60 + j19 does seem off. Is this ground mounted or with elevated radials?
An EZNEC free-space model reports *36 +j227* at 1800kHz. On perfect GND it reports 166 +j306 ohms. 10' above 0.005/13 GND it reports *37 +j262* ohms with resonance at 1510kHz. Dave KH6AQ On Wed, Dec 9, 2020 at 11:32 AM Jim Brown <[email protected]> wrote: > On 12/9/2020 12:00 PM, [email protected] wrote: > > My gut tells me the 60.25197 + J 18.63926 ohms impedance is to high, but > I don’t have enough experience to know if what what I am doing is correct > or not. I’m a neubie, at EZNEC and 160m. > > Those numbers tell you that the antenna is resonant below the band, and > the dimensions also show. It's a common trick to tune the antenna low so > that R is 50 ohms and X is inductive; we can then tune out the > inductance with series C. I'm using this technique with my Tee vertical > for 160M. > > Feedline loss on 160M is pretty low unless the line is pretty long, so > if your rig or power amp will drive it, I wouldn't worry about it. > > Another important observation. Four radials isn't enough of a > counterpoise unless they are well elevated -- N6BT, who's done lots with > verticals and is a fine antenna engineer, says at least 16 ft. A lot > of the R in your model could be ground loss. If those radials are > on-ground, you need a LOT more than four; they don't need to be any > specific length or even close to the same, but 100' is pretty close to a > quarter wave (thanks to soil modifying their VF), and more copper on the > ground is better. > > Also, soil parameters strongly affect that loss component -- try to > learn what your soil is like, and plug those parameters into the model. > In the soil parameters window, right click on the entry screen to get a > list of them. > > Here are slides for a talk I've done at Pacificon, Visalia, and to > several clubs. It's mostly about antennas and counterpoise/radial > systems. No original work, just summarizing a lot of great work by others. > http://k9yc.com/160MPacificon.pdf > > 73, Jim K9YC > > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
