Homebrew signal tracer

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Homebrew signal tracer

Post by Ragwire on Sun Oct 05, 2014 1:09 am

I don't know if anyone else is interested in homebrew test equipment--but here it is.
I thought it would be fun to build a signal tracer similar to my Superior Instruments CA-11 signal tracer, but with 2 stages of amplification so I can trace form antenna to speaker. The probe uses a 6088 subminiature pentode, connected in triode configuration as a grid leak detector/amplifier. The second stage is a 1T4 pentode similarly wired, but with a gain control. The entire unit will be powered by internal batteries. The single slide switch will have a center off position, an earphone position, and a meter position. I'm not saying this is UL approved or anything, but a just for fun project for me.

The schematic:


The probe is housed in 3/4" O.D. tubing about 5-1/4" long:


It clips to this collet that will be part of the main probe handle tube for easy removal for service:



A very small pentode amplifier (Those are little 1/4 watt resistors for an idea of scale):




The main case is just a Radio Shack aluminum project case. There will be a place to wind up the probe cable and snap the probe handle into for storage:

Coming along, but the meter needs a new face other than the "microamps" reading:



Tight fit inside, but the batteries have their spaces:


The revised meter scale:


Finally got it wrapped up (and tested on a radio):



I like this circuit because it picks up audio and modulated radio frequency equally well with no RF-Audio switching needed.
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Re: Homebrew signal tracer

Post by Guest on Sun Oct 05, 2014 9:09 am

Very impressive! Very Happy

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Re: Homebrew signal tracer

Post by Ragwire on Sun Oct 05, 2014 8:08 pm

Thanks, I think it will be useful. Once in a while I just gotta crank out a "make something" instead of a "fix something."
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Re: Homebrew signal tracer

Post by 75X11 on Sun Oct 05, 2014 8:51 pm

Great job! The graphics really give it that period look!
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Re: Homebrew signal tracer

Post by Ragwire on Mon Oct 06, 2014 7:56 am

Thanks man!
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Re: Homebrew signal tracer

Post by Dr. Radio on Wed Oct 08, 2014 3:02 pm

My goodness, that looks professional.

I can see a side ebay business in your future. Smile
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Re: Homebrew signal tracer

Post by Ragwire on Thu Oct 09, 2014 11:49 pm

Thanks fellas...I did make 2 small modifications. I had to downsize the output capacitor to the meter because the turn on surge blew the germanium diode with the bigger capacitor. I forgot I was dealing with a 36 volt B+. I also had a filament burn out in the probe, so I pulled the filament voltage down a bit with a 10 ohm resistor. Typical prototype bugs.
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Re: Homebrew signal tracer

Post by jerryhawthorne on Sun Oct 12, 2014 6:33 pm

Very nice job Ragwire. Impressive workmanship.
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Re: Homebrew signal tracer

Post by Ragwire on Sun Oct 12, 2014 8:37 pm

Thanks Jerry. I try.
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