How does your DIRECTV receiver know which satellite it’s listening to?

Now and again, the thousands of channels available on DIRECTV satellite aren’t quite enough to get your attention. Now and again, I can imagine your mind drifting off. Don’t be ashamed, mine does the same. When my mind drifts off, I think about topics for this blog, and it was on one such mental journey that I decided to write this article.

The basics

DIRECTV operates a fleet of ten satellites at four locations. Most of them are at the three primary locations at 99 degrees, 101 degrees, and 103 degrees west longitude (roughly.) When you tune to a channel using your remote, your receiver sends a signal requesting a specific satellite frequency. Your dish and multiswitch oblige. Maybe you never thought about more than that, but there’s so much more to the process.

Different frequencies

There are two different frequency ranges in use for DIRECTV. The Ku-band frequencies are more or less standard for satellite TV and they’re used at DIRECTV’s 101 and 119 degree locations. However, DIRECTV also has the North American license to use the Ka band for satellite TV. This is a higher frequency range with room for thousands of 4K channels and DIRECTV doesn’t have to worry about interfering with other satellite services. Its 99 and 103 satellite fleet use these frequencies to deliver HD and 4K. Two different groups of frequencies are used: the regular satellite frequencies that were initially licensed, and the reverse band which were originally only used for communications up to the sky, not down from the satellite.

Polarities and transponders

Every satellite has a fixed number of transponders. If you don’t want to go for the deep dive, just know that a transponder is a chunk of satellite stuff that can send several channels at once. To make the process easier (and indeed, to make it all work), the transponders are numbered. The odd ones all broadcast one particular way and the even ones broadcast another particular way. In order for us mere humans to understand the massive amount of physics involved, we say that the odd ones use right-hand circular polarity (RHCP) and the even ones use left-hand circular polarity (LHCP). What the heck does that mean? It’s a subject for another tutorial that I’ll get around to writing.

What happens when these frequencies get to the dish

Those super high frequencies don’t travel down cables real well. So, the LNB (the front part of the dish) does two things. It uses a super-low-noise amplifier to pump up those signals. And, it sends them down the cable at a different set of frequencies than the ones they came in on. There’s a third thing that happens as well.

Voltage and tone

In order for you to receive every single channel you want, you need six different kinds of lines. There’s too much stuff to put it all on one line. So how does the rest of the equipment know which line it’s connected to? The dish tells it using a combination of voltage and tone.

Signals from odd transponders from the Ku band are sent back down with 13 to 14 volts of current. Even ones get 16-20 volts of current. So, a simple voltage test can determine odd from even. Signals from odd transponders on Ka-band satellites also get 13-14, while the even ones get 16-20. But, there’s a little more. Those lines get a separate signal added at 22kHz just to let your equipment know what they are.

That accounts for four lines. The other two lines are also at 16-20 volts, but they are designed to go into specific parts of a multiswitch so there’s no other signaling necessary.

And then it gets fun

The single-wire multiswitch (SWM), whether built into the dish or separate, takes all these signals and holds onto them until they are needed. When a receiver, DVR, or server gets a request to tune to a channel, it uses a lookup table which tells it which transponder and which satellite type is used. All the satellites at 101 are treated as one set of transponders, for example. The system doesn’t need to know which actual satellite is in use. It’s automatic.

So, you tune to HGTV, and your Genie server finds out that it’s on the 99(c) satellite group at transponder 18. (Which it is, at the time I’m writing it, but they change all the time.) It sends a request to the SWM for all the even signals from the 99(c) satellite group. These are stuck on a group of frequencies and sent back to the Genie server. The SWM can manage 13 different requests at once with most hardware.

When your Genie server gets the frequency range it needs, it looks for the part that corresponds to transponder 18, decodes it, and sends it to your Genie client or straight to the TV.

Seriously? All that?

Yep, seriously. And honestly there are parts I’ve left out in the interest of simplicity. All this happens in a second or two. Feel guilty that you’re impatient when changing channels? Don’t be. You didn’t know all the work that went into that channel change. Now you do.

Oh, and if you want the best DIRECTV accessories, the same stuff the professionals use, shop at Solid Signal. You won’t find them anywhere else.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 8,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.