I used zip cord to feed a full wave 40m loop when I was in Alaska and broke a
pileup on Okino Tora-shima with 2 watts (about 2000 miles/watt). The higher
impedance worked fairly well with a loop.
The characteristics (for at least one type of Zip cord) are included in VK1OD's
transmission line loss calculator here: http://www.vk1od.net/calc/tl/tllc.php
You can check out the losses with various impedances at different frequencies.
Loss is about 2dB / 100' on 80m and close to 3dB on 40m. It is 3.5dB on 30m,
so keeping the length to 50' or less is a good idea. Losses increase quickly
from there, to about 6dB / 100' on 15m (with a perfect 105 ohm load, half
a dB higher in a 50 ohm system.)
I've also used some thin vinyl-coated speaker wire as a feedline. I don't know
what the impedance was, but I could never get the dipole to load properly on
40m when I was using something close to a quarter wave of feedline.
(If the dipole was 50 ohms and the feedline 100 ohms, the rig would see
200 ohms.) It was rather frustrating to sit in the middle of the wilderness
and listen to KC4AAA at the South Pole booming in but not being able to
get full output from my HW-8 due to the poor impedance match. (Getting
the antenna higher wasn't an option - there was only one tree on the
I now use RG-174 coax for my backpack feedlines - the losses are lower than
for Zip cord (about 2.1dB / 100' on 40m) and it has a 50 ohm impedance. And
it is smaller and lighter than zip cord.
I'd say it is worth trying if you want to experiment, or if that is what you have
on hand. You're likely to get better results on 80m and 40m than on 15m and
10m due to the high losses, but if you are running 100W into 100 feet of the
stuff you're still radiating more power than I do with my 5 watt station, and
I make plenty of contacts. Just plan for the 100 ohm impedance and you
should be OK.