Attenuation
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vince battle
Greetings,
I have always wondered why attenuation settings both hardware and software or in 10db increments and not variable? is this a hardware issue or software issue? Many times, 10-30db increments is too much and something between these settings is better. Vincent |
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Which radio?
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of vince battle via groups.io <muellertwo@...>
Sent: 22 November 2022 22:46 To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> Subject: [SDR-Radio] Attenuation Greetings,
I have always wondered why attenuation settings both hardware and software or in 10db increments and not variable? is this a hardware issue or software issue? Many times, 10-30db increments is too much and something between these settings is better. Vincent -- - + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems. |
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vince battle
From: Simon Brown
Sent: Tuesday, November 22, 2022 9:21 PM To: main@SDR-Radio.groups.io Subject: Re: [SDR-Radio] Attenuation
Which radio?
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of vince battle via groups.io <muellertwo@...>
Greetings,
- + - + - Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.
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OK,
Some of these radios have fixed attenuation options, for example NetSDR. HF+ - I'll have to check.
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of vince battle via groups.io <muellertwo@...>
Sent: 23 November 2022 15:34 To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> Subject: Re: [SDR-Radio] Attenuation Greetings, NetSDR, Icom RS-6500 and Airspy Discovery
Vincent
Sent from Mail for Windows
From: Simon Brown
Which radio?
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of vince battle via groups.io <muellertwo@...>
Greetings,
- + - + - Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.
-- - + - + -
Please use https://forum.sdr-radio.com:4499/ when posting questions or problems. |
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Siegfried Jackstien
don´t you have also "visual gain" in all sdr used?? that could be done in 1 db steps so finetune of any sdr to correct readings should be possible if no visual gain in all sdr setups under "radio" settings ... then you could add it where that is missing rtl for example has fine steps (but not exactly 1 db) and visual
gain in 5 db steps maybe a finer resolution also in visual gain possible instead
coarse 5 db steps?? pluto has fine steps on gain AND visual gain (perfect!) airspy hf+ has preamp on/off, att from 0-48 in 6 db stebs and
visual gain in 5 db steps (-40 to +30db) ... also there a finer
visual gain could be added in 1 db steps i think if you have at least the visual gain in fine steps on all different sdr setups a good s meter calibration should be possible on all sdr and visual gain does not depend on used hardware so change that to finer steps should be easy.. not?? maybe a number box with up down buttons instead a dropdown list??
(just thinking) dg9bfc sigi Am 23.11.2022 um 18:16 schrieb Simon
Brown:
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jdow
He was going to redo "Visual Gain" to make it a real visual gain control that simply scales the displays. As it is the last I knew the visual gain control was a literal digital gain applied to the entire system which led to some unfortunate behavior. Simon was going to doctor this last I knew. But, I may have missed his actually doing it as I do not think it's been fixed yet.
{^_^}
On 20221124 17:44:05, Siegfried
Jackstien wrote:
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vince battle
Hi Sigi, I have “visual gain” only when I use the Airspy Discovery, but the spectrum jumps up and down so much, I stopped using the Airspy for voice and only use it for “data” (FT8). Now I must confess I use remote (spyserver) for the Airspy. I do not use the Icom RS8600 with SDRC because the “scan” functions are not operational on SDRC. My “still rocking” NetSDR does not have “visual gain “available and I have too use the “RF gain”/
Vincent
Sent from Mail for Windows
From: jdow
Sent: Thursday, November 24, 2022 7:45 PM To: main@SDR-Radio.groups.io Subject: Re: [SDR-Radio] Attenuation
He was going to redo "Visual Gain" to make it a real visual gain control that simply scales the displays. As it is the last I knew the visual gain control was a literal digital gain applied to the entire system which led to some unfortunate behavior. Simon was going to doctor this last I knew. But, I may have missed his actually doing it as I do not think it's been fixed yet.
