Forum: GNU Radio tvrx lna questions

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B6181960f99b31fbc050499839f98b81?d=identicon&s=25 Engin Karabulut (engink)
on 2009-03-24 16:09
(Received via mailing list)
hi all,
I have usrp and tvrx daughterboard,but tvrx sensitivity
is very bad, minimum input signal level is 40 dBuV(equal to-68dBm).
and noise figure is 8-10 dB. even if you have hi gain antenna, weak
signals die in TVRX. then I decided to purchase LNA next to antenna.
LNA that I chose is minicircuit's ZX60-33LN+.

http://www.minicircuits.com/pdfs/ZX60-33LN+.pdf

If I use this LNA,can I receive weak signals(like -100dBm)?

best regards.
3596cfe1d579c65b9babd35e8787977c?d=identicon&s=25 Matt Ettus (Guest)
on 2009-03-24 20:08
(Received via mailing list)
Engin Karabulut wrote:
> hi all,
> I have usrp and tvrx daughterboard,but tvrx sensitivity
> is very bad, minimum input signal level is 40 dBuV(equal to-68dBm).
> and noise figure is 8-10 dB. even if you have hi gain antenna, weak
> signals die in TVRX. then I decided to purchase LNA next to antenna.
> LNA that I chose is minicircuit's ZX60-33LN+.

The noise figure is 8-10 dB.  However, it is meaningless to say that the
minimum input signal level is -68dBm.  Sensitivity numbers only have
meaning if you also specify a modulation system, bandwidth, and error
rate.  -68dBm would be very bad for AM radio, but would be perfectly
reasonable for 802.11n.

There's no reason you couldn't receive a signal at -200dBm on any
receiver, as long as the bandwidth was low enough, and you filtered
narrowly enough.

Also, are you sure you are controlling the gain properly?

>
> http://www.minicircuits.com/pdfs/ZX60-33LN+.pdf
>
> If I use this LNA,can I receive weak signals(like -100dBm)?

That LNA has a noise figure around 1 dB.  If everything else remained
the same, you could receive a signal which was about 6 or 7dB weaker
than without the LNA.

Matt
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