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Total 18 documents matching your query.

1. Topband: electrical wavelength (score: 1): Author: Bob Kupps <n6bk@yahoo.com>; Date: Sun, 9 Sep 2012 20:09:32 -0700 (PDT); Hi it's still flooded here but I wanted to fire up one of my verticals by itself on 160 and feed it with a half wave of Comscope RG6 since I don't have enough 50 ohm line to reach it. I have a AIM 41; /archives//html/Topband/2012-09/msg00034.html (6,679 bytes)
2. Re: Topband: electrical wavelength (score: 1): Author: HAROLD SMITH JR <w0rihps@sbcglobal.net>; Date: Mon, 10 Sep 2012 08:04:19 -0700 (PDT); Hello Bob, I have used the published velocity factors for years. I made a 4:1 balan for my Telrex 20M546 a few years ago with RG14 coax. After I cut it, I checked it with my GDO and all was fine. 73; /archives//html/Topband/2012-09/msg00035.html (7,190 bytes)
3. Re: Topband: electrical wavelength (score: 1): Author: Jim Hoge <knowkode@verizon.net>; Date: Mon, 10 Sep 2012 09:23:27 -0700 (PDT); Let's do some quick math.... 234/1.82=128.57 gives us the length in feet of a quarter wave at 1.820 mHz. Multiply that by a velocity factor ( say 85% for LMR-400) and you get a length of 109.29 feet.; /archives//html/Topband/2012-09/msg00036.html (8,149 bytes)
4. Re: Topband: electrical wavelength (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Mon, 10 Sep 2012 09:53:27 -0700; That math is a bit too simple, because Vf VARIES as function of frequency. The PUBLISHED Vf is for VHF, but the Vf is a few percent lower at 2 MHz. This happens with ALL transmission lines, and is pr; /archives//html/Topband/2012-09/msg00037.html (9,217 bytes)
5. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 10 Sep 2012 12:57:25 -0400; Let's do some quick math.... 234/1.82=128.57 gives us the length in feet of a quarter wave at 1.820 mHz. That's not correct. The number is 245.8926/F, which is rounded to 246/F. A quarter wave in fre; /archives//html/Topband/2012-09/msg00038.html (8,239 bytes)
6. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 10 Sep 2012 13:44:15 -0400; I think the big error, using 234 instead of ~246, is pretty important to everyone. That math is a bit too simple, because Vf VARIES as function of frequency. The PUBLISHED Vf is for VHF, but the Vf i; /archives//html/Topband/2012-09/msg00039.html (11,375 bytes)
7. Re: Topband: electrical wavelength (score: 1): Author: Jim Hoge <knowkode@verizon.net>; Date: Mon, 10 Sep 2012 10:52:15 -0700 (PDT); My apologies to the group. I stand corrected. My incorrect constant and overly simplified math clouded the point I was trying to make. The point was intended to be that at top band frequencies, each; /archives//html/Topband/2012-09/msg00040.html (7,995 bytes)
8. Re: Topband: electrical wavelength (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Mon, 10 Sep 2012 13:36:19 -0700; Velocity factor in cable is the square root of the inverse of dielectric constant. Tom, Respectfully, I suggest that you go back to your college textbook on the fundamentals of Transmission Lines. Th; /archives//html/Topband/2012-09/msg00041.html (11,099 bytes)
9. Re: Topband: electrical wavelength (score: 1): Author: Pete Smith N4ZR <n4zr@contesting.com>; Date: Mon, 10 Sep 2012 16:58:27 -0400; I thought we were talking about RF. 73, Pete N4ZR The World Contest Station Database, at www.conteststations.com The Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot; /archives//html/Topband/2012-09/msg00042.html (12,033 bytes)
10. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 10 Sep 2012 17:24:24 -0400; Likewise, Zo is only sqrt (L/C) at VHF. The more complete equation is sqrt [ (R+J omega L) /( G + J omega C) ] At VHF, the equation SIMPLIFIES to sqrt (L/C) At low audio frequencies, and up to VHF, G; /archives//html/Topband/2012-09/msg00043.html (12,872 bytes)
11. Re: Topband: electrical wavelength (score: 1): Author: DAVID CUTHBERT <telegrapher9@gmail.com>; Date: Mon, 10 Sep 2012 17:42:33 -0600; Run the numbers and for RG-6 we see that sq root of L/C is good above a couple hundred kHz. _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK; /archives//html/Topband/2012-09/msg00046.html (11,946 bytes)
12. Re: Topband: electrical wavelength (score: 1): Author: Rik van Riel <riel@surriel.com>; Date: Mon, 10 Sep 2012 19:51:48 -0400; Does that have any consequences when planning phasing lines for a receive 4-square that is to be used on eg. 137 kHz? Are there types of coax that are more predictable on LF? Would the quad-shield RG; /archives//html/Topband/2012-09/msg00047.html (8,702 bytes)
13. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 10 Sep 2012 21:28:46 -0400; Run the numbers and for RG-6 we see that sq root of L/C is good above a couple hundred kHz. Dave WX7G I just ran it in MathCAD and it showed a Zo and Vf slope starting down around 150 kHz, but I assu; /archives//html/Topband/2012-09/msg00048.html (9,464 bytes)
14. Re: Topband: electrical wavelength (score: 1): Author: "Wes Attaway $N5WA$" <wesattaway@bellsouth.net>; Date: Mon, 10 Sep 2012 21:37:16 -0500; Tom .... I think everything is real quiet while a bunch of folks are busy looking at manuals and crunching numbers with their analyzers. Someone wants to find a mistake in your opinion. Stand by. --; /archives//html/Topband/2012-09/msg00051.html (10,132 bytes)
15. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 11 Sep 2012 04:28:34 -0400; Tom .... I think everything is real quiet while a bunch of folks are busy looking at manuals and crunching numbers with their analyzers. Wes, The problem Jim suggests is real, but the numbers are so; /archives//html/Topband/2012-09/msg00052.html (11,776 bytes)
16. Re: Topband: electrical wavelength (score: 1): Author: "ZR" <zr@jeremy.mv.com>; Date: Mon, 10 Sep 2012 13:02:22 -0400; I never take anything for granted when accuracy is desired. I use a noise bridge and my receiver to zero in on the exact frequency, the noise backround null is very pronounced with good coax. Beats t; /archives//html/Topband/2012-09/msg00053.html (9,806 bytes)
17. Re: Topband: electrical wavelength (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Tue, 11 Sep 2012 10:20:00 -0400; Some flooded foam-core F-6 starts to show what could be problematic velocity factor changes, for critical phased arrays, below 1 MHz. Above 1 MHz any change is lost in either measurement errors or ca; /archives//html/Topband/2012-09/msg00057.html (9,101 bytes)
18. Re: Topband: electrical wavelength (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Tue, 11 Sep 2012 10:08:20 -0700; Not quite. Some measured Vf numbers for Commscope 3227 (#10 solid copper center, dimensions and shield like LMR400) are:0.8 at 194.5 kHz, 0.816 at about 900 kHz, 0.829 at 1.8 MHz, 0.836 at 4 MHz, 0.8; /archives//html/Topband/2012-09/msg00058.html (12,533 bytes)

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