Sounds like magic but we (US, USSR, etc...) were doing this with HF/VHF/UHF in the 70's for anti-jam (AJ), Low Probability of Intercept/Detection (LPI/ LPD) systems. The problem was, the gear was big, expensive and not very user friendly.

https://dsb.cto.mil/wp-content/uploads/reports/2000s/ADA428978.pdf

CDMA had been used in military systems since the 1970’s and developed into
a digital cellular telephone system standard, known as Interim Standard-95 (IS95) by the 1990’s. It may be noted that commercial utility of spread spectrum had
been advocated to the FCC long before the advent of IS-95. In a 1981 report on
the efficient modulation, the FCC observed, “The low power density and
interference suppression capability of spread spectrum systems suggests a
unique application,…band overlay. It may be possible in some circumstances to
overlay spread spectrum systems on spectrum used by conventional services
with little or no mutual interference….Short range systems, such as cordless
telephones, might prove ideal for such an application” [FCC1981]. In this and
related passages in the report, the FCC uses the term “spread spectrum”
narrowly, essentially equivalent to the present use of “CDMA.”

 

Channel hopping on the citizens band is as effective as hiding a tree in the forest. If the cloaked transmission is detected it will seem like every other bit of interference/intermod products. Not a perfect scheme but certainly simple. And if the link is kept active with realistic fake communications it might not even be noticed. BUT it won't work in an area without CB chatter