Need help with satellite comm network

[Targa]

Haven't played KSP since before the integrated satcom thing. I've read just about everything I can find on the subject, but can't figure out what I'm doing wrong in my current game. I have 2 comsats orbiting Minmus with HG-5 relay dishes on them. I have a probe orbiting Minmus and using a communotron 16. My tracking station is upgraded to level 3. The comsat is 1,872,000m away from the probe, which should be in easy distance for the communotron 16 (max 353Mm). The probe has "not connected".

http://imgur.com/gNub9bX

Any help or advice is appreciated!

 

Edit: No problems directly communicating with Kerbin when the probe is on the near side of Minmus, so it's just not relaying to the comsat with the HG-5 for some reason.

Edited July 13, 2017 by Targa

[Spricigo]

http://wiki.kerbalspaceprogram.com/wiki/CommNet

The important bit:

Range = SQRT ( Antenna Strength 1 * Antenna Strength 2 )

in case a Commonutron 16 talking to a HG-5:

Range = SQRT ( 500k * 5M ) =1.58M

 

25 minutes ago, Targa said:

The comsat is 1,872,000m away from the probe...

Oops!

[Aegolius13]

What @Spricigo said.   I assume you got that 353Mm number based on talking to a fully upgraded ground station (per the wiki Commnet page).  But when you use a relay in between,  that relay's power will bottleneck your range. And the HG 5 is a LOT less powerful than those ground stations.

[HvP]

As Spricigo and Aegolius13 have said, the 353Mm number for the HG-5 is the range when talking to the large ground stations on Kerbin. It's not sensitive enough to communicate with the Communotron in a one-thousand kilometer orbit. But if you move your relay satellite into a much lower orbit of Minmus it should work just fine. Try more like 50 kilometers or less.

Think of it like this. A big antenna is sensitive enough to pick up the faint signals from a small antenna, and a small antenna has no problem picking up the powerful transmissions from a big antenna; but two small antennas talking to each other aren't powerful enough to be heard by each other and aren't sensitive enough to resolve such faint signals.

The huge ground stations on Kerbin have such big dishes that they can easily resolve the extremely faint transmissions of Communotrons and still relatively weak HG-5. But the HG-5 still has a relatively small dish, and is only slightly more powerful than the Communotron. If you can get it closer to the Communotron it should be able to talk with it then. And since we know that the Kerbin ground stations can hear the HG-5's at Minmus you will then have a functional communication chain.

Edited July 14, 2017 by HvP

[Spricigo]

9 minutes ago, HvP said:

But if you move your relay satellite into a much lower orbit of Minmus it should work just fine. Try more like 50 kilometers or less.

Just a nitpick: It don’t need to be a much lower orbit, just 15-20% and it will be in range.  In any case there is a wide margin between too far up (cant connect to vessels in surface) and too low (get occluded by surface).

[HvP]

1 hour ago, Spricigo said:

Just a nitpick: It don’t need to be a much lower orbit, just 15-20% and it will be in range.  In any case there is a wide margin between too far up (cant connect to vessels in surface) and too low (get occluded by surface).

I'm sure that's true. It's been a while since I've tested it out.

Of course, for borderline orbits you may be close enough when the satellite is overhead but too far away when the satellite is coming over the horizon.