Topics

#sdrconsole. Frequency activity in center spectrum

F1ssf_Franck
 

Good evening,
I try to understand why I have an activity in center on frequency spectrum. I can found this signal on alls bands .
Do you have an ideas ? Thank you very much  (I have Pluto)
73 Franck F1SSF

Simon Brown
 

Please attach the screenshot, adjust the contrast so we can see the waterfall!

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of F1ssf_Franck via Groups.Io
Sent: 12 February 2020 20:03
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] #sdrconsole. Frequency activity in center spectrum

 

Good evening,
I try to understand why I have an activity in center on frequency spectrum. I can found this signal on alls bands .
Do you have an ideas ? Thank you very much  (I have Pluto)
73 Franck F1SSF

Siegfried Jackstien
 

with low gain setting you see the phase noise of the clock near the 0hz spot ... when i crank up the gain a bit the phase noise is hidden from the input noise (depending on the strength of the input signal, antenna used etc etc)

that "activity he sees .. is the damned 0hz spot (plus a noisy clock) ... nothing magic

as better the clock as less phase noise can be seen ... and if there is enough input signal it is completely invisible

on my qo100 setup ... i see NO phase noise ... not with the funcubedongle ... and not with the pluto

(spectrum is so clean that i sometimes forget that there is that 0hz area we sdr users try to avoid)

greetz sigi dg9bfc

Am 12.02.2020 um 20:09 schrieb Simon Brown:

Please attach the screenshot, adjust the contrast so we can see the waterfall!

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of F1ssf_Franck via Groups.Io
Sent: 12 February 2020 20:03
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] #sdrconsole. Frequency activity in center spectrum

 

Good evening,
I try to understand why I have an activity in center on frequency spectrum. I can found this signal on alls bands .
Do you have an ideas ? Thank you very much  (I have Pluto)
73 Franck F1SSF

F1ssf_Franck
 

Hi Simon and Jack

See attached dump screen receiver without antenna (50U load resistor only)

You can see center activity, and an other on left. It is surprising, if I clic on left signal, it shifts on left !

 

I have not understand Jack the 0Hz spot ?

73 Franck f1ssf

 

 

De : main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> De la part de Siegfried Jackstien
Envoyé : mercredi 12 février 2020 21:20
À : main@SDR-Radio.groups.io
Objet : Re: [SDR-Radio] #sdrconsole. Frequency activity in center spectrum

 

with low gain setting you see the phase noise of the clock near the 0hz spot ... when i crank up the gain a bit the phase noise is hidden from the input noise (depending on the strength of the input signal, antenna used etc etc)

that "activity he sees .. is the damned 0hz spot (plus a noisy clock) ... nothing magic

as better the clock as less phase noise can be seen ... and if there is enough input signal it is completely invisible

on my qo100 setup ... i see NO phase noise ... not with the funcubedongle ... and not with the pluto

(spectrum is so clean that i sometimes forget that there is that 0hz area we sdr users try to avoid)

greetz sigi dg9bfc

Am 12.02.2020 um 20:09 schrieb Simon Brown:

Please attach the screenshot, adjust the contrast so we can see the waterfall!

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of F1ssf_Franck via Groups.Io
Sent: 12 February 2020 20:03
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] #sdrconsole. Frequency activity in center spectrum

 

Good evening,
I try to understand why I have an activity in center on frequency spectrum. I can found this signal on alls bands .
Do you have an ideas ? Thank you very much  (I have Pluto)
73 Franck F1SSF

HF Seattle
 

On Wed, Feb 12, 2020 at 01:02 PM, F1ssf_Franck wrote:
f1ssf
Hello Franck it is normal for a zero IF receiver you are looking at baseband that is the LO. Look online about Zero IF or homodyne same thing that should help.

jdow
 

The mantra goes:
1) Start with gain low
2) Tune to a weak signal.
3) Raise gain a step
4) Did perceived signal to noise ratio improve
5) If so go to 2 else back off one step.

