Topics

Baseline

Allan Isaacs
 

I'm looking at signals below the broadcast band so I made a low pass filter which is set to around 110KHz to avoid cross modulation etc. from broadcasts.
It gives me an attenuation of 40-50dB at 190KHz and broadcast stations are so strong they are easily audible even with 50dB attenuation from the low pass filter..
I now notice my Andrus behaves a little differently with the filter in place. I cannot see baseline noise, just a flat line if I increase the gain to 0dB or -12dB..
Previously, any gain setting of greater than -24dB resulted in cross modulation of VLF signals so the filter is doing its job.

My question:  Is it possible to reduce the display cut off  below -150dBm which is position of the flat line?
I can add -160dBm using View, Scale, Low but the flat line stays at -150dBm
If I set the gain to say -24dB or -30dB from 0dB the baseline noise becomes visible but signal to noise is poor. Increasing the gain to -12dB improves S to N and to 0dB improves S to N even more but both settings give me a flat line as in the attached picture. Am I missing a setting or is it a limitation of an AD converter?
Allan G3PIY

Simon Brown
 

Allan,

 

I could reduce the cut-off below -150dBm but I don’t really want to – these signals do seem to be very weak.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Allan Isaacs
Sent: 24 March 2020 18:33
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Baseline

 

I'm looking at signals below the broadcast band so I made a low pass filter which is set to around 110KHz to avoid cross modulation etc. from broadcasts.
It gives me an attenuation of 40-50dB at 190KHz and broadcast stations are so strong they are easily audible even with 50dB attenuation from the low pass filter..
I now notice my Andrus behaves a little differently with the filter in place. I cannot see baseline noise, just a flat line if I increase the gain to 0dB or -12dB..
Previously, any gain setting of greater than -24dB resulted in cross modulation of VLF signals so the filter is doing its job.

My question:  Is it possible to reduce the display cut off  below -150dBm which is position of the flat line?
I can add -160dBm using View, Scale, Low but the flat line stays at -150dBm
If I set the gain to say -24dB or -30dB from 0dB the baseline noise becomes visible but signal to noise is poor. Increasing the gain to -12dB improves S to N and to 0dB improves S to N even more but both settings give me a flat line as in the attached picture. Am I missing a setting or is it a limitation of an AD converter?
Allan G3PIY

Allan Isaacs
 

OK Simon

Don’t worry. I thought it might have been something I hadn’t clicked on.

I’m using a 9:1 unun probably more HF orientated that I could remove, and there’s a 50 ohm resistor I might chop out to recover 10dB more signal.

Experiments continue.

73 Allan G3PIY

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Simon Brown
Sent: 24 March 2020 21:05
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Baseline

 

Allan,

 

I could reduce the cut-off below -150dBm but I don’t really want to – these signals do seem to be very weak.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Allan Isaacs
Sent: 24 March 2020 18:33
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Baseline

 

I'm looking at signals below the broadcast band so I made a low pass filter which is set to around 110KHz to avoid cross modulation etc. from broadcasts.
It gives me an attenuation of 40-50dB at 190KHz and broadcast stations are so strong they are easily audible even with 50dB attenuation from the low pass filter..
I now notice my Andrus behaves a little differently with the filter in place. I cannot see baseline noise, just a flat line if I increase the gain to 0dB or -12dB..
Previously, any gain setting of greater than -24dB resulted in cross modulation of VLF signals so the filter is doing its job.

My question:  Is it possible to reduce the display cut off  below -150dBm which is position of the flat line?
I can add -160dBm using View, Scale, Low but the flat line stays at -150dBm
If I set the gain to say -24dB or -30dB from 0dB the baseline noise becomes visible but signal to noise is poor. Increasing the gain to -12dB improves S to N and to 0dB improves S to N even more but both settings give me a flat line as in the attached picture. Am I missing a setting or is it a limitation of an AD converter?
Allan G3PIY

_._,_._,_

 

Siegfried Jackstien
 

does he have "visual gain" also?!? (depending on used hardware the gui or frontend is different)

here in my pluto settings i have gain (manual) and visual gain (shifts the whole shebang up or down)

with the funcube dongle visual ain is in 5 db steps (simon can you make that a bit finer in 1 db steps like in pluto with a slider?!?)

no need to set cutoff lower to 160... he just have to shift that up with visual gain

dg9bfc sigi

Am 24.03.2020 um 21:05 schrieb Simon Brown:

Allan,

 

I could reduce the cut-off below -150dBm but I don’t really want to – these signals do seem to be very weak.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Allan Isaacs
Sent: 24 March 2020 18:33
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Baseline

 

I'm looking at signals below the broadcast band so I made a low pass filter which is set to around 110KHz to avoid cross modulation etc. from broadcasts.
It gives me an attenuation of 40-50dB at 190KHz and broadcast stations are so strong they are easily audible even with 50dB attenuation from the low pass filter..
I now notice my Andrus behaves a little differently with the filter in place. I cannot see baseline noise, just a flat line if I increase the gain to 0dB or -12dB..
Previously, any gain setting of greater than -24dB resulted in cross modulation of VLF signals so the filter is doing its job.

