[Hackrf-dev] LNA / Power Amplifier question.

[Dr. Johannes Gerstlauer]

3dB, that is the noise figure of the internal LNA (MGA81563). The total 
cascaded NF is much higher. It has been measured at 7dB. So, adding a 
good (NF=1dB) external LNA will result in an 5dB improvement of 
sensitivity. The additional cost of  $30  ("LNA4ALL") may be well worth it.
However, please keep in mind:
- the transmitting path to the antenna will be blocked by the external 
amplifier.
- the external amplifier can not be activated by the osmocom block under 
grc.
- the internal LNA can not be deactivated by the osmocom source block. 
It is always on.

John


> Thanks,
>
> SDR receiver noise figures seem to be in the 3 to 4db figure for 
> VHF/UHF. So you don't want to add too much more to that.
>
> Stefan
>
> On Sun, Nov 9, 2014 at 9:03 PM, Ariel Diaz 
> <adiaz133 at mail.valenciacollege.edu 
> <mailto:adiaz133 at mail.valenciacollege.edu>> wrote:
>
>     Thank you for your prompt reply. I couldn't find anything about
>     the NF on the hackrf but isn't it close to that figure? Or perhaps
>     too far from it?
>
>
>     Thanks,
>
>     AD
>
>     ------------------------------------------------------------------------
>     *From:* Stefan Wagener <wageners at gmail.com
>     <mailto:wageners at gmail.com>>
>     *Sent:* Sunday, November 9, 2014 5:17 AM
>     *To:* Ariel Diaz
>     *Cc:* hackrf-dev at greatscottgadgets.com
>     <mailto:hackrf-dev at greatscottgadgets.com>
>     *Subject:* Re: [Hackrf-dev] LNA / Power Amplifier question.
>     Well,
>
>     According to the specs it will give you more than 25db in gain.
>     What is not so good (actually pretty bad) is the noise figure with
>     6db. Good preamps in VHF/UHF should have less than 1db noise added
>     to the signal.
>
>     my 2 cents,
>
>     Stefan
>
>     On Sun, Nov 9, 2014 at 6:53 AM, Ariel Diaz
>     <adiaz133 at mail.valenciacollege.edu
>     <mailto:adiaz133 at mail.valenciacollege.edu>> wrote:
>
>         Hello all,
>
>         While looking for a low noise amplifier for receiving, I got
>         mixed up with the model numbers from mini-circuits and ended
>         up getting what I thought it was a good deal on some
>         amplifiers ZHL-1042J+
>         <http://www.minicircuits.com/pdfs/ZHL-1042J.pdf>. Anyways,
>         question would be, will this amplifier provide any gain on the
>         Rx signal(since I already have it in hand) not interested in
>         Tx. Or should I sell this and buy something else. Any input
>         will be greatly appreciated.
>
>         _______________________________________________
>         HackRF-dev mailing list
>         HackRF-dev at greatscottgadgets.com
>         <mailto:HackRF-dev at greatscottgadgets.com>
>         https://pairlist9.pair.net/mailman/listinfo/hackrf-dev
>
>
>
>
>
> _______________________________________________
> HackRF-dev mailing list
> HackRF-dev at greatscottgadgets.com
> https://pairlist9.pair.net/mailman/listinfo/hackrf-dev


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://pairlist9.pair.net/pipermail/hackrf-dev/attachments/20141110/14c46d7d/attachment.html>