Hi If the TBolt is locked up and has stayed locked up for 24 hours it should be pretty accurate. Ideally you would like to be locked to at least 4 sats at all times for best accuracy. Lady Heather is your friend when it comes to checking this sort of thing.
How good is “pretty accurate”? At 8 GHz, it’s a good bet ( 99 %) that you are under 1 Hz of error. It’s a reasonable bet (> 80%) that you are under 0.1 Hz. Both assume a 100 second gate on your counter. Things degrade a bit if you go to shorter gate times. The numbers above are conservative for most TBolts. The Efratom drifts (ages) enough that a 300 Hz error at 8 GHz is not impossible. A lot depends on just how long it’s been since it last was set on frequency. Most examples are not that far off frequency …. Neither the TBolt *or* the LPRO should “drift” 300 to 400 Hz at 8 GHz over any reasonable amount of time ( hours, days, weeks). This assumes they stay powered up and in the TBolt’s case, locked to >4 sats. What to do? Best guess is the TBolt is right and the LPRO is wrong. Reset the LPRO so it agrees with the TBolt. Bob > On Aug 21, 2021, at 8:50 AM, [email protected] wrote: > > Hello Time-Nutters-- > > I am working on building a downlinking AZ/EL tracking dish set up to > receive the 8.2 GHz telemetry from the Suomi JPSS polar orbit > meteorological/environmental satellite. The receiver seems to be > working OK but it periodically appears to slowly drift frequency by > 300 Hz to 400 Hz. I need some way to accurately determine what > the actual RX receive frequency is. > > I have a vintage Efratom LPRO-101 Rubidium 10 MHz oscillator. > I originally got it thinking that it would provide a decent > phase-lock reference for my freq-counters, o-scopes, spectrum > analyzers and Agilent/HP vector network analyzer. > > The only other item I have that has (or should have) a reasonably > accurate 10 MHz reference output is a Trimble Thunderbolt. > However, there is a several hundred Hz freq difference between the > Efratom and the Trimble T-bolt. > > My question is how do I go confirming the frequency of the T-Bolt > or the Efratom Rubidium? The Efratom has an adjustment pot > to fine-tune its output frequency. How do Time-Nutters go about > confirming the accuracy of frequency references such as my > T-Bolt or Efratom rubidium oscillator? > > Thanks for any feedback / suggestions on this !! > > Off-list communications on this via my email is OK!! > > Mike Baker [email protected] > Micanopy/Gainesville North Central Florida > ********************** > > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send an > email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
