[Elecraft] KAT 500 and open wire

[K9MA]

There are limits, of course, as your example shows. A center fed quarter 
wave is a very low impedance. I'd expect the feedline loss for that G5RV 
system would be less than a couple dB on 80 through 10 meters, generally 
acceptable.

73,
Scott K9MA


On 1/7/2019 09:49, Wes Stewart wrote:
>
> With all due respect, you don't say what acceptable loss is.  Of 
> course, you can match whatever the impedance is, most tuners will 
> match an open circuit because their internal losses allow it.  But it 
> can be a fallacy that, "The line loss is so low it doesn't matter."  
> Absent voltage breakdown, line loss increases because of the increased 
> circulating current resulting from operating at elevated SWR.  That 
> increased current is an issue in some baluns and tuners as well.  
> *All* of these components must be considered when evaluating an 
> antenna "system."  Considering only one part in isolation is fraught 
> with danger.
>
> Try running that 102' long "G5RV" up 50' on 160 meters.  Feed it with 
> 100' of Wireman 553 "low loss" ladderline.  The 0.1 dB matched loss 
> turns into over 13 db at the input and that's without considering 
> tuner loss. (Source: EZNEC and TLDetails)
>
> Wes  N7WS
>
> On 1/6/2019 3:15 PM, K9MA wrote:
>> The really attractive thing about open line, and even window line, is 
>> that its loss is so low you can use it at a very high SWR, and take 
>> care of the matching at the station end. This is especially useful 
>> for multi-band antennas. The famous G5RV, for example, will work just 
>> exactly the same fed with window line and a tuner as it will with the 
>> usual matching section.
>>
>> 73,
>> Scott K9MA
>
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-- 
Scott  K9MA

k9ma at sdellington.us