The discussion about antenna cable delays made me think of the issue of the antenna delay. An antenna typically has a bandpass filter and amplifier so there clearly is some non-negligible delay associated with this. The issue is usually sidestepped by calibrating the delay of receiver+antenna (against what? A calibrated receiver + antenna from the BIPM of course...) But sometimes, after calibration, an antenna in the field has to be replaced with a different antenna and the original calibration is invalidated. It then becomes necessary to expand the uncertainty of the delay. I did read a NIST paper where they described measuring the delay by physically disassembling the antenna so that they could feed signals directly to the electronics. Delays like 30 ns were measured, I think. Myself, when changing antennas I have seen steps like 10 ns. Does anyone have any data points to add to this ? Cheers Michael

Hi There are a lot of variables in all this. If you have a good antenna, it’s got a filter ahead of the preamp. It may also have a filter after the preamp. Just how wide these filters are … that depends. If you grab a bunch of SAW filter data sheets, you see numbers in the 10 to 25 ns range. Older ceramic resonator filters are a bit hard to pin down. Bob > On Jun 29, 2016, at 5:46 PM, Michael Wouters <michaeljwouters@gmail.com> wrote: > > The discussion about antenna cable delays made me think of the issue of the > antenna delay. An antenna typically has a bandpass filter and amplifier so > there clearly is some non-negligible delay associated with this. > > The issue is usually sidestepped by calibrating the delay of > receiver+antenna (against what? A calibrated receiver + antenna from > the BIPM of course...) > > But sometimes, after calibration, an antenna in the field has to be > replaced with a different antenna and the original calibration is > invalidated. It then becomes necessary to expand the uncertainty of the > delay. > > I did read a NIST paper where they described measuring the delay by > physically disassembling the antenna so that they could feed signals > directly to the electronics. Delays like 30 ns were measured, I think. > Myself, when changing antennas I have seen steps like 10 ns. > > Does anyone have any data points to add to this ? > > Cheers > Michael > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.