I am using the Leo Bodnar Single output Mini GPSDO to generate 38.4 MHz as an input to a Wenzel Oscillator that locks to it and produces a low phase noise 80 MHz to drive my Perseus SDR. The Wenzel has a low loop bandwidth so the phase noise from the Bodnar above the 10-100 Hz range does not seem to get through. The issue is that there are sometimes some close in spurs from the Bodnar that do get through, about 31 and 62 Hz on either side of the 38.4 MHz output. I believe the GPSDO is based on a SI532X chip, as reported for the two output version. The spurs are only about 70 dB down, maybe 15-20 dB above the phase noise in the area. I tried several frequency plans as the SI532X can generate the same output with several different sets of dividers. I did find one that worked very well, with phase noise results and Allan Deviation that appear better than the reported phase noise for the two output version. I basically used the Bodnar software, SI's DSPLLSIM, some spreadsheet calculations and trial and error to determine the working frequency plan. I was hoping someone who knows these devices might have some insight into what the issue is and how to determine which plans will not provide close in spurs, without requiring testing. Any suggestions are appreciated. Below is the long part. I have listed the frequency plans I tried and the results below. Maybe someone can see a pattern. Thanks Mark *My First Try Plan * GPS 2,560,000 N31 1 N2_HS 7 N2_LS 300 N1_HS 7 NC1_LS 20 BW 15 F3 2,560,000 Fosc 5,376,000,000 Fout 38,400,000 Fout/F3 15 *No Spurs, F3 above data sheet spec* *My Plan with in spec F3* GPS 2,560,000 N31 2 N2_HS 7 N2_LS 600 N1_HS 7 NC1_LS 20 BW 15 F3 1,280,000 Fosc 5,376,000,000 Fout 38,400,000 Fout/F3 30 *Spurs* *Another Plan* GPS 2,560,000 N31 1 N2_HS 11 N2_LS 150 N1_HS 11 NC1_LS 10 BW 15 F3 2,560,000 Fosc 4,224,000,000 Fout 38,400,000 Fout/F3 15 *No Spurs, F3 above data sheet spec* *DSPLLSIMs Plan* GPS 2,560,000 N31 2 N2_HS 10 N2_LS 396 N1_HS 11 NC1_LS 12 BW 15 F3 1,280,000 Fosc 5,068,800,000 Fout 38,400,000 Fout/F3 30 *Spurs* *DSPLLSIMs Plan 2* GPS 1,920,000 N31 1 N2_HS 5 N2_LS 576 N1_HS 8 NC1_LS 18 BW 15 F3 1,920,000 Fosc 5,529,600,000 Fout 38,400,000 Fout/F3 20 *Bad Spurs* *DSPLLSIMs Plan 3 Using This One* GPS 1760000 N31 1 N2_HS 9 N2_LS 320 N1_HS 6 NC1_LS 22 BW 15 F3 1,760,000 Fosc 5,068,800,000 Fout 38,400,000 Fout/F3 21.8181818181818 *No Spurs*