Product Line, Customer and Geographic Information - Result of Product Line Revenues and Gross Profits (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Results of operations by segments
Revenues	$ 21,185	$ 18,923	$ 19,842	$ 17,506	$ 22,898	$ 23,630	$ 23,499	$ 20,590	$ 77,456	$ 90,617
Gross Profit	$ 10,616	$ 9,575	$ 9,521	$ 8,215	$ 11,513	$ 10,647	$ 10,694	$ 8,658	$ 37,927	$ 41,512
Gross Profit %									49.00%	45.80%
Operating Segments [Member] | Antennas & Industrial IoT Devices [Member]
Results of operations by segments
Revenues									$ 50,540	$ 62,708
Gross Profit									$ 17,665	$ 21,841
Gross Profit %									35.00%	34.80%
Operating Segments [Member] | Test & Measurement Products[Member]
Results of operations by segments
Revenues									$ 27,565	$ 28,115
Gross Profit									$ 20,244	$ 19,640
Gross Profit %									73.40%	69.90%
Corporate, Non-Segment [Member]
Results of operations by segments
Revenues									$ (649)	$ (206)
Gross Profit									$ 18	$ 31