I looked at the ones in the K2 antenna tuner,
but was not sure about the power rating.
My heathket tuner has blown out its diodes for the 2nd time,
and they are not identified in the diagram.
I suspect my roller inductor goes open (its worn out)
and allows a voltage spike to take the diodes
Brett,
The voltage rating and the forward voltage drop are the two most
important. The 1N5711 diodes seem to have a flatter output vs.
frequency characteristic than the 1N34s.
There are 2 cures to the blown diode problem - first is to do any tuning
at low power levels, and second is to
The 1N34 is a Germanium diode and will have a lower forward voltage drop
than a standard PN junction Silicon diode - so will work better on small
signals.
Low barrier Schottky diodes designed for small signals, like the 1N5711
should have performance similar to the 1N34, but will usually have
I've never had a problem with roller inductors IF they are clean.
They don't have to be shiny silver. Silver oxide (the dark black stuff that
forms on real silver) is an excellent conductor! If it offends your
sensibilities, use a tiny bit of silver polish to clean it up, but it has
nothing to
Brett,
Choices abound - 1N34s are common, 1N5711s work well. It mainly depends
on the directional coupler design. See chapter 27 of the ARRL Antenna
Book for additional information and projects.
73,
Don W3FPR
Brett gazdzinski wrote:
Anyone have any idea what sort of diodes
would work
Use a 1N5711. Breakdown voltage is 70 volts and voltage drop across the
diode is only a few tenths of a volt at low current. It makes a reasonable
detector up to 500 MHz.
-John
KI6WX
Anyone have any idea what sort of diodes
would work best in the swr bridge of a high power
antenna tuner?
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
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
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