I believe he is looking for something more like an antenna
coupler/tuner used in HF applications to tune and impedance match for
maximum power transfer:
http://en.wikipedia.org/wiki/Antenna_tuner
As for not talking about hardware on the GNU Radio mailing list - I
find that a little silly. While GNU Radio is more about a framework
for processing baseband signals, there's also the real need to
interface to the outside world. Dynamic range, gain, and all the
little hardware bits in the radio front end are all valid discussion
points and completely on topic, in my opinion.
Brian
I agree with Brian. If it's radio related and kinda-sorta touches on
SDR, it's a valid thing to discuss here.
A quick google yielded this:
http://www.universal-radio.com/catalog/hamtune/0323.html
There are probably others.
Also, some of the HF-only SDRs out there have a built-in switchable
filter bank.
Once you move beyond HF, it becomes increasingly difficult to *decide*
where to put your filter responses, which is why SDRs that are intended for
"DC to light" use tend not to have much in the way of front-end
selectable filters -- any choice the manufacturer makes would likely be
"wrong" in
as many cases as "right". Any any filters in the front-end, before
the first gain stage, will contribute to an increase in noise figure.
So you have to
filter after the LNA stage to maintain noise figure, but you're
still, then, in the tenuous situation of likely continuing to run into
analog non-linearity
problems with strong signals within the DC-light passband of the
first-stage LNA.
What we need is either:
(A) Microwave filters that have impossibly-low insertion loss (made
from super-cooled unobtanium, likely)
or
(B) HEMT/GaAs/SiGe transistor technology that can offer insanely-low
noise figure at the same time as offering insanely-high linearity, like
OIP3 of +50dBm with small-signal gains of 25dB or better, and
1dB or better noise figures :-)
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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