CQ CQ CQ!

I've been trying to figure out what transmitter I want to build next - spending a lot of time modeling it in LTSpice and trying to figure out how it will work.

But I wanted to actually get on the air.  I've been practicing my Morse a bit lately, so thought I should just see what I could throw together.

The things I had that were is somewhat working state (or could be made to be...) were my direct conversion receiver and a NS-40 CW transmitter.  First thing was I needed a way to connect them.  I wanted to make something with a relay and have the Arduino I was using for VFO switch it.  But I didn't have any lying around I could find.  But I did find a DPDT switch, so I made a little thing in a nuts tin

When the switch is in the transmit position, the transmitter is routed into the dummy load (I didn't want risk accidentally powering it with no load).  It doesn't give good isolation - the receiver screams when I key - but seems to somewhat do the trick.  Here it is spread over the table:

I tried to send with my homemade key but wasn't getting any responses.  I wasn't sure if it was my antenna setup, the low power, or my bad sending.  So I thought I should try using a keyer.  I found the k3ng Arduino keyer which looked like it would do the trick.

It went together pretty quickly.  The ns-40 had some interface circuits on the site that worked well.  Only thing is the circuit works on active being low, so I had to switch high and low in the software.

It was getting late, so I wanted to just do a quick test.  The keyer has a CW keyboard mode, so I sent CQ from there.  I didn't get anyone coming back.  But I did get spots on the reverse beacon network!

Very exciting!

Knock-off Nano Note

Quick note about how I got the random Nano I found in my junk box working.

1. It wasn't showing up in list when I plugged it in.  Found answer here to install new drivers for OSX so it could see the board (links to this github repo).
2. The upload wasn't working.  Kept getting a "not in sync" error.  Found answer here.  Turns out I needed to use the "old" bootloader under the "processor" section in the Arduino IDE.

Decoding CW from WebSDR with Fldigi on OSX

I got the urge to play around with WebSDR this morning.  After a bit, I got the further urge to try to use Fldigi with it.  I figured I already had Loopback from some music things I do, so I'd have a go.

Worked really well.  I just have a simple setup where I have the output of Safari into an output channel, and then am monitoring that.  Then in Fldigi, under "PortAudio" I have it use "Loopback Audio" for capture.  

Couple of notes:

• It didn't show up as a soundcard at first - probably want to setup Loopback before opening Fldigi
• It was initially doing some mode *not* cw.  It looked like I was supposed to change that in the lower left (where it said the mode), but you actually go up in the menu under "Op Mode"

Activities - 8dec19

Have been trying out WSPR with the Si5351 this morning.  I am using the sketch here.

Couple of learnings:

• Can list serial ports on a mac with `ls /dev/tty.*`
• The "serial" library it is talking about is pyserial (not serial).  I used pip to install the first and was confused why it wasn't working (the gist wasn't returning the error)
• You can't program the arduino while the script is running (as they both use the serial port)
• This script is set to run every 10 minutes.  Confused me why it wasn't working, but then it suddenly did.

No luck so far, though it isn't helping that the WSPRnet website doesn't seem to load very well.

So then I changed tact and decided to get my DC receiver back up and running.  Before even turning the VFO, I was getting in some local religious broadcast as strong and clear as could be.  Possibly need a stronger band pass filter...  Turning on the VFO, it was working, though I couldn't really hear anyone (some digital modes and someone speaking maybe spanish).  But it was 11am, so probably not the best time for 40m.  May try again tonight.

One thing I noticed this morning: powering my Arduino from my Mac works great.  Powering it from any power plug I can find is very noisy on the Si5351 output (either the 12v or usb).  Strange.

Si5351 VFO

A few years ago I made a VFO with an AD9850.  Now I changed it to be a Si5351.  I am using the same awesome setup from Jan again - he updated his for this chip.  I even still had the lcd/wires on a breadboard, so I just had to wire it back to the Arduino!

Several things I ran into:

• I had a hard time convincing it to use the right libraries.  I had some out of date versions of some, and it kept wanting to use the Adafruit library instead of the Etherkit one.  I finally deleted the Adafruit one to get it to work.  
• It didn't work at first, and I thought I had fried another Si5351.  I put another one in, and it didn't work, either.  I suspected my wiring, but then tried the Adafruit sketch I had made, and it worked.  Turns out it was the i2c address - I had to update it to be 0x60.
• The calibration was off.  It was actually off by about the same as the default BFO frequency, so I went down all sorts of rabbit holes trying to figure out why it was adding that in (which it wasn't).  Finally figured it was actually the calibration, and ran the calibration tool the Etherkit library has (which is kind of awesome) to fix it.
• I can't seem to get the Arduino to acknowledge changes I make to the 'definitions.h' file.  Or at least when I change those and reupload, they don't seem to have taken effect.  Maybe something with the eeprom, not sure.  I ended up changing the calibration in the .ino file for now while I look some more.

I had originally planned to use this with a Tayloe mixer.  But I screwed up my mouser order and the IC I got is the *smallest* I think it could possibly be.  It was one of the last things I put in that order and I was pretty tired at that point, and I swear I checked that it was larger than that...  Anyway, I decided I would try this with the EMRFD direct conversion receiver I had made a while back, but it is now pouring outside so don't want to go out in the rain to pull in then feedline.  So that is a project for another night.

Power in LTSpice

A quick note of something I found tonight.  I've been playing with some IRF510 designs, and for one of them, it looked like I was getting crazy good efficiency.  Like, not possible good.  I was evaluating this by running a transient simulation and then option-clicking (in osx) on the load resistor and on the IRF510 to get the power on those components, and then control-clicking on the labels in the graph to see the average power.  The power dissipation on the IRF510 was *way* too low (like 290mw when the output overall was 3.8w, which would be like 93%).  Turns out that when I was doing this, the current was negative some of the time, which was showing I guess as negative power.  So the average was much lower.  Wacky.  I guess I'm still learning this program.