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DF-1 Transistor Radio Direction Finder


The Heathkit Transistor Radio Direction Finder model DF-1 is a self-contained, self-powered, super heterodyne broadcast radio receiver incorporating six name brand (Texas Instrument) transistors, a directional loop antenna, indicating meter, and integral speaker. It is designed primarily as an aid to navigation when out of sight of familiar landmarks. The DF-1 can be used not only aboard yachts, fishing craft, tugs, and other vessels which navigate either out of sight of land or at night, but the hunter, hiker, camper, avaiator, etc., can use it as a radio compass in unfamiliar territory and use it as a portable radio as well.

The DF-1 is powered by a 9-volt battery (a spare is included with the kit which can be kept in the special clip provided for it in the cabinet). The frequency range covers the broadcast band from 540 to 1620 kc. The broadcast band was selected for this unit since broadcast stations are numerous, easy to identify and tune in.

A directional high-Q ferrite antenna is incorporated which is rotated from the front panel by a nylon right-angle gear drive to obtain a fix on a station. A 1 milliampere meter serves as the null and tuning indicator. The DF-1 is very easy to operate. You simply select a station and rotate the antenna for minimum deflection on the tune portion of the meter. To find the direction of a station you set the sensitivity control and rotate the antenna for maximum reading on the null portion of the meter. The maximum null will occur when the antenna is in line with the station being received. Direction can be read on the compass rose or antenna index incorporated. The controls consist of: tuning, volume and power (on-off), sensitivity, heading indicator (compass rose), and bearing indicator (antenna index). A six-to-one vernier is provided on the tuning condenser to allow precision tuning.

The DF-1 is supplied with slip-in-place mounting brackets, which allow easy removal from ship bulkheads or other similar places. Overall dimensions are 7½" W. x 5 7/8" H. x 5 3/8" D. Highest quality components are used throughout in construction with each part clearly marked to aid in identifiaction. In addition, moisture and fungus-proofing lacquer is supplied with the kit to coat all components after assembly and prevent corrosion. Construction is simplified through the use of detailed step-by-step instructions and pictorial diagrams. Even the beginner with little or no electrical experience can build this unit successfully. The IF transformers are prealigned so it is ready to operate as soon as construction is completed. For best results however, a slight toughing up of alignment would be recommended to compensate for minor variations in components and wiring as explained in the manual. Calibration instructions are simple and easy to accomplish with alignment tool furnished. No special equipment is required for alignment. Information is also given on the proper use of the completed unit. The bibliography section of the manual lists bulletins and publications which can be obtained for additional navigation information.

This light, compact unit will provide you with a means of enjoyment as well as serving a very useful function.

Specifications: Frequency Range... Broadcast Band (540 to 1620 Kilocycles). Sensitivity, at 50 mw. output reference level: Antenna... 120uv/meter; Converter Base... 0.44uv/meter. Power... 9 volt battery )spare included with kit). Current Drain... 9 ma. with no signal; 20 ma with 50mw output. Direction Indicator... Adjustable compass rose, calibrated in degrees. Null and Tuning Indicator... 0-1 ma meter. Antenna... High "Q" ferrite, rotated from panel. Transistor Complement... 2N252—RF amp, local OSC., & converter; 2N308—First IF amp; 2N309—Second IF amp; 2N238—First AF amp; 2N185 (pair)—push-pull AF output. Dimensions Overall... 7½" W. x 5 7/8" H. x 5 3/8" D.

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