Nuts & Volts - September 2005

Tech Forum

similar insulator. These circuits may cause trouble in a high humidity environment. Enclosure in a metal box (as much as possible) will shield against stray signal pickup induced by body capacitance. Or, you can sort-of test the circuit unshielded by bringing a static charged object near the input, deflecting the meter. Actually, this proves nothing about detecting radiation, just that the circuit is sensitive, as opposed to dead.

Read Wenzel's website for tips. The 12V battery should be bypassed by a 100 uF electrolytic capacitor, not shown. Start with simple circuits first, even though you may need the "gold" circui." If my Figure 4 does not work, move on to any of the other circuits. You may want to replace the neon lamp with Wenzel's "can sensor." If the simple circuits do not produce results, you might increase the 12V on the neon lamp to 45V (but not the

transistors) by snapping five 9V transistor radio batteries together. Finally, this is a very difficult project.

Dennis Crunkilton Abilene,TX

[#07056 - July 2005]

I would like to add FM radio signals to our prison cable system ( 94. 3 MHz on Channel 60, etc.). I’ll probably have to go “off the shelf” to keep it simple for staff to assemble. I’m told that RCA makes an AV accessory box for connecting AV inputs to TVs that only have a coaxial input. These boxes supposedly have an output signal tuneable to most UHF channels. I’ll connect an audio cable from a radio tuner to the AV input on this box. But I believe the boxes may not have a cable input. How can I combine the AV box output with the existing cable-ready feed? Can I use a CATV splitter in reverse? Could I

use one of those adapters for adding an in-line UHF antenna?

Smarthome ( www.smarthome .com) has a nifty device that converts your audio/video source into an unused TV channel (CATV 65-135 or UHF 14-69) for $50 (which is probably less than you can make one for). The manual is available online so you can verify that it will work with your application.

See www.smarthome.com/ 7715A.HTML

John Couture via Internet

[#07051 - July 2005]

I recently acquired about 20 four-channel 29 MHz radio-controlled cars and when used as-is, they range as far as 30 ft indoors. After slight mods, still good range, but once I install it in my car, the range becomes inches.

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SEPTEMBER 2005

Circle #82 on the Reader Service Card.

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