Mike,
You're matching the antenna system, the antenna and the feed line. You just
can't separate the two. When the antenna impedance at a particular frequency is
different from the feed line characteristic impedance, the impedance on the
line is different every place on the line. You're matching whatever it happens
to be at the shack end of the feed line.
Losses are the reason to put the balun near the station instead of near the
antenna. Open wire line has much lower losses than coax under conditions of
very high SWR. That's the reason we put up with the stuff which is a royal pain
in the arse, just so we can have a ridiculous SWR and not care about it. And
very high SWR is exactly what we have at almost all frequencies when using a
doublet as a multi-band antenna. The only reason we can get away with such a
thing is the low loss of open wire line. So you want to run that stuff as far
as you can before switching to coax. As long as you can is ideally right into a
balanced tuner, no balun at all.
Jon
On Jul 11, 2013, at 3:18 PM, Mike Bryce wrote:
> Interesting conversation!
>
> So what I am reading is this.
>
> Use a 1:1 current balun remote to the tuner to use my 600 ohm feedline.
>
> Now
>
> Somewhere along the way, depending on the length of the coax between the
> tuner and the balun, wouldn't I be just matching the say 14 foot run of coax
> from the tuner to the balun? And not necessarily matching the antenna?
>
> Lets take it one more step
>
> Place the 1:1 balun at the feed point 200 feet away and feed it with coax?
>
> Dosen't sound like a good idea.
>
>
> Mike wb8vge
>
> Sent from my iPhone
>
> On Jul 11, 2013, at 5:59 PM, "Robert Mcgraw" <rmcgraw@blomand.net> wrote:
>
>> Because your antenna impedance is not 600 ohms but is more lilkely 25 to
>> 75 ohms depending on height above ground. Only the feedline is 600 ohms
>> and that is really not an important issue.
>>
>> 73
>> Bob, K4TAX
>>
>>
>>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|