Hi Rein, > It is perhaps possible to turn the process around > on the zooming business. I have now added a couple of things to allow the user to set a lower and an upper frequency. Linrad will figure out what X-scale to use to make those limits fit on the screen.
> Instead of having the user select a full random zoom > window and executing this in a framework of allowed or > possible combinations, it is perhaps possible to develop > from the parameters in use, to inform the user of > possible zoom windows and let him or her select > on from a lis allowed or provided numbers. That list would be too long;-) > In the waterfall:, let the user select the window center and > provide standard selectable window widths around this > center, for example and so on. That could be done, two parameters govern the display. I implemented upper and lower frequencies instead:-) > From the sound card sampling rate to the horizon display > pixel numbers, there are likely simple fast relationships of > possible ( powers of 2 or 10 ) which can be calculated > and used for the suggestion of possible and/or only > allowed zoom windows. > > I hate to suggest this > There has to be a relative simple process scheme where it can > be shown how the a selection of a parameter effects or limits > the possibilities of other parameters. I do not think so. More below. > From these combinations, one could possibly show a scheme > how the selection effect the processing and the results. > As the designer you clearly know what is possible and what effects > what were. Firstly the user has to select the correct format so Linrad will read the data the way the hardware designer intended. That affects the X-scale. Then the user has to decide what sampling rate to use. Several choices may be possible and that would surely affect processing. Nevertheless, input sampling speed should not be selected for its influence on FFT sizes, zoom ranges etc. It should be selected to fit the hardware. When several different sampling speeds fit the hardware (e.g. Perseus) it is just a user preference. It would affect CPU load and blanker performance but not really anything else. The FFT size may differ but that does not affect performance. The number of FFT bins for 1 kHz on screen would be different but the scale would be correct. > I think without real serious work it is hard for an user to figure this and > understand it or be able to use is in the measurement or analytical > processor what Linrad is in the end. Hmmm, I can actually not follow your argument here. Except for the inconvenient mouse-clicking procedure that Linrad has had until now for setting the frequency range to show in the display, what is the problem? When the user can type e.g. 144.032 at the left side and 144.040 at the right side and then click a button to get that frequency range for the waterfall and main spectrum is there any other problem? The upper limit will often be higher than specified but the user can grab the right hand side of the window and move it to the left if he prefers a black screen over the data above the specified range. 1) Select a sampling speed. (Other parameters irrelevant) 2) Select a bin bandwidth. This will affect waterfall visibility and several other things. It will of course affect the numerical values of many internal variables. FFT bins per pixel is one of them. 3) Use the entire frequency range because the information may be essential in case you use the noise blanker. Otherwise select a suitable window zoom. Before with mouse clicks, but now by setting two frequency limits. 4) Read frequencies off the screen by use of the frequency scale and do not worry about the bin width. > While I sit and write all this here, I realize that all I am doing is is > just suggesting the standards used in instrumentation! > Nothing original but it happens to be the standard.. > > Hz / scale division > V / sd > Hours / cm > windom width in Hz > etc etc. > > The user can only select 1 -3 - 10 - 30 of whatever. It is a given. > ( Philips numbers ) In Linrad the scale is 1 -2 -5 -10 -20 of whatever. The scale is always written on screen but the number of pixels between two lines on the scale can be changed in fine steps. > And I think form a design point of few it makes things simpler I actually do not understand what you suggest. Do you mean that one unit (or 2, 5, ...) should always be 1 cm on the screen? Why? > One could then say : Yes but by doing this it limits my flexibility" > what might be true in a very limited number of cases. Everything is possible, but I do not understand what you suggest and why. 73 Leif
