Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Thu, 06 Jan 2011 16:12:02 -0600
A specific answer to your question, as compared to "my" vertical dipole, then I must say I believe the raised quarter wave vertical with 4 elevated radials, say about 10' off the ground will be the b
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
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
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) Masters Degre
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 17:11:46 -0600
There would be more than a little hint of NIHS at ARRL HQ (Not Invented Here Syndrome). Perhaps if it wasn't discussed by Hiram Percy Maxim or F. E. Handy, its inappropriate, though the latest QEX ha
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 17:14:55 -0600
A picture paints a thousand words: http://www.karinya.net/g3txq/temp/ladderline_zo.png What's that? a kink in the actual or is that because your horizontal axis is linear and mine is logrithmic (as a
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
On 1/7/2011 5:53 PM, Rsoifer@aol.com wrote: 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 arti
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 20:05:58 -0600
Like my curves its center to center. The upper trace is using the 276 log formula and the lower one is the 120 inv hyperbolic cosine function. Mine has the spacings on a log scale his is a liner scal
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 21:33:15 -0600
You can solve your willowy tubing with stay wire braces, probably want to use a poly rope instead of wire. Stay wire braces have been used on slim masts, elevator legs (for grain transfer at an angle
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Fri, 07 Jan 2011 23:33:31 -0600
Doesn't those in the electronics world refer to that as the "j" operator? 73, Jim, wd4air And the electric power world. Signifies a 90 degree phase angle away from resistive in impedance or voltage o
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 08 Jan 2011 13:58:42 -0600
On 1/8/2011 9:09 AM, Jack Mandelman wrote: Forget about the formulas! None of the discussed formulas is sufficiently accurate of the wide ranges of S/d discussed. All are approximations that are reas
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 08 Jan 2011 14:13:33 -0600
What I see is that the changes in isotropic reference definition in the presence of a ground cause the program to show greater gain numbers that make the casual user conclude that there is a gain cau
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 08 Jan 2011 15:27:38 -0600
We wish that to mean that the tuner will match at 10:1 SWR circle at all phase angles and frequencies and greater mismatches for some phase angles. Any given tuner has better chances of making good m
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 08 Jan 2011 17:58:18 -0600
On 1/8/2011 4:31 PM, Jack Mandelman wrote: Jerry, The point that I'm making is that the formulas discussed are applicable only for very specific geometries. The validity of formulas breaks down at th
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 08 Jan 2011 18:05:07 -0600
Tuner loss is complicate by most tuners that have a myriad of tuning positions with different tuned circuit loaded Qs and so circulating current in the resonant circuit with different losses and band
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sat, 08 Jan 2011 18:29:27 -0600
My dad and I did that to a rotating pipe mast in the late 1950s. 60 feet of 4" galvanized pipe with a bearing and guy wires at about 565 feet. It stood (except for the times we took it down to work o
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sun, 09 Jan 2011 11:48:28 -0600
But the TV grade line needs help in the support department. 22 gauge copper wires aren't strong enough to take the wind and ice load on the flat of the insulation. I figure on punching holes every 6
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sun, 09 Jan 2011 12:39:45 -0600
I had more trouble with wind with TV twinlead over the past 39 years in central Iowa. Ice was harder on the 18 gauge copperweld open line. The wire simply snapped when a breeze flexed the feed line w
Author: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Date: Sun, 09 Jan 2011 13:00:11 -0600
I made a test of ordinary TV twinlead years ago. I had a 200 watt PA and my only exciter was for 80 meters. I hooked a foot or two of twinlead with the end away from the tuner shorted to my link coup