[TenTec] SLIGHTLY OT

[Art Trampler]

Steve,
 
I'll post my settings later when back home (sometimes I have to work!), but I was not at max L.
 
My XYL objected to holes through the wall for ladder line, to go straight out, and even wanted me not to use a bulkhead arrangement under the window...so...I am going down through the A/C duct with the LMR, to through a grounded Alpha-Delta suppresor and into the the balun.
 
For what it's worth, it's the 1114LS found here:
 
http://www.balundesigns.com/servlet/the-98/isolation-choke-balun-common/Detail
 
There is a six inch piece of LMR400 from the Alpha Delta 350 to the balun. I could cut two feet off the of the LMR600.
 
This may all be changed. I warned my XYL about some of the possibilities faced by running ladder line under the house--hadn't realized it would be coming out the same vent in through which the phone (DSL) and satellite RG-6 run as well! We'll see what happens when I go QRO on 40 tonight.
 
I appreciate the feedback though.
Art

--- On Fri, 4/8/11, Steve Hunt <steve at karinya.net> wrote:


From: Steve Hunt <steve at karinya.net>
Subject: Re: [TenTec] SLIGHTLY OT
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Date: Friday, April 8, 2011, 2:35 PM



On 08/04/2011 19:29, Dr. Gerald N. Johnson wrote:
> A quarter wave center fed wire has low radiation resistance and is very
> capacitive. Bad phase angle.

Correct - an EZNEC model of his antenna puts the feedpoint impedance at 
around 11-j930 Ohms

> You run that through a 600 ohm line about a
> quarter wave long, converts low R to high R and C to L.

No, that's wrong. A quarter wavelength of 600 Ohm line transforms 
11-j930 to 4.5+j386.
His 110ft of open wire will transform 11-j930 to around 7+j290

> So your balun
> sees high impedance that may be causing core saturation (for sure in a
> voltage balun) and you see high Z at the tuner.

A true 1:1 Guanella balun will not saturate because of a High Z 
differential load. The core flux is driven by *Common-Mode* current, not 
by differential-mode voltage.

Perhaps surprisingly the 10ft of LMR600 then has a major effect - 
transforming 7+j290 to 206+j1573

If you look at the L-network needed to match that impedance to 50 Ohms 
it requires much more inductance than the 238B is capable of. I wonder 
if your tuner is at max L as well as being at max C?

73,
Steve G3TXQ
_______________________________________________
TenTec mailing list
TenTec at contesting.com
http://lists.contesting.com/mailman/listinfo/tentec