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 disconnect or ground the antenna
when not in use so static surges from the antenna are not coupled back
to the diodes.
Clean the contacts on that roller inductor <G>.
73,
Don W3FPR
Brett gazdzinski wrote:
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 out.
500 watts of carrier into a G5RV generates some voltage!
I was thinking about higher voltage diodes, I have 1n34a's,
had 1N270's in, tried 1n914's last night but they don't
give enough output...
1N34a's are rated to 60 volts, but I guess it does not
matter if the inductor opens up.
I was just curious as to what is important in the circuit,
switching speed?, low voltage drop?
Thanks for the info,
Brett
N2DTS
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 best in the swr bridge of a high power
antenna tuner?
What is normally used, fast switching or what?
Thanks for any info,
Brett
N2DTS
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