After the long and good use of the MGF1302
preamplifier designed by DJ9BV in the 90th...i decided
in winter 2012 to give my preamplifier an update.
Some is written about the use of preamplifiers in past...but
for EME there is the right goal to use the "best you can
So I needed a preamplifier with lowest noise
availiable, stability, linearity and selectivity.
At first I decided to go on the well known PA3BIY design
published in DUBUS some years
ago but there are no PCBs availiable anymore.
Then I found on the I0JXX homepage an interesting
information and also availiable PCBs.
I started an simulation and made an redesign of the preamp
with some small modifications on the
input circuit and on the working point of the transistor.
The preamplifier is working stable even with open input
UPDATE: APRIL 2012+ MAY2012
because of some detected instabilities with open cable on
the input i changed the value
of L1 to 4 turns 0.75mm CUL with 4.2mm inner
and I optimized the output bandpass filter to give a
Here is the modified circuit. (with permission of I0JXX)
Here are my simulation results using the modified components
(using ANSOFT DESIGNER SV)
S21, S11 and S22 after OPTIMIZATION of the BANDPASS FILTER
S21 (GAIN) is 24.8dB @ 145MHz, 0dB @ 115MHz and 0dB
S11 (INPUT RETURN LOSS) is
around 6 dB @ 145 MHZ
S22 (OUTPUT RETURN LOSS) is > 20dB @ 145 MHZ
VIEW OF THE PROTOTYPE
If you need more information please write an email