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361. Re: Topband: 1/2 wave tower.... (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 05 Apr 2009 13:08:40 -0700
According to my arithmetic, 380 ft would be something on the order of 0.7 wavelength on 160M, depending on the cross section of the tower. Shouldn't be too tough to load. It's favored vertical angle
/archives//html/Topband/2009-04/msg00004.html (7,319 bytes)

362. Re: Topband: 1/2 wave vertical.... (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 05 Apr 2009 20:40:31 -0700
Don't reduce anything. Load both of them with phasing between them to form an array. These towers should be VERY easy to load on 160M -- they will look something like 40 + JX, so add enough series C
/archives//html/Topband/2009-04/msg00006.html (7,186 bytes)

363. [TowerTalk] Present to NY Area Ham Clubs? (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 06 Apr 2009 08:33:22 -0700
I will be in the NYC area during October to attend the AES (ending Oct 12) and for a grandson's Bar Mitzva (Oct 16-17). I'll have some time during the week of Oct 12, and would be happy to fill it wi
/archives//html/Topband/2009-04/msg00007.html (7,072 bytes)

364. Re: Topband: lift station noise (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 07 Apr 2009 16:06:06 -0700
Not an easy solution, Larry. On YOUR end, you might be able to kill it by putting it in the null of a directional RX antenna, but that won't help for DX coming from the same direction. :) The root ca
/archives//html/Topband/2009-04/msg00014.html (8,544 bytes)

365. Re: Topband: lift station noise (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Wed, 08 Apr 2009 08:45:54 -0700
That is the generic name for the motor control system that I described in my previous post. So the advice you have received from Lee and me is the same. 73, Jim K9YC _________________________________
/archives//html/Topband/2009-04/msg00018.html (7,903 bytes)

366. Re: Topband: lift station noise (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Wed, 08 Apr 2009 17:59:04 -0700
I don't know, but my guess would be yes. If you are on good terms with your neighbor, you may get some relief with a good line filter. Corcom and Delta are good brands. They are not expensive, and sh
/archives//html/Topband/2009-04/msg00020.html (8,416 bytes)

367. Re: Topband: Gas well pump motor (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 03 May 2009 19:51:08 -0700
Correct on all counts. To understand the problem, study the section on variable frequency drives in the RFI tutorial on my website. The primary mechanism is the magnetic field generated by that curre
/archives//html/Topband/2009-05/msg00014.html (8,780 bytes)

368. Re: Topband: K7RAT Beacon (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 10 May 2009 08:31:35 -0700
Something that could be useful here is an instrumentation rig that record the level of the CW signal over time. I'd bet that there's an audio application like this around somewhere. We should poke ar
/archives//html/Topband/2009-05/msg00051.html (7,077 bytes)

369. Re: Topband: Probably-dumb question re current mode chokes on RX antennas (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 18 May 2009 20:00:17 -0700
Good question, Pete. Not dumb at all. The best answer I can think of is to note that 1) the common mode current is flowing on the coax shield, 2) the earth is far from an ideal conductor, so the conn
/archives//html/Topband/2009-05/msg00075.html (8,606 bytes)

370. Re: Topband: Probably-dumb question re current mode chokes on RX antennas (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 19 May 2009 09:17:23 -0700
The T-section sort of thing you're describing would be more important if you were using beads rather than coils. With the relatively high impedances you can achieve on 160 with 7-10 turns through tha
/archives//html/Topband/2009-05/msg00079.html (7,606 bytes)

371. Re: Topband: Fwd: Probably-dumb question re current mode chokes on RX antennas (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Wed, 20 May 2009 16:15:39 -0700
Nothing wrong with it, but the common mode impedance curve is strongly influenced by the physical size of the core, the transmission line, and the winding details. If you're prepared to wind some des
/archives//html/Topband/2009-05/msg00090.html (7,746 bytes)

372. Topband: Broadbanding a Vertical (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Fri, 22 May 2009 17:47:06 -0700
I'm sure this will come as no surprise to the old timers on the list, but I'm passing this along to the newer guys. In contests, activity often goes pretty high in the band, and it's nice to be able
/archives//html/Topband/2009-05/msg00099.html (7,680 bytes)

373. Re: Topband: down hill slope for a beverage (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sat, 23 May 2009 08:32:03 -0700
I can not provide a comparison, simply because my Beverages run up and down ravines, and terminate into the side of upslopes. I'd estimate the elevation change at 40-50 ft. For both beverages, both e
/archives//html/Topband/2009-05/msg00103.html (8,477 bytes)

374. Re: Topband: Vertical offset from center of radial field (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sat, 23 May 2009 13:12:18 -0700
That's fine. I suspect that differences from ideal will be small. If you want to improve things, add some short radials in the immediate vicinity of the base. 73, Jim Brown K9YC _____________________
/archives//html/Topband/2009-05/msg00107.html (7,681 bytes)

375. Re: Topband: Claiming 160m DXCC - Sending QSLs (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 25 May 2009 17:29:08 -0700
The story I've heard is that some dishonorable hams have submitted cards where 18 MHz QSOs were changed to 1.8 MHz. 73, Jim K9YC _______________________________________________ Topband mailing list T
/archives//html/Topband/2009-05/msg00121.html (8,135 bytes)

376. Re: Topband: Beverage Feed Line Choke Installation (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 31 May 2009 19:14:47 -0700
As the designer of the coax chokes using clamp-ons or toroids, I'll step up to respond. They are a real "brute force" design, adding a VERY high impedance in series with the common mode circuit. As a
/archives//html/Topband/2009-05/msg00134.html (8,221 bytes)

377. Re: Topband: Abysmal condx (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 31 May 2009 19:22:14 -0700
Yes, conditions were stinko. NR6O (N6RO) is about 100 miles from me. I spent a lot of time on 40 and 80, but only went to 160 long enough to grab Ken's mult. Didn't even tune up the amp. 40 was OK to
/archives//html/Topband/2009-05/msg00135.html (8,115 bytes)

378. Re: Topband: Beverage Feed Line Choke Installation (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 31 May 2009 21:48:04 -0700
Ground rods are now $21 at my local hardware store, and depending on where you live, getting another one into the ground can be a challenge. The effectiveness of chokes wound on mix 73 degrades signi
/archives//html/Topband/2009-06/msg00000.html (7,406 bytes)

379. Re: Topband: Beverage Feed Line Choke Installation (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 01 Jun 2009 09:27:33 -0700
I don't agree. The antenna is part of the common mode circuit. Disconnect it and you have a different circuit. 73, Jim K9YC _______________________________________________ Topband mailing list Topban
/archives//html/Topband/2009-06/msg00007.html (8,207 bytes)

380. Re: Topband: Beverage Feed Line Choke Installation (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 01 Jun 2009 09:59:45 -0700
Very interesting. Thanks for contributing this. Carlos's chokes are essentially the same as mine on 160M. See measured data on pages 43-44 of http://audiosystemsgroup.com/RFI-Ham.pdf and compare to t
/archives//html/Topband/2009-06/msg00008.html (8,376 bytes)


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