[TenTec] Built in SWR meter bannans

Tue Apr 23 18:20:10 EDT 2013

But what about the third "ground" conductor between the "hot" and "neutral" lines? Won't TNT screw things up?

Kim N5OP

"People that make music together cannot be enemies, at least as long as the music lasts." -- Paul Hindemith

On Apr 23, 2013, at 16:54, d.e.warnick at comcast.net wrote:

> 
> 
> THHN is that stuff they have at Home Depot or Lowe's for house wiring. It is in spools of single wire, many colors and usually 12 GA, though many guages are available. Simply put, it's single strand house wire 
> 
> 73 
> 
> Dave 
> 
> WA3F 
> 
> 
> 
> ----- Original Message -----
> 
> 
> From: "Rick - DJ0IP / NJ0IP" <Rick at DJ0IP.de> 
> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com> 
> Sent: Tuesday, April 23, 2013 4:47:36 PM 
> Subject: Re: [TenTec] Built in SWR meter bannans 
> 
> Jim, 
> 
> Thanks for the details.  I have noted your suggestion for future use. 
> I'm not sure what THHN wire is, but I will google it.  I'm sure we have it 
> here, but under a different name. 
> You said ordinary house wire, but I don't know what ordinary (American) 
> house wire is.  Is that like Zip Cord? 
> 
> I had so much trouble burning up baluns back in the 80s that I have switched 
> to using only Teflon insulated wire for my chokes and baluns. What I 
> typically use is a Teflon-coated twin-wire sourced locally with 0,75mm 
> diameter.  This would be about AWG-21. You don't even have to tape it 
> together.  For more power, then I use thicker Teflon insulated wire and tape 
> it together, which is work I totally detest.  That's the hardest part of 
> making a choke or balun.  And the special tape I bought must be gold-plated; 
> I paid 25 EURO ($30) for a tiny little roll. (hi) 
> 
> The balun I referred to earlier is quite like the W2DU balun except I 
> slipped the beads over two thick insulated wires instead of coax. Then I fed 
> openwire into one end and the other end was connected to a matchbox.  Why 
> did I build it that way?  Because I read about it somewhere and I like to 
> try things I read about.  That was about 20 years ago.  I wouldn't do it 
> that way today, I would use toroids.   
> 
> The only reason I mentioned it is, somebody asked how you do a CMC choke for 
> open wire.  My comment was "just as easy as for coax".  Unfortunately I have 
> not found a source for -31 toroids here, so I am still using -43. After 
> reading you long paper on chokes yesterday, I'm going to intensify my search 
> for -31.  I'm sure they're available here somewhere. 
> 
> The one place I clearly prefer the W2DU approach over using a toroid is when 
> the choke is mounted high on a lightweight telescoping fiberglass pole.  You 
> have a much greater chance breaking the pole if you use a toroid.  The W2DU 
> distributes the weight a little better and has far less wind load than a 
> toroid, especially if you place the toroid in an enclosure. 
> 
> 73 
> Rick, DJ0IP 
> 
> -----Original Message----- 
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Jim Brown 
> Sent: Tuesday, April 23, 2013 6:55 PM 
> To: tentec at contesting.com 
> Subject: Re: [TenTec] Built in SWR meter bannans 
> 
> On 4/22/2013 12:15 AM, Rick - DJ0IP / NJ0IP wrote: 
>> With openwire you can build a CMC choke just as easily as with coax.
> 
> It's not clear to me what sort of choke you are imagining, but it is 
> trivially easy to build a VERY effective common mode choke by first taping 
> together a pair of insulated conductors to form a parallel wire transmission 
> line, then winding enough turns of that pair around a #31 or #43 toroid to 
> place the high resistive impedance that results from resonance where it is 
> needed.  16 turns (x2) of such a line made from 
> #12 THHN (ordinary house wire) on a #31 core is a VERY effective choke from 
> 1 MHz to about 15 MHz. 12 turns on the same core makes a fine choke for 3-30 
> MHz. 
> 
> Such a choke is a short length of transmission line, with Zo on the order of 
> 90 ohms, Vf on the order of 0.66, and VERY low loss below 30 MHz (the loss 
> is all copper, and #12 is bigger than most coax. THHN insulation starts 
> introducing dielectric loss above that range. I've measured all of these 
> parameters with real chokes. It's difficult to get much precision, but I 
> trust the data to about 25%, which is certainly good enough for our 
> purposes. The short length of line (2.5 ft - 3 ft) introduces some small 
> mismatch, and the result can easily be modeled in software like Sim Smith, 
> which runs in Java and is free. To do the model, you will, of course, need 
> to measure and import the antenna Z or provide comparable data from an NEC 
> model. I've done both. 
> 
> For all practical purposes, the mismatch doesn't matter -- the length is too 
> small as a fraction of a wavelength, and it's at the load end. 
> 
> 73, Jim K9YC 
> 
> . 
> 
> 
> _______________________________________________ 
> TenTec mailing list 
> TenTec at contesting.com 
> http://lists.contesting.com/mailman/listinfo/tentec 
> 
> _______________________________________________ 
> TenTec mailing list 
> TenTec at contesting.com 
> http://lists.contesting.com/mailman/listinfo/tentec 
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec