Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Wed, 04 Jun 2008 22:25:57 -0600
The feed point of the Bazooka as originally done has two stubs in series with each other in parallel with the feed point. Those stubs are one quarter wave long shorted at the other end. So they prese
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Thu, 05 Jun 2008 10:30:41 -0600
Some VHF and UHF beams have used a folded dipole driven element. Many use a T match or some other scheme. The choice is generally based on the loading of the driven element by the directors and refle
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Fri, 06 Jun 2008 10:21:36 -0600
The mica washers can probably be split to make them thinner. They require thermal grease on both faces. Thinly applied. The silicone pads don't crack like mica, don't have conductive inclusions like
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Fri, 06 Jun 2008 10:37:49 -0600
Large diameter tubing alone gives wider bandwidth. The only thing you can reliably compute is end effect from the fat ends of the folded dipole. NEC programs don't handle closed spaced wires well. My
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Fri, 06 Jun 2008 10:41:02 -0600
Too many connections under tensile stress made worse by the wind (and ice) cross section being mostly plastic with only a small copper cross section for tensile strength. That's what kills the reliab
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Fri, 06 Jun 2008 23:03:34 -0600
That's true when the static is precipitation static, e.g. charged snow or rain collecting on the bare wire. Or not contacting the wire because of the insulation. There won't be any effect on static f
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Fri, 06 Jun 2008 23:22:08 -0600
That will shake loose hardware. I've had the noise level come up from that. Listen on AM for 120 Hz modulation of the noise level. Listen higher in frequency for better location. 2m AM is a lot bette
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Sat, 07 Jun 2008 15:56:41 -0600
All the nuances of a dipole and its feed won't do nearly as much about opening up a band as a serious antenna array. Like one of the several 20m arrays at N0NI not far from here. A 200' rotating towe
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Sat, 07 Jun 2008 16:03:57 -0600
Many have alleged the vertical matches the polarization of noise. Part of that may be true, also the quarter wave vertical usually has a low radiation angle and equal sensitive in all directions. The
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Sun, 08 Jun 2008 10:38:13 -0600
Its great that the computer agrees with my design. If I recall correctly, the 75 ohm line theoretically needed to be 56 feet long in solid polyethylene dielectric, but users built it (with my suggest
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Mon, 09 Jun 2008 10:35:11 -0600
Since removing ground wires and rods generally doesn't fry the thief, they probably had such grounds but they've all been "recycled" to cash. Audacious "recyclers" try to recycle live power lines, bu
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Mon, 09 Jun 2008 10:39:31 -0600
I don't see the benefit of choking the outside of the coax AT the radio. Unless the coax connector is loose at the radio, there's no way for any RF on the outside of the coax getting into the inside
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Mon, 09 Jun 2008 17:18:42 -0600
At least the dimensions and permeability are listed at Amidon. The material numbers may not match from Amidon as commonly used by hams to Fair Rite parts and materials. Typical materials good up to 3
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 10 Jun 2008 10:51:47 -0600
True, but there are permeability classes or groups (typical of a material at some convenient flux for simple measuring) and those with initial permeability ratings of 50 and 125 tend to be good for H
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 10 Jun 2008 11:13:49 -0600
That can be true for the parallel resonance, but the series resonance of the unused portion is mostly due to the length of the wire. That resonance is very close to where the wire length is 1/4 or 3/
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 10 Jun 2008 11:23:09 -0600
Different display devices need a different plastic filter to hide the hardware but still pass the light from the device. That makes a considerable contrast improvement. But the plastic's perceived co
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 10 Jun 2008 16:43:36 -0600
Well, I figure I couldn't say 6" was too wide on 160m while I allowed 1/4" on 1296 or even 1/2" on 2m, though I know 3/4" is probably actually too wide at 6m. The closer the spacing, the better. And
Author: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Date: Tue, 10 Jun 2008 16:46:44 -0600
Lightning arrestors go faster than insulators and DO make lots of noise sometimes. Sometimes the noise lasts only milliseconds, then you sweep up the pieces of the arrestor from the street and neighb