Beacon Station MO 189.500 KHz

Lowfer beacon MO is active again from a new QTH near Aurora, Missouri.  Please see LWCA web site for current status:

This page is retained only for reference information. 

This site is dedicated to experimental low frequency operation in the 160 to 190 kHz spectrum. Unlicensed low power radio transmission in this band is permitted under Part 15 of the FCC rules.

MO BeaconThe photo to the left shows the MO beacon equipment in the corner of the radio shack.

ExciterThe exciter is contained in a temperature controlled enclosure (a picnic cooler). The exciter is crystal controlled using an 11 MHz region crystal and a HCF4060B oscillator / divider chip. The crystal frequency is divided by 64 to reach 189.500 kHz. A varactor VXO tuning circuit allows the frequency to be fine tuned using a panel mounted 10 turn potentiometer. The tuning range is about 7 Hz over the 10 turns of rotation. The oscillator / divider runs 24 hours a day.

The 4060 chip is followed by a 74LS00 quad NAND gate chip that is keyed for CW transmission and acts a buffer amplifier and for counter test port isolation.

Temperature control is achieved by placing the exciter board in a plastic box, insulated by two layers of Styrofoam insulation. Low value resistors on the exciter board provide a heat source for the exciter box. Additionally, a thermostatically controlled 15 watt light bulb is used for a heat source in the picnic cooler. Frequency stability is maintained within about .2 Hz of the desired frequency.

The exciter (picnic cooler) is sitting an industrial control computer running BCN-2SP software that keys the beacon transmitter in QRSS-30 mode.

RF Final AmplifierThe amplifier stage is mounted on the base of the loading coil and protected by a plastic food container. The power has been set to one watt DC input. There is a 47 K 2 watt resistor across the amplifier output terminals for antenna static discharge.

Loading coil and amplifierThe loading coil is wound on a trash can purchased at Lowes and is 27 inches high with a diameter of 14 inches on the large end. The coil is wound with 500 feet of 12AWG solid wire. There are a total of 135 turns of wire. Starting at the bottom, there are 110 turns with a tap every 10 turns below the variometer shaft. Above the variometer shaft, there are 25 turns, with a tap at 15, 17,19,21,23 and 25 turns. The antenna current meter is fastened to the wall beside the antenna disconnect switch.


The variometer is constructed from a 4 inch PVC pipe coupling and is mounted on a 1/2 inch dowel rod for a shaft. The winding has 22 turns of 16 gauge stranded wire. The tuning shaft for the variometer extends 18 inches from the outside of the loading coil to minimize hand capacity effects.


The beacon transmitting antenna is a vertical monopole constructed with a 10 AWG vertical wire and a 10 foot radius wire capacity hat.