Communication Relay Satellite

[Fadly]

I want to send a probe to Duna. To save weight, I will only equip it with 3 communotron 16 antenna. I also plan on deploying 3 long range relay satellites on geosync orbit above Kerbin. will the relay satellite powerful enough to receive signal from communotron 16 antenna on Duna?

[bewing]

Kerbin already has super-powerful antennas on it (the ground stations). Adding relay antennas around Kerbin may be fun, but it's basically worthless. If you have a probe going to Duna, the place you need the relay sat to be is right next to the probe. ie. you send both craft together.

 

[Streetwind]

Welcome to the forums, @Fadly 

In addition to what @bewing said: commsats in Kerbin orbit can make sense if you have "Extra Ground Stations" turned off in the difficulty settings, so that KSC is the only ground antenna available. But by default, the additional ground stations are active and give Kerbin global coverage, and the ground stations are always better than spacecraft based antennas unless you add in mods or stack ridiculous numbers of stock antennas.

I recommend you also consult https://wiki.kerbalspaceprogram.com/wiki/CommNet - specifically the section on "Range Calculation". The equations there look huge and scary, but that's an illusion. You'll discover that, once you actually start filling in the numbers you want to calculate with, they very quickly simplify into one or two straightforward multiplications.