Forum: GNU Radio manually dc offset useful

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feldmaus (Guest)
on 2009-03-31 17:51
(Received via mailing list)
Hi All,

At this time i am thinking is the dc offset, which i tried to
set up for my db LFRX, useful ?
Or is it useful to disable the automatically dc offset loop ?

The dc offset changes every time depending on the temperatur
and the decimation and maybe other factors !?

So is the use of LFRX useful for measurement device ?

I want to measure some unknown peaks from dc to 1.5MHz, with
a gnuradio peak detector.

My big Problem is the unknown peak in the middle of my FFT-Plot,
which also may influence my Measurement ?

Any comments ?

Regards Markus
feldmaus (Guest)
on 2009-04-01 11:47
(Received via mailing list)
feldmaus <feldmann_markus <at> gmx.de> writes:

> Any comments ?
>
I noticed that the dc offset changes if i change the frequency forward
and then back to last frequency.

Will the automatic dc loop enabled if i change the frequency ?

Regards Markus
feldmaus (Guest)
on 2009-04-01 12:02
(Received via mailing list)
feldmaus <feldmann_markus <at> gmx.de> writes:

> Any comments ?
>
I also noticed the dc offset, which is needed, changes from
signal generator to signal generator.
Could this be true ?
How to avoid this ?

Regards Markus
Don W. (Guest)
on 2009-04-01 17:10
(Received via mailing list)
"feldmaus" <removed_email_address@domain.invalid> wrote:

> I also noticed the dc offset, which is needed, changes from
> signal generator to signal generator.
> Could this be true ?
> How to avoid this ?

With the LFRX, the DC offset will depend on the DC resistance of your
signal
source.  You need 50 ohms (at DC) on the input to get (approximately)
zero
offset.

-- Don W.
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