Hello David, another hint: If the dynamic range is not so important and for system tests you can use one of these RTL28xx chips providing 8-Bit I,Q samples for direct access or a complete VHF/UHF-RX. See http://sdr.osmocom.org/trac/wiki/rtl-sdr
73, Helmut, DC6NY -----Ursprüngliche Nachricht----- Von: Helmut [mailto:[email protected]] Gesendet: Donnerstag, 29. Oktober 2015 08:17 An: [email protected] Betreff: [Freetel-codec2] WG: gain before ADC Ups,....seems I got a problem also with to less coffee.... BPF insertion loss refers to pass band not stop band, hi. 73, Helmut, DC6NY -----Ursprüngliche Nachricht----- Von: Helmut [mailto:[email protected]] Gesendet: Mittwoch, 28. Oktober 2015 23:29 An: [email protected] Betreff: Re: [Freetel-codec2] gain before ADC Hi David, I understood what you plan, but analogue down conversion is another story. The example I sent you should demonstrate how this attached system calculation tool works. It shows a VHF frontend for digital down conversion, i.e. the ADC has to be sampled with 300 Msps. The BPF of 144 to 146 MHz exhibits an insertion loss of 2 dB in the stop band and consequently a noise figure of 2 dB. In your case NF or MDS is mainly not determined by the ADC in the base band, but on all analogue stages in front. It depends e.g. on what kind of mixer you intend to use: balanced passive mixers exhibit an insertion loss of 7-8 dB (equal NF 7- 8 dB), while modern active mixer provide even conversion gain. BTW negative NF doesnt exist. I guess you meant negative gain (loss) of the BPF. Nevertheless you can use that SYScal tool of course also for your approach to calculate the necessary gain of preamp and IF amp. 73, Helmut, DC6NY ---------------------------------------------------------------------------- -- _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2 ------------------------------------------------------------------------------ _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
