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61. Re: Topband: Beverage antennas (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 24 Jul 2012 10:53:01 -0400; This can be nothing but an end-fire antenna consisting of two elements. It is similar to the K9AY, EWE, Flag, and Pennant antennas, which are really nothing but the equivalent of two short verticals; /archives//html/Topband/2012-07/msg00324.html (9,268 bytes)
62. Re: Topband: How to Measure Beverage Common Mode Noise (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 24 Jul 2012 14:19:41 -0400; While a dummy load test for signals (as Mike says, noise is often too weak) might confirm a poor shield connection, especially if the cable is connected to normal grounds, it certainly does not test; /archives//html/Topband/2012-07/msg00329.html (9,155 bytes)
63. Re: Topband: How to Measure Beverage Common Mode Noise (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 24 Jul 2012 15:02:42 -0400; Yes. Cable grounds are isolated from signal grounds. That unit uses primary-secondary isolation transformers. _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK; /archives//html/Topband/2012-07/msg00331.html (8,069 bytes)
64. Re: Topband: Beverage antennas (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 24 Jul 2012 16:16:31 -0400; What Brian describes in paper 6 is totally different, and does not apply to large elongated single "loop" antennas. These antennas are so large in circumference phase is not uniform at all points on; /archives//html/Topband/2012-07/msg00335.html (10,135 bytes)
65. Re: Topband: Loops (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 24 Jul 2012 17:04:47 -0400; I do have an old page up about this: http://www.w8ji.com/k9ay_flag_pennant_ewe.htm _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK; /archives//html/Topband/2012-07/msg00337.html (9,059 bytes)
66. Re: Topband: Choke Construction Info Needed (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 26 Jul 2012 16:30:12 -0400; Phil, This is like any shunt or series choke problem. The choke needs to be several times the impedance at the insertion point. In a case like this you don't want too much choke, which many people t; /archives//html/Topband/2012-07/msg00347.html (9,662 bytes)
67. Re: Topband: Choke Construction Info Needed (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 26 Jul 2012 18:01:29 -0400; That choke is probably too small and will change SWR, but thankfully reactance in reactances does not dissipate power. Reactance simply stores and returns energy. 226 ohms of resistance would be abo; /archives//html/Topband/2012-07/msg00352.html (8,914 bytes)
68. Re: Topband: Choke Construction Info Needed (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 26 Jul 2012 18:12:32 -0400; 70 turns 2" diameter over 4" length would be 100 uH, and with an air core and #16 magnet wire would have a Q of about 200 or so. That's 1000 ohms impedance, a few hundred thousand ohms parallel resis; /archives//html/Topband/2012-07/msg00353.html (8,620 bytes)
69. Re: Topband: Choke Construction Info Needed (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 26 Jul 2012 18:23:30 -0400; No, it isn't. 1500 watts is 273 volts into 50 ohms. If Q is 226, and reactance 226 ohms, Rp is 51,077 ohms. 273 volts is 1.46 watts heat. To get 30 watts of heat with 226 ohms reactance, Q would hav; /archives//html/Topband/2012-07/msg00354.html (8,520 bytes)
70. Re: Topband: Choke Construction Info Needed (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 26 Jul 2012 19:22:06 -0400; My Mistake: I misplaced a decimal. Q would have to be near ten in the coil with 226 ohms reactance and 1500 watts to make 30W heat, not near 1. The other numbers are correct. A Q of ~200 is about 1.5; /archives//html/Topband/2012-07/msg00355.html (9,031 bytes)
71. Topband: Spark gaps (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Fri, 27 Jul 2012 10:09:16 -0400; Has anyone looked at, or looked for, cheap electric fence gaps?? My system copper pipes near tower legs work great for me on rigid towers, I can bend them so they spring away from the tower and then; /archives//html/Topband/2012-07/msg00359.html (8,874 bytes)
72. Re: Topband: Spark gaps (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Fri, 27 Jul 2012 11:52:06 -0400; I agree. The last thing we want is high surface resistivity, unless we want something to heat and vaporize. With high core resistivity, we could make it explode. :-) _________________________________; /archives//html/Topband/2012-07/msg00369.html (9,049 bytes)
73. Re: Topband: Spark gaps (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Fri, 27 Jul 2012 16:29:15 -0400; I've never seen a carbon ball in a lightning gap application. I'd have to see a few after being in action a long time before trusting them. Broadcast stations use hard metallic balls, as do electric; /archives//html/Topband/2012-07/msg00373.html (9,778 bytes)
74. Topband: FCP model (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 30 Jul 2012 12:22:14 -0400; Some food for thought on this that might make limited space counterpoise systems work a little better and be easier, faster, and cheaper to install. This is just intended to get people to think about; /archives//html/Topband/2012-07/msg00404.html (9,518 bytes)
75. Re: Topband: elevated counterpoise and lightning (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 30 Jul 2012 12:54:50 -0400; I have a picture of a very expensive broadcast suppressor on my web page. It is nothing more than a long solenoid of thin wire. Down this page: http://www.w8ji.com/ground_systems.htm There are a lot; /archives//html/Topband/2012-07/msg00406.html (8,740 bytes)
76. Re: Topband: FCP model (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 31 Jul 2012 10:19:16 -0400; I did a little more looking at the FCP system. I said this: The answer to this question is quite evident. The 66-foot wide FCP system is not even close to resonance on 160 meters. It appears the capa; /archives//html/Topband/2012-07/msg00410.html (9,389 bytes)
77. Re: Topband: FCP model (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 31 Jul 2012 14:04:44 -0400; Thanks, not really so elegant though. Any common common mode choke will work, if the system were made resonant. The problem is the counterpoise system appears to be pretty far removed from resonance; /archives//html/Topband/2012-07/msg00412.html (9,970 bytes)
78. Re: Topband: FCP model (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 31 Jul 2012 21:01:54 -0400; Hi Guy, A counterpoise that fully cancels its own fields, by definiton, cannot be a counterpoise. Following that logic, because it is true, the lowest loss counterpoise or counterpoise with lowest ex; /archives//html/Topband/2012-07/msg00438.html (14,900 bytes)
79. Re: Topband: FCP model (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 31 Jul 2012 21:15:39 -0400; Guy, If one thing is 100% certain and beyond debate, it is this... If a counterpoise does not radiate and has no fields, it is not a counterpoise. That's just the way it is. The very thing that make; /archives//html/Topband/2012-07/msg00439.html (9,592 bytes)
80. Re: Topband: K2AV FCP with 43' vertical (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Wed, 1 Aug 2012 08:31:36 -0400; The major problem with ANY 43 ft vertical is it is nearly like a mobile antenna on 160. Unless the system has huge losses, RF voltages are off the map. With low-loss ground systems and loading coils; /archives//html/Topband/2012-08/msg00002.html (8,932 bytes)

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