Screwdriver antenna - Revision history

Carlb: /* Theory of operation */

2009-04-11T18:57:59Z

Theory of operation

← Older revision		Revision as of 11:57, 11 April 2009
Line 4:		Line 4:

	== Theory of operation ==		== Theory of operation ==
	[[Image:W6aaq-dk3.gif\|~~right~~]]		[[Image:W6aaq-dk3.gif\|thumb\|300px]]
	The screwdriver antenna is based on the use of a loading coil with a [[whip antenna]] (typically 102"-120", like those used for 11-metre CB radio installations). It differs in that the loading coil is adjustable to cover multiple HF bands.		The screwdriver antenna is based on the use of a loading coil with a [[whip antenna]] (typically 102"-120", like those used for 11-metre CB radio installations). It differs in that the loading coil is adjustable to cover multiple HF bands.

Carlb: /* Theory of operation */

2009-04-11T18:41:34Z

Theory of operation

← Older revision		Revision as of 11:41, 11 April 2009
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	The base of the antenna is a hollow tube. The signal is applied to the outside; concealed inside is a reversible DC motor. The motor, operated remotely by a momentary DPDT switch, moves the whip and loading coil so that part of the coil is inside the base (and electrically bypassed, or inactive) and the rest of the coil is in use as a loading coil tuned for the selected band.		The base of the antenna is a hollow tube. The signal is applied to the outside; concealed inside is a reversible DC motor. The motor, operated remotely by a momentary DPDT switch, moves the whip and loading coil so that part of the coil is inside the base (and electrically bypassed, or inactive) and the rest of the coil is in use as a loading coil tuned for the selected band.

	When changing frequencies, the antenna loading coil is extended or retracted to tune the antenna to the new band.		When changing frequencies, the antenna loading coil is extended or retracted to tune the antenna to the new band. As this adjusts the inductive loading coil to resonance, no external antenna tuner is required.

	== References ==		== References ==

Carlb: /* Theory of operation */

2009-04-11T18:37:00Z

Theory of operation

← Older revision		Revision as of 11:37, 11 April 2009
Line 1:		Line 1:
	A '''screwdriver antenna''' is a [[vertical antenna]] with a remotely-adjustable centre-loading coil. Intended for mobile operation, it may be adjusted to cover any band from 10m to 75m. The antenna takes its name from the use of a reversible DC electric motor like that of an electric screwdriver.		A '''screwdriver antenna''' is a [[vertical antenna]] with a remotely-adjustable centre-loading coil. Intended for mobile operation, it may be adjusted to cover any band from 10m to 75m. The antenna takes its name from the use of a reversible DC electric motor like that of an electric screwdriver.

			The original DK-3 Screwdriver Antenna design was created by Don Johnson W6AAQ, author of a series of three books on "HF mobileering", and was first patented in 1991.

	== Theory of operation ==		== Theory of operation ==
Line 5:		Line 7:
	The screwdriver antenna is based on the use of a loading coil with a [[whip antenna]] (typically 102"-120", like those used for 11-metre CB radio installations). It differs in that the loading coil is adjustable to cover multiple HF bands.		The screwdriver antenna is based on the use of a loading coil with a [[whip antenna]] (typically 102"-120", like those used for 11-metre CB radio installations). It differs in that the loading coil is adjustable to cover multiple HF bands.

	The base of the antenna is a hollow tube. The signal is applied to the outside; concealed inside is a reversible DC motor. The motor moves the whip and loading coil so that part of the coil is inside the base (and electrically bypassed, or inactive) and the rest of the coil is in use as a loading coil tuned for the selected band.		The base of the antenna is a hollow tube. The signal is applied to the outside; concealed inside is a reversible DC motor. The motor, operated remotely by a momentary DPDT switch, moves the whip and loading coil so that part of the coil is inside the base (and electrically bypassed, or inactive) and the rest of the coil is in use as a loading coil tuned for the selected band.

	When changing frequencies, the antenna loading coil is extended or retracted to tune the antenna to the new band.		When changing frequencies, the antenna loading coil is extended or retracted to tune the antenna to the new band.

Carlb: New page: A '''screwdriver antenna''' is a vertical antenna with a remotely-adjustable centre-loading coil. Intended for mobile operation, it may be adjusted to cover any band from 10m to 75m. T...

2009-04-11T18:34:05Z

New page: A '''screwdriver antenna''' is a vertical antenna with a remotely-adjustable centre-loading coil. Intended for mobile operation, it may be adjusted to cover any band from 10m to 75m. T...

New page

A '''screwdriver antenna''' is a [[vertical antenna]] with a remotely-adjustable centre-loading coil. Intended for mobile operation, it may be adjusted to cover any band from 10m to 75m. The antenna takes its name from the use of a reversible DC electric motor like that of an electric screwdriver.

== Theory of operation ==
[[Image:W6aaq-dk3.gif|right]]
The screwdriver antenna is based on the use of a loading coil with a [[whip antenna]] (typically 102"-120", like those used for 11-metre CB radio installations). It differs in that the loading coil is adjustable to cover multiple HF bands.

The base of the antenna is a hollow tube. The signal is applied to the outside; concealed inside is a reversible DC motor. The motor moves the whip and loading coil so that part of the coil is inside the base (and electrically bypassed, or inactive) and the rest of the coil is in use as a loading coil tuned for the selected band.

When changing frequencies, the antenna loading coil is extended or retracted to tune the antenna to the new band.

== References ==
* [http://www.arrl.org/news/features/1999/11/05/1/ HF Mobile On The Shoulders Of Giants], Raymond J. Schneider W6JXW, ARRL, November 1999
* [http://www.radioroom.org/page5.html HF Mobileering], KI6LO
* [http://users.rio.com/kg7fu/mobile.html Mobileering Information Page], KG7FU
* [http://home.earthlink.net/~w6rmk/antenna/screwdriver.htm Screwdriver Antennas], W6RMK

{{antennas}}