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Very basic question, sorry
On 05/01/2022 11:21, michel soldevila wrote:
Welcome to the group!
It's undesirable to have very sharp filters, as they can introduce ringing and
distort the signals being passed. Hence it's usually better to restrict the
bandwidth by smooth filters rather than ones with sharp edges. Hence the
difference. I'm sure others will give more reasons too.
Simon may have an option to allow sharp filters, so that you can investigate
the effects yourself. What radio are you using?
73,
David GM8ARV
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv
Hi group,Michel,
The receiver bandwidth is set to 1MHz in SDR Console. I wonder why the "useful"
bandwidth seen in the waterfall display is only about 750 kHz ...
Michel, F1GOC
Welcome to the group!
It's undesirable to have very sharp filters, as they can introduce ringing and
distort the signals being passed. Hence it's usually better to restrict the
bandwidth by smooth filters rather than ones with sharp edges. Hence the
difference. I'm sure others will give more reasons too.
Simon may have an option to allow sharp filters, so that you can investigate
the effects yourself. What radio are you using?
73,
David GM8ARV
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv
Max
On Wed, Jan 5, 2022 at 11:21 AM, michel soldevila wrote:
Maybe this helps to explain it (comment from Jon Hudson at SDR Play). I'm still not much the wiser!
https://www.rtl-sdr.com/sdrplay-api-updated/
He says within the rolled off area it's only cosmetic because the overall S/N of the signal is unaffected in those areas.
73
Max
Hi group,I see exactly the same with my RSP2. Seems is a feature of the SDR Play receivers. Something to do with the filtering I would guess. I don't see any of this roll off on my Hermes Lite 2 but that is a direct sampling receiver. It is totally flat to the extremes of the sample bandwidth window (maximum 384 kHz in that particular case).The receiver bandwidth is set to 1MHz in SDR Console. I wonder why the "useful" bandwidth seen in the waterfall display is only about 750 kHz ...
Michel, F1GOC
Maybe this helps to explain it (comment from Jon Hudson at SDR Play). I'm still not much the wiser!
https://www.rtl-sdr.com/sdrplay-api-updated/
He says within the rolled off area it's only cosmetic because the overall S/N of the signal is unaffected in those areas.
73
Max
Max
On Thu, Jan 6, 2022 at 12:26 AM, Max wrote:
No doubt someone on here can give a precise explanation?
73
Max
I see exactly the same with my RSP2. Seems is a feature of the SDR Play receivers. Something to do with the filtering I would guess. I don't see any of this roll off on my Hermes Lite 2 but that is a direct sampling receiver. It is totally flat to the extremes of the sample bandwidth window (maximum 384 kHz in that particular case).Just checked my Airspy HF+ Discovery. Has the same roll off at extreme ends of the bandwidth window. Seems a feature of SDRs with analogue front ends/mixers. My guess it it's analogue filtering in the IF that's tailored to the sampling bandwidth?
No doubt someone on here can give a precise explanation?
73
Max
I have the RSP1A, and for general
monitoring, I tend to use the 2.048 MHz bandwidth, and zoom set to
about +/- 150 KHz, which for the RSP1A, seems to offer the best
visual tuning resolution, bandwidth, and control of the display
window. I think that the faded out ends that you showed is when
the SDR has reached it's maximum bandwidth, where in some cases,
SDRC allows the display to be wider than the SDR itself.
From your screenshot, it looks like you set your bandwidth to 1 MHz, +/- 500 KHz (no zoom). If you set it to say +/- 300 KHz, you wouldn't see that rolloff. If you try to click outside the ends, you hear virtually nothing. The 2.048 bandwidth, for HF listening, for me seems to offer the best performance.
73's, Bill
On 1/5/2022 7:37 PM, Max wrote:
From your screenshot, it looks like you set your bandwidth to 1 MHz, +/- 500 KHz (no zoom). If you set it to say +/- 300 KHz, you wouldn't see that rolloff. If you try to click outside the ends, you hear virtually nothing. The 2.048 bandwidth, for HF listening, for me seems to offer the best performance.
73's, Bill
On 1/5/2022 7:37 PM, Max wrote:
On Thu, Jan 6, 2022 at 12:26 AM, Max wrote:
I see exactly the same with my RSP2. Seems is a feature of the SDR Play receivers. Something to do with the filtering I would guess. I don't see any of this roll off on my Hermes Lite 2 but that is a direct sampling receiver. It is totally flat to the extremes of the sample bandwidth window (maximum 384 kHz in that particular case).Just checked my Airspy HF+ Discovery. Has the same roll off at extreme ends of the bandwidth window. Seems a feature of SDRs with analogue front ends/mixers. My guess it it's analogue filtering in the IF that's tailored to the sampling bandwidth?
No doubt someone on here can give a precise explanation?
73
Max
jdow
If your front end is sampling at 1 Msps then your
bandwidth is 1 MHz. That is not, however, your alias free
bandwidth. That requires some filtering which reduces the alias
free bandwidth to 750 kHz in this case, (Think of aliasing as
images around the band edges.)
{^_^}
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{^_^}
On 20220105 16:26:36, Max wrote:
On Wed, Jan 5, 2022 at 11:21 AM, michel soldevila wrote:
Hi group,I see exactly the same with my RSP2. Seems is a feature of the SDR Play receivers. Something to do with the filtering I would guess. I don't see any of this roll off on my Hermes Lite 2 but that is a direct sampling receiver. It is totally flat to the extremes of the sample bandwidth window (maximum 384 kHz in that particular case).The receiver bandwidth is set to 1MHz in SDR Console. I wonder why the "useful" bandwidth seen in the waterfall display is only about 750 kHz ...
Michel, F1GOC
Maybe this helps to explain it (comment from Jon Hudson at SDR Play). I'm still not much the wiser!
https://www.rtl-sdr.com/sdrplay-api-updated/
He says within the rolled off area it's only cosmetic because the overall S/N of the signal is unaffected in those areas.
73
Max