Posting this for Cliff - Thanks so much for the response and sharing -
Bruno:

Hi Bruno, I tried to post a response to your post but it won't go for
some reason. Feel free to post this in my stead if you feel it will
help:

I too have and love my MRX. I had the same problem with mine but the
issue was not the filter but the connection where the antenna attaches
to the board the solder joints failed. This is a weak spot, and mine
was out of warranty and they charged me $150 to repair it. That being
said, they also upgraded the software and latest updates when they did
it. The weak spot is in that the antenna tightens down too easily and
when you remove the antenna it is easy to put a lot of pressure on the
solder joints to get the antenna to loosen up and there is no way to
hold the fitting the antenna attaches to. Mine is mounted under my
glare shield and the antenna is sticking up through the glare shield.
when I removed it to work behind the panel I must have broken it. And
as you said it doesn't tell you it is broken it just doesn't pick up
any aircraft. I am VERY careful with it now and have not had any
further problems

Cliff Hilty (CH) Ventus B