Archive for January 14th, 2016

Ham It Up Noise Source

An RTL-SDR receiver & Ham It Up RF upconverter arrived, with the intent of poking at LF signals. The upconverter circuit board also contains a mostly populated RF noise source:

Ham-It-Up v1.3 noise source - schematic

Ham-It-Up v1.3 noise source – schematic

Being a sucker for noise sources, I spent some time pondering the circuitry.

The as-built board has a 0 Ω jumper instead of the 6 dB pad along the upper right edge:

Ham-It-Up v1.3 - noise components

Ham-It-Up v1.3 – noise components

The previous version had a pi bandpass filter in place of the pad and you could certainly repopulate it with two caps and a teeny inductor if you so desired.

I added the SMA connector, which isn’t quite identical to the IF output connector above it:

Ham-It-Up v1.3 - noise SMA

Ham-It-Up v1.3 – noise SMA

That will require a new hole in the end plate that I’ll get around to shortly. It also needs an external switch connected to the Enable jumper, but that’s in the nature of fine tuning.

I’m awaiting a handful of adapters & cables from halfway around the planet…