VK5TM


News, Updates and Other Minutiae

I have, for quite a while, provided modified versions of the code for my projects free of charge. However, the cost of webhosting for this site has tripled in the last couple of years and the little I make out of the pcbs I sell goes nowhere near covering this cost.

As of October 2017, I will be asking for a donation in exchange for providing custom modified code for my projects to help keep this site available.

February 2018

Updated Australian Band Plan page with the latest info (under 'Misc' heading).

November 2017

A modification plus software to allow the Simple DDS VFO to be re-calibrated as often as you want without having to re-program the PIC has been added to the Simple DDS VFO page. Simple DDS VFO bug problem fixed. Code uploaded to webpage as version 'c'.

October 2017

There is a bug in the Simple DDS VFO code. See Simple DDS VFO page for the problem and updated code. Included an add-on for the Simple VFO project to indicate which step size has been selected. Simple DDS VFO project updated and software file uploaded. The pushbutton on the encoder is used to change step size (step sizes 10Hz, 1kHz and 10kHz).

September 2017

Noise Canceller kits now available.

July 2017

Updated both the DDS Xtal Substitute and DDS Xtal Substitute Mark 2 projects into one project. The original webpages are available to download as PDF's.

May 2017

New project added - my version of the X-Phase noise canceller. PCB available and a kit of parts to follow soon

3v3 DDS Module Mods

There have been various discussions on the net about 3v3 versions of the cheap Chinese DDS modules. It seems to affect only the AD9850 modules. In fact, if you look carefully at some of the images on the popular selling sites, you can see 3v3 engraved into some of the oscillator modules. Some are not that obvious however. If you are lucky, you may have a module with a manufacturers mark and code on it that you can look up. Otherwise, the only other possible way of telling is, that when running, the 3v3 oscillator blocks will get warm to the touch. I can only conclude that these modules are 'mistakes' or 'rejects', because the AD9850 is only rated to an oscillator value of 110MHz at 3v3 and the AD9851 125MHz at 3v3. See the link between the two? How well they run like this I don't know, as my modules are definitely 5v oscillator types. Egbert PA0EJH, sent me an email with the details of his fix for this situation, along with a note to say that the 3v3 oscillator on his modules died after a week running at 5v. The extra components are shown in red. Click pic for larger version. DDS mods The other obvious solution is to replace the oscillator module with a known 5v version if you feel so inclined. So if yours have suddenly stopped working, this may be why.