Rhil wrote:
"Is there any half-way decent indoor ant I can use on an old
Hallicrafter S-40 B? I mainly want to extend peception for nighttime
MW."

Satisfactory reception depends on signal to noise (and interference)
ratio.

At night, diatant BCB reception is via the skywave which is reflected
from the ionosphere. On reflection, both polarizations, horizontal and
vertical are produced by the ionosphere. Only vertical polarization is
sent by transmitters as the local audience is the only one that can be
sold to advertisers. Vertical polarization propagates very well by
groundwave beyond the line of sight, day and night. Horizontally
polarized waves are not propagated by the groundwave at all. The earth
short-circuits horizontal polarization.

Thus, a balanced horizontal doublet antenna will pickup the DX while
rejecting local noise and interference which is overwhelmingly
vertically polarized. Never mind that the antenna is much shorter than
1/2-wave. The S-40 has s lot of gain and can overcome low signal levels.
Its big problem will be interference from undesired noise and
interfering signals, much of which the doublet will reject.

Another antenna will produce the same benefits. It is the resonant loop
antenna or loopsrick. It can be oriented to reject vertically polarized
reception. It is also small and can be easily aimed to reject some
horizontally polartized signals as well. I don`t see anyone rotating a
BCB doublet to do thia, but it`s possible.

Loops and loopsticks are offered ready-made. I have no recommendations.
In 1938 I had a new GE super console which came with a "Vee Doublet
Antenna". It worked as advertised for mediumwave and shortwave.

Reg Edwards, G4FGQ has some free programs for those who would built
their own loop antennas. He frequently posts messegages in this
newsgroiup. Search for the URL`s you want. I hope I got Reg`s callsign
right.

Best regards, Richard Harrison, KB5WZI