. > > 73, Steve > Steve Instead of waxing lyrically try doing some estimates of the averaging time required for a given accuracy: You need to measure the ADEV of the reference source (ie the relevant NMEA sentence).

After an hour, you pick the correlation bucket that correlated best and have an instant estimate of the difference between your local clock and the average of that hours transmissions. If xmitted as NFSK at around 100kHz and digitized at 1MSPS, you would get 1µsec resolution without resorting to interpolation.

It is estimated that over 12 million radio receive clocks and watches have been sold in the US. The new scheme will allow new devices to be constructed that can receive the frequency also. I will add your name to my list to be contacted when we have a work-around.

Photocells don't work for situations where the desired on or off times are civil times (not turning on the water sprinklers until 11 PM for example or turning off the tennis court lights at 10 PM)... at best it takes lots of software to convert light and dark from them to anything approximating a 10 minute accurate estimate of the time of day and shadows and

The original quest was for delay, so accurate time at the venue is only to measure delay until decoded, so all that delay can be estimated. Cheers, Magnus

My estimate is that all harmonics are at least -50 and most probably -60 down. The 10MHz is probably the worst. My Lab is not really set up for RF work, so this is probably an area where one of the hams could do lot more competent job than me.

It fact that is the whole point of it's being, to estimate the variance in round trip point times and use this to determine how much to weight the results. NOW, the key assumption NTP makes might be wrong and this is a large source of error. It assumes the one-way jitter is 1/2 the round trip jitter.

Applying this type of phase-comparison, estimate stability, weighing and updating ensamble stability should indeed be possible to do. You need three or more clocks, but one of these can be the GPS when you have it. Jim Gray pointed out that it is important to watch your data. At NBS/NIST they started to see some 1/f⁴ noise on one of their standards.

An estimation of the propagation delay from the transmitter to our site was taken into account when analysing the records. The xtal oven was adjusted for a drift (fast) of a few mS for the day, this ensured that the scope was triggered before the time signal was received , making it easier for the operator to check and measure the daily drift.

The plot is averaged to get the signal out of the noise, The P-P calibration offset on the left allows you to estimate the deviation of the other parts of the plot. The short term stability of the 5065A at 1 sec is causing the noise you see. 2) how do you set the offset of the op-amp trimmer ?