Understanding Antennas?

[Hs.Panda]

can anybody explain antenna packet size and bandwith and how this affects transmissions?

also what is the difference between a direct and relay antenna?

[Aegolius13]

15 minutes ago, Hs.Panda said:

can anybody explain antenna packet size and bandwith and how this affects transmissions?

99% of the time, the only meaningful effects of these stats are the time and (probably more importantly) the amount of electric charge it will take to transmit science results.  As far as I know, these stats have no effect whatsoever when your antenna is being used to control a non-piloted craft rather then send science.

 

17 minutes ago, Hs.Panda said:

also what is the difference between a direct and relay antenna?

A direct antenna can only be used for one thing - to initiate a link back to Kerbin for that ship's own use (either for probe control or science). 

A relay antenna can do the same thing, but can also help out other ships by relaying their signals to Kerbin.   For example, if you had a lander on the dark side of the Mun (queue the Pink Floyd), it could not transmit to Kerbin by itself.  But a relay antenna on something in Munar orbit could pick of the lander's signal and bounce it to Kerbin (or to another relay antenna).

Relay antennas can also be used for a fairly obscure function called Remote Probe Control, which lets the ship with the relay control a probe core directly, without needing a link back to Kerbin.  I have never actually found the need to use this.

Note that despite their name, direct antennas do not have to transmit directly back to Kerbin.  They can make use of relay antennas on other craft, but cannot help out other craft that want to transmit.  I think of them as selfish antennas. 

Thus, relay antennas are more versatile, but they tend to be larger, heavier and more expensive as a result. 

 

 

 

[Hs.Panda]

4 hours ago, Aegolius13 said:

99% of the time, the only meaningful effects of these stats are the time and (probably more importantly) the amount of electric charge it will take to transmit science results.  As far as I know, these stats have no effect whatsoever when your antenna is being used to control a non-piloted craft rather then send science.

 

A direct antenna can only be used for one thing - to initiate a link back to Kerbin for that ship's own use (either for probe control or science). 

A relay antenna can do the same thing, but can also help out other ships by relaying their signals to Kerbin.   For example, if you had a lander on the dark side of the Mun (queue the Pink Floyd), it could not transmit to Kerbin by itself.  But a relay antenna on something in Munar orbit could pick of the lander's signal and bounce it to Kerbin (or to another relay antenna).

Relay antennas can also be used for a fairly obscure function called Remote Probe Control, which lets the ship with the relay control a probe core directly, without needing a link back to Kerbin.  I have never actually found the need to use this.

Note that despite their name, direct antennas do not have to transmit directly back to Kerbin.  They can make use of relay antennas on other craft, but cannot help out other craft that want to transmit.  I think of them as selfish antennas. 

Thus, relay antennas are more versatile, but they tend to be larger, heavier and more expensive as a result. 

 

 

 

oh, ok. thx for the explaination

[Geschosskopf]

On 12/19/2017 at 8:28 AM, Hs.Panda said:

can anybody explain antenna packet size and bandwith and how this affects transmissions?

As @Aegolius13 say, the bottom line is the amount of EC required to transmit the full message.  But it also affects how long it takes, too.  IIRC, it works like something like this:

• Science reports contain X total amount of "information" based, I think, roughly on how many science points you get for it.
• Each type of antenna can only transmit Y amount of "information" in a given amount of time.  This is its "packet size".  Thus, the smaller the packet size of the antenna, the more packets it must send to complete sending the whole science report, in the ratio of X/Y.
• Bandwidth IIRC is the measure of time for how long it takes the antenna to send 1 packet.  The higher the bandwidth, the faster it sends a packet.  Thus, the time required for a given antenna to send a given science report completely is a function of both its packet size and its bandwidth.
• IIRC, EC is always figured in units/second.  Thus, the longer the transmission takes, the more EC it costs.  Therefore, OT1H antennae with large packets and high bandwidth tend to use less EC in total to send the same report.  But OTOH, different antennae also have different EC/sec ratings, with higher EC/sec use related to longer antenna range, and perhaps also to higher bandwidth and bigger packets.

All of this is pretty much meaningless, though, because there's no real way to know in advance how much EC it will take to send a given report with a given antenna.  What matters is 2 things:

• If you have the antenna set to "require complete" and don't have enough battery, you will run out of EC before you finish sending the message and the transmission will abort, even if the ship has solar panels, RTGs, etc., producing EC. At some point, you'll still have 0 EC aboard. IOW, you will never be able to send that report, unless you have advanced tweakables and set the antenna to "allow partial", which you can do in flight.
• If you have the antenna set for "allow partial" and you don't have enough battery, the transmission will pause, until the solar panels or whatever give you more EC, then will use it to send the next packet.  So your ship will effectively be with zero EC for perhaps many minutes until the transmission is finally complete.  This might cause other problems, such as loss of control, life support failure, etc.

