Friday 27 December 2019

USB VFO for SDR

I bought one of those USB audio control knobs and reprogrammed it as a VFO, as per instructions here

It does work as a VFO, but as standard the encoder has detents which doesn't make for 'free running' rotation.
So, de-solder the encoder from the PCB, strip it and remove the little detent ring, re-assemble it, solder it back and now it feels much nicer to rotate with just a finger tip (you can see the little detent ring in the pic below, beside the USB/serial adapter).  The knob is a push fit on the splined encoder shaft.

It does work, but it is basically only a VFO spinner with long press of the knob to mute audio.

To re-programme it, I simply soldered a jumper wire from 3v3 to pin1 (as in the link above and then removed it after programming) but used a 4 pin header 'wedged' into the holes on the PCB adjacent the USB connector wired to an FTDI USB to serial converter for 5v/GND/Tx/Rx and held the header over by hand to make contact during programming.

It was a bit of fun to do, but as it stands, doesn't do much more than the scroll wheel of my normal mouse in Quisk and I wish I knew something about software to be able to maybe take it a step further as in adding another encoder for audio volume and possibly another button or two...

Click the images to go 'supersized'



It looks as though there are some pins available on the chip and the code could be tweaked - if only I knew what I was doing !!
Sure would be nice to get at least audio volume up & down at the least.
Anyone up for a coding challenge?





Sunday 8 December 2019

7 MHz interference

I've recently been plagued by some 7 MHz / 40 Metre interference.
Below is a screen grab from my SDR radio showing just how strong and wide the signals are.
I suspect VSDL and video streaming, but can't be sure.
During weekdays it usually starts late afternoon/early evening and at weekends, just about anytime.
Have you seen/experienced anything like it?

Click the image for a larger view...


I made a short video of the offending QRM, watch it on YouTube here:



Might be the 'Kontayner' OTH radar from Russia?  2nd one down, here:
https://www.sigidwiki.com/wiki/HF