I hope you guys can help me again.

I gather from posts here that RG6 is better than RG59, is that right?

Could the use of of RG59, 33 feet, for at least one tv be responsible
for my bad reception on that tv?

I'm using co-ax for distributing tv from my DVDR to TVs throughout the
house. (The DVDR tunes in the over-the-air digital signal and I have
an RF modulator to change the DVDR output to analog. I did the wiring
to the tvs 25 years ago, and I used left-over and scrap co-ax, so the
co-ax is older than 25 years. Did they have RG-6 25 or 30 years ago?
I didn't pay attention then so I don't know what most of it is, but
the 33 foot piece going to this one tv is RMS Electonics Inc. 59/U.

Everything was fine until the digital conversion, and now this tv that
I watch a lot shows a grainy picture. All the other tvs have great
pictures, and even for this one, when I supply a signal directly from
a set-top digital converter box, only 3 feet of cable, it shows a
perfect picture**.

Do you think replacing the RG59 with RG6 will get me the perfect
picture other sets get? I didn't use home-runs, just splitters and
every two splitters a signal amp, a total of three signal amps, one
with 2 or 4 outputs, and two with 2. Would an additional signal amp
at the start of the RG-59 also give me perfect or at least improved
reception?

**(But the set-top box isn't connected to the main antenna and
doesn't get several stations I watch, nor will it play what is
recorded on the DVDR.)