So the moral is, if you plan on transmitting a lot of science, always include big batteries regardless of your antenna.

 

Edited December 21, 2017 by Geschosskopf

[Superfluous J]

27 minutes ago, Geschosskopf said:

If you have the antenna set for "allow partial" and you don't have enough battery, the transmission will pause, until the solar panels or whatever give you more EC, then will use it to send the next packet.  So your ship will effectively be with EC for perhaps many minutes until the transmission is finally complete.  This might cause other problems, such as loss of control, life support failure, etc.

Also, due to handwavy math reasons, you'll get less transmitted science points.

[Daniel Prates]

On 19/12/2017 at 10:51 AM, Aegolius13 said:

Relay antennas can also be used for a fairly obscure function called Remote Probe Control, which lets the ship with the relay control a probe core directly, without needing a link back to Kerbin.  I have never actually found the need to use this.

I am not really sure about this since I've never done it,  but it seems an unmanned rover or satellite does not have to backtrack its signal all the way to KSC,  if it can track it down to a MANNED spacecraft,  which works independently from a link to KSC,  and thus would be reputed as being "controlling" said probe. 

I read that somewhere. Does anybody know if this is true?

Edited December 24, 2017 by Daniel Prates

[Urses]

You need not only a manned craft but a manned craft that have a control point and have right personal in it. As Example the Mark 2-1 for 3 persons as you read you need a pilot for the pod and a pilot for remote control option. This means you need at least 2 pilots to get it work. If you only have 1 there you don't get the control probe ability. As funny example, if you build a ship of a simpelst probe core and a Mark1 Crew cabin you can actually stear with full pilot ability as you can controll the vehicle from the cabin through probe but if the prob is decoupled you have only the probe controlable. Try it in moon shadow.

[Geschosskopf]

46 minutes ago, Daniel Prates said:

I am not really sure about this since I've never done it,  but it seems an unmanned rover or satellite does not have to backtrack its signal all the way to KSC,  if it can track it down to a MANNED spacecraft,  which works independently from a link to KSC,  and thus would be reputed as being "controlling" said probe. 

Yes, the purpose is to be able to control probes in the absence of a link from the probes themselves back to Kerbin.  As @Urses says, you a specially equipped command pod (like the Mk 1-2 and various mod capsules) and you need 2 pilots in the controlling craft.  Which also needs at least 1 relay antenna.

I have used this a couple of times and it works OK.  The main problem is, the probe can only be "1 hop" from the controlling ship.  I take this to mean there can't be any other relays between the probe and the controlling ship.

The whole idea is relatively useless IMHO.  It seems to have been intended to allow you to control probes far from Kerbin before you've upgraded the Tracking Station much if at all and unlocked the bigger relay antennae.  But OTOH, you need to have unlocked the Mk 1-2 pod and enough rocket parts to get it all the way out there, which means you probably have all the other stuff as well.  I suppose, therefore, that would be of most use if you use OPM, but for some reason don't also use other mods that give you big enough antennae to talk all the way out there, or didn't use the game option sliders to increase your DSN range.

[Daniel Prates]

45 minutes ago, Geschosskopf said:

Yes, the purpose is to be able to control probes in the absence of a link from the probes themselves back to Kerbin.  As @Urses says, you a specially equipped command pod (like the Mk 1-2 and various mod capsules) and you need 2 pilots in the controlling craft.  Which also needs at least 1 relay antenna.

I have used this a couple of times and it works OK.  The main problem is, the probe can only be "1 hop" from the controlling ship.  I take this to mean there can't be any other relays between the probe and the controlling ship.

The whole idea is relatively useless IMHO.  It seems to have been intended to allow you to control probes far from Kerbin before you've upgraded the Tracking Station much if at all and unlocked the bigger relay antennae.  But OTOH, you need to have unlocked the Mk 1-2 pod and enough rocket parts to get it all the way out there, which means you probably have all the other stuff as well.  I suppose, therefore, that would be of most use if you use OPM, but for some reason don't also use other mods that give you big enough antennae to talk all the way out there, or didn't use the game option sliders to increase your DSN range.

Agreed.... the usefulness would be for a manned craft to dialogue with, say, a lander probe on the surface of a distant body.... or one that does not face kerbin ever,  like the mun. A strange situation,  as the craft flying above could just as well be a large,  hightech probe itself,  by the time you reached the science nodes required for the first situation!