My New Year gift to TW: A new theremin circuit

Posted: 2/25/2020 8:06:44 PM
zevot

Joined: 2/24/2020

Hello Thierry, I followed the Keystones video and build this circuit but havent get sound from the antenna. I used J113 instead of 2N5484 and all the other components are identical. I got some strange radio like sound from amplifier but the antenna is not function at all. 

Btw, is your C13 1.5nf? 

Posted: 3/18/2020 10:21:42 PM
Imberlimerence

Joined: 3/18/2020

Hi all! I am using this design for my senior project and have unfortunately hit a block. I am using a guitar amp as the audio out and an currently only getting static. If I unground the audio jack connected to the guitar amp, I can get a slight pitch variation in the feedback if I pinch the antenna. I don't know what I'm doing wrong and have re built the circuit three times on a breadboard. Any help would be much appreciated as I need to fix this to graduate!

Posted: 3/18/2020 11:22:27 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014


Tune your Analog AM Radio to around 900 khz and you will find two blank spots in the static on the AM band if both oscillators are working. This is 2 x 450 khz or whatever it is.  If you find the two blank spots tune to overlap them. This is fun stuff. Thierry a genius but I got the edge. I have a pdf toner transfer print out for this circuit I can share if you know what that is.

Your coils are probably 10% so the oscillators could be out of tuning reach of each other, you might need to add a few PF's to one side. Also have a length of wire for the antenna mounted. This should drive your amplifier for the experiment.

In my graphic below I added a spot for a LDR volume control.

There is a lot to learn from this design, like why I avoid using FET's.

Christopher
www.Hwy79.com


70 mm x 100 mm

Posted: 3/20/2020 7:49:39 PM
tinkeringdude

From: Germany

Joined: 8/30/2014

The beauty of the layout almost rivals that of the bird.

(no, I don't like the sight of P-to-P tube amp circuits, either )

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