Radio Shack 21-940A mag mount CB antenna
The Radio Shack 21-940A mag mount 27 MHz CB antenna spanned over two decades of sales with a well-performing, economical design. A trunk-mount variant 21-908A is said to have been featured on the “Dukes of Hazzard” program, which has led to abnormally high valuation even for well-used examples. The 21-940A mag mount is only capable of 25 watts transmit power and can easily permanently burn out with common 10 meter mobile transmit power. The coil is shunt wound, meaning it normally reads as a short from center pin of the UHF connector to shield (ground). The SWR is under 1.5:1 across the 26.965 - 27.405 MHz CB band, and is usable over about 1.2 MHz of total bandwidth. The antenna is just over 1 meter tall and performs similarly to the modern Wilson Little Wil, Tram 300, and similar - except these antennas are generally well capable of the transmit power of a typical 10 meter mobile radio, while the 21-940A is not.