Is it safe to use DIY CB antenna if the SWR is under 1.5 and can you use longwire antenna for receiving CB radio?
A standing wave ratio of 1.5 is still a bit high. You should
couple the antenna via some sort of antenna tuner and tune as close
to 1:00 SWR. While t is possible to use a longwire antenna for CB
reception purposes, the performance won't be too great. If,
however, you are planning on transmitting, again, the longwire
antenna should be coupled to the transmitter via some form of
antenna tuner, to match impeadances, lower the SWR, and protect the
final stage of the transceiver. A resonant long wire antenna only
requires that the length of the wire is approximately resonant at
the frequency of operation. For CB this means the wire must be a
multiple of 11.1m (36ft 6.5 inches). Therefore, a three wave long
wire would be 33.3 m (109' 9") and four-wave long wire would be
44.4m (146' 3") in length.