Paul Davies has bad FM reception in his kitchen and would like to try an
external antenna. Problem is that transmission lines require 2 wires or
else they become part of the antenna themselves. The FM set has only a
lone antenna wire and no ground connection.

Note that many FM sets have no antenna wire but use a clamp on the power
cord to capacitively couple signal from the powerline.

Since Paul has an antenna wire, he can use the same sort of capacitive
connection but to connect with the chassis (ground) that many other sets
use for the "signal" connection to the set.

The clamp Paul adds around his power cord near the set chassis should
connect to the inside of his coax cable shield, directly or indirectly.
The antenna wire of his set can be shortened to insignificance and
connected to the inner conductor of his coax.

In the loft, Paul can make a ground plane antenna to connect with his
coax to the radio. The wavelength is 3 meters or about 10 feet. He could
spread1/4-wave radials in a balanced and symmetrical manner to construct
the horizontal part of his antenna. This would screen the vertical part
of his antenna from interference and provide a terminal for the ground
plane`s circulating capacitive current. Paul`s coax shield would connect
with all the radial wires (2, 4, 6, or 8). Odd numbers work too so long
as symmetry is preserved.

The vertical part of his antenna is a 2.5 ft. length of wire above the
center of the ground plane. The center conductor of his coax connects to
the vertical wire.

Paul could wind a half dozen turns in his coax directly beneath his
ground plane to discourage signal on the outside of the coax. A W2DU
ferrite choke could also be used. Chokes at both ends of the coax might
be better. But operation may be entirely satisfactory with no chokes at
all. It depends on local conditions.

Paul would have connections at both ends of his coax so it could operate
as a proper transmission line,

Best regards, Richard Harrison, KB5WZI