The Helical Whip for RV and Mobile Use

followed by a close- spaced loading coil several inches long, and topped by a metal tuning tip with a set screw and 2 or 3 inches of 1/8- inch steel rod. I replaced this rod with one the same diameter about 24 inches long, and cut and adjusted it unit it resonated at the proper point of the 20- meter band.

It is important not to extend this rod into loading coil, as it will likely heat up if much power is applied. Your local hardware store is a good source of brass brazing rod. While I did not try this antenna on other bands, it should work on 12, 15, or 17 meters if you use different lengths of pre-adjusted rod. For 10 meters, it will probably be necessary to remove a few turns from the loading coil.

Neighborhood garage sales and flea markets are good, inexpensive sources for CB antennas. Because most late model, top loaded CB antennas do not have tuning tip, you may need to improve one (details on how to do this later).

Building Fiber Glass Rod Helicals

The light weight of fiber glass fishing rods makes them useful in helical antenna construction. Weight can be important when four or five antennas are placed on one spring mount.

Choosing a Fiber Glass Rod

You can find fiber glass rod at garage sales and flea markets. Poles with broken or missed guides and

Figure 2

Remove the entire handle, unless it appears that an inch or

handles can often be bought for almost nothing. Look for hollow rods at least 4 or 5 feet long with a 3/8 to ½- inch diameter near the handle. You can use smaller, solid rods, but they require heavier, larger loading coils. Use one- piece rods with no metal ferrules or joints. It is possible to use larger rods with metal ferrules if you cut them out and rejoin the rod pieces with epoxy.

One way to do this is to slide one end into the other, or use a tight- fitting piece from a solid rod as an internal splint. Refer to Figure 3 for construction details.

Base

Remove all windings, wire, and thread, along with the tip, guides, and any foil of metal bands.

two would make a good base mount. There are so many different types of handle attachments that it is difficult to prescribe a standard of construction. Keep in mind the cross- section drawing of Figure 3. You need to mount a 3/8- inch diameter steel or brass bolt with no. 24 thread 1-1/2 to 2 inches long in the base after cutting off the head of the bolt. Use two-part epoxy to hold this bolt in place. The 5 minute kind will save construction time.

How drill and tap through the bolt and handle to provide an electrical connection. Brass bolt (8- 32) are ideal. Use a solder lug to attach the antenna wire, soldering to both the lug and the screw head. You should cover the complete base with shrink or several coats of good enamel, or both.

Stem

Cut a length of wire, preferably no. 18 copper enameled (no. 20 or 16 will do), for frequency desired.

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