The original Alfa Romeo Montreal radio installation publication recommends drilling the antenna mounting hole on the left side 40 cm forward of the rear of the vehicle. This will position it right above the battery, leaving very little room for any telescopic model. I recommend 46 cm which, with a typical rake angle, will allow a motorised antenna to be just fitted in between the battery and the rear wheel arch. The overall length of the interior part of the antenna measured from the body shell to the lower end of the motor mechanism must not exceed 30 cm. 5-stage antennas with an extended length of 1 m (such as Interconti Model RA30911C) are available which meet this criterion.
The easiest way to route the antenna coaxial, power and control cables from the boot to the front of the car is as follows: Remove the rubberized rear seat base assembly by extracting the 4 screws of the luggage strap securing plates, bending the assembly slightly in the middle and lifting it out of the car. Note how very heavy this assembly is if you are seeking a simple way to lighten the vehicle! Now remove the 4 screws of the luggage strap securing plates on the dossier of the rear seat and edge the top of the dossier forwards by a few cm. (It is unnecessary to extract the less accessible lower screws and remove the dossier). The cables can now be passed through the slot from the boot and down the back of the dossier, through the holes in the compartment in the front of the wheel arch, and under the chrome trim strip to the fusebox and radio.
I prefer to route the wire from the antenna control output of the radio through an additional toggle switch so that antenna extension can be inhibited even when the radio is on. This is particularly useful in the case of autoradios which energize the antenna control output even when only the cassette player is being used. In a Montreal without air conditioner the vacant hole to the left of the cigarette lighter is fine for this switch.
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