Hi Glen Sorry for disagreeing!
You probably refer to ready assembled boards. The bottleneck are NOT the chips or their design. The problem are the cheap VTCXOs on PLUTO or LIMESDR. When applying an external low phase noise reference at 40 MHz the concept hits e.g. the praised IC9700. On 1.Ghz the RX and TX phase noise of the a/m Lime was measured far better (offsets at 100Hz up to 200 kHz). With these advanced chips from Analog Devices or Lime microsystems cleaner microwave radios can be designed than any of these old analoge radios + noisy transverters. Take care. 73, Helmut, DC6NY -----Ursprüngliche Nachricht----- Von: glen english [mailto:[email protected]] Gesendet: Mittwoch, 8. April 2020 12:48 An: [email protected] Betreff: [Freetel-codec2] A warning on using single chip transceiver chipsets. While on this discussion, I think a caution neds to be applied here to the single chip radios about, IE transcievers used for DV hot spots, and SDRs like Lime SDR. Their wideband phase noise is TERRIBLE. They polute the band . And many do not understand the implications and effects. As well as wideband noise, they use fractional synthesisers and their spurs are many and broad over a wide spectrum These type of single chip transceivers are not designed for operating in a space where there are sensitive radio service in the same 20 MHz.... Well they are but the limit is an ERP of about 100mW before harmful interference is caused to, for example the local repeater. Happy to discuss/ advise, suggest / comment. So, from this POV, its pretty hard to do a low cost simple chipset that can be connected to a 25Watt amplifer and any sort of decent antenna. There are options, but they're not necessarily expensive and they need to be carefully implemented. cheers glen VK1XX On 4/2/2020 7:07 AM, David Rowe wrote: > Hi Mooneer, > >> As for the SM2000, it might be useful to resurrect at some point. Or >> perhaps include the lessons learned in a future project. :) > There is a lot of scope for open source DV and VHF/UHF > experimentation, as Jeroen and several others are showing us. > > The idea of a low MDS VHF/UHF stand alone radio embodying some of the > concepts of the SM2000 is still intriguing to me: > > + efficient modems and low noise figure, so it runs DV in the < > + -130dBm > range (20dB better than FM and 1st gen DV) > + LPCNet style wideband codec > + something stand alone/portable/HT form factor minimal hardware > + lockdown/high performance modem (avoid chipsets with > the modem inside) > + a few watts power output, proper PA filtering that meets commercial > + specs > > But not sure what hardware I'd use these days. > > Cheers, > David > > _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2 -- Diese E-Mail wurde von AVG auf Viren geprüft. http://www.avg.com _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
