Coach Thrasher

Cox Box Interference

We experienced some interesting behavior from our cox box recording device today. The first cox box we used had a battery die - most likely because it wasn't fully charged. But the second box we used emitted a humming sound. When our coxswain touched the metal BNC connector on the Pelican box the humming would stop. This happened while we were on the water, after about 45 minutes of rowing.

Propable causes for the humming could be:

• faulty coax cable (short between shield and inner conductor, bad F connector crimp)
• impeadance mismatch (I'm using 75 ohm cable TV coax, instead of 50 ohm cable)
• Speaker short to ground
• RF interference
• the straight copper connector to the digital recorder

I'll have to do some investigation to find the problem. Right now we're not using the radios hooked into the cox box until we can get the digital recorder working smoothly.

Today's setup had our coxswain (Meredith Bohling) holding the Pelican box in her lap. This was a little cumbersome because it was one item that she shouldn't have as a distraction. I'd like to make a longer coax cable and mount the Pelican behind her, on the stern deck, or create a gunwale mount for rowing instrumentation. I think the later would be easier, and keep cable runs short.

Posted at 12:47PM Feb 02, 2006 by jason in Rowing  |  Comments[0]