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U2 step tests
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g3zjo
Hans / Lads
I have increased the resolution of my Grabber for clearer understanding of the step tests. Currently on 3.5MHz band and the frequency indicated. The 3.5MHz band produces decodeable WSPR but the shift is not correct. I have annotated a blow up of the steps which is attached and will be in my Group Folder. 73 Eddie G3ZJO |
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Hans Summers
Hi Eddie I think that at 80m, some of what you observe is just features of the decode process on such a strong signal. Can you put in some attenuation so that the line is thinner?
I think the tone spacing is probably Ok on 80m, once you do that. The problems come in, at the higher bands where too much precision is lost. 73 Hans G0UPL
On Mon, May 20, 2013 at 7:50 AM, g3zjo <g3zjo@...> wrote:
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g3zjo
On 20/05/2013 07:56, Hans Summers wrote:
I think that at 80m, some of what you observe is just features of the decode process on such a strong signal. Can you put in some attenuation so that the line is thinner?Hi Hans The wide line is due to the resolution which I have pushed up, to make it clearer in fact. Yes there is some inevitable spread. Of course I will add some attenuation for you and see what I can do. However please observe and consider:- I have increase the requested steps to 10 Hz total There are 12 steps in the message Only 8 discreet steps are present The total pattern does not achieve the 10Hz expected Each step will be 0.833Hz The shift achieved is around 6Hz 8 steps times 0.833 equals 6.666Hz I am glad I did the test then I was not sure at what stage you were at in the solution. 73 Eddie |
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Barry Chambers
On 20/05/2013 08:32, g3zjo wrote:
On 20/05/2013 07:56, Hans Summers wrote:Hans, EddieI think that at 80m, some of what you observe is just features of theHi Hans Are you running out of resolution in step size here? What's the actual min resolution the DDS can give with a 125MHz xtal? -- 73 Barry, G8AGN |
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g3zjo
On 20/05/2013 08:43, Barry Chambers wrote:
Are you running out of resolution in step size here? What's the actualI think it is more like 0.08Hz min I have reduced signal level and the blow up of the width, Thing is I cant write on those.:-) There is an anomaly repeated every time on steps 6,7 and 12 where the actual width of the signal is greater this can be seen by the with of the waterfall peak (if you guys looking at capture are lucky enough to catch it) is the DDS indecisive trying to achieve a freq and deviating (aliasing)? Another way of observing is to watch the time spent at each frequency by the waterfall peak, I can do that of course and can see the double time at some steps. Also I can see the wide peak at 6,7 which stays on the same freq for twice the unit time. Eddie |
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g3zjo
On 20/05/2013 07:56, Hans Summers wrote:
I think that at 80m, some of what you observe is just features of the decode process on such a strong signal. Can you put in some attenuation so that the line is thinner?Well I am still trying to make 8 beans equal 12. No matter how yo look at it there are only 8 distinct levels on 3.5MHz Eddie |
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Hans Summers
Hi Eddie ? I have increase the requested steps to 10 Hz total How did you increase the requested steps to 10Hz total? The FSK (Hz) size parameter is ignored here. In the custom message mode, the size of each step is always 0.5Hz. So if you have 12 steps, it should go from 0 to 5.5Hz always.?
I believe that the observations of only 8 steps being apparent on 3.5MHz are just a feature of the settings you are using in your spectral analysis program. If you changed the settings or used a different program I think that you would see the 12 steps correctly. I think at the settings you have, the resolution of the spectral analysis is limited to a "bucket" size of more than 0.5Hz, which mean you can't observe all the 12 steps accurately.?
Anyway I don't think we need to lose any more sleep over this stuff. I think I understand the problem adequately now. Regardless of whether it is there on 3.5MHz or not, it clearly arises as you go up in frequency and at 10m the steps are much too inaccurate or non-existent. I don't need any more experimental observations now, I think the experiments to date have been extremely helpful.?
Many thanks to Eddie and all those of you who have provided the observations. Now I have to just change the part of the code which calculates the DDS tuning word.? 73 Hans G0UPL |
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g3zjo
On 20/05/2013 22:07, Hans Summers wrote:
Anyway I don't think we need to lose any more sleep over this stuff. I think I understand the problem adequately now.Hi Hans Jolly good. Personally I think it shows what we have found with WSR, the results on each U2 are inconsistent, Andy FTD had prety good linearity and my steps are not linear on 3.5MHz. Some of the steps, (now back using your settings and 5.5Hz) give the same no or very tiny shifts on several pairs of steps. All noted re bucket size but I do it see better the steps and the difference is consistent for each step and repeated accurately. Anyway irrelevant now if you have the full understanding so looking forward to the sorted version. 73 Eddie |
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