Do you get the unsquelch on all channels or just 16?
I think just 16.
How much rotation of the squelch knob is required to restore squelch - a little? alot?
alot
Despite the unsquelching, can you still hear conversations on the handheld? Can you still transmit?
difficult doing both
Have you tried seeing how far away you can get with the handhelds before the handheld squelches again?
about 3 feet w/a uniden, about 2 with a standard horizon
Do you have a mounted VHF with a masthead antenna, and if so, is it affected?
Not affected even though it is mounted right next to the computer unit
Was there a time when your autopilot did not affect handhelds?
Just installed the AP this year, so no.
Anything digital puts out some electromagnetic junk; it's just the nature of digital devices. Even just driving a display creates some hash. It would take alot of testing to determine what your autopilot head is radiating, whether it's at VHF frequencies or at one of the internal frequencies used by most receivers.
There are a few possibilities, assuming the handhelds are all to spec:
1 - something in the autopilot, like shielding or filtering, has malfunctioned
2 - the autopilot head is poorly shielded
3 - the autopilot meets spec, but it just so happens that radios in close proximity may be affected.
My gut is saying #3 is most likely, and receivers were not expected to be operated within 2 ft of the control head. Check your autopilot's manual - close to the front there may be a FCC compliance notice that warns about interference.
The manual does say:
EMC installation guidelines
Raymarine equipment and accessories conform to the appropriate Electromagnetic
Compatibility (EMC) regulations. This minimizes electromagnetic interference
between equipment, which could otherwise affect the performance of your system.
Correct installation is required to ensure that EMC performance is not compromised.
For optimum EMC performance, we recommend that:
• Raymarine equipment and the cables connected to it are:
i. At least 3 ft (1 m) from any equipment transmitting or cables carrying radio signals
e.g. VHF radios, cables and antennas. In the case of SSB radios, the distance
should be increased to 7 ft (2 m).
ii. More than 7 ft (2 m) from the path of a radar beam. A radar beam can normally
be assumed to spread 20 degrees above and below the radiating element.
• The product is supplied from a separate battery from that used for engine start.
This is important to prevent erratic behavior and data loss which can occur if the
engine start does not have a separate battery.
• Raymarine specified cables are used.
• Cables are not cut or extended unless doing so is detailed in the installation
manual.
Remember
Where constraints on the installation prevent any of the above recommendations:
• Always allow the maximum separation possible between different items of
electrical equipment. This will provide the best conditions for EMC performance
for the installation.
