Nice day for space birds

My lovely family got me an sdr dongle for christmas, and I had been itching to use it to receive weather satellite images.  But most of the discussions around it talk about building a somewhat fancy antenna, which I didn't really want to do.  So I started looking to see if I could use the rabbit ears that come with the kit, and turns out you can.  Following instructions here and here, I got decent results!

Couple of notes:

• I started off measuring the VSWR with my NanoVNA.  I did as the instructions said (length/angle), and immediately got <1.5, so was happy there.
• Had to restart computer (CubicSDR wasn't putting out sound), and had to switch my SDR back to *not* use direct sampling (I had it setup for HF stations).  Finally managed it to tune in an FM station.
• I was using my compass on my iphone to point the antenna, and I noticed it thought north was very much the wrong direction.  Finally found that sometimes you have to do a funny "figure 8" motion with your phone to tell it to recalibrate the compass.  Weird.
• I set wxtoimg to autorecord, and it started right on time.  However, the image was all black.  Eventually, played around in loopback turned up the "pass through" volume, and it started showing an image!  It had the same artifacts on the side that the blog had, too (not pictured above).  In any case, I should have calibrated from the start like the wxtoimg instructions said (but I don't think were in the blog entry).

A little amplifier success

Charlie Morris had a youtube video on Class E amplifiers, so it made me want to try to get mine working.

I had tried previously using an Ixys driver, but I I think I may have blown it.  It is hard to tell.  I ended up pulling it out along with the IRF510 and putting a new IRF510 in with a bjt push-pull driving it, and a 2n7000 in front of that.

After wiring this up, I started with a lower Vcc and immediately got an output of about a watt.  Encouraged, I started slowing upping the voltage.  But at some point it stopped working - the power supply over current safety was tripping, and I wasn't getting an output, same as before.  But this time I went though and wiggled all the components and did continuity tests and tried again.  Then it started working again.  So maybe this is what was happening before - some stray whisker or something.  In any case, I upped the voltage up to 15v and got out about 4 watts.  I didn't want to go higher than that because I don't know the voltage ratings on the capacitors I used (the shunt cap should end up with about 3x Vcc if I remember correctly).

So, a bit of a success.  However, LTSpice thinks I should be getting out 14 watts at that voltage.  Also, the supply says I am drawing 694mA, which would be 10.4W, so not sure where that other 6.4W is going.  Nothing was getting that hot (I didn't even have a heat sink on the IRF510).  I probably need to go look at the waveforms at all the different points, but don't have time to do that right now.