[Elecraft] SWR bridge diodes

[Ron Willcocks]

OK Thanks Don and Tom,
                                             QRP below 5w is rarely used 
here on the K2. I pull the K1 out for those events.....
Anyway, I will get a bundle of 1N5711's off Elecraft next time I put an 
order in just to bring everything up to standard.  I'm sure I will need 
more eventually with the memory I have, even with a disconnect/grounding 
switch installed ....unless I make it switch automatically when I turn the 
K2 off [G]
73 ......Ron ZL1TW

At 07:53 a.m. 10/12/2006 -0500, you wrote:

>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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