2019-03-11 Dipper, Wavemeter PT. 1

from FB group Building Transistor Radios Mar 11

I watched a YouTube video from Alan Yates VK2ZAY, he built a combination Dipper, wavemeter, receiver and RF generator. I built his schematic ‘right side up,’ he admitted he built it upside down with positive ground and drew the schematic, see:

https://youtu.be/0pJw0m2Lz6o

I didn’t attempt to build it with the switch, I chose only the wavemeter function. I’ve been trying to get it to work but it’s acting funny, probably like superregenerative. I’ll have to adjust some resistors to see how it works.

Update Mar 12 – I found one problem, I connected the two BF199 transistors base to base and collector to collector; they should be bases to collectors. It wouldn’t have happened if they hadn’t been BF199s, which have the emitter on the center lead. Now that I straightened that out I have a superregenerative oscillator that squeggs at audio frequencies, not above (ultrasonic). It makes a loud squeal at any and all tuning capacitor settings. The tone varies in frequency from low growl at low voltage to high pitch at 9 volts. I put a loopstick with a tuning capacitor next to the coil of the Dipper/wavemeter and tried to get them to interact but I had no success. I need to investigate with a frequency counter to find out what its frequency limits are.

Update Mar 12 – I changed some resistor values to change the tone. It works great for generating a tone. I ran my signal gen to a few loops of wire around the coil. When I tune it or the signal gen to the same frequency the tone gets much higher until it peaks where both are the same. So it’s working as an audible wavemeter, sensing the external RF.

I am making more modifications. They will be on the next blog, Pt. 2.

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