Coupling a commercial VHF handheld to an external antenna

Some good commercial VHF handhelds have only one drawback - no external antenna connector.

Modification is also a problem as the rubber ducky is either integral or screwed on to a threaded stud, with no access to ground.

The result is a frustrated, repeater-bound ham. When a fellow ham in such a predicament set me pondering, realisation dawned that another rubber ducky could be used to couple the rig to an external antenna.

My own rig (which has a BNC connector!) was used to check it out. The coupling rubber ducky was mounted on the input of a homebrew SWR meter, with a dial lamp loading the output.

Rubber ducky coupling to a dial lamp

The glow of the dial lamp indicated a coupling efficiency of about 20% (2.5W to 0.5W).

A 2m external antenna was then connected instead of the dial lamp.

Rubber ducky coupling to an external antenna

On-the-air tests were successful. Comfortable simplex QSOs, not possible with the rubber ducky alone, were now possible.

Related post: SWR Meter - Easymatch

______________________________

Handy 1 kW HF Dummy Load

Years ago, after replacing the tubes of a Heathkit SB-200 Linear Amplifier, I was on the lookout for a dummy load to test it.

It then struck me that a 230V ~ 1kW electric hot plate, with its heating element resistance close to 50Ω, would do.

Handy 1 kW HF Dummy Load

The mains plug of the hot plate was replaced with a PL-259 before connecting it to the output of the linear amplifier.

The amplifier was successfully tested, with its Pi tank circuit providing a proper match to the dummy load.

At a later date, the same exercise was repeated with a Dentron GLA-1000.
______________________________