[TowerTalk] Relay lightening protection

[Jim Hargrave]

   >Those sorts of tradeoffs are why they pay engineers to design
   >things..eh?

I told myself not to enter this endless discussion. However the above
comment got my attention.
I fully agree with the statement especially when it comes to engineering Car
batteries.

They are the most proficient engineers in the country. They reliably program
a 36 month battery to fail at 37 months etc....

Regardless of what the engineers say, I have always used diodes/resistors to
protect the switching transistors. I have never had a failed relay coil in
my 55 years as a Ham. However the lack of, or failure of the swamping diode
will almost assuredly result in the eventual failure of the relay switching
transistor. As the operating coil voltage increases, this becomes more of a
necessity with solid state switchers. The old tube switchers were a lot more
forgiving and in most cases the swamping diode was not required.

Common sense usually bridges the gap between paper engineering and practical
operation.


   * 73's Jim W5IFP *