Product Line, Customer and Geographic Information - Result of Product Line Revenues and Gross Profits (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Results of operations by segments
Revenues	$ 18,923	$ 23,630	$ 56,271	$ 67,720
Gross Profit	$ 9,575	$ 10,647	$ 27,311	$ 30,000
Gross Profit %	50.60%	45.10%	48.50%	44.30%
Operating Segments [Member] | Antenna Products [Member]
Results of operations by segments
Revenues	$ 12,326	$ 16,463	$ 37,696	$ 47,565
Gross Profit	$ 4,336	$ 5,712	$ 13,228	$ 16,142
Gross Profit %	35.20%	34.70%	35.10%	33.90%
Operating Segments [Member] | Test & Measurement Product Line [Member]
Results of operations by segments
Revenues	$ 6,810	$ 7,240	$ 19,011	$ 20,301
Gross Profit	$ 5,203	$ 4,937	$ 14,109	$ 13,834
Gross Profit %	76.40%	68.20%	74.20%	68.10%
Corporate, Non-Segment [Member]
Results of operations by segments
Revenues	$ (213)	$ (73)	$ (436)	$ (146)
Gross Profit	$ 36	$ (2)	$ (26)	$ 24