Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Thu, 06 Jan 2011 11:07:39 -0600
NEC modeling of a ground plane is not all that dependable. NEC has some significant foibles, it doesn't couple currents to that ground plane, it just reflects from that ground plane to the distant re
Jerry makes some good points about taking care when using NEC. I have a few comments to add, interspersed below. The improvement in accuracy followed by degradation as the number of segments increase
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Thu, 06 Jan 2011 16:46:35 -0600
Trouble with that "understood" 3 dB error is that ARRL and other publishers don't understand and all their publications show the 3 dB inflated gains from EZNEC. HQ can be most stubborn about correcti
Jerry, That's interesting! Similar response on half a dozen other issues, either within QST articles or the Antenna Book; I've now given up trying :) 73, Steve G3TXQ _________________________________
Jerry, Please don't think I'm trying to be contentious, but your comment challenged my established view of what "dBi" represents. That led me on a literature search starting with my (very old) Master
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 16:44:09 -0600
I've published the same article twice now, once in The VHF'er in 1966 and last year in the proceedings of the 2010 Central States VHF Conference. So I have it available on line but not in a format th
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 16:53:45 -0600
I fear its not a commonly held view though I'd think in broadcast circles NEC would be held in contempt because it seems by my analysis to predict twice the field power than would be measured in the
Jerry, A picture paints a thousand words: http://www.karinya.net/g3txq/temp/ladderline_zo.png 73, Steve G3TXQ _______________________________________________ TenTec mailing list TenTec@contesting.com
Jerry, Then we'll probably have to agree to disagree :) Not so! If you calculated the power density you would expect to see at that range from an isotropic radiator in Free Space - one which radiates
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 17:14:55 -0600
What's that? a kink in the actual or is that because your horizontal axis is linear and mine is logrithmic (as are most references)? ;<) 73, Jerry, K0CQ ______________________________________________
When I was an undergraduate at MIT, there was a requirement for a Bachelor's degree thesis. Mine was about bouncing 2m signals off Echo II (see my QST articles about that in 1962). Anyway, they invit
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 18:20:59 -0600
My conundrum is that I expect equal power intensity at the the measuring point from the isotropic source whether a ground plane is involved or not and that I also expect equal intensity from a vertic
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 18:31:12 -0600
One of those trick questions. They are the same ONLY if impedance is preserved for the voltage measurements. If impedance is not preserved they are not the same. In a job interview I was asked if I c
Doesn't those in the electronics world refer to that as the "j" operator? 73, Jim, wd4air _______________________________________________ TenTec mailing list TenTec@contesting.com http://lists.contes
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 23:33:31 -0600
And the electric power world. Signifies a 90 degree phase angle away from resistive in impedance or voltage or current in complex arithmetic. Math types use i and call it the "imaginary" operator ins
Jerry, I think I had one of the curve "smoothing" options invoked on the spreadsheet graphing - that may account for it! 73, Steve G3TXQ _______________________________________________ TenTec mailing
Jerry, I can understand that the interpretation of dBi which appears in most engineering texts (and possibly the IEEE definition?) throws up conundrums with which you are uncomfortable. But what I th
Ray, If that had happened to me, I would have had little respect for professors who can't resolve such a simple issue! Steve G3TXQ _______________________________________________ TenTec mailing list
Jerry, That's a point that never came up in their discussion! 73 Ray In a message dated 1/8/2011 12:31:29 A.M. GMT Standard Time, geraldj@weather.net writes: II (see my quickly got dB One of those tr
Steve, Quite right! I was laughing under my breath, but did my best not to let it show. 73 Ray In a message dated 1/8/2011 12:50:36 P.M. GMT Standard Time, steve@karinya.net writes: Ray, If that had