RV Screwdriver Antenna

Antenna Modelling Result

There are many ways to deploy a screwdriver antenna on an RV, this one is optimized for NVIS and convenience. The antenna is mounted on a corner of the roof of the RV, angled back at 45 degrees. The counterpoise is a closed loop of #12 wire on the roof of the RV, 25 x 8 feet. The height of the roof is taken to be 10 feet above ground.

This is a large screwdriver. The lower section is about 6 feet long and two inches in diameter and the whip is about 12 feet long and 1/4" in diameter.

Note that the choice of counterpoise in this calculation is just a wire loop. Using the frame of the RV could improve the situation.

80 meters

• impedance at feedpoint 9.6 ohms resistive
• 100W 31V 3.2A at feedpoint
• coil 50uH, Q 400, 1120 ohms X, 3 ohms R
• gain -4.5 dbi at 45 degrees
• NVIS gain -5.5 dbi at 90 degrees
• pattern broad and full toward the groundplane
• pattern minimum toward tip of screwdriver, and about -12 dbi at 20 degrees above horizon toward the rear of the RV
• 37 watts loss in coil, 2dB
• Note that this is a really good screwdriver coil, not many are this good

Conclusions
This is a very convenient antenna to deploy and tune. The performance is pretty good, especially considering the convenience. It will take a balun (or tuner) to match the source impedance properly. A mount could be set up to lay the Screwdriver on the roof during travel, and permanently mount the counterpose (or use the frame). Then deployment could be a stand-up operation, or even motorized.

AlanB, WB6ZQZ

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CategoryHamRadio CategoryRV