[ICOM] Icom, Grounds and Mikes

[William Lambing]

Audio can be a real problem.....in aircraft.  Baker Electronics (in Florida) developed, years ago, what they called "SPASE".  That being Single Point Audio System Earth.  Shielded wires were grounded at one point only and this point was a "Single Point" ground.  Nice idea in theory, in practice...gets to be a real bear.  The concept, as has been discussed is a great idea.  One point to ground everything.  But, as stated, in practice gets to be a real hair tearer outer..!  Some insisted that the transmit (source) be grounded.  Others insisted just the opposite.  Both had problems.

Data Busses usually have grounds at both ends.  It is a form of transmission line.  One organization took the Baker solution into the Data Buss realm.  Remember data busses are high speed (read high frequency). In one installation, the ground return was exactly 1/4 wl at 120.0 mhz.  Right in the middle of the comm band.  Needless to say, they had problems that took weeks to cure.  The ground turned into an antenna and radiated.

I do not know the real answer.  I know what worked with airplanes.  But, I tend to agree with Sheldon and others, too many ground returns can be a real pain.  This is what Bill Diamond found out with his mics.

If someone finds a good solution, let us all know.  I have followed this thread with great interest.  I would bet that no two installations will be totally identical.

Keep the info coming.

73

Bill, W0LPQ