The antenna is a make-or-break item in a base station.
You can hear a lot of stuff with a poor and inefficient antenna. But the transmit range will stink.
Height is might. The higher it is, the more effective it will be.
General rule, the larger the antenna the more effective it tends to be. You could make a simple "weeping willow" ground plane from four 9-foot long pieces of wire and a bracket with a coax socket on it. Just need a support to hang the top of the vertical element and a way to stretch the three 'ground plane' wires out at 45 degrees. Manufactured vertical antennas that are 18, 21 feet or longer tend to be more efficient than the home-made weeping willow, or one made commercially from metal rods.
The quality of the coax connections is a big deal. The standard "PL-259" connector was designed for use inside an aircraft, away from the weather. To use it outdoors, you must weather seal it. You only have to get that plug wet on the outside surface for capillary forces to suck that moisture inside the plug, and possibly down the tiny gap between the outer jacket and the strands of the shield braid. If you see a mysterious puddle on the desk surface under the end of the antenna coax, you have filled that gap inside the coax with rain water.
The shield should be soldered to the plug body for any plug used outdoors, and sealed from any intrusion of moisture.
The radio is around 45 years old. If it were a 1973 car, you would know that any original belts, tires, hoses, seals, gaskets or bushings to be bad from age alone, even if the odometer says 750 miles.
It is possible that the radio's channel crystals have drifted so far off frequency that your clarifier control can't tune in anyone who is ON the channel frequency.
Maybe.
If you hopped behind the wheel of a 1973 GTO you would doubtless find the need for a tuneup at the very least if it hasn't had one for decades.
Might be the situation with this radio.
73
