Hi Glen,
no need for an ideological discussion :) … Linear Technology, today a divison of Analog Devices, brought a lot of experience into the marriage. LTC's new frac-N PLL devices mitigate these disadvantages. VCO coves 300 MHz to 6 GHz. They are designed to yield very low integer boundary spurs, and their fractional divider uses an advanced, 4th order ΔΣ modulator, which produces no fractionalization spurs. Published features of the normalized in-band phase noise floor, the normalized 1/f noise and the wideband out-of-band phase noise floor are -226dBc/Hz, -274dBc/Hz and -157dBc/Hz. BTW I’m no AD guy, only an old retired analog fossil, playing since more then 10 years with advanced SDR technolgies including the assistance of some test equipment in my backyard. Greetings to down under. 73, Helmut, DC6NY -----Ursprüngliche Nachricht----- Von: glen english [mailto:[email protected]] Gesendet: Donnerstag, 9. April 2020 00:43 An: [email protected] Betreff: Re: [Freetel-codec2] A warning on using single chip transceiver chipsets. Hi Helmut I think you are incorrect. an old analog radio is usually miles ahead of the little chip radios >= 1MHz phase noise... and fractional spurs. Happy to bet my house on it. Are you ??? The IC9700 is not very good at 1 MHz offset. Sur eit is good on RX but not good on TX wideband. It is because the microwave VCO in the chip has insufficient Q, and is contaminated by the other currents on the die and chip, that you cant do much about unless you move it off chip ! spurs and noise leak in. For an integer setup, the loop bandwidth doesnt go much beyond 400kHz, and so it relies on the VCO performance at 1MHz-10 MHz which isusually poor. For a fractional setup, the very idea of a SDM is that noise is moved from the low freq to the high freq, so you cannot run high loop bandwidths anyway . You are limited to < 60 to 80kHz in most cases, and so this does nothing for the 500kHz to 5 Mhz ish phase noise . and as all the chips are designed for DC to daylight, there is NO bandpass of anything, meaning wideband noise is radiated over a whole band or octave of spectrum. On 8/04/2020 10:00 pm, Helmut Oeller wrote: > 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]> mailto:[email protected]] > Gesendet: Mittwoch, 8. April 2020 12:48 > An: <mailto:[email protected]> > [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 > <mailto:[email protected]> > [email protected] > <https://lists.sourceforge.net/lists/listinfo/freetel-codec2> > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > > -- > Diese E-Mail wurde von AVG auf Viren geprüft. > <http://www.avg.com> http://www.avg.com > > > > _______________________________________________ > Freetel-codec2 mailing list > <mailto:[email protected]> > [email protected] > <https://lists.sourceforge.net/lists/listinfo/freetel-codec2> > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 -- Glen English RF Communications and Electronics Engineer CORTEX RF & Pacific Media Technologies Pty Ltd ABN 40 075 532 008 PO Box 5231 Lyneham ACT 2602, Australia. au mobile : +61 (0)418 975077 _______________________________________________ Freetel-codec2 mailing list <mailto:[email protected]> [email protected] <https://lists.sourceforge.net/lists/listinfo/freetel-codec2> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 -- Diese E-Mail wurde von AVG auf Viren geprüft. http://www.avg.com
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