{^_^}
On 20221124 17:44:05, Siegfried Jackstien wrote:
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jdow
The AirSpy discovery is pretty much designed to run with its own
agc active. But that is likely to be awkward for SSB reception
with the usual receiver AGC active. The hope is that the time
constant for the Discovery's AGC is long (for release at least)
compared to that used inside the SDR software. Otherwise you get
odd phenomena as you described. This is compounded when you use
the Discovery as an IF for the 8600. It's not really designed for
that use but you can in both cases switch over to manual gain. Setting up manual gain is not trivial. Maybe somebody who knows noise figure work and has a Discovery in MGC mode can describe their configuration. {^_^} On 20221125 17:03:44, vince battle
wrote:
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vince battle
Joanne, I DO NOT use the Discovery with the 8600, not sure where you got that. Ok, perhaps I didn’t ask my question correctly, I understand that Simone only supports what the hardware manufacture gives him to work with, So the question is WHY doesn’t the hardware manufactures make attenuation variable instead of fixed?
Sent from Mail for Windows
From: jdow
Sent: Friday, November 25, 2022 6:31 PM To: main@SDR-Radio.groups.io Subject: Re: [SDR-Radio] Attenuation
The AirSpy discovery is pretty much designed to run with its own agc active. But that is likely to be awkward for SSB reception with the usual receiver AGC active. The hope is that the time constant for the Discovery's AGC is long (for release at least) compared to that used inside the SDR software. Otherwise you get odd phenomena as you described. This is compounded when you use the Discovery as an IF for the 8600. It's not really designed for that use but you can in both cases switch over to manual gain. Setting up manual gain is not trivial. Maybe somebody who knows noise figure work and has a Discovery in MGC mode can describe their configuration. {^_^} On 20221125 17:03:44, vince battle wrote:
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Vince, please explain/post video of this "jumping of the spectrum up and down". I have a fleet (and growing) of Airspy Discovery's on SDRC Servers and always run mine (on large antennas) with the AGC ON, ATT OFF, PreAmp OFF unless 17M and higher, and visual gain of about 5 or 10dB. The only time I see the spectrum jump is when my electric cattle fence has leakage. Which it is currently doing despite my efforts to locate the problem. (The thin horizontal lines at 1 second intervals on the waterfall)
73 Kriss KA1GJU |
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vince battle
From: Kriss Kliegle KA1GJU
Sent: Saturday, November 26, 2022 9:26 AM To: main@SDR-Radio.groups.io Subject: Re: [SDR-Radio] Attenuation
Vince, please explain/post video of this "jumping of the spectrum up and down". I have a fleet (and growing) of Airspy Discovery's on SDRC Servers and always run mine (on large antennas) with the AGC ON, ATT OFF, PreAmp OFF unless 17M
and higher, and visual gain of about 5 or 10dB. The only time I see the spectrum jump is when my electric cattle fence has leakage. Which it is currently doing despite my efforts to locate the problem. (The thin horizontal lines at 1 second intervals on the
waterfall) Attachments:
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vince battle
From: vince battle
Sent: Saturday, November 26, 2022 11:30 AM To: main@SDR-Radio.groups.io Subject: Re: [SDR-Radio] Attenuation
Kriss, I never recorded anything before, but I’ll give it a try
Sent from Mail for Windows
From: Kriss Kliegle KA1GJU
Vince, please explain/post video of this "jumping of the spectrum up and down". I have a fleet (and growing) of Airspy Discovery's on SDRC Servers and always run mine (on large antennas) with the AGC ON, ATT OFF, PreAmp OFF unless 17M
and higher, and visual gain of about 5 or 10dB. The only time I see the spectrum jump is when my electric cattle fence has leakage. Which it is currently doing despite my efforts to locate the problem. (The thin horizontal lines at 1 second intervals on the
waterfall) Attachments:
Attachments:
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What kind of server are you running it from? I don't recognize the radio settings options vs mine. Operating an Airspy or any SDR has the same options whether you are using one locally or via the SDRC Server (which I do 99% of the time). How does it behave when operated locally? I couldn't make out what bandwidth in the lower left tool bar, but was there a strong signal present w/in the selected bandwidth? There is a CW contest going on, but not on 17M. I used to have a contester 1/2 mile away and I was right smack in his beam path. I could hear his products on every band I listened on, WARC bands as well!
