RE: [amsat-bb] Converter Protection

[Tony Langdon <tlangdon@xxxxxxxxxxxxxxxxxx>]

> All of us will at sometime transmit into a converter or 
> pre-amp.  One of the
> great advantages of being a home brewer is that the repair of 
> your equipment
> is usually trival after one of these mistakes.  Been there, 
> smoked it :-)!

Hehehe, I haven't yet, as all my "converters" are actually transverters.
Have shoved 25W where 1W should go, but not for long enough to cause damage.
I'm planning on transverters for my AO-40 station as well.  Might sound like
overkill, but I would like to use the gear for VHF/UHF Field Days as well as
satellite, and the higher bands are great point scorers in these contests.
:-)  As I already have an established "standard" of a 1W PEP power level for
2m interconnects, this is likely to be factored into the design of the new
transverters.  Speaking of transverters, for 10m - 2m, overloading the
transverter isn't an issue anyway, it's driven by an IC-745, using the
transverter output.  I leave the transverter permanently connected, and use
the transverter control line to switch between 2m and HF.  Incidentally,
this is the setup I use for the AO-40 beacon, it's more sensitive than my 2m
multimode box, and has much nicer VFO action.

> In practical terms your best protection is a squencer.  The ARRL 
> handbook has an excellent design for one.  I modified mine so when I 
> turn on the power for the "S" converter, I disable the two 
> meter rigs PTT.
> This took only the addition of a couple of switching diodes 
> as I recall.
> Turning on the power also activates the coax relay that switches the
> radio from its normal antenna to the converter output.

Neat idea!  

> Another idea I have seen is to use a MMIC amp stage in line with the
> converter as a sort of RF fuse.  In other words, if there is 
> an accident,
> you burn out the $1.50 MMIC (like a ERA-1 or MAR-1, etc) instead of
> the expensive guts of your converter.

Provided the power doesn't sneak past the MMIC, this might be a good
strategy.  I agree, would much rather smoke one of these than a whole
converter. :)
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