I have also been trying to determine the difference between these two radios for some time, hoping to understand why communications
and marine authorities in places like the UK/Europe and Australia would choose to remove the M802 off their list of HF/SSB radios approved for new installations/purchases. The price
difference is significant so why do it and generate a lot of flack from boat owners?
From what I can determine, the principle difference is that the M802 relies on a fan to draw air - salt
and dust laden - through the radio components to cool them. Beacuse the radio box has slots to allow the air through, these can aslo let water
, coffee etc inside.
The M801E has a completely sealed container with the radio components inside. That container is aluminium and functions as a heat sink. There is no fan to consume electricity, and no holes to let in water
, coffee etc. Apparently it weighs about 10kg; considerably heavier than the M802.
I understand it's this robustness, and therefore the ability to keep working when circumstances are at their worst, which is the reason communications
and maritime authorities specify it over the M802.
The M801GMDSS is another step up again, Apparently the difference from the M801E is that it has a completely protected power supply, so no spikes from alternators, generators and other electrical equipment
can get through to damage the radio. The M801E is the cheaper version of the full GMDSS radio. The authorities think they are doing recreational owners a good deed by approving the M801E for sale/registration; which is much lower cost compared to the full GMDSS radio.
My understanding is these decisions have been made by people who are familiar with the causes of common marine radio faults and the consequences these have for Search and Rescue
operations. This is to help make sure that the official maritime safety
(ie: HF/SSB with DSC) used around the world, can perform for people as they might reasonably expect, when they need it. Like a lifejacket, it needs to work when things go wrong; not when everything is perfect and it is not actually needed.
Hope that helps your deliberations.
Perhaps other people have more information to contribute on this topic?