How far is to far?

[payge2001]

I'm just getting set up in gmrs. I just got my first mobile set up as a base. I have a Radioddity DB20-g with a Sirio CX455 base antenna on a 20' mast. I have the radio programmed and can hit a local repeater. I trying to hit a linked repeater that is 51 driving miles from me with no luck. Is that to far away or do I need a better radio or my antenna to be higher? 

[Borage257]

Height will certainly help, also check the terrain between you two. 
 

Another thing to try would be a higher gain vertical or a yagi.

I have a a similar repeater about 45 miles distant as the crow flies. My jpole is at 30’ and I can barely get in most of time. But with a HT and yagi (at 10’) I can always get in very well.

In order I usually go to (1) height (2/3) gain (2/3) cable (look at LMR400 or KMR400) (4) radio/ radio power.

 

I’ve done 75 miles to a repeater with an HT and a yagi on my roof top (32’).

[DONE]

Hmmm, UHF is line of site.  The horizon at ground level on flat land is 11 miles.

At 100 feet it's 14 miles.  So you would need to know how high the repeater antenna is in the air to do the actual calculation.

https://www.qsl.net/w4sat/horizon.htm

Link to the calculator.

But if the antenna is at 200 feet for the repeater, to have true LOS (line of site) from your base station YOUR antenna would need to be around 500 feet in the air to have LOS at 50 miles. 

Now, not knowing where you are, what the topography of your area is (flat, hilly, mountainous) I can't say for sure what would be required. 

With both specific locations there are ways of figuring it out however.  Try RadioMobile.  It's a free software package that references different online topo maps to figure out the LOS heights required and what the actual path loss would be.  You can change antenna height, antenna gain and power levels in the software to figure out whats required.

It will also calculate the expected coverage mapping for a repeater or base station with its specific parameters.

 

[Borage257]

This is also pretty good RF line of sight and topography calculator 

 

https://www.scadacore.com/tools/rf-path/rf-line-of-sight/

[payge2001]

[payge2001]

Does this help out any?

[Borage257]

20 minutes ago, payge2001 said:

Does this help out any?

Add yours and the repeaters antenna height, if known in meters (divide ft by 3.3).

 

looks like there are some hills in the way (left hand side of the plot).

[MichaelLAX]

No mountains in Indiana.

[AdmiralCochrane]

Yes, too far