for welcoming me on board.
I have posted my query in https://www.rdforum.org/threads/109799/#post-1587824,
and I have got some helpful link to look for a suitable directional antenna,
just need additional knowledge...
I refer to Novelda X4M300 presence sensor
I intended to purchase a budget 2nd hand spectrum analyzer with a directional antenna that can detect the presence of intruding RF,
In page 10 of the datasheet of the above...