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Question about Comms - since that's new to me as well...


JoeSchmuckatelli
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I've a tiny probe orbiting Mun with an HG-5 High Gain Antenna (one of the early tech, small ones - the one with the dish).  I thought it would act as a relay for me when I don't have LOS with Kerbin… but I kinda don't think it is.  Do I need to do something different, or is it simply not powerful enough?

 

FWIW - it does have solar panels and batteries on the relay probe; so electricity isn't the issue.  I just keep finding my active lander nodes impossible to remove b/c no contact with KSC - unless the lander I'm flying has LOS.  I figured having the relay probe would extend my ability to communicate with KSC (trying to land a scientist with an OCTO as pilot).

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I guess the most important things have already been said, but some additional information.

6 hours ago, JoeSchmuckatelli said:

FWIW - it does have solar panels and batteries on the relay probe; so electricity isn't the issue. 

Electricity on the relay is (nearly?) never the issue. Relaying radio signals does not consume electricity! (Yes, yes, that's strange and not how it is in RL, but in KSP it is.) So as long as the relay had some ECs in it's batteries when you last visited it it will be able to relay signals.

It is also possible that your lander doesn't have LOS to the relay, but I guess you already checked that.;) More importantly: you can activate a display of the commnet connectivity in the map view, or the tracking station. That can show you between which craft you do have a working commnet link.

There is a rather comprehensive wiki page about how the CommNet works. You can also increase the effective antenna power of a vessel by putting more antennas on the vessel (except for the Communotron 16S which doesn't play together with any other antenna), but this quickly runs into diminishing returns (see the explanation on the wiki page). I usually put up to eight HG-5 antennas on my early game relays, not because they have much more range than relays with four of them but because the HG-5 are cheap and weight next to nothing so it just doesn't matter.

 

Edited by AHHans
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There is something called the antenna equation. Total max range = sqrt (Antenna1Range * Antenna2Range)

This is almost certainly your problem. Check your relay's connection to Kerbin -- it's probably got a good connection. So the question is whether your lander has enough communication range to talk to the relay. The OKTO has a range of 5km, unless you have an additional deployed antenna on the lander. The HG5 has a range of 5Mm. If you calculate out your maximum range, you are probably too far.

 

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Hi @JoeSchmuckatelli

It's easy to get confused concerning the antenna ranges because we get spoiled by the strength and sensitivity of the ground relays all over Kerbin. Those massive dishes at the KSC can "hear" incredibly weak communotrons out at the Mun and Minmus, and they can also beam out VERY strong signals that are easy for the small antennas to pick up. The huge size of the tracking station dishes can compensate for the weak signals and poor sensitivity of the antennas they are communicating with.

But your relay in orbit of the Mun can't rely on the ground stations to communicate with the Mun surface. The two probes have to do that all by themselves. In order to compensate for both the weak signals from smaller antennas and their poor sensitivity it's necessary to keep them closer together. For an HG-5 (5000k) communicating with a Communotron (500k) that means being less than 1,500km away. For an HG-5 communicating with a probe body built in antenna (5k) you have to be within about 150km to work.

Now once the the connection between Mun orbit and the Mun's surface is taken care of, it's easy for the ground stations at the KSC to complete the rest of the path from Kerbin to the Mun.

Edited by HvP
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57 minutes ago, JoeSchmuckatelli said:

@AHHans - eight antennae on one probe?  Really?  

Why not? Negligible gains vs. negligible costs. It's not like I put 19 RA-100 antennas on a single craft or so.:cool:

P.S. Turns out that in my latest career game I used only four HG-5 for my early-game relays. Well, by now I have two VKAs in orbit.

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One more thing I can think of right now: Make sure the antennae is deployed by right-clicking and choosing the deploy option in the part action window.

The HG-5 will swing outwards when it is deployed and working. I know it's a simple, trivial thing, but it never hurts to make sure.

Edited by HvP
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7 minutes ago, HvP said:

One more thing I can think of right now: Make sure the antennae is deployed by right-clicking and choosing the deploy option in the part action window.

The HG-5 will swing outwards when it is deployed and working. I know it's a simple, trivial thing, but it never hurts to make sure.

I love the animations - so I'm all about manually deploying stuff. 

I especially like the solar panels - because they actually turn to face the sun. 

Also - I cannot (just can't) engage stages from the map screen. I have to watch every separation and lighting up the next stage. (I mean otherwise why even play the game if you are not going to watch the rocket you built lose all guidance control and begin to spin lazily around for no apparent reason!) 

 

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I actually did some experimentation with the HG-5 on relay sats a couple of months ago.

Three relays of two HG-5s each, located in geosynchronous orbit above the Mun and spaced out 120° relative of each other, are just barely strong enough to pick up a single Communotron sitting on the far side of the Mun, bounce the signal between each other and make contact with Kerbin at DSN level 2. Signal strength for the Communotron will be very weak (~5%) but will never lose connection completely. You might have some interruptions in non-equatorial valleys and polar latitudes, though.

Taking this relay design, adding on two more HG-5s and launching this quadruple-antenna version into a 300 km orbit around Kerbin will result in the Kerbin sat being able to briefly pick up signals from the munar relay constellation during closest approach. This quadruple-antenna version will also be more than strong enough to reach Kerbin from Minmus at DSN level 2.

So if you want a relay within Kerbin's SOI, quadruple HG-5s per sat are a good choice unless you want direct Mun-to-Minmus communication. On the other hand, I was recently considering whether it would be more effective to use dual antenna relays around the Mun at below-geosynchronous altitude plus a single quadruple-antenna relay sitting on the Mun's surface facing Kerbin. I mean, it's going to be in the shade for several days per orbit, but since relays don't need power to transmit...

Edited by Fraktal
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Always with the new layers of complexity, eh KSP? 

 

Thanks for the info @Fraktal.  Now I have to boot up the game and pore over my plans for satellites and research stations.

 

... And add batteries and solar panels to my space planes (because while an unmanned relay satellite may not use power... The dadgummed antenna on the plane won't talk to base without the engine revving). 

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Actually, you may want to look at the Antenna Helper mod, I use it myself. When you make a craft in the VAB, you can add it to a list, then open another craft and see how far you can get a signal between the two, including calculating exact signal strength/orbital coverage between Kerbin and any other celestial object.

If you select any of your existing craft in the Tracking Station or on the map during flight, you can also visually display the exact range with any craft you've put on the list in the VAB.

Edited by Fraktal
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I believe the answer to your question is:

 

ADD MOAR!!!

HG-5 is a pretty puny little relay dish, and the Communotron 16/16S are even punier. In order for those two to talk to each other, you need more of them. A lot more. Don't even bother trying to use the built-in probe antennae, there are TV remotes with better range than those...

Relay satellites should be placed in relatively high and inclined orbits to cover more of the surface, but this means they're generally further away from any particular spot at any given time so you need more signal power. Unlocking a more powerful direct antenna like the DTS or HG types (I can't remember their exact names and I'm fairly sure Restock+ adds more with very similar names just to confuse me even more) will make those relays work much better, but for now you'll need to use more HG-5s. Stick 4 or possibly 8 of them on a single satellite and save your science up to unlock better comms equipment as soon as you can. There's more than enough science available within Kerbin's sphere of influence and quite possibly on Kerbin itself to unlock everything even with science gains turned down considerably and better communications will help you even more when you start planning missions to other planets.

Once you unlock the RA-2 relay dish communicating around the Mun and Minmus becomes a doddle, but you'll have a similar problem trying to communicate from other planets. I'll refer you to a post I did last month on that particular topic (because I'm lazy and don't want to type it out again :P)

 

 

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