In article , Frank writes:
Not sure the OP cares anymore but it's always nice to
change the pace from the usual TRUMP talk.

Amen.

For receiving, antenna currents on the feedline won't do much beside alter
the pattern a bit. I suppose the feed will pick up more interference but
I expect this radio and antenna will be in the same room, anyway.

I used to think something like that. But losses in transmission,
scaled down, are losses in receiving as well. Just that you have
AGC - and therefore rather impressive changes in RF/IF gain - at your
disposal to swamp out so many of the receiving losses. Until you get
down to the noise floor, at which point antenna gain becomes important
in the same way it is in transmitting.

Well, the hams use 468/f for a dipole, 234/f for a 1/4 wave. So for a center
frequency of 100Mhz, that would translate to 2.34' .

Well, ya got me there. 5 feet would be more like a end fed half
wave dipole which would be a severe mismatch to a low Z input.

Don't give up too easily. After I posted I realized a 100Mhz 5/8
wave would be only slightly longer than what you suggested. It has
gain relative to a dipole, I believe, but requires a ground plane
for best results. For reasons mentioned below - a 5/8 wave in
the middle of the band is close to a 1/2 wave at the low end of
the band - that might not be ideal for the OP, though.

A couple more feet and it would be a 3/4 wave end fed antenna
which would be a better match and give some offset lobes which[...]

If I REALLY want a resonant antenna I check them with a grid
dip meter.

Mine died quite some time ago. Guess I need to start
replacing capacitors. Then there's that Heathkit Tunnel
Dipper I found at a swap meet. Might even work. Now if
I knew what box I put it was in when I moved...

But we are most likely not going to want a resonant antenna.
Middle of the road, broadband if possible, should be the
target. The problem, as you mention, for an end fed
1/2 wave as with a full wave dipole - is that it just
doesn't match up very well to ANY low inpedance input.

The formulas usually are off a bit in the real world but,
for receiving, they're plenty close.

Just speed of light divided by twice the frequency (four
times for 1/4 wave), with a minor adjustment for velocity
factor of a typical HF antenna.

A quarter wave without the adjustment would be 246/f .

I find the top of the refrigerator makes an easy,
kinda sorta ground plane for a FM portable.

Actually should be quite good.

The top of my old Harmon Kardon receiver is probably
reasonable, though at ~18" wide it is not nearly as
good as a typical refrigerator.

I vote for a 2' x 3' quad, 18-22 AWG, glued to the back
of a slightly larger, preferably framed, movie poster.

George