Wednesday, January 27, 2016

Arduino UNO, SI5351A breakout as 144 & 222MHz CW beacon

I've been working on ways to extend the use of the Etherkit Breakout Board & Arduino CW beacon I recently posted about *here*  

I want to TRY to do UPCONVERSION where I use CLK0 as an LO frequency (on the Si5351a) and CLK2 as the IF frequency through a cheap Mini Circuits frequency mixer.  I had in my junk box model number ZX05-1L-S+ which has SMA connectors and covers 2-500MHz.

You can see in the photo above how this is connected.  The coax trailing off the right of the pix goes to a dummy load in this video below which is just resting next to a HackRF One and the beacon above reception is being shown via HDSDR.

So CLK0 (the top connector off the Si5351a) in the photo above is set to 94.208 MHz (and change) and CLK2 (the bottom connector) is set to 50.069.75 MHz.  The resulting output from the Mixer is the sum of both and equals 144.287.75 Mhz (more or less it wasn't all warmed up when I made the video).

Now just to be fair the Si5351a can output up to nearly 160 MHz so this isn't really necessary for 144 MHz.  But it was a starting point.

The next band up is 222 MHz, so all that is needed to change in the Arduino sketch is to change CLK2 to output at 127.847 MHz and presto the output from the mixer is at 222.055.75 MHz.  This works too!  I didn't have time to video it in time to post this blog, but it works the same way.

So at this point this beacon could operate on any HF band, 50, 144 and 222 MHz as well as is.

This mixer can go as high as 500 MHz.  So in theory I could get up to 432 MHz with a setup like this, except that the Si5351a's max output frequency = 160 MHz.  160 x 160 = 320 MHz would be the max in this configuration and that's just not enough.

However, I also have a MK-3 Frequency Doubler :-)  It requires a fairly high input and there is about 13db loss in the conversion.  So a amp will likely be needed to do this.  Just so happens I think I have just what I need for that too.  I've been muxing around with little RF projects for quite a few years, and the junk box is full of things like these.  

So that'll be my next post as I work on trying to make that a reality.


The reason I'm trying to do this, this way, is that I would like to make a beacon that can operate on as many bands as possible and programatically (within the Arduino Sketch) change bands and 'beacon' on each that it's capable of on a timer.

Really this is just something to do while it's too cold outside.  I'm not sure I'll ever really put something like this on the air.  But it's a lot of fun and combines a lot of things I've learned the past few years with these winter projects.