My question:  Is it possible to reduce the display cut off  below -150dBm which is position of the flat line?
I can add -160dBm using View, Scale, Low but the flat line stays at -150dBm
If I set the gain to say -24dB or -30dB from 0dB the baseline noise becomes visible but signal to noise is poor. Increasing the gain to -12dB improves S to N and to 0dB improves S to N even more but both settings give me a flat line as in the attached picture. Am I missing a setting or is it a limitation of an AD converter?
Allan G3PIY

Allan Isaacs
 

I do not have any adjustments Sigi, just Gain which has 4 settings: 0, -12, -24 and -30dB; no visual gain. The SDR is the Andrus Mk1.5 which runs over my Ethernet.

Two gain settings 0 and -12dB are not useable with a large aerial due to overloading so I have made a low pass filter which now allows me to use 0 and -12db on the VLF band where the aerial is short in respect of wavelength. If I use that aerial for VLF without a filter I get cross mod and spurii from long wave broadcasts.

73 Allan G3PIY

 

 

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Siegfried Jackstien
Sent: 25 March 2020 13:43
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Baseline

 

does he have "visual gain" also?!? (depending on used hardware the gui or frontend is different)

here in my pluto settings i have gain (manual) and visual gain (shifts the whole shebang up or down)

with the funcube dongle visual ain is in 5 db steps (simon can you make that a bit finer in 1 db steps like in pluto with a slider?!?)

no need to set cutoff lower to 160... he just have to shift that up with visual gain

dg9bfc sigi

Am 24.03.2020 um 21:05 schrieb Simon Brown:

Allan,

 

I could reduce the cut-off below -150dBm but I don’t really want to – these signals do seem to be very weak.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Allan Isaacs
Sent: 24 March 2020 18:33
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Baseline

 

I'm looking at signals below the broadcast band so I made a low pass filter which is set to around 110KHz to avoid cross modulation etc. from broadcasts.
It gives me an attenuation of 40-50dB at 190KHz and broadcast stations are so strong they are easily audible even with 50dB attenuation from the low pass filter..
I now notice my Andrus behaves a little differently with the filter in place. I cannot see baseline noise, just a flat line if I increase the gain to 0dB or -12dB..
Previously, any gain setting of greater than -24dB resulted in cross modulation of VLF signals so the filter is doing its job.

My question:  Is it possible to reduce the display cut off  below -150dBm which is position of the flat line?
I can add -160dBm using View, Scale, Low but the flat line stays at -150dBm
If I set the gain to say -24dB or -30dB from 0dB the baseline noise becomes visible but signal to noise is poor. Increasing the gain to -12dB improves S to N and to 0dB improves S to N even more but both settings give me a flat line as in the attached picture. Am I missing a setting or is it a limitation of an AD converter?
Allan G3PIY

 

Siegfried Jackstien
 

so then ask simon to add visual gain ... :-)

greetz sigi dg9bfc

Am 25.03.2020 um 14:41 schrieb Allan Isaacs:

I do not have any adjustments Sigi, just Gain which has 4 settings: 0, -12, -24 and -30dB; no visual gain. The SDR is the Andrus Mk1.5 which runs over my Ethernet.

Two gain settings 0 and -12dB are not useable with a large aerial due to overloading so I have made a low pass filter which now allows me to use 0 and -12db on the VLF band where the aerial is short in respect of wavelength. If I use that aerial for VLF without a filter I get cross mod and spurii from long wave broadcasts.

