What were they thinking ?
"Own one for emergency use - if your mast or antenna comes down (heaven forbid) and your backstay is gone, deploy the RopeAntenna to call for help, and be amazed (and thankful) that it works even better that your dearly departed backstay as it an be used effectively strung along the deck." (was that how 'sky hooks' were invented ?)
The best reason for a halyard antenna is having a length that will resonate with the HF frequency that will be used for communicating with other boats, maritime nets, email providers etc.
Backstay antennas are generally less efficient for a number of reasons including the following :-
# 1 Often cut to an arbitrary length.
# 2 Usually not long enough.
# 3 Because the backstay is furthest from the mast - the angle to horizontal is such that the radio wave is neither horizontally nor vertically polarized. There again the further an antenna is from the mast the better - less shielding by the mast..
# 4 The backstay's stainless steel section between the ceramic insulators, although of a greater diameter than is needed for effeciency is not comparable to that of tinned copper hard drawn wire.
If one is looking for a halyard antenna as a back up, then make one or more up - easy enough, cut some wire to the frequencies required - form a small eye at the top end attach 1/4 nylon line, feed it to a pulley somewhere high on the mast, the bottom end attach to insulated copper wire (part of the frequency length) send this to the radio or tuner.
As an alternative to backstay and halyard antennas, go for a vertical whip antenna
(eg : Shakespeare)