Satellite Receiver Requirements


Most of the literature about setting up a wx satellite receiving station state that you need a FM receiver with a bandwidth of 40-50kHz to get ideal results. At first I took that at face value and thought that simply meant this was a heavily modulated signal. However, I then started to get an inkling the only reason they were stating this requirement was to facilitate Doppler effect.

Upon a bit more thinking and a bit more reading (specifically, the APT specification) I see that the APT data is simply transmitted by the data stream AM modulating a 2.4kHz carrier which is then in turn used to to produce a FM signal – which is what we receive. Now with out any further information but knowing that AM for speech normally has a bandwidth of 6kHz, I'm going to make a leap of faith and state that the required bandwidth of both my Yaesu FT-7800 and FT-817ND on FM of 12kHz and 15kHz respectively is more than sufficient.

However, if one wants to get the best images from these receivers then they're going to need to actively adjust for Doppler as the NOAA birds pass overhead. WxToImg has automatica support for this through computer control – as do programs such as GPredict and other satellite tracking programs.

So, to perfect my station I think I probably only need two things:
1. A better antenna; and
2. CAT cable for one of my radios – my the FT-817 which will also help with the data work I want to do after my license upgrade.

Anyway, for comparison image you see is one I just received with my FT-817ND from NOAA-19 (previous images were from my FT-7800).

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