A clever way of doing this might be connecting an antenna at the "unused" port, placing it in the middle between your two RX antennas, and transmitting a short known sequence on it, detecting it with your RX and estimating the phase offset between RX and TX with that -- you'd also have a way of knowing the pure loopback delay in your current configuration like

We had an error in our metadata recording code which was causing the mean time delay estimation between multiple B200s to be on the order of microseconds (~25uS) at 25 MSPS. Now, we have all three B200s sync’d within a sample on UHD 3.8.5 using a timing reference and 10 MHz/1PPS.

. > > > AFAIK, Ashtec's patented "Z-code" receivers generate a hardware > > > estimate of this code and (nearly) coherently demodulate the signal. > > > Other brands have similar tricks up their sleeve. > > > >The Y-code is the P-code xored with the A-code (sometimes also referred > >to as the W-code). The A-code is indeed ~500 kbis/sec.

When one obtains a pair of interpolated points that are sufficiently close to each other and preferably straddling the threshold crossing linear interpolation will suffice for the final estimate. One advantage of this technique is that a model of the signal waveform isn't required.

. > > > Bruce > > Mike > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Here is the response to your next post to save time: > > > Mike > > > Its well worthwhile estimating the additional jitter due to this > > effect when using such a circuit to square up the output of an OCXO: > > > If the input signal characteristics

But I believe the power failure did throw my estimates off a bit more than usual. Dave > --- On Mon, 28/12/09, Dr. David Kirkby wrote: > >> From: Dr. David Kirkby >> Subject: Re: [time-nuts] Can a quartz crystal go off by 2% ?

A TPLL does not suffer from that particular problem, as it > cranks out its frequency estimation by a different method. Yes, but I thought that we were calculating the required averages from the frequency (EFC) samples by approximating the required integrals.

It can however send its estimate on how wrong the 1PPS signal is via the serial port. Newer receivers have hardware with better 1PPS resolution - and better tracking/position etc. Tom probably has a much better explaination...

This enables us to *estimate* the error and make allowances for it, but not to eliminate it. Would that we could... Precision, in process control, is often defined as the standard deviation of the stochastic error distribution. That, too, can be improved but never made perfect.

. ** Dual-frequency receivers -- a large gain in performance since it allows the receiver, in real-time, to estimate and remove propagation errors. Requires L1/L2 GPS antennas. ** Carrier Phase -- also a large gain in performance. There are dozens of papers in the last decade that show graphs of code vs. carrier performance.