How does relay work?

[Carrot]

For example: I have a network at Duna and kerbin. Do I need to connect to kerbin relay first and connect to kerbin? Or can i shoot the signal directly from there?

Does the kerbin relay need to connect to the kerbin itself with normal antenna?

Does the relay on Duna need to be high powered like the kerbin one or just with the shortest one will work fine or a short ranged relay but long ranged antenna so I can connect to kerbin?

Thanks!

Edited November 16, 2016 by Carrot

[bewing]

The relay antennas will automatically try to pick a path to Kerbin if they have enough range to contact Kerbin or another relay. The relay antennas also act like normal antennas, you do not need both types.

The important thing to understand is the antenna power equation: range = sqrt (RelayPower1 * RelayPower2)

The other thing you need to understand is that the Tracking Station on Kerbin has an extremely powerful antenna. So a small antenna can connect to Kerbin fairly easily. But two small relay antennas will only have a very short range talking to each other.

 

[Geschosskopf]

10 hours ago, Carrot said:

For example: I have a network at Duna and kerbin. Do I need to connect to kerbin relay first and connect to kerbin? Or can i shoot the signal directly from there?

Does the kerbin relay need to connect to the kerbin itself with normal antenna?

Does the relay on Duna need to be high powered like the kerbin one or just with the shortest one will work fine or a short ranged relay but long ranged antenna so I can connect to kerbin?

@bewing had some important points to remember.  I'll give you a few more.

To be able to communicate, you need 1 or more links between your ship and Kerbin (Kerbin now has antennae all over it so you don't need to talk just to KSC unless you disable the other ground antennae).  Being able to do this depends mostly on 3 things:  the range (all antennae have a max range which increases as you upgrade the Tracking Station), the type of antenna(e) involved (direct and/or relay). and whether some celestial body is in the way (but you can work around that for the most part).  As to range, the more excess range the antennae have compared to how far you're talking, the better the connection (more bars) so the less time (and thus, EC) it takes to transmit data.

As to antenna type, there are 2 general types:  direct and relay.  Direct antennae include all the original stock antennae, the new stock dipole, and all the ground-based antennae on Kerbin (KSC and all the new ones).  Direct antenna on ships can talk to Kerbin and relay antennae on other ships, but NOT to direct antennae on other ships.  Relay antennae are all new and can talk to anything:  direct antennae on other ships, relay antennae on other ships, and Kerbin.  Thus, the only way to have ship-to-ship communications is if at least one of the ships has a relay antenna.

The ground-based antennae on Kerbin are the most powerful you have at any level of Tracking Station upgrade.  At Level 3, they can talk to ships at Jool, provided the ship has a big direct antenna like the 88-88.  But they're direct antennae, so the signal can be blocked by celestial bodies.  Thus, the main reason you need relays is to provide bank shots around intervening bodies.  You can turn blocking off in the options and thus will never need relays, but what's the fun in that?  So assuming you haven't done that, you need to consider the sources of blocking.

• The planet your at.  This happens all the time due to the planet's rotation (if you're on the ground) or your orbit around it.  This is the hardest to completely eliminate but you can reduce it to an acceptable minimum with a few relays.
• Intervening planets between the planet you're at and Kerbin.  This is very easy to eliminate completely.
• The sun.  This always happens at some point during interplanetary missions and can only be solved by relays at other planets, to make a path around the sun.

So, let's say you have a lander on Duna and want to be able to talk to KSC most of the time.  For game purposes, you only need a connection when you're trying to transmit science or fly a ship without a pilot aboard, which really isn't all that often compared to the total mission time.  But for role-playing purposes, you might want the ABILITY to communicate as often as possible, at least every few hours throughout the mission.  This will require a network kinda like this:

1. Your lander on Duna has a mid-range direct antenna.  This talks to...
2. A short-range relay antenna in low-medium Duna equatorial orbit.  This is so the lander can talk home when Duna is facing away from Kerbin.  The link will only exist when the satellite is above the lander, so will only provide coverage for about 1/2 of Duna's day.  If you want more than that, you need multiple satellites like this spaced out around Duna's equator.  Anyway, this talks to....
3. A long-range relay antenna in a highly eccentric polar orbit at Duna.  This is to be able to see above or below Ike towards Kerbin.  This talks to....
4. A long-range relay antenna in a highly eccentric polar orbit at Eve or Dres.  This is to talk around the sun when it's between Duna and Kerbin.  This talks to....
5. A long-range relay antenna in a highly eccentric polar orbit at Kerbin.  This is to be able to talk under/over Mun.  This talks to...
6. Ground antennae on Kerbin.

[Carrot]

1 hour ago, Geschosskopf said:

@bewing had some important points to remember.  I'll give you a few more.

To be able to communicate, you need 1 or more links between your ship and Kerbin (Kerbin now has antennae all over it so you don't need to talk just to KSC unless you disable the other ground antennae).  Being able to do this depends mostly on 3 things:  the range (all antennae have a max range which increases as you upgrade the Tracking Station), the type of antenna(e) involved (direct and/or relay). and whether some celestial body is in the way (but you can work around that for the most part).  As to range, the more excess range the antennae have compared to how far you're talking, the better the connection (more bars) so the less time (and thus, EC) it takes to transmit data.

