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41. Re: Topband: T - vertical improvement (score: 1)
Author: K4SAV <>
Date: Thu, 23 Jul 2009 23:34:23 -0500
WX5G wrote: At 1.5 kW the 370 pF cap will see 10 kV RMS. You are looking at a vacuum variable capacitor. Mike wrote: Great discussion, is there a good source of vacuum variables (at reasonable prices
/archives//html/Topband/2009-07/msg00106.html (8,211 bytes)

42. Re: Topband: "T" Antenna VS 30m high vertical (score: 1)
Author: K4SAV <>
Date: Sat, 25 Jul 2009 16:18:04 -0500
IK0YVV wrote: "Looking on the Low band bible by ON4UN and modelling the 30m vertical with eznec it seems that the antenna i'm using now has a better efficency of the 30m one." .... I don't get the sa
/archives//html/Topband/2009-07/msg00124.html (9,521 bytes)

43. Re: Topband: W1BB-Style Extended Inverted "L" (score: 1)
Author: K4SAV <>
Date: Sat, 25 Jul 2009 16:24:56 -0500
VE3CUI wrote: Has anyone ever validated, via computer modelling, Stew Perry's claim that 165' - to 175' was the "optimal" length for a series-tuned (variable capacitor) extended inverted "L"...? If b
/archives//html/Topband/2009-07/msg00125.html (7,555 bytes)

44. Re: Topband: Receive antenna switching - Thanks! (score: 1)
Author: K4SAV <>
Date: Thu, 06 Aug 2009 07:54:10 -0500
N6RK wrote: The real deciding factor to me was the discovery that if any water gets into the coax anywhere, if there is DC on the coax, there will be a small DC leakage current that generates 40 dB o
/archives//html/Topband/2009-08/msg00017.html (7,816 bytes)

45. Re: Topband: EZNEC Shunt Feed Model Gain (score: 1)
Author: K4SAV <>
Date: Wed, 19 Aug 2009 09:31:13 -0500
Modeling a gamma match for a tower is almost impossible to do in NEC2. It can't handle a junction of wires that have large differences in diameters. Check to see if the program is making errors. If y
/archives//html/Topband/2009-08/msg00080.html (7,637 bytes)

46. Re: Topband: EZNEC Model earth for Inv. L Re: EZNEC Shunt Feed Model Gain (score: 1)
Author: K4SAV <>
Date: Fri, 21 Aug 2009 14:33:25 -0500
Modeling shunt fed towers (if the shunt wire is included) and inverted Ls are two very difficult antennas to model in EZNEC (if you want an accurate answer) because you run up against rule limitation
/archives//html/Topband/2009-08/msg00087.html (12,077 bytes)

47. Re: Topband: Make 80m vertical work on 160 (score: 1)
Author: K4SAV <>
Date: Mon, 05 Oct 2009 10:44:11 -0500
There are at least three problems associated with using a 1/8 wavelength vertical on 160 meters. Those are feedpoint impedance, bandwidth, and coil dissipation. To give you an example, for a 20 meter
/archives//html/Topband/2009-10/msg00083.html (9,742 bytes)

48. Re: Topband: Coax Choke Balun (score: 1)
Author: K4SAV <>
Date: Wed, 11 Nov 2009 09:29:51 -0600
The choke balun will work (depending on how much impedance you really need). There are some advantages to using a ferrite core, but obtaining the core(s) is sometimes a problem. 30 turns of RG213 sho
/archives//html/Topband/2009-11/msg00304.html (8,472 bytes)

49. Re: Topband: Coax Choke Balun (score: 1)
Author: K4SAV <>
Date: Wed, 11 Nov 2009 20:26:05 -0600
K9YC is correct in pointing out that a coax choke's impedance is due to its reactance and the impedance obtained when using a ferrite is predominately resistive. In some situations this can cause pro
/archives//html/Topband/2009-11/msg00316.html (9,716 bytes)

50. Re: Topband: Coax Choke Balun (score: 1)
Author: K4SAV <>
Date: Wed, 11 Nov 2009 22:07:05 -0600
K4SAV wrote: I'm just trying to be accurate in describing what happens when you use a coax choke. Well I was TRYING to be accurate, but I missed the description of what happens at the 1/2 wavelength
/archives//html/Topband/2009-11/msg00317.html (7,821 bytes)

