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Total 27 documents matching your query.

1. Topband: T Vertical feed (score: 1): Author: ct1ilt@sapo.pt; Date: Wed, 25 Jan 2012 19:27:57 +0000; Hi Everyone, just finishing puting up a T Vertical (exactly in T shape) using 2 supports at the ends. The vertical portion is 18m and the T is 17m to each side (34m total). I am laying radials from 2; /archives//html/Topband/2012-01/msg00310.html (8,041 bytes)
2. Re: Topband: T Vertical feed (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Wed, 25 Jan 2012 11:48:20 -0800; Hi Filipe, That's the best solution, assuming that you have a tuner in the shack (or an amplifier with a tuned output that can handle a modest mismatch), and that you are using big coax (RG8, RG213).; /archives//html/Topband/2012-01/msg00311.html (8,290 bytes)
3. Re: Topband: T Vertical feed (score: 1): Author: DAVID CUTHBERT <telegrapher9@gmail.com>; Date: Wed, 25 Jan 2012 13:25:52 -0700; The radiation resistance is 25 ohms. I estimate your base referred ground loss resistance to be 10 ohms. So, you should expect a VSWR of 1.4:1 fed directly with 50 ohm coax. To obtain a better match; /archives//html/Topband/2012-01/msg00312.html (9,180 bytes)
4. Re: Topband: T Vertical feed (score: 1): Author: Dave Mueller <daven2nl@gmail.com>; Date: Thu, 26 Jan 2012 11:40:54 +1000; Fil, My 80/160m antenna is configured identically to yours on 160m. Same dimensions. In my case, with 90 radials of various lengths, I measured an Rr of 16 ohms at the feed point. The SWR exceeded 2:; /archives//html/Topband/2012-01/msg00315.html (9,311 bytes)
5. Re: Topband: T Vertical feed (score: 1): Author: "Jerry Keller $K3BZ$" <k3bz@verizon.net>; Date: Wed, 25 Jan 2012 21:56:09 -0500; Dave, Filipe, anyone..... my helix-wound vertical has a couple of elevated radials, which are not grounded. Everything sits above "ground", fed direct with 50 ohm coax, about 20 ohms R at feedpoint.; /archives//html/Topband/2012-01/msg00318.html (10,435 bytes)
6. Re: Topband: T Vertical feed (score: 1): Author: "ZR" <zr@jeremy.mv.com>; Date: Thu, 26 Jan 2012 08:43:24 -0500; All coils have loss so its a decision as to which one do you want? If the coax loss is minimal and the amp loads into it thats the one Id take and then add radials until there is no further meaningfu; /archives//html/Topband/2012-01/msg00322.html (12,080 bytes)
7. Re: Topband: T Vertical feed (score: 1): Author: "Paul Christensen" <w9ac@arrl.net>; Date: Thu, 26 Jan 2012 12:10:13 -0500; Based on your description, I just ran your "T" in 4Nec2 with the NEC/4.2 engine. Your T should have a base Z near 21+j110 at 1825 kHz and will be resonant at 1620 kHz which will help to push the max; /archives//html/Topband/2012-01/msg00323.html (10,802 bytes)
8. Re: Topband: T Vertical feed (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Thu, 26 Jan 2012 10:48:56 -0800; The relatively high VSWR of this impedance can be VERY easily converted to 2:1 by simply adding a series capacitance equal to 110 ohms at 1825 kHz. This brings the drive point Z to 25 ohms, which is; /archives//html/Topband/2012-01/msg00325.html (9,523 bytes)
9. Re: Topband: T Vertical feed (score: 1): Author: "Paul Christensen" <w9ac@arrl.net>; Date: Thu, 26 Jan 2012 14:31:09 -0500; Good point, Jim. Or, go the extra distance and add L too and make it a complete low-pass L as was mentioned. Then, the ATU on the shack table can breath a sigh of relief when needed with reasonable; /archives//html/Topband/2012-01/msg00326.html (8,911 bytes)
10. Re: Topband: T Vertical feed (score: 1): Author: ct1ilt@sapo.pt; Date: Thu, 26 Jan 2012 21:48:56 +0000; Hi everyone, thanks for the answers, I finished today laying down radials in a total of 48 that vary from 20m to 40m (tomorrow will add a few more). I tuned the antenna and the final measurements of; /archives//html/Topband/2012-01/msg00327.html (12,177 bytes)
