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#11
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wrote:
Hi Cecil, thanks for the info, I will take a look. BTW I used one of Reg Edwards programs to get 56'. I'd say 2' is close enough for engineering approximations. Have you bumped your program with his to see how they compare? Reg once compared them and they were close enough for government work. I assume a VF of 0.9 for 450 ohm window- line. Reg may assume something different or allow the user to enter the VF. In any case, it won't be exactly 54' or 56'. Some adjustment will always be necessary. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#12
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Cecil Moore wrote: wrote: Hi Cecil, thanks for the info, I will take a look. BTW I used one of Reg Edwards programs to get 56'. I'd say 2' is close enough for engineering approximations. Have you bumped your program with his to see how they compare? Reg once compared them and they were close enough for government work. I assume a VF of 0.9 for 450 ohm window- line. Reg may assume something different or allow the user to enter the VF. In any case, it won't be exactly 54' or 56'. Some adjustment will always be necessary. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- Good enough! Gary N4AST |
#13
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On Thu, 17 Mar 2005 01:10:07 GMT, Carter Grabarczyk
wrote: I am using a Johnson KW Matchbox antenna tuner with a 130 foot long, 30 foot high dipole fed with about 40 feet of ladder (window) line. It works well on all bands including the WARC bands *except* for 30 meters. (it doesn't make any difference if the band switch is on 20 or 40--it will not tune 30 in either case). The question is, does anyone have any tips/suggestions/modifications to make this also operate on 30 meters? By the way, modifying the antenna is not an option--lucky to have it up at all with city and subdivision restrictions. Maybe could add extra ladder line in the basement shack, but would have to loop it around the basement ceiling??? Dear Carter, As the owner of a cherry Viking Kilowatt Matchbox Tuner, I would want to avoid any modifications of the tuner itself. So, what I do is build up a modular approach for connecting feedlines to the tuner's balanced terminals. I use the General Radio design banana plug adapters as the basic building block. They are available from Radio Shack and have the advantages of having the exact spacing to match the 450 ohm ladder line and being both a jack and a plug at the same time as screwing down the ladder line. My approach is t ohave a short piece of 450 ohm ladder line from the Tuner Terminals to a GR banana connector. The antenna feed line has a similar GR banana connector at its end. When lighting is in the vicinity I disconncect the connectors and throw the feedline to the floor or to an earthing. Whenever I need a matching network for a given antenna due to extreme mismatches, I build that network between two GR banana connectors and just plug it in series with the line and tuner. The network is usually as simple as two inductors wound on PVC or it could be just a mica transmitting cap or a vacuum cap or any combination or balanced L or Pi circuit components. It helps to have a means of measuring the misbehaving antenna's impedance at the end of the feedline at the frequency in question and then design and build the necessary matching network based on the Smith Chart solution. Bob, W9DMK, Dahlgren, VA Replace "nobody" with my callsign for e-mail http://www.qsl.net/w9dmk http://zaffora/f2o.org/W9DMK/W9dmk.html |
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