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21. Re: Topband: Terminating Resistors (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sun, 27 Sep 2009 08:46:36 -0600
Wirewound resistors are not robust for high energy surges such as lightning induced current. The 'non-inductive' wirewound resistors are not good for high voltage surges due to the contra-winding of
/archives//html/Topband/2009-09/msg00141.html (10,430 bytes)

22. Re: Topband: electrically shortening a tall grounded tower (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sun, 27 Sep 2009 08:58:51 -0600
Bob, rather than using a series hi-Z (trap) to decouple the upper portion of the tower a low-Z shunt element can be used. At the 130' point a loaded 'radial' sysatem of sorts is attached. An example
/archives//html/Topband/2009-09/msg00142.html (9,452 bytes)

23. Re: Topband: MFJ 259B on 160M (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sun, 27 Sep 2009 09:16:00 -0600
Glen, Try using the MFJ after 6 PM. The AM BC station will have reduced power. Dave WX7G _______________________________________________ Topband mailing list Topband@contesting.com http://lists.conte
/archives//html/Topband/2009-09/msg00144.html (8,193 bytes)

24. Re: Topband: electrically shortening a tall grounded tower (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sun, 27 Sep 2009 11:24:46 -0600
Bob, the base of the tower needs to be ungrounded. The tower can be fed at the base via a parallel LC or it can be fed at the junction of the tower and the decoupling wires or tubes. The disadvantage
/archives//html/Topband/2009-09/msg00146.html (11,083 bytes)

25. Re: Topband: relay-switched inverted L for 40/80/160 (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Tue, 29 Sep 2009 06:35:54 -0600
Jim, this will work. If you are going to put the wire lengths in series (33', 33', and 66') you will need a way to decouple the the relay coil wires between the wire sections; two relays. The decoupl
/archives//html/Topband/2009-09/msg00161.html (10,135 bytes)

26. Re: Topband: Ground Radials and an inv-L antenna (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Fri, 2 Oct 2009 09:05:17 -0600
Dennis, it appears that the near field losses are equivalent to 25 ohms at the antenna base. Since adding more radials does not improve this I suspect the nearby trees are the source of the loss. Dav
/archives//html/Topband/2009-10/msg00032.html (10,479 bytes)

27. Re: Topband: Make 80m vertical work on 160 (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sun, 4 Oct 2009 18:45:47 -0600
Franki, your 80 meter resonant vertical I assume is about 20 meters tall. You might want to consider top loading. That allows for two band operation with not active switching circuits. For example, t
/archives//html/Topband/2009-10/msg00078.html (9,598 bytes)

28. Re: Topband: INV-L with traps (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sat, 10 Oct 2009 10:45:51 -0600
Cris, your VSWR measurements point to a system loss resistance, referrred to the antenna feedpoint, of 5 to 10 ohms. This assumes that the matching transformer is working well. The radiation resistan
/archives//html/Topband/2009-10/msg00132.html (12,022 bytes)

29. Re: Topband: noise floor (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sun, 18 Oct 2009 09:13:09 -0600
Pete, what is the measurement bandwidth? Dave WX7G _______________________________________________ Topband mailing list Topband@contesting.com http://lists.contesting.com/mailman/listinfo/topband
/archives//html/Topband/2009-10/msg00195.html (8,844 bytes)

30. Re: Topband: Beverage Resistors (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sun, 18 Oct 2009 10:02:33 -0600
Dave, metal film resistors do not have much thermal mass in the metal film. For a short term overload such as lighting induced current the metal film can be damaged as it reaches vaporization. Carbon
/archives//html/Topband/2009-10/msg00198.html (8,851 bytes)

31. Re: Topband: Okay guys-----here's the full scoop (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sat, 31 Oct 2009 09:44:22 -0600
Dennis, I think a summer top band contest would be great. Who wants to sponser one? Dave WX7G On Sat, Oct 31, 2009 at 9:32 AM, Dennis Peterson <dennisissure@comporium.net ____________________________
/archives//html/Topband/2009-10/msg00471.html (9,294 bytes)

32. Re: Topband: The East Coast Advantage (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Sat, 31 Oct 2009 09:56:53 -0600
Being in Utah I cannot break into the top 5. I am satisfied with winning my state and working to beat the competiion from my QTH to the US West coast. Dave WX7G ______________________________________
/archives//html/Topband/2009-10/msg00474.html (10,728 bytes)

33. Re: Topband: Improve efficiency? (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Tue, 3 Nov 2009 02:38:46 -0700
Lew, I'm thinking that the close spacing between each tree and each vertical is absorbing a significant amount of signal. How much I don't know. If it is clear between the two trees I could see strin
/archives//html/Topband/2009-11/msg00043.html (8,749 bytes)

34. Re: Topband: Trees And RF (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Wed, 4 Nov 2009 19:34:22 -0700
AntenneX had an article a few years ago on a tree antenna. Dave WX7G _______________________________________________ 160 meters is a serious band, it should be treated with respect. - TF4M
/archives//html/Topband/2009-11/msg00152.html (7,540 bytes)

35. Re: Topband: Ground radials (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Fri, 6 Nov 2009 09:30:35 -0700
Something does not appear to be right. The total radial current will be equal to the antenna base current. You indicate that while the ground mounted radial current did not change while the elevated
/archives//html/Topband/2009-11/msg00208.html (8,100 bytes)

36. Re: Topband: Electrical height of short shunt fed tower? (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Mon, 9 Nov 2009 19:14:09 -0700
Mike, with the bottom Yagi only the modeled tower resonant frequency is 2.6 MHz. With the top Yagi added the resonant frequency is 2.0 MHz. The current is uniform along the first 48' and drops to one
/archives//html/Topband/2009-11/msg00282.html (10,116 bytes)

37. Re: Topband: Coax Choke Balun (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Wed, 11 Nov 2009 01:38:26 -0700
Bill, your new choke has an inductance of 110 uH and presents an impedance of +j1300 ohms. Dave WX7G _______________________________________________ 160 meters is a serious band, it should be treated
/archives//html/Topband/2009-11/msg00301.html (7,590 bytes)

38. Re: Topband: 2 Element Parasitic Vertical (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Mon, 23 Nov 2009 15:04:16 -0700
Stan, that is correct, the smaller diameter vertical wire with top loading will appear electrically longer. I would model this over Perfect GND rather than Mininec GND. It is good that you have so ma
/archives//html/Topband/2009-11/msg00398.html (8,699 bytes)

39. Re: Topband: 5/8 vertical (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Fri, 4 Dec 2009 09:56:18 -0700
If you are asking about a monopole with elevated radials the radials should be 1/4 wavelength. If ground mounted with radials on or in the ground the length is not that important. The feedpoint resis
/archives//html/Topband/2009-12/msg00043.html (8,276 bytes)

40. Re: Topband: inverted L pointers please (score: 1)
Author: DAVID CUTHBERT <telegrapher9@gmail.com>
Date: Tue, 8 Dec 2009 19:45:43 -0700
John, the goal is to make an inverted-L that works as well as a quarter wavelength vertical. Given a very good ground system a rather vertically short inverted-L is nearly as efficient as the vertica
/archives//html/Topband/2009-12/msg00096.html (8,068 bytes)

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