6500 HW question - int OCXO vs 10 MHz Locked vs GPSDO

Simon Lewis

My 6500 is in flight and should be with me soon. Reading the documents on the 6500 HW ... the int oscillator looks like its .5ppm, but the 6500 can be locked to 10 MHz, or alternatively, install the GPSDO. Question is ... what is the difference in stability between the internal GPSDO option and the base 0.5ppm unit being locked to my common 10 MHz GPS derived source that I am already using? I guess it depends how the 10 MHz source controls the internal oscillator vs the GPSDO tracking a higher frequency reference oscillator. Anyway ... some info would be helpful to decide if I am going to need the GPS DO or just plug in my 10 MHz source btw my main use will be moonbounce and driving VHF-SHF transverters thanks Simon ZL4PLM

ai6re

Simon, your external GPS clock should serve your needs perfectly. I have a Flex 6500 with an external GPS clock and it typically shows about 0.3 HZ error to WWV. I believe this is due to my ability to measure the difference any closer. Without the external clock I see an error of about 7 hz on 20M. The clock will also need to correct your Transverter, as I am sure you know. Good luck and I know you will really enjoy your new radio. Don AI6RE

Simon Lewis

HI Don ... while accuracy is one thing .. I am more interested in the short/mid/long term stability ... where it counts on JT modes off the moon and LTI modes  

the 6500 using int osc if the specs are right are 0.5ppm - which is fine .. no stability factors give 

the 6700 is 0.02ppm - same

the gps however:

• GPSDO Frequency Stability (GPS locked): 5 x 10 (-12) over 24 hours

my 10 MHz GPS locked sources is the same .. .about 10 -12

just interested in the stability of the 10 MHz locked reference ie any worse  than the GPS DO Flex osc (does this lock the 900 MHz osc or the 10 MHz osc) ??

 So interested if a GPS locked 10 MHz source is as good as GPSDO in the 6500 using the add odd or I can save my 700 bucks

ai6re

Simon, The 6500 has a TCXO unlike the 6700 which has the OCXO. Without the external clock I see an error of about 7 to 10 HZ on 20M. My Kenwood TS2000X has a TCXO and drifts as much as 200 hz on our 1.2ghz net from power on to the end of the net 30 minutes later. It is also more than 1 khz of frequency on 1296 mhz.. I doubt there is any difference in the GPDDO and your internal clock. I believe you can install the internal GPSDO later if you need to. I am sure someone will correct me here if this is not correct. Don AI6RE

Tim - W4TME

I agree with Don, that you are probably not going to see a difference between the GPSDO and the external GPS disciplined XO.  Can you save your $700 bucks?  Probably, but I love for you to buy one ;-)