Thursday, August 1, 2019

Lamp Cord as an RF Feedline. Post 1946.


If you can't see the video, please insert this title URL into your browser search box: https://www.youtube.com/watch?v=ZmMAnGRLNfw.

Although radio amateurs have used "Zip"cord/Lamp cord successfully for antenna elements and ground radial wires for decades, lamp cord as a balanced feedline has been problematic.

The main drawback to lamp cord feedlines has been excessive line loss, especially on amateur radio bands above 40 meters.

Yet, properly used, zip cord/lamp cord can be used to make usable portable antennas for emergency field use.

In this video, Stan Gibilisco (W1GV) examines the pros and cons of using inexpensive zip cord for HF antenna feedlines.  Basically, this type of antenna is a half-wavelength, center-fed dipole using two conductor lamp cord as a temporary balanced feedline.

Do these antennas work?  As Stan says, "It depends."  The only good news in using zip cord for feedlines is that an electrical 1/2 wavelength of any feedline will repeat the impedance of the load.  In other words, the impedance of the dipole will be repeated at the end of the 1/2 wave length feedline and should provide an approximate match of 1.5:1 at the designated frequency. If the dipole shows an impedance of 50 to 75 ohms, you should be able to match this impedance to your transceiver's 50 ohm impedance with a suitable tuner or balun.

While I wouldn't recommend zip cord as a preferred feedline, it will work in an emergency.  If you can allow for some line loss, zip cord/line cord may be suitable for a small, lightweight portable HF antenna.

If you want more information on this topic, please visit this website from KE8DI:

https://www.qsl.net/ke8di/zipcord.html.

Thanks for joining us today.

Aloha es 73 de Russ (KH6JRM).


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Aloha es 73 de Russ (KH6JRM).