Project update 7 of 8
Hey there, backers and subscribers. Recently, we’ve received several messages in different social media platforms about supporting ham radio frequencies. Don’t worry, we got you!
As you might know, we initially planned to have an up-converter mixer to extend the receiving frequency range, but the initial performance was not great. Since receiving early feedback on this feature, part of our team really puzzled to get it working. After a few fixes, experiments, and tweaks of hardware and some software optimization, we made it usable! It’s available in native mode (e.g., GQRX) and in the web interface as well.
We’re using an LTC5562IUC mixer in an up-converter configuration with LO around 300 Mhz. LO is generated by the SI5332A chip we’re using for variable ADC/DAC clock generation. Also, we decided to add LPF filter with a cutoff <400 Mhz to get rid of unwanted mirrors and harmonic signals in the final product revision.
The uSDR has a dedicated antenna port for HF/VHF because antenna switching IC limits lower frequency range and you’ll need a special low-frequency antenna anyway.
(This configuration doesn’t have an LPF, but we’ll add one in the final product)
To test the radio band, we used a simple 1:9 antenna balun with ~30 feet of wire connected to it. The reception was okay.
The FM band works fine as well on the same antenna.
So you’ll be getting a ~1Mhz-300Mhz receive extension at no additional cost, all uSDRs will be equipped with an external mixer. This change doesn’t affect projected shipping dates since all the changes are being integrated into manufacture documentation now.