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CW Skimmer decoded bandwidth
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Hi all
Is anyone achieving a decoded bandwidth greater than about 23KHz in CW Skimmer? Is this possible? I note a few past posts about the setup but did not see anything specifically addressing this question unless I missed it. I am using Virtual Audio Cable as per the setup here - https://www.sdr-radio.com/cw-skimmer Its a good weekend to try it as there is a contest on and 20M is packed with CW. Cheers Grant |
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Max
Hi Grant
Quite a lot of people mention this as a limitation of CWS. The height of the window is fixed and there is no zoom feature (in or out) on the waterfall so you are stuck with whatever bandwidth you can view on your particular monitor. For me I have two 1920x1200 monitors, but one of them I have in portrait mode. This was actually was for an totally different reason, but is often very useful, including for CWS because of course it is taller (1920 tall instead of 1200 of course). So for example on my main (landscape) monitor I can see about 12 kHz of spectrum on CW skimmer, but if I put CWS on my portrait monitor I can see nearly double.... about 22kHz. Sorry, it seems this is the only solution. Odd but true, it seems. 73 Max |
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Hi Max
I also observed this on my monitor and while I agree its odd, its not my main concern. Are you getting a decoding bandwidth of greater than 22 kHz? In other words, for any set tuner frequency, if you view the list of decodes and sort the frequency column in the list, is there greater than 22 kHz or so between the lowest and highest? Cheers Grant |
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48K or more with an IQ stream from the right rig. Settings are crucial to make it work.
-- 73 de Bill / KG6NRV |
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Max
Hi Grant
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I never really looked at this before, but since you asked, I did what you suggest. Set a tuner frequency on CWS in the middle of a very active CW section (easy today..... CQ WPX!). Then I close CWS and re-open to make sure of a fresh start. open the station list and sort by frequency. No, I don't see any stations on the list that are outside the window I can see on the monitor, so for me, as you say, that is 22kHz. If I then retune on CWS to top of the list (which then centres it) I can then see the decodes on the fresh part of the "revealed" screen are only just starting. So no, it does not seem to decode any station that is outside of the visible window of 22kHz, for me at least. I don't see anything like the 48kHz that Bill has mentioned. Bill, what there settings are there to adjust? I don't see any. I must admit it made me think what CWS is actually doing, and what the point is of the selectable sample rates if the window of received frequencies is limited to the visible window. I tried all three sample rates available 48 kHz. 96 and 192. I personally could see no visible difference in behaviour of CWS between any of them. I actually did the main test above set to 192kHz. To be honest it's so fast to "scan" the active section by a quick scroll up and down the band on CWS to generate a full callsign list that I don't find it a restriction. Maybe it would be for a serious contester? I can fill a callsign list covering the full CW section of 20m in less than 30 seconds of "scanning" with CWS. Hope it helps. 73 Max On Sun, May 31, 2020 at 02:15 AM, Grant Rawstorn VK2LX wrote:
Are you getting a decoding bandwidth of greater than 22 kHz? In other words, for any set tuner frequency, if you view the list of decodes and sort the frequency column in the list, is there greater than 22 kHz or so between the lowest and highest? |
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paul newcombe <G6YZC@...>
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From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Max <radiomax@...>
Sent: Sunday, May 31, 2020 5:53:24 AM To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> Subject: Re: [SDR-Radio] CW Skimmer decoded bandwidth Hi Grant I never really looked at this before, but since you asked, I did what you suggest. Set a tuner frequency on CWS in the middle of a very active CW section (easy today..... CQ WPX!). Then I close CWS and re-open to make sure of a fresh start. open the station list and sort by frequency. No, I don't see any stations on the list that are outside the window I can see on the monitor, so for me, as you say, that is 22kHz. If I then retune on CWS to top of the list (which then centres it) I can then see the decodes on the fresh part of the "revealed" screen are only just starting. So no, it does not seem to decode any station that is outside of the visible window of 22kHz, for me at least. I don't see anything like the 48kHz that Bill has mentioned. Bill, what there settings are there to adjust? I don't see any. I must admit it made me think what CWS is actually doing, and what the point is of the selectable sample rates if the window of received frequencies is limited to the visible window. I tried all three sample rates available 48 kHz. 96 and 192. I personally could see no visible difference in behaviour of CWS between any of them. I actually did the main test above set to 192kHz. To be honest it's so fast to "scan" the active section by a quick scroll up and down the band on CWS to generate a full callsign list that I don't find it a restriction. Maybe it would be for a serious contester? I can fill a callsign list covering the full CW section of 20m in less than 30 seconds of "scanning" with CWS. Hope it helps. 73 Max On Sun, May 31, 2020 at 02:15 AM, Grant Rawstorn VK2LX wrote: Are you getting a decoding bandwidth of greater than 22 kHz? In other words, for any set tuner frequency, if you view the list of decodes and sort the frequency column in the list, is there greater than 22 kHz or so between the lowest and highest? |
