Re: Direct Sampling frequency limit in r 1628 onwards #sdrsharp #spyserver


Martin - G8JNJ
 

Hi,

OK, it's your call, and I understand why you may wish to do it for both technical and commercial reasons.

As I said previously, there is a Nyquist Alias wrapped around 14.4MHz, but adding this restriction alone still won't completely stop alias signals from above this frequency appearing at lower frequencies. RTL dongles used in this way will always be a compromise, so I've never considered this particular issue to ever be a major problem. Especially as there are other sampling aliases present depending upon the sampling rate chosen in SDR Sharp (and others).

RTL dongles are never going to compete with hardware like Airspy's or HF+'s. But they do provide a good introduction to SDR's and facilitate a lot of experimentation and other applications that may otherwise be too costly to implement by casual or 'hobby' users.

I often use a diplexing filter to minimise this problem when running RTL dongles in direct sampling mode with SDR Sharp (and others), so my plan was to use three dongles connected by a triplexer to cover 0-14.4 / 14.4-28.8 / 28.8 and above.

The suggestion was intended to try and maintain the same functionality of SDR Sharp in both normal and Spyserver mode  wherever possible.

Personally I'd appreciate it if you didn't put this restriction in, but as I said before it's your call.

Regards,

Martin - G8JNJ

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