Monday, February 28, 2011
I really like long term grabs as a way to see how the band is doing over time. I utilize simultaneous instances of Spectrum Lab, one a ten minute span useful for ID'ing calls and the other a five hour span which has several advantages. It has a much better noise performance due to the averaging feature in SL which improves SNR by the square root of the ratio of averaging times, 5.5x in this case. This is readily seen in my 5hr grabs where signals not visible at all on the regular 10min one show up as easily noticed traces.
I've also found that for long-term images made by stitching together a number of shorter images the SNR also improves by what seems to be the same as above. That is true for QRSS Stitcher from VD Labs. I should add, not just stitched but also "squished" to screen size. The squishing process also averages the pixels in a way to improve the SNR.
How to Stitch
Download QRSS Stitcher and watch Scott's video on how to use it, on the download page. Next you will need a folder of images to be stitched. Do this with your own grabber or by capturing images from one of the online grabbers using SiteShoter which I described on a previous post. Run Stitcher and follow the prompts, making sure you select "Create a squished image too" and enter the number of images in"Squish to" box....then "Stitch". The results will be deposited in a sub folder named "Stitched". I usually have to lighten the squished image a bit. Otherwise that's all there is to it.
You can see in the above images how closely the stitched-squished image looks like the 5 hr grab.
73 bill w4hbk