This is my completed san2pc, a spectrum analyzer to PC interface. This is a project designed by Roland Cordesses, F2DC and published in the November/December 2007 issue of QEX. See the author's website at:

This unit interfaces with my old HP spectrum analyzer (HP8555A, HP8552B in a HP141T frame) and digitizes the screen output, resulting in a file with xy coordinates that you can later plot with a PC.

A circuit board and pre-programmed PIC is available from FAR circuits, but I did the whole thing myself. I print the negative of the board on the cover sheets of MSDN magazine, and then I iron these on to clean copper circuit board. When you iron the pattern on, most of the toner sticks to the clean copper and peels away from the glossy magazine paper. There's a little bit of touch-up that needs to happen, but it's pretty good. After that, I etch the board. Once that's done, I have an X-Y sliding vice under my drill press that I use to help get the holes straight, etc. The top layer is unetched copper, and I use a 1/4" bit to remove the copper around holes where a through lead is needed.

This project is kinda ugly because I wanted to use as many junkbox parts as possible. I had to purchase the 18F2525, the DC-DC converter and a 79L05, that's it.

Programming the 18F2525 was kinda a pain, but I got it done. I'm using a PIC-PG1 ICSP programmer from sparkfun. Check out this link and be sure to use the bypass caps and resistor, skip the PGM pin on the ICSP header, just tie it to ground. That'll do it.

The project goes together easily and works just fine, with two hitches: make sure the scan speed of your spectrum analyzer is set to something equal to or slower than 5 ms/div (I think I have the number and units) or it won't calibrate right. To be fair, I think that was mentioned somewhere in the docs, but I didn't catch it.

I don't have any nice pictures (the whole point, right) from my spectrum analyzer because I couldn't get the python utility to not crap out on my win98 test box. I understand it should work, but it's failing within a python library. (update: it works fine on XP and redhat linux)

The enclosure I have is pretty big. Someday I'd like to fab up another board with some buffer amplifiers so that I can have the scan output also routed to this unit along with an output for video/audio.

More pretty pictures later.

Sun Feb 10 18:41:38 CST 2008

As anticipated, works perfectly. As promised, some example output:

Scan centered at 530MHz, 10MHz/division -- well, you can read it yourself.

Comparison of a photograph of the spectrum analyzer screen and the san2pc output. Note the two images were taken about 30 minutes apart. I'll re-check my calibration and later post a capture and photo that are closer time-wise. As stated in the article, the accuracy of the san2pc is better than the accuracy of the spectrum analyzer. This is is a whole lot easier than setting up the digital camera.

Wed Nov 12 20:58:54 CST 2008

It appears as if the DC-DC converter specified in this article is unobtanium. I directly substituted a MuRata NKA0512SC in mine. As of today's date, both DigiKey and Mouser have them in stock. In some follow-up email, the project author pointed out that this dc-dc converter isn't necessary for use with an HP141T frame. But here's a substitute just in case you need it.

This page last modified Wed Nov 12 21:00:43 CST 2008 by timc!