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LH series

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Portable Direction Finders

No longer available.  This page is for informational purposes only.  Factory repair service and some accessories are still available

These units are so rugged and of such value to their owners that many are still in first-line use after over 40 years.

The system consists of a two-element, electrically switched yagi antenna and a double-conversion, crystal-controlled receiver mounted on a wooden frame. Its 3 dB antenna gain and .08 uV typical DF sensitivity allow this unit to hear and positively track a weak signal at very long ranges. The built-in RF gain control with 120 dB range permits positive DF to within a foot of a 1-watt transmitter.

It has no 180-degree ambiguity and the antenna can be rotated for horizontal polarization. The meter functions as a left-right homing indicator in normal use. The simple "turn toward the needle" operation permits inexperienced personnel to get good free-field accuracy even with intermittent or varying signals after a few minutes of instruction. The unit will DF on a signal that is too weak to be audible. Less than a half-second of signal is needed to register on the meter. A sensitive signal strength indicating mode is also provided for use with the supplied yagi or with other beam-type antennas.

With accessory antennas it can be used in a vehicle, boat, aircraft or fixed station, and as an interferometer.

Standard features include a lighted meter and shaped switch knobs for night operation, 12/24V auxiliary power jack; external phone jack, battery check push-button, and remote meter connector. The unit is designed for rough field use; the receiver is housed in a well shielded die-cast aluminum case and is water resistant to allow continuous operation in rain or snow and at sub-zero temperatures. The aluminum antenna elements will fold or bend, not break, on impact. Up to 30 hours’ operation is possible on a single pair of 9V alkaline batteries.

The LH Series Little L-PerRegister.jpg (2200 bytes)  units come complete with receiver/DF, antenna (one for each band), 46" standard folding mast and 13" short mast, batteries, and operating and maintenance manual; some models include crystals (see price list). Two independent frequency ranges, such as 121.5/243 MHz aircraft, 121.5/VHF Marine, or 145/222 MHz Amateur can be covered in a single unit. A maximum of four crystals can be installed per tuner or six per receiver. Crystals are of a plug-in type and easily accessible to add at a later date for additional capability.

SPECIFICATIONS  DF sensitivity + or - 10deg. for full-scale left/right at 2 u V or higher signal input.    Minimum usable signal 0.08 u V on VHF, 0.12 u V on UHF.     Usable dynamic range, 140 dB min.     Receiver: crystal-controlled double-conversion with crystal filter, 14 kHz BW, 6 RF frequencies.     Image rejection 55 dB VHF, 40 dB UHF.      Spurious rejection 80 dB.     S-meter range 10-20 dB at a single sensitivity control setting; 120 dB total indicating range.     Audio output 0.25 W.     Power: Internal, two 9 V batteries; external 10-28 V neg ground, reverse polarity protected;      Current ;17 mA no signal, 130 mA max volume;   dial light 7 mA.     Battery life: up to 40 hours at low volume.     Operating temperature range -20 to +140 deg F.      Size: 3-11/16" x 4-11/16" x 2".      Antenna: switched yagi. Gain 2.5 dBd. Front to back ratio 12 dB typ.    Size: VHF 21" elements, 24" crossbar;     Amateur 18" elements, 18" crossbar;     UHF 10.5" elements, 12" crossbar.     Long  mast, 46";    short mast 12"     Total Weight , including antennas; 34 oz.

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L-Per extended ready for use

L-Per in folded configuration

L-Per on short mast with 243 antenna


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