[TenTec] Built in SWR meter bannans

[Steve Hunt]

What Rick reported is perfectly sound!

If the currents in each of the bifilar pair are balanced - that is they 
are equal magnitude and opposite phase - there will be no net flux in 
the core. If they are *not* balanced, there *is* then a CM component 
that will tend to drive flux in the core, and be opposed by that flux.

In other words, that arrangement tends to drive current balance in the 
two legs of the ladderline.

It's exactly the system I use to transition from ladderline on my 
multiband doublet to my unbalanced 238 tuner.

73,
Steve G3TXQ



On 22/04/2013 15:16, Walt K8CV wrote:
> Sorry, I find this a wee bit hard to swallow. I picture a big lump of 
> large toroids, with two plastic pieces of coax jacket going through 
> them, with one wire in each that connect to the open wire. This 
> conglomeration is serving some useful purpose? The little RF electrons 
> going NORTH to the antenna are passed by the gate keeper in the 
> conglomeration? WOW, that's interesting, as to the little electrons 
> reflected from the antenna he says " no, you can't pass "! Is there 
> some magic DSP going on here? How does this toroid know all this? Have 
> toroids become sentient and aware over night? I can see the scenario 
> when the ( sic ) good RF is on the inside of a coaxial cable and 
> protected from the toroid by the cable shield, getting to the antenna 
> and the ( sic ) bad RF, ON THE OUTSIDE OF THE COAX SHIELD, getting 
> stopped when they are reflected, but the open wire setup looks a 
> little DODGY to ME! This is the month of APRIL, but not APRIL 1 :-) 
> right ??
>
> FLAME SUIT ON !!
>
> Walt K8CV
>
> ----- Original Message ----- From: "Rick - DJ0IP / NJ0IP" <Rick at DJ0IP.de>
> To: "'Discussion of Ten-Tec Equipment'" <tentec at contesting.com>
> Sent: Monday, April 22, 2013 8:53 AM
> Subject: Re: [TenTec] Built in SWR meter bannans
>
>
>> Dave,
>>
>> Sorry, my memory failed me there.
>> It was long ago that I did this.
>> I had to search for my notes and drawings (file).  Found them.
>>
>> Actually I removed the center cable from coax, and discarded the 
>> shield and insulation. Then I put two pieces in parallel and ran them 
>> through the same beads; lots of beads.
>> Then I covered it with heat-shrink tubing and fed the open wire into 
>> one end, and connected the other end through a short coax stub to my 
>> antenna tuner.
>>
>> So yes, I did use only the center of two pieces of coax, but they ran 
>> through the same string of beads, not separate beads.
>>
>> 73
>> Rick
>>