Coaxial cable and antenna question

[Templeton]

I am looking at setting up a temporary "base station" GMRS antenna at my house with a handheld. I notice that I have a Comcast (xfinity) traditional cable TV (also internet) coaxial cable junction going through my household wall, but the junction is unused on both sides (using ATT fiber for internet). So here is my question: if got one of these antennas (link below) mounted on a metal ground or on a steel vehicle roof, would the antenna cable essentially be the same (or be compatible with using adapters) to the standard traditional coaxial comcast cable junction? This would make it easier to run the antenna from the outside of my house to the inside of my house without adding a new hole to my wall or floor.

This is the antenna I am hoping to connect to the comcast coaxial cable junction:

https://www.amazon.com/gp/product/B09TPZ221K/ref=ox_sc_act_title_5?smid=A3KP78Z860PGLG&th=1

[SteveShannon]

27 minutes ago, Templeton said:

I am looking at setting up a temporary "base station" GMRS antenna at my house with a handheld. I notice that I have a Comcast (xfinity) traditional cable TV (also internet) coaxial cable junction going through my household wall, but the junction is unused on both sides (using ATT fiber for internet). So here is my question: if got one of these antennas (link below) mounted on a metal ground or on a steel vehicle roof, would the antenna cable essentially be the same (or be compatible with using adapters) to the standard traditional coaxial comcast cable junction? This would make it easier to run the antenna from the outside of my house to the inside of my house without adding a new hole to my wall or floor.

This is the antenna I am hoping to connect to the comcast coaxial cable junction:

https://www.amazon.com/gp/product/B09TPZ221K/ref=ox_sc_act_title_5?smid=A3KP78Z860PGLG&th=1

Not well. TV cable and related fittings are 75 ohm. Two way radios expect 50 ohms. Using it for your radio will introduce an impedance transition that results in a higher SWR than usually desirable. 
But, people do it. 
You can use the hole that currently exists.

[Templeton]

Ok, good to know. Making a new hole is not a big deal.

Also, if I use appropriate antenna cable, does the total length of the cable make a big difference, or small difference, in the effectiveness of my base station antenna? For example, I can run a short cable to an antenna on my roof (but house is just one story). Or, I can run a longer antenna cable (25 to 50 ft longer) and put an antenna up on a considerably taller tree (more like two stories). The taller tree wins out for line-of-sight, but it would require a longer antenna cable. Any way of knowing which way should I go?

And, if I need to buy some antenna cable, what kind of specs or impedance am I looking for? For this kind of home base station set up? Thanks!

[SteveShannon]

Your question made me look for a video that would explain this better:

Stan Gibilisco passed away within the last few years but I liked his videos:

 

As for your other questions, almost all communications cable is 50 ohm. The antenna you showed is also 50 ohms. The port on your radio expects 50 ohms. 
But, there are lots of different types of cable and different types have losses that increase proportionally to length. Those losses are simply characteristics of the cable. 
Unfortunately, the rate of loss increases dramatically as frequency increases. At GMRS frequencies some cables lose half or more of their power in less than 50 feet.  
But, a good antenna, raised high can compensate for that somewhat. 
I wouldn’t select less than LMR400 and if I was going longer than 50 feet total I’d look for something even better. 

[Templeton]

Thanks for the help. If I want to put a gmrs antenna on my house roof (like maybe an Ed Fong J-pole), is there any good guidance that I should consult regarding grounding the antenna? We get summer thunderstorms, so I don't want to burn my house down!

[SteveShannon]

This is one of my favorite short guides for grounding and bonding but there are lots of threads here that cover it in great detail. The Bible is a document from Motorola that’s available on a BLM site, but it’s pretty deep. Also ARRL has a book on grounding and bonding. 
https://reeve.com/Documents/Articles Papers/Reeve_AntennaSystemGroundingRequirements.pdf

[Templeton]

Excellent document, and thanks for the help and input.

[WRUU653]

17 hours ago, Sshannon said:

This is one of my favorite short guides for grounding and bonding but there are lots of threads here that cover it in great detail. The Bible is a document from Motorola that’s available on a BLM site, but it’s pretty deep. Also ARRL has a book on grounding and bonding. 
https://reeve.com/Documents/Articles Papers/Reeve_AntennaSystemGroundingRequirements.pdf

I'll second that "excellent document"