[TenTec] OCF antennas evolution

[k6jek]

Right. I was answering your question, "Why not move the balun 200 feet away, right up to the feed point?" At high SWR coax is lossy compared to OWL.

I believe an 80 meter dipole used on 40 has an impedance of something like 2400 + j1700 for an SWR of about 75:1.

The 4:1 vs 1:1 balun question I'll leave to others.

Jon


On Jul 11, 2013, at 6:50 PM, Mike Bryce wrote:

> I quite aware that open line is generally considered lost less feed line. 
> 
> What threw me was the use of a 1:1 balun instead of a 4:1. 
> 
> That's the head scratcher. 
> 
> Mike wb8vge
> 
> Sent from my iPhone
> 
> On Jul 11, 2013, at 9:32 PM, k6jek <k6jek at comcast.net> wrote:
> 
>> 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
>> 
>> 
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