73 Allan G3PIY

 

 

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Siegfried Jackstien
Sent: 25 March 2020 13:43
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Baseline

 

does he have "visual gain" also?!? (depending on used hardware the gui or frontend is different)

here in my pluto settings i have gain (manual) and visual gain (shifts the whole shebang up or down)

with the funcube dongle visual ain is in 5 db steps (simon can you make that a bit finer in 1 db steps like in pluto with a slider?!?)

no need to set cutoff lower to 160... he just have to shift that up with visual gain

dg9bfc sigi

Am 24.03.2020 um 21:05 schrieb Simon Brown:

Allan,

 

I could reduce the cut-off below -150dBm but I don’t really want to – these signals do seem to be very weak.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Allan Isaacs
Sent: 24 March 2020 18:33
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Baseline

 

I'm looking at signals below the broadcast band so I made a low pass filter which is set to around 110KHz to avoid cross modulation etc. from broadcasts.
It gives me an attenuation of 40-50dB at 190KHz and broadcast stations are so strong they are easily audible even with 50dB attenuation from the low pass filter..
I now notice my Andrus behaves a little differently with the filter in place. I cannot see baseline noise, just a flat line if I increase the gain to 0dB or -12dB..
Previously, any gain setting of greater than -24dB resulted in cross modulation of VLF signals so the filter is doing its job.

My question:  Is it possible to reduce the display cut off  below -150dBm which is position of the flat line?
I can add -160dBm using View, Scale, Low but the flat line stays at -150dBm
If I set the gain to say -24dB or -30dB from 0dB the baseline noise becomes visible but signal to noise is poor. Increasing the gain to -12dB improves S to N and to 0dB improves S to N even more but both settings give me a flat line as in the attached picture. Am I missing a setting or is it a limitation of an AD converter?
Allan G3PIY

 

jdow
 

Insert a large attenuator - as much as 30 dB. Of course, really low frequencies will suffer. A sharp high quality 450 kHz LPF will do wonders.
{^_^}

On 20200325 07:41:29, Allan Isaacs wrote:
I do not have any adjustments Sigi, just Gain which has 4 settings: 0, -12, -24 and -30dB; no visual gain. The SDR is the Andrus Mk1.5 which runs over my Ethernet.
Two gain settings 0 and -12dB are not useable with a large aerial due to overloading so I have made a low pass filter which now allows me to use 0 and -12db on the VLF band where the aerial is short in respect of wavelength. If I use that aerial for VLF without a filter I get cross mod and spurii from long wave broadcasts.
73 Allan G3PIY
--------------------------------------------------------------------------------
*From:*main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] *On Behalf Of *Siegfried Jackstien
*Sent:* 25 March 2020 13:43
*To:* main@SDR-Radio.groups.io
*Subject:* Re: [SDR-Radio] Baseline
does he have "visual gain" also?!? (depending on used hardware the gui or frontend is different)
here in my pluto settings i have gain (manual) and visual gain (shifts the whole shebang up or down)
with the funcube dongle visual ain is in 5 db steps (simon can you make that a bit finer in 1 db steps like in pluto with a slider?!?)
no need to set cutoff lower to 160... he just have to shift that up with visual gain
dg9bfc sigi
Am 24.03.2020 um 21:05 schrieb Simon Brown:

Allan,

I could reduce the cut-off below -150dBm but I don’t really want to – these signals do seem to be very weak.

Simon Brown, G4ELI

https://www.sdr-radio.com

*From:*main@SDR-Radio.groups.io <mailto:main@SDR-Radio.groups.io> <main@SDR-Radio.groups.io> <mailto:main@SDR-Radio.groups.io> *On Behalf Of *Allan Isaacs
*Sent:* 24 March 2020 18:33
*To:* main@SDR-Radio.groups.io <mailto:main@SDR-Radio.groups.io>
*Subject:* [SDR-Radio] Baseline

I'm looking at signals below the broadcast band so I made a low pass filter which is set to around 110KHz to avoid cross modulation etc. from broadcasts.
It gives me an attenuation of 40-50dB at 190KHz and broadcast stations are so strong they are easily audible even with 50dB attenuation from the low pass filter..
I now notice my Andrus behaves a little differently with the filter in place. I cannot see baseline noise, just a flat line if I increase the gain to 0dB or -12dB..
Previously, any gain setting of greater than -24dB resulted in cross modulation of VLF signals so the filter is doing its job.

My question:  Is it possible to reduce the display cut off  below -150dBm which is position of the flat line?
I can add -160dBm using View, Scale, Low but the flat line stays at -150dBm
If I set the gain to say -24dB or -30dB from 0dB the baseline noise becomes visible but signal to noise is poor. Increasing the gain to -12dB improves S to N and to 0dB improves S to N even more but both settings give me a flat line as in the attached picture. Am I missing a setting or is it a limitation of an AD converter?
Allan G3PIY