Larry Kayser wrote:
> For me, my concerns with solid state is to have an effective
> controller that will protect my investment. After some consideraton
> what I want is a G3SEK type box that will look after my dollar
> investment in solid state RF modules.
Very tricky, unless the operating conditions are chosen to keep the device
within survival limits either all the time, or at least long enough for
protection to kick in. More often than not, the ultimate cause of a device
blowing is the die overheating, whether that's caused by bad load VSWR, or
spurious oscillation, or whatever. Under bad fault conditions, the die will
heat to destruction in the order of 100us. Detecting a fault and removing
power in that sort of timescale while maintaining proper lf decoupling is
not so simple.
>
> I am basing this on my experience in the LF world, 136 KHz where I had
> an ex Decca amplifier, MosFets at up to 100V and 30 Amps and more, yet
> it was unconditionally protected, antenna ON or OFF it did not matter
> - the amplifier was protected by a wonderful protection design.
I'd guess that the choice of output transistor was more significant than the
complexity of the protection circuitry - it's the combination of the two
that delivers.
Steve
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