sdr receiver

[agurney]

Is that something to do with the circular polarization?

No, it's a cool feature of SDR. The satellites transmit on WFM, however because the frequency appears to shift as satellites pass overhead the centre frequency appears to shift; by stretching the bandwidth, for example in something like SDR#, you can capture the whole shebang.

I presume you mean that you just look for the peak single around 137 Mhz and that's where the images are?

These are the frequencies I use:

NOAA15 : 137.6173 MHz
NOAA18 : 137.9097 MHz
NOAA19 : 137.100 MHz

and here's where/when to find them:

http://www.n2yo.com/?s=28654|25338|33591

 

[dgadee]

Many thanks - is the length of wire antenna important?

 

[agurney]

Many thanks - is the length of wire antenna important?

There are plenty of experts around who will recommend an appropriate balun and cable parameters .. in my case I just use a couple of metres of wire with a crocodile clip at one end to attach to the backstay and a bare end (or BNC/UHF) to connect to the receiver. It's not perfect but there's little RF interference near the boat (at home's a different story though).

The antenna length's important, but only because in my case it's supporting my mast I inserted nylon thimbles in my backstay connections so it's possibly insulated .. 50p compared to a couple of hundred quid, and it appears to work (receive only, and only in coastal waters; I'd probably take it more seriously if I was going for an extended trip offshore).