Seabat wrote:
"So, if I took the "rinky-dink" plastic loop antenna outside and placed
it abive the roof, it would work?"

Most likely. Seabat said his car radio worked on the site. An a-c radio
should normally be sensitive enough to operate on the same site.

An AM radio antenna does not need to be st high altitude as medium waves
follow the earth`s curvature as they propagate in most cases. The
existing metal roof in combination with the earth itself form a sandwich
with the loop antenna in the middle. This has proved unsatisfactory.
Seabat has "The Tin Riof Blues". It`s only necessary to get the AM
antenna in effect out from under the metal roof.

I suspect that just extending loop wires would be fraught with problems.
A variable capacitance in the radio likely tunes the loop. This loop in
parallel with the capacitance makes a high impedance parallel-resonant
circuit. Its impedance rises to about Q times the inductive reactance.
This circuit is susceptible to upset due to stray capacitance from any
long high-Z feeders. That`s why I proposed two additional loops to
capture the signal and to transfer it to the radio. A tuned loop in the
clear would capture in the signal, and the untuned loop would transfer
the signal to the radio`s "rinky-dinky" plastic antenna loop on the
radio shelf. These two loops would be interconnected with a twisted-pair
of wires.

Seabat also wrote:
"I suppose an pld car antenna would work for the FM if placed up high,
also?"

Yes. It`s exactly what I`ve long used as a 2-meter antenna. It is
collapsed telescopically to about 19 inches. I added (4) equally spaced,
drooping by 45-degrees, radials under the vertical radiator. They are
also 19 inches long. With full forward power into the antenna, the
reflected power is very low. The rig talks and listens very well.

For the FM broadcast band the elements would need to be lengthened to
almost 30 inches.

Construction details are given in books such as the "ARRL Antenna Book"

Best regards, Richard Harrison, KB5WZI