USB and Noise in Audio

If you connect your Radio to your computer, you may have noise which is generated by the computer and is relatively independent of the quality of your USB > Audio interface and what you have paid for it. There is a solution for that which took me some time to find. You will find it i.e. in Amazon as “USB Isolator 5000 V signal isolation – Interference Suppressor – ultra low noise” This little device which costs 30€ or 35 US$ really eliminates a sound which is a kind of beeping which changes in the pitch when the computer goes busy or you move the mouse. I installed it between my USB-Hub and the USB-Audio Adapter and the noise was gone.

These adapters support USB full speed, USB audio class 1.0 up to 24bit/96kHz, but do not work USB Audio Class 2.0. Higher speeds than 12Mb/s are not supported.

If you use studio equipment like I do, it is likely that the noise will be eliminated anyway by the input and output transformers of the studio equipment. Also a so called studio “DI-Box” may help. I have integrated a Behringer Ultra-DI Pro Mod. DI4000 which costs as much as two of the USB Isolators but has 4 channels and gives me in addition the flexibility to adjust Line- and Microphone Level on all 4 In-/Outputs to my needs. My supplier for all kind of studio equipment and microphones here in Germany is Thomann which delivers worldwide and is often cheaper than amazon.

See also Mic-/Line Level and XLR in the audio posts

Creating the right Windows PC

Since 4+ years a multi-media PC with a small form factor, quite powerful and with a lot of interfaces (WLAN, LAN, 4 USB-2, 2 USB-3, surround sound, mic, speakers, optical and coax digital in- and outputs, hdmi, vga and dvi) was standing unused in the living room and was now selected as the perfect victim for my new amateur radio activity. with 4GByte of RAM definitely too low on storage but the harddisk with 500GByte ATA Interface big and fast enough. Upgraded the memory to 16GByte, bought a Windows 7 professional license (Windows 10 is too much for my taste) and installed the base system. After 4 days all 300+ windows patches were downloaded and together with about 50 restarts installed.

OK,  the thing was finally up !

As the first radio which I bought was a Yaesu FT-857D, I got the CAT-Serial to USB Interface-Cable and the SignaLink USB Modem installed as prescribed in the manuals and it worked together with the applications nearly everyone uses, from FlDigi, FlRig to HRD and so on, like a charm. Unfortunately the SignaLink has it’s own VOX PTT, which makes it difficult to use the SignaLink as a modem for voice from the computer to the radio. If you run your microphone signals through sound processing software in the PC, every noise around you triggers the VOX PTT in the SignaLink and makes the Radio transmit.

For sure I am not telling you new stuff here, but my aim was to have a complete remotely controlled setup in my shack which I can use from anywhere in the world without modifying my router, creating DYNdns entries, piercing the firewall (opening incoming ports) of the DSL-Router, just to have one or two applications remotely available. I wanted the whole PC and all radios everywhere and on other computers (independent of operating system), mobile devices (Android and iOS) and for experiments also on a Raspberry Pi 3+ or higher.

Furthermore I wanted when in the shack a complete wireless setup, that I do not have to be glued to the chair in front of the radios, including wireless PTT.

How to do this I explain in the following posts.