11. Re: Topband: T Vertical feed (score: 1): Author: "Paul Christensen" <w9ac@arrl.net>; Date: Thu, 26 Jan 2012 16:58:26 -0500; of 2 to 1. Good job in getting the X value down -- even if it wasn't planned that way! What device did you use to measure base Z? Paul, W9AC _______________________________________________ UR RST IS; /archives//html/Topband/2012-01/msg00328.html (8,904 bytes)
12. Re: Topband: T Vertical feed (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Thu, 26 Jan 2012 14:03:11 -0800; If that is a good measurement, i wouldn't bother with a matching network. What do you mean by "balun?" Did you wind turns of the coax around a ferrite core? That is NOT a balun, it is a common mode c; /archives//html/Topband/2012-01/msg00329.html (9,690 bytes)
13. Re: Topband: T Vertical feed (score: 1): Author: ct1ilt@sapo.pt; Date: Thu, 26 Jan 2012 22:12:04 +0000; Jim, you are right, it is not a balun, it is a common mode choke, you can see it this picture from an Vertical I had ( http://paginas.fe.up.pt/~ee04056/CT1ILT/pics/tvertical/version1/thumbs/15.JPG ); /archives//html/Topband/2012-01/msg00330.html (10,152 bytes)
14. Re: Topband: T Vertical feed (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Thu, 26 Jan 2012 14:56:35 -0800; You can build a MUCH better choke with MUCH less coax by winding turns through #31 Fair-Rite cores. See my website for details. http://audiosysemsgroup.com/RFI-Ham.pdf 73, Jim K9YC __________________; /archives//html/Topband/2012-01/msg00331.html (9,080 bytes)
15. Re: Topband: T Vertical feed (score: 1): Author: DAVID CUTHBERT <telegrapher9@gmail.com>; Date: Thu, 26 Jan 2012 17:08:04 -0700; The simulated radiation resistance is 16 ohms, your GND loss is 9 ohms and efficiency is 64%. No balun is needed. _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? B; /archives//html/Topband/2012-01/msg00332.html (9,686 bytes)
16. Re: Topband: T Vertical feed (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Thu, 26 Jan 2012 20:48:47 -0800; What you mean, I think, is that no IMPEDANCE TRANSFORMATION is needed. Yet another example of why I object to the word "balun." And I agree that no impedance transformation is needed at the antenna a; /archives//html/Topband/2012-01/msg00335.html (9,186 bytes)
17. Re: Topband: T Vertical feed (score: 1): Author: DAVID CUTHBERT <telegrapher9@gmail.com>; Date: Thu, 26 Jan 2012 21:55:16 -0700; No I mean no balun is needed. The coaxial cable external shield current will be roughly that of one radial. With so many radials the shield current will be low. ______________________________________; /archives//html/Topband/2012-01/msg00336.html (9,533 bytes)
18. Re: Topband: T Vertical feed (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Fri, 27 Jan 2012 01:02:17 -0500; This is a terrible error in logic. Current on the radials will divide based on the impedance of each radial. If the feedline happens to be a "pathological" length its (outer) shield can carry *all* o; /archives//html/Topband/2012-01/msg00337.html (10,694 bytes)
19. Re: Topband: T Vertical feed (score: 1): Author: "Paul Christensen" <w9ac@arrl.net>; Date: Fri, 27 Jan 2012 10:20:16 -0500; To Joe's point, I don't think we want the feedline to become a radial. It also seems that placement of the line should occur under the radial field and not on top of it, but I have not seen any stud; /archives//html/Topband/2012-01/msg00340.html (9,453 bytes)
20. Re: Topband: T Vertical feed (score: 1): Author: Charles Moizeau <w2sh@msn.com>; Date: Fri, 27 Jan 2012 11:40:21 -0500; My radial field consists of 55 radials, 75' to 150' in length, buried 0.5" to 1" deep. My coax feedline, encased by a 1.25" gray pvc conduit, is 12'' deep and 80' long. It passes beneath several radi; /archives//html/Topband/2012-01/msg00342.html (11,093 bytes)

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