[Elecraft] SWR bridge diodes

[Don Wilhelm]

Ron,

2 reasons for the use of 1N5711 diodes rather than 1N4148 (or even 1N34A) -
1) the 1N5711s have been shown to produce a more consistent voltage over the
frequency range than any of the others, and 2) the Shottky design has a low
diode drop (the 1N34A does too) which will produce readings that are more
correct at low powers (less than 2 watts).

With the KPA100 installed, the low power factor may not be a large
consideration for you, so the 1N4148s could stay, but if the greater
frequency dependency produces a problem, swap back to the 1N5711s.

Yes, keep those antennas shorted when not in use and when thunderstorms
approach.

73,
Don W3FPR

> -----Original Message-----

> Hi,
>       The other night I left my K2/100 and KAT100 still attached to the
> antenna, and we must have had a thunderstorm or the like pass through. I
> had been using the rig before I hit the sack, and everything was
> fine, but
> in the morning I got the dreaded "Hi Cur" warning if I tried to transmit
> anything higher than 10w.
> Subsequent testing proved the SWR bridge diodes in both the KPA100
> *and*  the KAT100 had changed from being diodes to short-circuits. A trip
> to the local (dead loss) Electronics store to get some more 1N1755 diodes
> produced 1 diode ! ( typical)
> What's a bloke going to do with the Christmas postal rush in full
> swing and
> Elecraft thousands of miles away?
> In the end I replaced the 4 diodes with common old 1N4148's and
> everything
> appears to be working fine......which brings me to the question......why
> are the 1N5711's used anyway? does their being Shottky diodes
> make them any
> better in this application?
>
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