Virtual Reality Sound Labs VR3 Mod

My mother emailed the other day with a request - provide her with an inexpensive way to broadcast streamed audio from the office computer to a radio in the shop. One of the guys in the shop listens to NPR which drives my mother nuts, she being an ultra-conservative.

Any of you tech savvy readers will probably think "no biggie. Just get an iPod transmitter and plug it into the computer." Great idea, but the radio is about 100' or so from the computer and through a concrete wall or two. Additionally, batteries will get expensive and purchasing a 12 volt power supply would be an added expense. I had a Virtual Reality Sound Labs VR3 on hand so I cracked it open and found out the chipset. After a quick search on the internet I found some specs on the FCC website, including the schematic for the transmitter circuit including the IC pinout. I found where the antenna connection was located on the PCB and powered up the unit. After testing to make sure the range was actually improved, it hit me - the schematic stated that the IC was running off 5v, I could power this off the computer's USB port. 

I grabbed an A-B USB cable and hacked off the unneeded end (B, I think). I soldered in the cable at the 7805 output and it worked. I then soldered in an RCA cable to the antenna solder pad and fired it all up. It works rather well in my tests with a Yaesu VX-5R as my receiver. Line of site it received about 75'; however, I was using a hand held receiver and there was local interference on the channel I was using. 

The cables both fit nicely where the fuse used to sit and I gorilla glued them in place. The whole thing is rather slick and I really don't want to part with it now. I don't know if it will transmit far enough for my mothers uses but she can probably just attach the antenna to the steel frame of the building and be fine.

The great thing about this mod is that you can still use the transmitter in your car with one of those 12V-USB adapters. It also works with SD card readers so you can play from pretty much any flash media. If you have any questions about anything I did, comment this post and I'll hit you back.