[Lowfer] multiple transmitters allowed?

[Lyle Koehler]

To add to what John has said about receiving LF, it's not uncommon for a
receiver to be "deaf" on LF. Usually a preamp is in order -- or an active
whip like the one published in QST a couple of years ago. An inexpensive FET
can be substituted for the fancy device in that design and operated at lower
current with fairly decent results. I've seen other designs for active
antennas that consisted simply of a FET source follower with a short whip
connected to the gate, and the output to the receiver taken across a 100 ohm
resistor in the source.

Other things to try: If the receiver is actually a ham transceiver, make
sure that there is no HF tuner in line with the antenna, either internal or
external. And if the dipole antenna has a voltage balun, it probably looks
like a short at LF. An ohmmeter check at the coax terminals will tell you
whether or not there is a DC path across the line.

An electrically short antenna looks like a very high impedance and is a
terrible match to the 50-ohm input of a modern receiver. Sometimes a simple
LF "antenna tuner" like a 2.5 millihenry choke in series with the random
wire, with a 365 pF variable between antenna and ground, can help a lot.

Lyle, K0LR