Sunday, June 21, 2009

Preventing a 'reversal of fortune' in the field

The July 2009 edition of WorldRadio Online magazine's Trail-Friendly Radio column, by Richard Fisher, KI6SN, features details on a simple field-operation accessory that can spare the operator a ton of headaches caused by fried equipment, as well as a ton of embarrassment.

This reverse polarity protector can help you to avoid a reversal of fortune when out on the trail.

All it takes is inadvertently hooking up your battery cables backward: POSITIVE lead to the NEGATIVE battery terminal, and vice versa. The WRO article has full construction details. Pictured here is the circuitry housed in a nice plastic box.

A black power cable with large alligator-style clip leads goes to the battery. An RCA jack with appropriate cable goes from the unit to your transceiver.

With this accessory in line, if you mistakenly get battery polarity reversed, a protecting diode shorts the DC to ground and the fuse blows - saving your equipment.

Two spare fuses are wrapped in white tissue and stored in the box, ready to be called upon if any knuckleheaded battery connections are made.

Here's the circuit's schematic:

Click here to see the latest edition of WorldRadio Online magazine.

(For an enlarged view, click on the image.)

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