Losing CommNet Connection

[SkippydaHippie]

So I've been away from the game awhile and I remember getting this to work not long after 1.2 came out. I messed around in stock and then shelved it because I need my mods. Anyways I'm attempting to set up a basic relay network in Kerbin's SOI, I want to be able to see behind the Mun essentially, and put an equatorial satellite there. My relay satellites are at highly elliptical polar orbits, roughly 78Mm Ap. They each have an HG-5. Those connect to the ground just fine. However the attempts at a satellite around the Mun leave me blind when I'm passing over the far side. I've had them equipped with HG-5s and 3 Communotron 16s, and I can't get the connection. There is a clear line of sight no doubt about that. Am I missing something? They all should be well within their respective ranges.

[FancyMouse]

18 minutes ago, SkippydaHippie said:

78Mm Ap

Are you sure HG-5 and Comm16 can talk to each other at this distance? There's a matrix in KSPedia talking about the max distance between different tiers of antenna. In particular, ground station is really powerful, but not most relays. It's not a good assumption that if Ground->A1 and Ground->A2 can connect (even with both full signal strength), then A1->A2 can connect.

[SkippydaHippie]

Well so it says in the VAB that just one of those relays can communicate up to 200Mm which should definitely be enough. Thats also why I stacked 3 of the communotrons to get that max range. Furthermore I have OPM installed, which as I understand changes these max ranges to be pretty strong. I'll have a gander at the KSPedia but I feel like that isn't whats wrong.

[FullMetalMachinist]

1 hour ago, FancyMouse said:

It's not a good assumption that if Ground->A1 and Ground->A2 can connect (even with both full signal strength), then A1->A2 can connect.

Correct. More specifically, the maximum range for two antennas to connect is: sqrt(antenna1 * antenna2). 

[renhanxue]

The HG-5 has absolutely pitiful range - to reach it at all from LKO when it's at apoapsis in that eccentric orbit you need a DTS-M1/RA-2 or better. Max range between two antennas - assuming you only have one on the craft in each end - is the square root of the product of their ratings (in other words, sqrt(rating_a * rating_b)). If you have one antenna each on the relay and the craft that you want to communicate with, you can use this simple table (all ranges are in meters):

As you can see, a HG-5 trying to talk to a Communotron 16 will lose signal completely at just over 1581 km. You're nowhere near reaching the Mun from LKO with that, much less the edge of the SOI.

I did the exact same mistake you did when first setting up my Kerbin relay network (the exact same polar setup, too - I still use it). The HG-5 just isn't useful for that kind of work, but nobody will tell you that. It works for Apollo-style missions and for very short range relays (like around moons for example, when you have bigger relays around the planet), but for everything else it's too weak. For the eccentric polar orbit setup to really work you need at least the RA-15 but preferably the RA-100, unless you want to drag around DTS-M1's on everything you fly inside the Kerbin SOI.

Edited January 31, 2017 by renhanxue

[SkippydaHippie]

Mkay, I think I can figure it out now. Thanks to all for the info!

Edited January 31, 2017 by SkippydaHippie

[Snark]

The thing to remember is that the antenna power of DSN on Kerbin is HUGELY more powerful than that of the early-career antennas. So they can talk to KSC from a nice long range... but they have a much shorter range when they're talking to each other.

You can still use the HG-5 for a Mun relay to give you visibility to the "back side", it works great for that-- just not in the way you're trying to do it.

You can accomplish it by putting a trio of HG-5 relays around the Mun itself, not too high-- say, just a few hundred km altitude. Two of them can see Kerbin at all times, and they can therefore talk to KSC just fine. They can also communicate with each other, and with anything on the Mun's surface.