As to antenna type, there are 2 general types:  direct and relay.  Direct antennae include all the original stock antennae, the new stock dipole, and all the ground-based antennae on Kerbin (KSC and all the new ones).  Direct antenna on ships can talk to Kerbin and relay antennae on other ships, but NOT to direct antennae on other ships.  Relay antennae are all new and can talk to anything:  direct antennae on other ships, relay antennae on other ships, and Kerbin.  Thus, the only way to have ship-to-ship communications is if at least one of the ships has a relay antenna.

The ground-based antennae on Kerbin are the most powerful you have at any level of Tracking Station upgrade.  At Level 3, they can talk to ships at Jool, provided the ship has a big direct antenna like the 88-88.  But they're direct antennae, so the signal can be blocked by celestial bodies.  Thus, the main reason you need relays is to provide bank shots around intervening bodies.  You can turn blocking off in the options and thus will never need relays, but what's the fun in that?  So assuming you haven't done that, you need to consider the sources of blocking.

• The planet your at.  This happens all the time due to the planet's rotation (if you're on the ground) or your orbit around it.  This is the hardest to completely eliminate but you can reduce it to an acceptable minimum with a few relays.
• Intervening planets between the planet you're at and Kerbin.  This is very easy to eliminate completely.
• The sun.  This always happens at some point during interplanetary missions and can only be solved by relays at other planets, to make a path around the sun.

So, let's say you have a lander on Duna and want to be able to talk to KSC most of the time.  For game purposes, you only need a connection when you're trying to transmit science or fly a ship without a pilot aboard, which really isn't all that often compared to the total mission time.  But for role-playing purposes, you might want the ABILITY to communicate as often as possible, at least every few hours throughout the mission.  This will require a network kinda like this:

1. Your lander on Duna has a mid-range direct antenna.  This talks to...
2. A short-range relay antenna in low-medium Duna equatorial orbit.  This is so the lander can talk home when Duna is facing away from Kerbin.  The link will only exist when the satellite is above the lander, so will only provide coverage for about 1/2 of Duna's day.  If you want more than that, you need multiple satellites like this spaced out around Duna's equator.  Anyway, this talks to....
3. A long-range relay antenna in a highly eccentric polar orbit at Duna.  This is to be able to see above or below Ike towards Kerbin.  This talks to....
4. A long-range relay antenna in a highly eccentric polar orbit at Eve or Dres.  This is to talk around the sun when it's between Duna and Kerbin.  This talks to....
5. A long-range relay antenna in a highly eccentric polar orbit at Kerbin.  This is to be able to talk under/over Mun.  This talks to...
6. Ground antennae on Kerbin.

Thanks for the detail explanation BUT! if you are talking about highly eccentric polar orbit, how highly eccentric is that? like an orbit with PE at the LKO and AP at the SOI? Will it be influenced by mun/minmus or any other moon from other bodies(for example Tylo if I am around Jool)?

Thanks!

[Geschosskopf]

18 minutes ago, Carrot said:

Thanks for the detail explanation BUT! if you are talking about highly eccentric polar orbit, how highly eccentric is that? like an orbit with PE at the LKO and AP at the SOI? Will it be influenced by mun/minmus or any other moon from other bodies(for example Tylo if I am around Jool)?

Well, here's the nutshell version.  If you want all the gory details, check out the tutorial I wrote on relays, the link for which is in my signature.

Anyway, in general you want the relay orbits to be as eccentric as possible and/or practical.  So yeah, at Kerbin, a relay's Pe should be down in LKO and its Ap out near SOI.  This is way more than you need just to see over or under Mun.  The real reason for this is to maximize the amount of time the relay spends well above or below the ecliptic, so no nearby moon can possibly block its signal for most of its orbit.  And because the orbit is very eccentric, it whips through its Pe at huge speed so is only blocked for a few hours to a day or so at most.  And to avoid even that little amount of blackout, you deploy relays in pairs at each planet, set up so that when one is at Ap, the other is at Pe, and 1 goes up, the other down..  That way, 1 or the other, but usually both, will provide links.  But whether you use 1 or 2 relays, because the Pe is so close to the central planet, the orbit won't come anywhere close to any of its moons so you don't have to worry about unwanted encounters.

At Jool, it costs huge dV to get such an eccentric orbit, so in practical terms you can usually only get the relay into an egg-shaped orbit.  Somewhere around 2000-3000dV above/below Jool's ecliptic.  But that's enough.  Jool is the tallest obstacle in the solar system other than the sun, so any amount of altitude above or below it and you can talk around it.  Still, because the relay's orbit won't be very big, ti won't take very long, so it's more important at Jool than the rocky planets to have 2 relays 180^ out of phase with each other. 

[Carrot]

Thanks for the help!