Showing posts with label Valve/Tube. Show all posts
Showing posts with label Valve/Tube. Show all posts

Friday, March 25, 2011

ECC82 Downconverter

I bough a spare ECC82 valve when I built the ECC82 regen receiver, already tried a valve VFO (worked), now decided to tryout a valve down converter as a first test to a tube direct conversion receiver.



Basically one half of the ECC82 is running as vfo then there's a single balanced mixer and will be an audio amplifier using the other half of the ECC82.
Interesting thing is that this circuit worked first time, I even forget to count the turns in the mixer core, the rfc was the first coil I found from an old PSU and the mixer output termination was the first small cap I found...
Signal out is not much but hell what do you expect from a lousy mixer made from a binocular core and 2 diodes and 4m of cable laying in the floor working as antenna...

video


The oscillator was running at 6.7Mhz and I was listening on 365Khz so one of the received frequencies was 7.067Mhz... I promise a schematic soon.

Add: here is the schematic used:

Tuesday, March 08, 2011

Tube/Valve receiver... the schematic

..And the finished product...


..Sort of, there are still somethings to improve like putting a volume pot and antenna coupling. I didn't found yet the optimal antenna setting so will improve it in the future.
The schematic used:
My valve/tube is the ECC82 which is an European version of the American 12AU7

Reference articles from here and here

Saturday, March 05, 2011

ECC82 (12AU7) 12V VFO

Now that I de-freezed, on to work:
Found a nice article on a 12AU7(ECC82) vfo here, decided to try out the circuit using less lethal voltages (I had my fair share of electric shocks if you know what I mean).

Here's the prototype:

...admire the beautifull wiring work...and circuit...you can find a clear one in the article link provided above.



It works! The only hard part is to make the a coil for it. Mine was done with the cientific methot of trial and error...oscilates around 800-1200khz but I intend to make one for 5-5.5Mhz.

This was just a proof of concept but working with 12V supply and no buffer it can deliver about 0dBm measured from my NCY (Not Calibrated Yet) AD8307 power meter.

It takes a little to get into oscillation due to valve warming as you can see in the video:

video

Having time and a nice box to put it, looks like a nice little external vfo for one of my vintage HF radios....one of this days....