73 Kriss KA1GJU |
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vince battle
Kriss, I’m running the Discovery remotely using the spyserver from SDRC. I’m also running the newest SDRC version as of today. If I operate the Discovery locally the behavior running remote is not there The first video was 225khz and the second video was at 57khz
Vincent Sent from Mail for Windows
From: Kriss Kliegle KA1GJU
Sent: Saturday, November 26, 2022 12:25 PM To: main@SDR-Radio.groups.io Subject: Re: [SDR-Radio] Attenuation
What kind of server are you running it from? I don't recognize the radio settings options vs mine. Operating an Airspy or any SDR has the same options whether you are using one locally or via the SDRC Server (which I do 99% of the time).
How does it behave when operated locally? I couldn't make out what bandwidth in the lower left tool bar, but was there a strong signal present w/in the selected bandwidth? There is a CW contest going on, but not on 17M. I used to have a contester 1/2 mile
away and I was right smack in his beam path. I could hear his products on every band I listened on, WARC bands as well!
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Use Simon's SDRC Server and don't look back! hi hi
We could use more good servers (ie functioning properly, online, with decent antennas w/o massive QRM) on SDRC: http://onairv3.sdrspace.com/onair-v3.xml 73 Kriss KA1GJU |
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Don Moman VE6JY
That link refreshes so often, and returns you to the beginning of the list so can't even begin to see who is online.... On Sat, Nov 26, 2022 at 3:49 PM Kriss Kliegle KA1GJU <kliegle@...> wrote: Use Simon's SDRC Server and don't look back! hi hi |
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vince battle
From: Kriss Kliegle KA1GJU
Sent: Saturday, November 26, 2022 2:49 PM To: main@SDR-Radio.groups.io Subject: Re: [SDR-Radio] Attenuation
Use Simon's SDRC Server and don't look back! hi hi
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jdow
That's a longish coffee table discussion and some digging into how semiconductors really work. I do not know if I can do it justice. So I'll make a grand statement with a very brief descriptions of why. Every variable attenuator I know for this use has very nasty downsides. This also applies to variable gain amplifier stages. For an example a diode can, for small signals, be a current variable attenuator, roughly 25 ohms at 1ma current, 12.5 at 2 ma , 50 at 0.5 ma. When the signal level becomes significant compared to the current setting the nice exponential curve, a fancy Taylor Series expansion for the nonlinearity involved) starts generating appreciable IMD. So this sort of variable attenuator is best at near zero attenuation and at maximum attenuation. At middle settings IMD will increase. Another example, a typical voltage variable gain stage for a bipolar transistor amplifier can use this same resistance effect to vary the gains. But, at mid range settings, IMD goes up. J-Fets can do moderately well, some MOSFETs can do pretty well as voltage variable resistors, especially in balanced configurations. Since the control voltage on the device is higher than for bipolars the IMD issue is mitigated maybe 20 dB. This is good enough it is sometimes seen in some analog mixer designs. The whole picture is much more complex; but, I keep running into the same basic issues. You have to work at quite low impedance with LOTS of current in your devices to have it all work well for you with minimal IMD. "LOTS" of current is an excessive term for AirSpies. It is excessive even for RX888 MKII models. (The real unfortunate situation is that the high attenuation
attenuator and reduced gain amplifier are MORE susceptible to IMD
in most conditions making the control VERY undesirable. It gets
worse when you need better.) {^_^} On 20221126 08:58:21, vince battle
wrote:
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Max
On Sat, Nov 26, 2022 at 11:07 PM, Don Moman VE6JY wrote:
That link refreshes so often, and returns you to the beginning of the list so can't even begin to see who is online....Agree Don the auto-refresh is annoying as it keeps returning the list back to the top every 10 seconds. Could it be disabled to let people manually refresh, or at least have a tick-box option on the web page? Or I guess maybe as it is XML it's not intended to be viewed? Maybe it's for input to the server list in SDRC? Max |
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If you place the scroll bar on the righthand side to where you want to view, leave it there. When screen refreshes, just click and hold and it will return back there. But you gotta read what you need real fast!
I believe it remains where you scrolled to on the iPad though. I just use that to get an idea how my 5 servers are working and find where all the activity is. Too bad it only publishes the center frequency and bandwidth, not the actual frequency in use. hint hint nudge nudge 73 Kriss KA1GJU |
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