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