KX1 - We need to develop the ideal antenna

[daleputnam]

Hi Geoff,
  I think your last statement figures into the mix quite strong. What I made measurements with, and was talking about...is zip cord that was likely manufactured 40 maybe 50 years ago... I don't through antenna stuff away, much at all, especially when it is new... i.e. not used. So.. K1TD's figures are much closer to what I had and what I remember from my novice days... which were pretty much on 80, with the occasional excursion off to 40.
  Good point, the new stuff... pretty much isn't what it used to be either. No, I wasn't using cloth covered, but its replacement.
thanks Geoff,

--... ...-- Dale - WC7S in Wy


 

>
> Hi Dale,
>
> K1TD made some measurements back in 1979 on a transmission line made from
> dry Zip Cord, and reported that its nominal characteristic impedance at HF
> was 105 ohms and its velocity factor was 0.69.
>
> He also measured the loss per 100ft at various frequencies when the line was
> terminated by a 105 ohm load (105 +j0).
>
> F MHz Loss db per 100ft
>
> 3.5 0.7
> 7.0 1.8
> 14.1 4.0
> 28.1 7.5
>
> Maybe modern ZIP Cord is different, but I hope that this helps.
>
> 73,
> Geoff
> GM4ESD
>
>
> On Monday, May 16, 2011 at 5:02 PM, Dale Putnam WC7S wrote:
>
>
> > Zip cord, at 50 - 72 ohm or so impedance, is a whole lot closer to the
> center fed impedance of a "close to the ground" dipole.
> > Makes a fair amount of sense, to use it for feedline, clear down to the
> > rig, when the rig has a balanced output.. or to the balanced to
> > unbalanced, 1 to 1 ratio apparatus. And with a stranded, larger than RG-58
> > or RG-59 coax center, it won't have any additional I-R loss than that
> > coax, and our HF freq. And of course, making the distinction that we are
> > talking about a single band dipole... not a multiband, center fed with
> > what ever the tx is dialed to balanced antenna.
> >
> > --... ...-- Dale - WC7S in Wy
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

     
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Jack Smith-6]

I measured 108 ohms for the sample I tested in 2001, black AC power type
zip, vf around 0.65, but varied with frequency.  Also looked at paired
red/black wire usually used for low voltage DC and found it a bit higher
Zo, around 118 to 125 ohms, not constant with frequency. Higher Zo is
probably due to the red/black wire having thicker insulation for
mechanical protection reasons, as a sales and marketing gimmick to make
purchasers think they are getting more copper due to the larger wire +
insulation size.

My loss data is quite similar to the values Geoff found.

Jack K8ZOA


On 5/16/2011 2:55 PM, Geoffrey Mackenzie-Kennedy wrote:

> Hi Dale,
>
> K1TD made some measurements back in 1979 on a transmission line made from
> dry Zip Cord, and reported that its nominal characteristic impedance at HF
> was 105 ohms and its velocity factor was 0.69.
>
> He also measured the loss per 100ft at various frequencies when the line was
> terminated by a 105 ohm load (105 +j0).
>
> F MHz     Loss db per 100ft
>
>    3.5                0.7
>    7.0                1.8
> 14.1                4.0
> 28.1                7.5
>
> Maybe modern ZIP Cord is different, but I hope that this helps.
>
> 73,
> Geoff
> GM4ESD
>
>
> On Monday, May 16, 2011 at 5:02 PM, Dale Putnam WC7S wrote:
>
>
>   >  Zip cord, at 50 - 72 ohm or so impedance, is a whole lot closer to the
> center fed impedance of a "close to the ground" dipole.
>> Makes a fair amount of sense, to use it for feedline, clear down to the
>> rig, when the rig has a balanced output.. or to the balanced to
>> unbalanced, 1 to 1 ratio apparatus. And with a stranded, larger than RG-58
>> or RG-59 coax center, it won't have any additional I-R loss than that
>> coax, and our HF freq. And of course, making the distinction that we are
>> talking about a single band dipole... not a multiband, center fed with
>> what ever the tx is dialed to balanced antenna.
>>
>> --... ...-- Dale - WC7S in Wy
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html