Improvised Signal Tracer

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Improvised Signal Tracer

Post by harold wright on Wed Aug 07, 2013 10:30 pm

Someone gave me a Panasonic RQ-830S portable 8 trk. player. Can be powered by 6 C cells or AC. The tape transport did not function, so I decided to make something usable from the amplifier. I disconn. the audio leads from tape head, added a shielded cable about 2 ft. long and made it into an audio signal tracer. Since the tape head output is so weak (millivolts ?) I knew the amplifier had considerable gain. I tested it by conn. a magnetic phono cartridge to the input leads and it worked fine. It could be a useful portable audio amp., esp. when dealing with weak audio signals. Maybe an amp. for a crystal radio?

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Re: Improvised Signal Tracer

Post by willy3486 on Thu Aug 08, 2013 9:02 am

One of the electronics mags of the late 70s/early 80s had a homemade signal tracer out of a old transistor radio. I made one and then made a 9 volt power supply to run it. I put it in a dead CB radio case. It still works great and I made it in the early 80s. If you are interested in it send me a email or PM with a direct email and I will send you the info. I like it a lot better than the store bought one I have at work. Your 8 track should work fine as one. you added a few parts like caps and tied it to the volume control IIRC.

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Re: Improvised Signal Tracer

Post by Resistance is Futile on Fri Aug 09, 2013 2:32 am

Make your self a probe and be sure to add a switch and a capacitor to block DC. with the switch add a diode for checking the RF and IF signals also. You should limit the input signal with a resistor for higher voltage signals to prevent overload of the signal tracer on its input. There are descriptions on the web on how to build RF probes.
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Re: Improvised Signal Tracer

Post by Ragwire on Mon Aug 12, 2013 7:37 am

Good job!
I used a cheap, relatively newer, pocket sized AM/FM radio. I have RF (using the radio's own RF and detectors circuits) and audio input wires with the blocking capacitors inside the case. I only hooked it up to use the AM band side, but I suppose it would work for FM, too, if I wired it that way. For front end work, I just inductively couple it to prevent loading, and listen for the beat frequency squeal of the local oscillator or I can tune it slightly off channel and see if the radio under test will "pull" it in to the channel I'm tuning on the tested radio.
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