I used ExpressPCB to build the boards, and built up three units. This is what they look like….

I decided to try my hand at building my own transmitter module. I did this mostly to save weight rather than lofting a heavy handheld radio. The Radiometrix 300mw HX1 radio seemed to be a solution that worked for many,  so my brother and I bought three of them and proceeded to design the custom radio module.

I started with some simple design goals:

• Low battery voltage cutoff feature
• Interface that matches the TinyTrak
• Pre-emphasis circuit to compensate for the digital only nature of the transmitter module
• SMA output

Circuit Diagram