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For my power amp for 20 meters I built
a 5 pole Chebychev filter-2 -0.9 uH inductors 270 pf for input
and output caps and 430 pf for the center cap. This is a 75 ohm
design, my dipoles are closer to 75 ohms then 50. At 42 MHz the
filter has a theoretical insertion loss of 60 dB. With a 2 pf cap
from input to output the insertion loss drops to -57 dB. If the
relay's capacitance is around 2 pF from input to output in the
board, I seriously doubt this is the root cause of the non
compliance issue. Something else is amiss. I am going to be
working on these issues over the next few days and will report my
On 8/4/2018 9:10 PM, Gordon Gibby wrote:
Looking closer at what you folks (Warren the first to report...)
E.g.: “In my testing I also found the isolation across one
relay was barely 45db in one configuration and 50 in
another.Using one relay to switch both ends of a filter will
compromise the filter “
It may be worth it to now
look at the physical construction of the relays first.
Perhaps there is a way to insert a shield between sets of
contacts. I have it disassembled any of mine yet and couldn’t
find an image but the construction might be similar to this:
On Aug 4, 2018, at 20:07, ajparent1/KB1GMX <kb1gmx@...
Tim, no on the Diz amp.
First mine is linear (class AB1 150ma per irf510), the base
amp was class C.
About all I did use was a few passives and the board itself.
Used a differnt wind for
all the coils going from bipolar to mosfet FYI the results
were at 13.6V. At 20V
it does a nice 16W and the 10M power is 10W. Power supply
runs out at 20V
and I didn't need that much anyway but had to turn it up and
see. Due to the
really good RF layout of the board it has proved to be
stable and blast proof.
Years of design and build I have a lot of unobtainium and
And a junk box with stuff that dates back to the 60s. I
lived in Grumman