Two Tone Oscillator

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Another nice and useful add to every Ham station is a two tone oscillator, also named two tone generator or dual tone... You can see here how to use it and why it belongs to each radio station. I found several options to get one.

 P1020391mailThe first I ordered and paid from a US kit dealer ,sadly it never arrived. A word of warning about this, if you pay some goods on eBay using PayPal pay attention that the announced delivery time isn't longer as 45 days otherwise you can't claim anything after 45 days, don't wait too long to make your claim if necessary.

The second option I found was this one. 239.50$ plus shipping cost, must be gold plated. The third one is from Elecraft and seemed to be OK, but can't get it as fast as I want.

Looking further I found as usual a good DIY Ham Solution, this time the call from the Ham offering the solution is VK5JST Jim. You can find his site here, and all the informations for his very high quality two tone oscillator are here. P1020403mailI quickly ordered all necessary components (I ordered 1% precision component when possible), nothing special, all parts are easy to be found or replacement parts are available. I made some boards and begun to built the generator. Don't worry you won't need all the parts you can see on the picture. I ordered the parts to make several generators and having spare parts. Does it work, at once no, bouhhh, why, no idea. I double checked my work and P1020390mailchecked again and didn't found anything wrong. My item just doesn't want to oscillate or better to say, start to oscillate and after some oscillation stop to work. At that time I decided to contact Jim to ask him if there were any probs with this generator or if I missed something important. A few mails later He pointed out that the FET I was using, the 2N5485 in place from the original 2N3819 (not in stock at the moment I ordered) has another pinout. When I measured some FET to pair it regarding the Rds value as recommended by Jim, it made no difference but in use it just can't work in real word. Thanks Jim for the quick reply.

P1020414_700mail P1020413_1900mail P1020415bothmailYou can see pictures from the board, the components, the mounted circuit under test, The 700Hz (706Hz) , the 1900Hz (1868Hz), and both waves on the scope. Jim gives an output voltage from 300mV RMS (425mV pk), I measure 333mV RMS (471mV pk) at max output, the informations given by Jim are also very close to mine and conservative. Such a good instrument must have a nice enclosure, you can see below the result with just the two buttons covers missing. Blue is the color.

P1020416enclosuremail As usual, enjoy and replicate.





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