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Continuing Interest in Open Wire Lines

20 Apr

I wrote a short blurb on why I am using, and think that, OWL (open wire line) us eminently practical and more efficient than coaxial cables if you intend to use a single antenna on more than a single band. My Blog tools keep recording hits on that short write up so I thought I would add a little more color to the info already published. One of the best pages on the subject is that of Vk1OD. It can be found here . In particular, Owen has made a loss calculator and modeled the ever popular G5RV with various feed schemes and corresponding loss models attached. His website is dynamically served and so links vary from day to day however it is an article that is titled “Feeding a G5RV” and can be searched in his search block if this link to it does not work properly here . I would take a serious look at the loss graphs from top to bottom and really study the last entry. Running true open wire line all the way from feedpoint to tuner and shack is the least expensive and most efficient solution by far. If one looks at the cost of such a installation there is no contest.

I used a loss calculator designed by Owen earlier this morning to see how my very large home made feedline would fair if operated on a extremely short antenna for 3.5 Mhz. If you recall my flat top dipole is a minimalist 50 feet overall with the last 5 feet on each end dropping down vertical. Electrically it is too short for efficient operation on 3.5 Mhz but I sometimes listen and try to work someone there and my curiosity was at work. It turns out that my 1/8th inch phosphor bronze constructed OWL operating with my short antenna (FP impedance on 3.5 Mhz of 1.525-j1216) would lose over 6 DB on that band. It gets worse of you used common (Wireman) 55X window line as that 6 DB loss runs up to 13 DB or more! Ideally, a longer antenna would be in order but that is impossible here so I just make due.  Of course this does not address in any way the loss that may be in my tuner which would only add to the problem. I only wish I could string up a flat top dipole of 110 feet as in a G5RV.

BTW Owen also has a Blog which has slightly more frequent content additions so be sure to check it out.It is linked from his web page referenced above.

Thanks for reading my Blog. Best, Chas W5PG

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Posted by on April 20, 2010 in Radio, Stuff

 

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