This page is being kept around for historical reasons, some of the links are getting an update now... Lance 8/29/2001

 

This projects page is starting to come together... let me know if you have any suggestions.

The software downloads are towards the bottom.

for the most recent  info on the the software tools I've made publicly available, go to tools.rfdude.com


Software projects...

DSP audio filters (ham radio DSP filter box)

More recently I've been getting back into DSP programming. With the intent of using surplus target hardware around the office, I've written the microcontroller code to load the dsp, and several utility programs to automatically convert coefficients into assembly files, assembled code into C data structures, etc. With some kind donations of hardware from some other guys at work I've implemented the following audio filters for ham radio use:

I'm now scoping out the task of doing SSB modulation/demodulation using the DSP. I've got some sort of bug in my way of thinking about this, so not all that much progress has been made. Hopefully this winter (1998/1999) I'll pick it up again and figure out what's going on.

Iambic memory keyer (functionality added to my ham radio DSP filter box. It's just software, right?)

During the summer of 1998 I decided I needed a memory keyer... so I wrote some HC11 microcontroller code and made my DSP filter box into a "DSP filter box and memory keyer". Here are it's key features (no pun intended)

Analog radio software for (baseband) DSP based data transceivers (active work being done 11/1998 through 2/1999)

This is the same hardware platform as the other projects above were done with, but with the radio parts functional.

Current features include:

Someday I would like to have a block diagram here. The basic circuit uses a microcontroller and DSP working together. The DSP does all of the analog processing beyond the discriminator on RX and after the microphone on TX. I've had fun implementing polyphase decimators and interpolators. There are also several other FIR and IIR filters in the system. Squelch is implemented digitally on RX and adjustable speech clipping is implemented digitally on TX. The CTCSS tone generation is done using direct digital synthesis (DDS or a fancy way of saying "table lookup").

The input/output sampling rate for my system is 200 kHz and the intermediate processing is mostly done at a 25 kHz sampling rate.

I don't have too much more to say here, I'm having lots of fun working on this in lots of ways. The DSP stuff is obviously neat, but also working out the user interface and the DSP<-> micro communications has provided fun little challenges here and there.

 


 

2m Transverter

main transverter

Close up of my low-level RX/TX sections


This transverter is nothing special. I was happy that none of the low-level circuitry required tuning except for the 116 MHz LO (fifth overtone xtal osc. circuit popular in amateur circles these days). The LNA has a couple dB NF as I recall, which is fine in my book since it is doable in a no-tune circuit and it has high dynamic range. For most terrestrial work, this NF is just fine (send me email if you want to argue this point, it's a favorite of mine). I used coilcraft SMT inductors, which allowed the filters to be no-tune. Later, I added a tunable BPF for the front end since where I live is very RF "rich". It's hard to build a selective, low-loss bandpass filter without adjustments. Someday it might be nice to do a circuit board layout of this design... but I haven't found the right layout program or the time to do so!

download partial schematics of 2m transverter, including some of the filters and amplifiers (zipped postscript)



Here are some fragments from my portion my senior design project… John Barenys, KE4IBF was my partner on the project


LNA PICS 2304 & 3456 MHz LNA's (all self-biased PHEMT no-tune designs)





Last modified July 12, 2012 12:08:10 PM