[time-nuts] z3801a gps signal reflection and EFC woes

[mike cook]

My Z3801A's EFC is being affected by sharp offsets in PPS TI due to the Oncore VP  not filtering reflected satellite signals .
My antenna is not well placed as it is on my office window sill in a 3rd floor appartment facing north. Not quite urban canyon land, but I still see reflected signals with a mask angle of 60° :(. Up there there are few birds passing, so the box is in holdover for a good part of the day if I leave it at that value.

I have attached a couple of pngs to show how Z38XX is reporting this. This is of the most flagrant event I am seeing , but there are lots that I can see when referencing the azimuth/elevation display that I can correlate with the spikes seen in the PPS TI trace. 
I forgot to note this particular satellite ID, but it is the strongest signal I am seeing, reported at a relative signal strength of 255.

You can see that the EFC immediately tries to follow the value calculated during the incident, regardless of any historical data the box is holding, if any. I haven't yet checked to see how much the violent swing in EFC effects  the 10MHz output, but I suppose there must be some.
 I have tried 2 different VPs  , but they appear to be suffering the same issue. Both have different firmware levels.

Anyone seen this and know of a way of limiting the effect? I have thought about moving the Z3801A to my south balcony, where I shouldn't see so many reflections, or better, to the appartment roof, but that needs permission from the management.

Mike

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