[Elecraft] KX1 - We need to develop the ideal antenna

[Jack Smith]

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
>
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