51. Re: Topband: Power Line Noise (long) (score: 1)
Author: K4SAV <>
Date: Thu, 26 Nov 2009 14:42:15 -0600
I use one of these: I did modify it and make some design improvements. If you decide to build it, I can send you info on what I did to it. Jerry, K4SAV ____
/archives//html/Topband/2009-11/msg00419.html (7,277 bytes)

52. Re: Topband: Need to know more about beverages... (score: 1)
Author: K4SAV <>
Date: Sun, 31 Jan 2010 14:37:20 -0600
I wouldn't expect much performance from a Beverage built like that. A bi-directional Beverage will have a lot more noise than an single direction one, and connecting the ground to the station ground
/archives//html/Topband/2010-01/msg00253.html (7,915 bytes)

53. Re: Topband: "Linear Loading" & 160-Meters (score: 1)
Author: K4SAV <>
Date: Tue, 23 Feb 2010 13:41:36 -0600
I thought there might be significant loss due to the shortness of the elements, but I didn't really know how much, so I put it on EZNEC. I first started with a full size 160 bobtail with the top at 1
/archives//html/Topband/2010-02/msg00189.html (8,795 bytes)

54. Re: Topband: "Linear Loading" & 160-Meters (score: 1)
Author: K4SAV <>
Date: Wed, 24 Feb 2010 16:09:52 -0600
No I didn't model a Robert Tail. It was a Bobtail. There are two methods for feeding a Bobtail, either voltage fed at the bottom of the center element or at the top of the center element (a low imped
/archives//html/Topband/2010-02/msg00202.html (10,116 bytes)

55. Re: Topband: "Linear Loading" & 160-Meters (score: 1)
Author: K4SAV <>
Date: Thu, 25 Feb 2010 12:16:29 -0600
It may be true that a "classic" Bobtail is fed at the bottom, but that doesn't mean feeding it at the top won't work. If you want to call it some other name when fed at the top, have at it. If you ta
/archives//html/Topband/2010-02/msg00208.html (9,577 bytes)

56. Re: Topband: Magic Antenna Land (score: 1)
Author: K4SAV <>
Date: Wed, 03 Mar 2010 16:29:01 -0600
There seems to be little information available on the subject of radials over/in salt water and ground rods. Not many people have salt water to play with, and data is lacking. I can give you my opini
/archives//html/Topband/2010-03/msg00018.html (10,840 bytes)

57. Re: Topband: sudden increase in noise level on topband (score: 1)
Author: K4SAV <>
Date: Mon, 08 Mar 2010 22:15:05 -0600
If that noise is just a short pop occuring every second, it could be an electric fence. If it is a longer duration with a repetition rate of 1 second then it could possibly be a power pole problem (b
/archives//html/Topband/2010-03/msg00051.html (7,661 bytes)

58. Re: Topband: wire on the ground antenna (score: 1)
Author: K4SAV <>
Date: Fri, 30 Jul 2010 12:25:47 -0500
Has anyone ever tried a BUG (Beverage under ground)? No, I'm asking seriously. Maybe just at the grass roots. I expect you would need a good preamp, but that can be done. NEC2 can't even attempt to a
/archives//html/Topband/2010-07/msg00136.html (9,336 bytes)

59. Re: Topband: Antenna Engineers gone wild (score: 1)
Author: K4SAV <>
Date: Wed, 08 Sep 2010 13:27:32 -0500
Everything works. It's just a matter of degree. This one can easily be evaluated with EZNEC. The conductivity of seawater is 5 s/m. You can plug that number (in ohm-meters) into EZNEC instead of copp
/archives//html/Topband/2010-09/msg00029.html (8,705 bytes)

60. Re: Topband: Inverted L Dimensions (score: 1)
Author: K4SAV <>
Date: Mon, 27 Sep 2010 12:43:20 -0500
KJ4FDV: "Sounds great if the ground resistance stays the same for a given ground system with different antenna lengths. But that is an assumption." .... KJ4FDV: "I will lengthen my inverted L to 3/8
/archives//html/Topband/2010-09/msg00096.html (9,499 bytes)

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