A little sloppy, I should have said "transforms to some other SWR on an SWR bridge". We agree there are a couple of much better measurement means. Your "lacking that" example still requires a measuri
I have the Force 12 EF240X. This is the wire loaded elements that are about 45 ft long and a 24ft boom. I have tuned this antenna and have found the resonance (not the 1:1 SWR) changes pretty signifi
Well, now we're making some progress at reaching common ground. I created a dipole model with 1.5" diameter aluminum wires and adjusted the length for precise resonance at 7.15 MHz in free space. The
A little sloppy, I should have said "transforms to some other SWR on an SWR bridge". We agree there are a couple of much better measurement means. Your "lacking that" example still requires a measuri
Not really -- they were for tri-band Yagis that were popular at the time. The F12 antennas that were the best performers in both size classes are NOT trapped. Mosley has no clue how to design anythin
Author: Dan Maguire via TowerTalk <towertalk@contesting.com>
Date: Wed, 1 Jun 2016 19:19:03 +0000 (UTC)
and: http://www.karinya.net/g3txq/temp/dipole_vs_cobweb_tuning.png I see you beat me to it! You and I discussed this several months ago. Here are a few relevant posts from a qrz.com thread: https://f
Thanks Dan - I thought I remembered a discussion, but couldn't find it! Suffering badly from last week's "chemo" session at the moment :( Steve G3TXQ I see you beat me to it! You and I discussed this
There is a better way for at least some F12 40m yagis. My EF240S has two identical linear loaded dipoles, and I had tried the part-height tuning without success Finally, I put it up at full height an
Author: Dan Maguire via TowerTalk <towertalk@contesting.com>
Date: Thu, 2 Jun 2016 20:30:22 +0000 (UTC)
Using a dipole model with a 1" diameter aluminum wire over "Very Good" EZNEC ground, I adjusted the length to match the G3TXQ measured resonant frequency at the 15 ft height. That made the length 15.
What a great effort by G3TXQ and AC6LA showing how close actual resonances are to modeled ones. Modeling has some limitations, especially NEC2, but if done properly the results are amazingly accurate
John KK9A The variations are almost certainly due to a difference in the assumed epsilon and conductivity from reality. I'm sure if Dan fooled around a while, you could get a closer match. And then t
Plus, EZNEC assumes homogenous ground to infinite depth whereas I have this: http://www.karinya.net/bungalow/preparation/prep2.jpg Steve G3TXQ I'm sure if Dan fooled around a while, you could get a c
Steve G3TXQ Indeed.. Although I've not modeled it, I would think that it's the top layer of soil that really affects things. Skin depth at 7m is about a meter or two (for 5mS-m conductivity) - that's