Tuesday, January 8, 2019

Radar 4980 kHz US East Coast

While monitoring WBHF signals on 4950 kHz, a radar-like signal was spotted around 4980 kHz. Note that its bandwidth exceeds the maximum bandwidth of the used KiwiSDR (20250kHz), so the full characteristics of this signal cannot be determined. It was active every few minutes but I was not patient enough to determine its schedule. Within the limited bandwidth the following can be seen:

1) The auto-correlation has peaks at multiples of 405/20250Hz = 0.02 sec = 1/50Hz:


2) Plotting abs(IQ) in frames of 1/50Hz reveals a pair of pulses, each apparently consisting of three separate sub-pulses:

abs(IQ) in terms of 1/50Hz frames

3) TDoA analysis locates this is a real signal somewhere in upstate NY (and demonstrates that it is not local QRM):
KiwiSDR TDoA 4980 kHz
(This is an example of successfully using KiwiSDRs with different sampling rate in TDoA, cf.,  http://valentfx.com/vanilla/discussion/1424/possible-tdoa-problem-when-using-kiwis-in-3-ch-mode)

If anyone knows what kind of HF radar signal this is I would be grateful to know.

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