Sony AVD-C70ES Mode D'emploi page 24

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If you have poor FM reception
Use a 75-ohms coaxial cable (not supplied) to connect the receiver to an outdoor FM antenna as shown below.
Outdoor FM antenna
Note
If you connect the receiver to an outdoor antenna, ground it to protect against lightning. To prevent a gas explosion,
do not connect the earth wire to a gas pipe.
US
24
Receiver
ANTENNA
Earth wire
AM
(not supplied)
FM
75Ω
COAXIAL
To earth