Hello Graham,
Looking on the specs of my Isotemp 134-10 oscillator showed that spurious attenuation should be >60 dB. Looking at the 10 MHz signal on the 1500 showed a lot of spurii about 60 dB down. In my scrapbox I found a 10 MHz 8-pole quarzfilter. Putting this filter in line with the 10 MHz signal cleaned it up. I do not have ground loops and the power supplies are clean. But the 60 dB attenuated +/- 10 kHz spurious are still there when I lock the 1500 to the GPSDO. And they disappear when using the internal reference. Kjeld/OZ1FF Fra: gra...@flex-radio.com [mailto:gra...@flex-radio.com] På vegne af Graham Haddock Sendt: 2011-04-13 05:07 Til: Kjeld Bülow Thomsen; FLEXRADIO Emne: Re: [Flexradio] Flex-1500 spurious when using external reference Kjeld: Do you have access to another 10 MHz reference that could be substituted and used to compare? It does not have to be high accuracy for the comparison test. I suspect a 10 kHz switching power supply or some other 10 kHz source associated with your GPSDO as causing the problem. You might also try making sure the case of the FLEX-1500 shares a common ground with the GPSDO. Do not depend on the shield of the 10 MHz coax, since it floats at the FLEX-1500 input, to allow the 1500 to reject ground loop noise. --- Graham / KE9H == On Tue, Apr 12, 2011 at 10:23 AM, Kjeld Bülow Thomsen <oz...@mail.dk> wrote: Im using my Flex-1500 with transverters on 1,3 24 GHz. The radio and most of the transverters are locked to a 10 MHz GPS-disciplined oscillator. When working weak signals there are only very few spurious frequencies. During the last weeks there has been tropo conditions with signals in the 59 +20-30 dB range. All these signals appeared full of spurious +/- 20 kHz. As all signals was looking in the same way when exceeding S9 I decided to investigate the problem. The pictures on http://www.oz1ff.dk/pages/flexradio.html a screen dump of a -60 dBm signal on 28,2 MHz from a clean source. Dia1 is with external reference and shows +/- 10 kHz spurious. Dia2 shows the signal with the 10 MHz reference switched off. Increasing the signal generator level to more than -40 dBm with 30 dB preamp gain overloads the receiver. But that is as specified. The level from the external 10 MHz source is +2 dBm and sine wave. The external reference is essential for weak signal work. I dont expect this to be a software problem. Any suggestions for a solution to this annoying problem? Vy 73 de OZ1FF - Kjeld Phone +45 7352 6050 SMS +45 4021 1119 Skype oz1ff-1 <mailto:kj...@oz1ff.dk> mailto:kj...@oz1ff.dk <http://www.oz1ff.dk/> http://www.oz1ff.dk _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/ _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
