Re: gain in SG

[john brzustowski]

On Tue, May 17, 2016, at 09:08, Dmitry Kishkinev wrote:

> What is an analogue of "gain" we set at LOTEK receivers for SG? Is it "SNR"
> parameter in deployment.txt or something else? Thanks.
>
> Dmitry
> PhD, Research Fellow,
> School of Biological Sciences,
> Bangor University,
> Bangor, Gwynedd, UK
> Email: dmitry.k...@gmail.com;
> *d*.kish...@bangor.ac.uk <kish...@qub.ac.uk>
> Mobile phone: +44-(0)77-194-181-41

The minSNR parameter in deployment.txt is a filter setting: it only
allows pulses of at least X dB above "background noise" through.
Setting it lower will result in larger file sizes, but may also
increase detection range a bit. Test this before long-term
deployment if you plan on changing it.

Lotek's gain parameter is a hardware amplification setting, and there
are three of these available on the funcubedongle Pro+. The SG
doesn't currently provide a graphical interface to change these
settings while running, but you can configure a fixed value in
deployment.txt:

- lna_gain ("low noise amplifier gain") is 0 or 1 (default 1);
amplifies everything coming into the antenna, in or out of the
desired listening band

- mixer_gain is 0 or 1 (default 1); amplifies what comes out
of the mixer, which should be only frequencies in the listening
This gain is around

- if_gain is 0...29 in dB; default is 0; further amplifies output of
the mixer by the given number of dB.

Older funcubedongles ("Pro" without the "+") have a more complicated
set of gain parameters.

If your current deployment.txt file doesn't include settings for these
parameters, you can find a version that does here:

http://public.sensorgnome.org/default_deployment.txt

We haven't done any testing on the effects these parameters have
on detection range, except that turning off lna_gain can be helpful
at very noisy sites where detection range is not too important
(we did this on an offshore gas platform where it was only birds
close to the platform which were of interest; the platform had
very high levels of radio noise).

It is possible that setting if_gain to positive values will increase
detection range, likely at the cost of larger file sizes.

Sorting this out is high on our TODO list once the sensorgnome/motus
transition is working.
--
J.