Narrow versus Wide FM

December 16, 2007 | General | By: Mark VandeWettering

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.

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