Daily Archives: 12/16/2007

Narrow versus Wide FM

While discussing my experiments with weather satellite reception, I talked about how I made my recordings using the “WFM” or wide FM settings on my Radio Shack Pro 60 scanner. If you read up on this subject, you’ll find that the signals transmitted by these satellites have about a 50khz bandwidth. The normal “narrow” FM mode used by most HTs and scanners have about 15khz bandwidth. The wide FM settings have 200khz bandwidth. If you record a signal this way, you are about 6db down, and you have the potential to capture strong signals which would normally be out of band, but if it works, it works pretty well. But someone asked me “What happens if you record with the normal 15khz setting?”

So I did the experiment.

Narrow Versus Wide FM

The first bit of this run was recorded in the narrow setting. The majority was recorded in the wide setting. These were done using my VX-3R, which was handier than my Pro60. If you look at the top, you can see that the results are noisy, and we get no darks. If I thought really hard about this, I probably could tell you why this happens, but that’s what you get.

Addendum: I worked a bit on the image, cropped out the noisy bit, and adjusted the balance and color a bit. This is what you get.

GIMP’ed version of the same picture, cropped, rectified.

Chatting on AO-51

It was positively chatty on the westward pass of AO-51 this morning. For fun, I reduced power to just 1w on my HT, and nobody seemed to notice, although it did get scratchy at the end of the pass.

Dec 16 pass of AO-51, 8:57 Local Time

The beginning of the pass is a little noisy, because for some reason I thought the pass was going to the east, when it was in fact a western pass. I was fishing around with the antenna, trying to track it to the east. Once I realize how stupid I was, it settles in to a fairly strong signal.