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301. Re: [TowerTalk] Antenna/Tower Grounding (Lightning Protection) (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Thu, 04 Jan 2007 10:15:08 -0800
Think AM Broadcast -- according to IEEE data, on average, the energy in lightning has a VERY broad peak around 1 MHz (so broad that there's lots at 2-4x that frequency and 0.2X that frequency). It is
/archives//html/Towertalk/2007-01/msg00107.html (10,211 bytes)

302. Re: [TowerTalk] Antenna/Tower Grounding (Lightning Protection) (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Fri, 05 Jan 2007 09:54:32 -0800
Not ideal. The BEST, by far, is for all cables -- power, antennas, CATV, telco to enter at the same point so that the ground connections between them can be as short as possible. Remember that the MO
/archives//html/Towertalk/2007-01/msg00174.html (10,386 bytes)

303. Re: [TowerTalk] W2DU Balun Bead Source (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 09 Jan 2007 17:23:21 -0800
VERY good advice. As it turns out, I'm about 90% done with a tutorial on RFI and ferrites that includes a discussion of baluns, a lot of measured data, and specific advice on troubleshooting RFI and
/archives//html/Towertalk/2007-01/msg00365.html (8,648 bytes)

304. [TowerTalk] Understanding Baluns and This Ferrite Thing (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Wed, 10 Jan 2007 23:21:39 -0800
http://audiosystemsgroup.com/RFI-Ham.pdf is a tutorial that, among other things, attempts to answer most of your questions and many you probably never thought to ask. It's a work in progress, posted
/archives//html/Towertalk/2007-01/msg00406.html (9,245 bytes)

305. Re: [TowerTalk] 80m yagi / quad question (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Thu, 25 Jan 2007 07:32:58 -0800
Robert, Consider a half wave dipole sloping off the tower in the desired direction(s). I've done that at an old microwave site that has a massive 140 ft tower (roughly 10m square at the base, 8m squa
/archives//html/Towertalk/2007-01/msg00698.html (7,097 bytes)

306. Re: [TowerTalk] RG-316 choke cables (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Thu, 01 Feb 2007 14:52:26 -0800
You didn't say how much power you wanted to run through it. My tutorial on RFI includes an extended discussion of choke baluns. I suggest you study it before proceeding. It will also point you to som
/archives//html/Towertalk/2007-02/msg00019.html (7,070 bytes)

307. Re: [TowerTalk] Subject: Re: Managing Balanced line transitions (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 05 Feb 2007 07:08:32 -0800
There are some serious misconceptions here. Transformer baluns and choke baluns are fundamentally different. A transformer balun MUST have low loss (all the transmitter power goes through the core, s
/archives//html/Towertalk/2007-02/msg00061.html (8,419 bytes)

308. Re: [TowerTalk] 40 meter vertical ant (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 11 Feb 2007 21:13:17 -0800
Until I moved to California this spring, I never had a decent antenna, let alone two decent antennas. Now that I have some good high dipoles and a pretty good vertical, I've learned firsthand that ve
/archives//html/Towertalk/2007-02/msg00191.html (8,577 bytes)

309. Re: [TowerTalk] Stacking Opposite Polarity 2/440 Beams (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Fri, 02 Mar 2007 12:39:20 -0800
An important quibble about the word "polarity" -- the correct meaning is describing the voltage reference for the signal in an electrical circuit -- what in the old days, before we knew better, we c
/archives//html/Towertalk/2007-03/msg00005.html (8,015 bytes)

310. Re: [TowerTalk] [RFI] HIGH POWER and RFI... (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 06 Mar 2007 07:32:47 -0800
Ferrite chokes are essentially very low Q parallel resonant circuits. Antenna analyzers are not very useful for measuring ferrite chokes, for at least two reasons. First, they have a fairly low input
/archives//html/Towertalk/2007-03/msg00065.html (9,597 bytes)

311. Re: [TowerTalk] [RFI] HIGH POWER and RFI... (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 06 Mar 2007 08:02:24 -0800
I agree (although it has to guess at the sign of the impedance). The most important thing is that we understand the limitations of our test equipment, which you clearly do. 73, Jim __________________
/archives//html/Towertalk/2007-03/msg00067.html (7,550 bytes)

312. Re: [TowerTalk] [RFI] HIGH POWER and RFI... (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 06 Mar 2007 10:11:00 -0800
Good question. See below. Yes. If you're buying surplus clamp-ons and cylinders used for RFI suppression, it's most likely that they're #43, and a single turn (that is, the wire going through the cor
/archives//html/Towertalk/2007-03/msg00069.html (10,939 bytes)

313. Re: [TowerTalk] ferrite beads was...Re: [RFI] HIGH POWER and RFI... (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Fri, 09 Mar 2007 08:03:22 -0800
That's pretty vague. What sort of trouble? What sort of system? What is the ethernet doing? Ferrite chokes can effectively kill common-mode antenna behavior of ethernet lines at HF if you use the rig
/archives//html/Towertalk/2007-03/msg00119.html (9,649 bytes)

314. Re: [TowerTalk] ferrite beads was...Re: [RFI] HIGH POWER and RFI... (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sat, 10 Mar 2007 06:57:42 -0800
I would start by listening for Ethernet birdies on the frequencies listed in my tutorial that are on the ham bands that bother the ethernet system, and adding ferrite chokes as described in the tutor
/archives//html/Towertalk/2007-03/msg00145.html (9,324 bytes)

315. Re: [TowerTalk] ferrite beads was...Re: [RFI] HIGH POWER and RFI... (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 11 Mar 2007 08:57:18 -0800
Study the tutorial. It's written for guys with your background. Jim K9YC _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTa
/archives//html/Towertalk/2007-03/msg00154.html (9,168 bytes)

316. Re: [TowerTalk] 75 to 50 ohm connection question (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Fri, 16 Mar 2007 19:52:15 -0700
The mismatch between 75 ohm cable and a 50 ohm load is no big deal, except to the extent that the somewhat higher SWR might cause your transmitter to be a bit unhappy and pull back the power. This is
/archives//html/Towertalk/2007-03/msg00281.html (7,666 bytes)

317. Re: [TowerTalk] Mobile antenna for SUV (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 26 Mar 2007 07:55:40 -0700
Yes. I have been quite pleased with Hamsticks. Not as convenient as a screwdriver, but they work fine if you install them well, especially on the higher bands. The key to a good mobile antenna is a g
/archives//html/Towertalk/2007-03/msg00530.html (9,932 bytes)

318. Re: [TowerTalk] Mobile antenna for SUV (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 26 Mar 2007 08:09:52 -0700
I've always been primarily a CW op, even in the car, although I will work SSB on long trips. My first HF mobile rig (back in the early 80's) was my only HF radio, a TenTec Omni A (bought new, when it
/archives//html/Towertalk/2007-03/msg00532.html (9,222 bytes)

319. Re: [TowerTalk] Cushcraft balun power handling? (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 26 Mar 2007 08:42:21 -0700
You can increase the power handling and performance of any choke balun by adding a second choke balun in series with it (that is, between the first balun and the transmitter). See the tutorial below
/archives//html/Towertalk/2007-03/msg00535.html (8,398 bytes)

320. Re: [TowerTalk] Mobile antenna for SUV (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 26 Mar 2007 10:26:13 -0700
Hi Dennis, I have five of the big clamshells on the positive lead right at the battery, and several turns around the toroid where it runs as a pair. I haven't had time (or the motivation of a long ro
/archives//html/Towertalk/2007-03/msg00545.html (9,224 bytes)


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