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Hi Max and Bill
It appears to me that when configured in Softrock-IF mode CW Skimmer defaults to 48KHz sampling (even with 192 selected) and it is only possible to see 24 KHz of decoded bandwidth. Bill am I right in assuming that you are not using Softrock-IF as the selected radio in CWS? Cheers Grant |
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Hi Paul
sampling rate range min 11025, max 192000 min bits 8 max bits 32 cheers Grant |
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Max
Hi Grant
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Had some time to re-think this over lunch. Surely the ultimate bandwidth ib=n CWS with SDRC should only be to do with the sample rate of the VAC? I checked my VAC and it was set to 48kHz, which would have usually explained the bandwidth seen in CWS, because as far as I know one would expect a decode bandwidth of half of 48kHz (Nyquist?) = 24 kHz (yes, not 22!). So I reset my VAC to 192kHz, and also changed CWS setting in SDRC to match, 192 kHz, hoping I would see decode bandwidth in CWS of 1/2 x 192 = 96 kHz. But no, I still see decode bandwidth of 24 kHz. So at that point I have realised I am missing something I think. Only correction for me is the 22kHz I mentioned earlier is obviously 24 kHz. Anyway, if you find any more I would be interested to know myself, so I await further input from those that understand it better than I do. 73 Max On Sun, May 31, 2020 at 11:21 AM, Grant Rawstorn VK2LX wrote: Hi Max and Bill |
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Max
Hi again Grant
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This article seems to confirm your findings re: Softrock interface mode, so seems it is irrelevant what is set in VAC or SDRC as the maximum decode bandwidth is 24kHz. No idea why the rig control setting should affect the bandwidth delivered to CWS by the VAC? https://sites.google.com/site/g4zfqradio/hdsdr-cwskimmer-and-Other-Digimodes 73 Max On Sun, May 31, 2020 at 11:21 AM, Grant Rawstorn VK2LX wrote: Hi Max and Bill |
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Alan G4ZFQ
So I reset my VAC to 192kHz, and also changed CWS setting in SDRC to match, 192 kHz, hoping I would see decode bandwidth in CWS of 1/2 x 192 = 96 kHz. But no, I still see decode bandwidth of 24 kHz.Max, If Skimmer is fed IQ signals then at 48KHz it will see centre frequency +/-24KHz =48KHz span. This is because IQ signals are actually 2 signals 90° apart one representing below centre, the other above centre just as all SDRs use. It is possible to see 192KHz using Skimmer in "Softrock" mode but I'm not sure SDR-Radio supports this. 73 Alan G4ZFQ |
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Alan
Max
Says "A simple way of using CW Skimmer with a Softrock would be to use it stand-alone in this way 192KHz can be seen with a suitable soundcard. " But by the design of Skimmer "*/when in "Softrock IF" mode CW Skimmer defaults to 48KHz sampling. It is only possible to see 24 KHz bandwidth." It is a long time since I wrote that page but it does say that 48KHz may be seen if the output of the SDR program can be set to 96KHz as can HDSDR. I guess I tested that. I did talk to Alex about this, it can not be changed. /*Dick Williams, W3OA made a utility to enable 192KHz and full control but only with Softrocks. 73 Alan G4ZFQ |
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Max
Sorry Alan.... did not check the author on that item! Thanks for your comments. Yes, of course. I see now (the IQ theory) but not why there is a 24 kHz restriction. For me personally it's not a limitation. I've got more than I can cope with in 24 kHz! But I guess would be nice to see a table of all stations active in a larger window as far as DX or contesting goes. I never actually thought of using it that way as I am not a major DXer or contester, so I am learning too.
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73 Max On Sun, May 31, 2020 at 03:24 PM, Alan wrote:
ays "A simple way of using CW Skimmer with a Softrock would be to use it stand-alone in this way 192KHz can be seen with a suitable soundcard. " |
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Alan
Sorry Alan.... did not check the author on that item! Thanks for your comments. Yes, of course. I see now (the IQ theory) but not why there is a 24 kHz restriction.Max, No, I've not got a SDR-radio setup at the moment but as i described I thought the Softrock IF mode was capable of 48KHz span. The pictures on Simon's page are not clear enough for me to see the span shown there. 73 Alan G4ZFQ |
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jdow
24 kHz if you ignore decimation anti-aliasing filters. 22 kHs is with the anti-aliasing filters.
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{^_^} On 20200531 06:46:11, Max wrote:
Hi Grant |
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