on the desired frequency.
The large heavy inductor was wound on a 4" O.D. PVC tube some 3' long wound with a bunch of #14 THHN stranded copper wire. NEC calculated the feedpoint impedance and from that I was able to insert into the model the resonating inductance.
Once resonant I needed to raise the resulting pure (low) resistance up to 50-ohms since I wanted to directly feed the antenna with a 200' length of LMR400. I did NOT want to fiddle around with any tuners every time the weather changed and I wanted to operate. Thus in NEC I designed and inserted a gamma matching network. The resulting model predicted resonance at the right frequency with a near perfect 1:1 SWR and a 3-4 kHz operating BW.
I went ahead and built up this lil beast and hoisted it up to the top of the tower mast using 3/8" Nylon rope. I stretched out each end of the antenna and to my surprise, when viewed from the side hundreds of feet away it looked not too bad with very little sag in each leg.
I used (IIRC 13 Ga) aluminum coated steel electric fence wire which is incredibly strong and does not stretch. It does have slightly more resistive loss since it is not copper but this loss helped me lower the Q slightly and gave me the 2:1 SWR BW I needed to cover the band.
Amazingly on the very first tune up the resonant frequency was only off by a couple kHz ! I had to shorten each side of the dipole by several feet. Once I did that the antenna lasted through crazy winds and rains and even with thick ice along the entire length of the antenna the resonance did not go nuts with the SWR staying lower than a 1.6:1. Once the ice melted the SWR returned right back to the design frequency. It never had a failure and lasted me several years until I moved on to a top loaded T antenna.
I was quite impressed by the fact that NEC correctly calculated the feedpoint impedance perfectly, modeled the loading inductor and gamma match and nailed everything to within several kHz. While everyone on 630m were using Variometers to constantly tune and re-tune their antennas every time it rained or snowed I never had to do anything. This antenna was fed with 50-ohm coax and I could operate rain or shine. I made hundreds of CW and digital contacts all over the states and even Europe. Since I was running QRP I could hear stations from VK land and Europe and KH6 land almost every evening but they could not always hear me. Despite being the wrong polarization, for me, the antenna was a success. It was a blast to model, built, then operate.
Anyway, sorry for being long winded but if you need anything modeled just hollar. 73 Gedas W8BYA