Tuesday, March 26, 2013

Tuning the gyrator3

The gyrator board has 3 variable resistors:
  R3 for tuning the frontend
  R6 for setting the gain
  R16 for zeroing the output
  R21 to set the range for the frontpanel meter
  R22 to set the range for the A/D

The procedure I used was:
 - set R16 to zero the meter and A/D
 - center the R3 and R6
 - adjust R3 for max signal.
 - adjust R21 so meter is mid scale. I may need a bigger value for R21 as the meter is offscale.
 - tweak R6 for max. This seems sensitive, maybe pushing the circuit into oscillation?

In the pic above I am using my voltmeter, which has recording software, to monitor the signal. I've set the outputs to about 2.4V.

I can clearly see the signal change as I rotate the antenna, so its receiving something. I've adjusted it to max signal. That's pointing off to the NE, so I may indeed be receiving from Skilton, UK.

I'll let it run to night to see if I can record the sunset events.

Sunday, March 24, 2013

Basic construction of the Simple Sid Monitor antenna

No major difficulties so far. Be patient while winding the wire. I glued it down with liquid nail. The project description mentions building a monitor for $10. But that doesn't count the $50 of copper wire!
Tuning the Gyrator's antenna

Here is a pic of the antenna
Tuning capacitors go here. The ic socket makes it easy to add more to select the frequency.
I'm using a signal generator, simply coupling it to the antenna with a wire wrapped around the antenna. Watching on the scope the line from the antenna I look for the biggest signal while varying the signal generator output.

The current setup resonates best at 22.05kHz. That should be good for GQD in Skelton, UK which is at 22.10Hz.

The next step is to get the Gyrator 3 board operational. Here I've made the final connections.

Tuesday, March 19, 2013

Current state of the Gyrator 3

Here is a pic of the package. This is from below. You can see the meter. None of the panel controls are hooked up yet. The green board is a WinDaq acquistion board. But it is an old model (DI-194). Since the software for this is no longer supported on 64-bit computers I plan to replace it with a USB model (DI-145)
Here is another view, showing the power supply.
Things to do:
- Bring out R3 (tuning) and R6 (gain) to the front panel
- Bring out the Time Constant capacitor selector to the front panel.


Tuning Tools

One step common to the Sid receivers is that they will be tuned by selecting capacitors to adjust the resonance of the antenna. The Simple Sid instructions describe a way to do this. Here is my take:
Here you add in the caps with the dip-switches. The advantage here is that once you find the setting you want, you can take those exact capacitors and solder them into your circuit. Handy since there is quite a variation between caps of the same nominal value. 
Welcome to the Sid Monitor Construction Site!

What I would like to do here is document 2 projects I'm working on directed at monitoring Sids. What is a Sid? It is a Sudden Ionospheric Disturbance. These are caused by solar flares and gamma ray out bursts from our sun. The principle of detection is to build a VLF receiver that looks for the affect of these events on the VLF carrier waves that the government uses to communicate to the submarine fleet. So, its a kind of a radio telescope.

The first project is to complete a Gyrator 3 receiver. The second is to build a simpler version described at http://www.aavso.org/print/simple-easy-build-sid-receiver .

The Gyrator3 project was started years ago. It's time to get it done! I set up a Google Group to share the learning curve. This still exists at https://groups.google.com/forum/?fromgroups=#!forum/gyrator-3-construction . But Google Groups devolved into a basic email focus rather than a blog where you could share files and pictures, so hence this blog.

So I'll try to capture progress and lessons-learned here. If you are interested in joining the fun, do sign into the Google Group mentioned above.