That give you maximum sensitivity coupled with minimum IMD susceptibility.

{^_^}

On 20200212 12:20:03, Siegfried Jackstien wrote:
with low gain setting you see the phase noise of the clock near the 0hz spot ... when i crank up the gain a bit the phase noise is hidden from the input noise (depending on the strength of the input signal, antenna used etc etc)
that "activity he sees .. is the damned 0hz spot (plus a noisy clock) ... nothing magic
as better the clock as less phase noise can be seen ... and if there is enough input signal it is completely invisible
on my qo100 setup ... i see NO phase noise ... not with the funcubedongle ... and not with the pluto
(spectrum is so clean that i sometimes forget that there is that 0hz area we sdr users try to avoid)
greetz sigi dg9bfc
Am 12.02.2020 um 20:09 schrieb Simon Brown:

Please attach the screenshot, adjust the contrast so we can see the waterfall!

Simon Brown, G4ELI

https://www.sdr-radio.com

*From:*main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> *On Behalf Of *F1ssf_Franck via Groups.Io
*Sent:* 12 February 2020 20:03
*To:* main@SDR-Radio.groups.io
*Subject:* [SDR-Radio] #sdrconsole. Frequency activity in center spectrum

Good evening,
I try to understand why I have an activity in center on frequency spectrum. I can found this signal on alls bands .
Do you have an ideas ? Thank you very much  (I have Pluto)
73 Franck F1SSF

Siegfried Jackstien
 

At point 2. Tune that weak station a bit shifted away from 0hz spot!!!
Greetz sigi dg9bfc 

Am 13.02.2020 05:36 schrieb jdow <jdow@...>:

The mantra goes:
1) Start with gain low
2) Tune to a weak signal.
3) Raise gain a step
4) Did perceived signal to noise ratio improve
5) If so go to 2 else back off one step.

That give you maximum sensitivity coupled with minimum IMD susceptibility.

{^_^}

On 20200212 12:20:03, Siegfried Jackstien wrote:
> with low gain setting you see the phase noise of the clock near the 0hz spot ...
> when i crank up the gain a bit the phase noise is hidden from the input noise
> (depending on the strength of the input signal, antenna used etc etc)
>
> that "activity he sees .. is the damned 0hz spot (plus a noisy clock) ...
> nothing magic
>
> as better the clock as less phase noise can be seen ... and if there is enough
> input signal it is completely invisible
>
> on my qo100 setup ... i see NO phase noise ... not with the funcubedongle ...
> and not with the pluto
>
> (spectrum is so clean that i sometimes forget that there is that 0hz area we sdr
> users try to avoid)
>
> greetz sigi dg9bfc
>
> Am 12.02.2020 um 20:09 schrieb Simon Brown:
>>
>> Please attach the screenshot, adjust the contrast so we can see the waterfall!
>>
>> Simon Brown, G4ELI
>>
>> https://www.sdr-radio.com
>>
>> *From:*main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> *On Behalf Of
>> *F1ssf_Franck via Groups.Io
>> *Sent:* 12 February 2020 20:03
>> *To:* main@SDR-Radio.groups.io
>> *Subject:* [SDR-Radio] #sdrconsole. Frequency activity in center spectrum
>>
>> Good evening,
>> I try to understand why I have an activity in center on frequency spectrum. I
>> can found this signal on alls bands .
>> Do you have an ideas ? Thank you very much  (I have Pluto)
>> 73 Franck F1SSF
>>
>




F1ssf_Franck
 

Thank you alls,
I will read informations about zero IF, and I will experiment yours remarks.
It is important to understand what we are doing.
73 Franck

F1ssf_Franck
 

Good evening,
Yes I have understood Zero IF. at the output mixer there is directly audio frequency. OL is nearly equal at input frequency .
I have done some trying to transcribe in pratice.. I have selected 150Mhz on my generateur, but I can't find the exacte relationship between my input frequency, OL, image frequency.......on spectrum.
See an example screen, is somone can explain to me ?
Thank you 73 Franck