However some people only pull some of the cord apart, using the remaining together section as a feedline.
This sounds a bit crude. The cord's impedance is a long way from 50 ohm. And there can be significant losses, particularly towards the upper end of the HF range.
You may need an antenna coupler between the transceiver and the feedline. But with any luck the types built in to some transceivers, only good for a limited impedance range, may suffice.
I've never used a zip cord dipole myself. But here's some experiences from others with them:
* K1TD QST article on zip cord antennas (pdf)
* KE8DI zip cord antenna
*Zip cord portable receiving antenna
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