Business Segments - Product Category (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 29, 2019	Sep. 30, 2018	Sep. 29, 2019	Sep. 30, 2018
Revenue and Gross Profit from External Customers
Revenues	$ 141,810,900	$ 158,636,100	$ 272,540,200	$ 309,555,500
Gross Profit	26,319,300	31,394,700	51,582,800	62,092,800
Base station infrastructure
Revenue and Gross Profit from External Customers
Revenues	71,473,000	75,515,000	140,542,000	149,829,000
Gross Profit	14,565,000	15,534,000	29,086,000	31,250,000
Network systems
Revenue and Gross Profit from External Customers
Revenues	22,855,000	22,564,000	45,407,000	45,341,000
Gross Profit	3,463,000	3,561,000	7,390,000	7,224,000
Installation, test and maintenance
Revenue and Gross Profit from External Customers
Revenues	7,240,000	8,891,000	13,265,000	16,322,000
Gross Profit	1,229,000	1,803,000	2,313,000	3,276,000
Mobile device accessories
Revenue and Gross Profit from External Customers
Revenues	40,243,000	51,666,000	73,326,000	98,063,000
Gross Profit	$ 7,062,000	$ 10,497,000	$ 12,794,000	$ 20,343,000