Joe Leggio WB2HOL
This FOX transmitter is equipped with a timer. It can be set to start transmitting up to 24 hours later.
The timer consists of a Radio Shack travel alarm. I disconnected the pizeo-ceramic beeper and used the signal to set a flip-flop built from a CMOS 4011. The output of the flip flop is connected to a switching transistor which supplies voltage to the CW ID. I used an R/C combination on the flip/flop so it would be reset when first powered up. A push button is provided so the flip/flop can be set manually (turning on the transmitter)
The transmitter consists of three stages: a 45 MHz oscillator, a tripler, and a "power" amplifier. I know the heat sink on the final is a bit of overkill at 250 milliwatts output. I used a 6 volt gell cell for power. This thing can go for days.
The CW ID consists of a CMOS 4011 clock and a CMOS 4020 binary counter connected to a 2k EPROM. One bit on the EPROM is used for the CW ID, a second is used to control the switching transistor which supplies power to the transmitter oscillator. It is set up to transmit once every few minutes and stay on the air for about one minute.
Normally, the travel alarm timer is attached to the outside of the 3x5 file card box with velcro. This makes it easy to change the clock battery when needed.
A word of advice. Do not try to take a device like this through the security gate at an airport. It looks too much like something you would see in a "Die Hard" movie. Please make sure it is plainly labeled as an Amateur Radio Transmitter Location Device (or some other official title) and put your name and address on it in case it is discovered by someone not familiar with fox hunting. They *might* think the FOX looks suspicious and call officials to investigate. (You might want to notify officials in advance about your FOX-HUNT. We usually do just to eliminate problems when neighbors call in reporting *strange* people in the neighborhood)
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Copyright 1997 - Joseph Leggio - all rights reserved.