[Elecraft] 270 foot (ish) Doublet & K3 ATU

[Fred Jensen]

On 5/17/2014 2:29 PM, Wes (N7WS) wrote:
> My apologies for confusing two different posters to this thread.  Partly
> a consequence of threading and me using two different computers and two
> different email clients.
>
I thought that's what having an email client thread emails was supposed 
to prevent.  Then again, I tried it in T-bird and quickly quit -- 
couldn't find anything again. :-))

> Rick claims that when using a series connection of two different
> transmission lines, one coaxial, one window line, changing the length of
> one (coax) affects something or the other, while changing the length of
> the other portion (window line) has no effect whatsoever.

I could certainly be wrong on this but I believe the post(s) were simply 
pointing out that increasing the length of the "balanced" line affects 
the losses much less than making it shorter with a correspondingly 
longer coax line.

400 or 600 ohm "ladder line" [open wire line with a minimum number of 
spreaders] *is* very low loss at HF even at high SWR, so long as the 
separation is a very small fraction of a wavelength.  That's what the 
coastal marine and HF point-to-point stations used in mid-20th century 
and KPH/KSM still do.  Plastic insulated "window line" is significantly 
more lossy than ladder line, but still less than coax at higher SWR's. 
Window line is also sensitive to weather conditions.  I have window line 
down the tower to a DXE 4:1 balun and coax to the shack.  KAT500 needs 
to retune between a rainy and dry day.

There was a day when we brought open wire line into the shack.  With 
today's equipment, I really don't recommend that. :-))

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org