Tom,
The modification you mention for using a BF981 with the KD9SV preamp is as
follows :
Install a 22 ohm resistor between the 100 ohm resistor and the source of
the dual gate mosfet. The 100 ohm resistor is currently connected to the
source of the dual gate mosfet and ground, so you need to cut the trace that
connects the 100 ohm resistor to the source of the dual gate mosfet and
place the 22 ohm resistor across this cut in the trace.
When done with the mod you will have a 22 ohm resistor connected to the
source of the mosfet, and then a 100 ohm resistor connected to the other side
of this 22 ohm resistor and ground (with a 0.1 or 0.05 ufd cap in parallel
with the 100 ohm resistor).
(The 100 ohm resistor and the 0.1 or 0.05 ufd cap already exist in your
preamp, you are just adding the 22 ohm resistor as described above).
I obtained this info direct from Gary (KD9SV) a few months ago.
Don
In a message dated 3/5/2011 11:09:53 A.M. Eastern Standard Time,
thomas.hoeppe@asamnet.de writes:
Hello Topbanders,
today I forgot to hook the keying line to my KD9SV preamp. I destroyed the
OMRON G6A relay, witch bypasses the preamp. It is available in DL.
The problem is the 3SK88 transistor. I heard KD9SV is now using BF-981
with a small modification (cut one trace and add one resistor)
Anyone knows the details?
TNX in advance!
Tom, DJ5RE
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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