Rik van Riel wrote:
> On 11/29/2010 09:25 AM, jimlux wrote:
>> Rik van Riel wrote:
>>> On 11/28/2010 10:56 PM, DJ7WW wrote:
>>>> A tuner working into a 5:1 mismatch would not improve the antenna and
>>>> feed
>>>> line loss anyway.
>>>> A tuner is the wrong approach to compensate a bad antenna design.
>>>
>>> A 5:1 mismatch can be entirely reasonable depending on the band,
>>> the antenna, etc...
>>>
>>> For example on 160m and 80m it is common to have high impedances
>>> at the band edges, because these bands are just so wide (as a
>>> percentage of the center freq).
>>>
>>> However, a 5:1 mismatch at 2 MHz with 100' of LMR-400 coax only
>>> results in an SWR loss of 0.4 dB.
>>
>> It's too early in the morning for me to run the numbers, but in a
>> mismatch situation, the coax loss could be much higher:
>
> Go to the URL below, then type in the numbers:
>
>>> http://www.saarsham.net/coax.html
>
> 0.17 dB matched loss
> 0.26 dB SWR loss
> 0.43 dB total loss
>
>
that program has just the flaw I was describing. Since it doesn't ask
whether the mismatch is lowZ or highZ, for a length of coax shorter than
a half wavelength, you don't know whether you are running the coax at
high current (more loss) or low current (less loss).
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