Well, at the risk of offending Fred ...
A PIN diode has an intrinsic (I) region between the P and N junctions.
The I region is almost completely undoped and therefore the carrier
lifetimes are long relative to the frequency of the signal being
switched. A PIN diode is turned on with
On 2021-08-26 15:19, David Gilbert wrote:
Pedantic? If those were truly PIN diodes like you called them the
270v bias wouldn't have been used there.
Actually, I'm finding this interesting. So with real PIN diodes, you
don't have
to strongly bias them off?
The HV is obtained in various
Pedantic? If those were truly PIN diodes like you called them the 270v
bias wouldn't have been used there.
Dave AB7E
On 8/26/2021 2:56 PM, Fred Jensen wrote:
This morphed into a pedantic discussion of solid state diodes.
Chuck's original question was about the 270 V error. I'm fairly
This morphed into a pedantic discussion of solid state diodes. Chuck's
original question was about the 270 V error. I'm fairly sure the only
purpose for the 270 V in a KPA500 is bias for the T-R switch. He asked
for suggestions. The T-R switch and the source for the 270 V might be a
good
High voltage rectifier diodes would have very low doped N-regions, which
means fairly long carrier lifetimes so no doubt they work somewhat like
a PIN diode if properly biased. But they aren't really the same thing,
and I still say that a PIN diode has performance advantages in many
Using 1N4007's and 1N5208's ( I could have the last # wrong ) as "Poor
Man PIN
diodes" is pretty established practice in the amateur community. Look
up
W6JL on QRZ.com. He has an extensive article about it on his page
there.
Also Hans Summers of qrp-labs uses them in his 50W QSK amplifier.
My schematic shows TR Switch diode type is S1M. Datasheet easily found on-line.
I doubt this has any influence of 270 V failure.
Andy, k3wyc
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Help:
That sounds odd to me. True PIN diodes are current actuated devices.
The carrier lifetimes are long enough that the devices are "on" even if
the signal peaks exceed the voltage of the control current ... as long,
of course, as the control current exceeds the signal current.
On the other
I think the 270 V circuit is DC bias for the PIN diodes in the TR-switch.
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
On 8/26/2021 10:32 AM, Chuck Chandler wrote:
My KPA-500 has been running great for several years. Recently I noticed it
was making the occasional extra "click" or
Well if it were mine I'd check the voltage on the nominal 270 V connector on
the PA module then work back from there.
I keep notes from discussion of other peoples problems and their resolution.
You can find all this in the archive but this is what I have in my notes for
KPA 270 V problems:
My KPA-500 has been running great for several years. Recently I noticed it
was making the occasional extra "click" or "thunk" upon powering up or
down. Usually it would "click" when powered up and again when powered
down, but recently a few seconds after the first click there would be
another
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