4874Re: [perseus_SDR] Re: Amazing Preamp
- Apr 1, 2009Hello Alberto,
Thank you for the tuneable pre-amp information.
I have been using similar amplifiers for years and they work very well
There are some finer points to consider.
At full gain the bandwidth can be very small, especially at LF.
So small that it will effect the readability of a broadcast AM signal.
At 400 kHz it is easy to peak the signal at either sideband of a NDB with
1020 Hz modulation.
This problem can be solved by placing a 1 to 5 K RF-gain potentiometer at
Reducing the gain to 20 dB, the bandwidth is large enough for all
I have build one covering the 100 kHz to 1600 kHz range in four 1:2 bands,
with a gain variation of smaller than +/- 2 dB. This was not a trivial
task. See the attachment.
The amplifier is just a buffer and the (noiseless?) gain results from the
impedance transformation from low to high. Before PERSEUS, I used it to
prevent overload in my SPM-30 selective level meter.
With the excellent strong signal handling properties of PERSEUS, I do not
longer use it.
It has been used here also as a narrow band amplifier for an EWE antenna.
Is it possible to use SPICE for noise figure simulation of this amplifier?
Roelof Bakker, pa0rdt
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