In article t,
Ralph Mowery wrote:

However the portable picks up the hams with just the whip, where with
wire the same length or even longer the ham transceivers picks up almost
nothing. Checking them out on a service monitor, they are sensitive
enough. However when the ham gear is used with a antenna only a few
feet long tuned to frequency in a car they pick up lots of signals.

I suspect that your guess about impedance matching is probably "on the
mark". Since the ham transceiver is normally hooked up to a 50-ohm
(or so) trqansmission line, it's probably designed to terminate the
incoming signal into 50 ohms or thereabouts when it's in receive mode.

If you hook a short wire to it, the short wire is going to have a very
high (and very capacitive) impedance. The 50-ohm termination will
look very much like a short-to-ground compared to that high impedance,
and there will only be a trace of signal left for the receiver to
detect.

A short-wave receiver is designed to work with a short antenna (wire
or whip). The antenna is a lot shorter than a wavelength, and so
there's no real need to terminate it into a matched impedance. The
short-wave receiver can use a high-impedance receiving circuit (e.g. a
JFET) and doesn't lose signal into an inappropriately-low termination
impedance.

Some ham transceivers have a separate "receive antenna" jack - the
Kenwood TS-2000 has one. These may be high-impedance inputs suitable
for a wire or whip, or they might be 50-ohm antennas.

If you were to provide a small battery-powered buffer for your random
wire (say, a J310 JFET set up as a source follower) you could reduce
the effects of the mismatch and you'd probably find your transceiver
able to receive quite nicely.