TV is sputtering on hot days

I'm not sure if this is the right palce for this question.  Now that summer is here (UGH) we are having the same problem as last summer.  Around noon and later the tv will have sputtering spells.  Besides being annoying, it can't be good for the television.  We had a tech out for another matter last year and he said that the hot sun on our outside connection was causing it. 

Question 1. Is it true that the hot sun on our outside connections can cause reception problems

Question 2   If so, what can we do to stop it

I am also wondering if maybe we have weak cables somewhere in the connections.  It only happens on the main TV in the living room.  I do use coax cable to connect our service to that tv and it goes thru a DVD player and a Laser disc player to get to the tv set.

Question 1   Could the coax cable be the probelm

Question 2   Is it bad to run the service thru so many other devices

Question 3   What is the best kind of cable to use on our connections.  I'm not up on the latest technology terms, so be kind.  I thought I could use the red/yellow/white A/V cables.  There is a spot for HDMI (?).  I don't know what that is or what kind of cable that would be.

Our TV is High Def, but we don't subscribe to High Def programming.