If you search Solid Signal for “combiner” you’ll find pages and pages of what seem like the very same thing. Not only that, you’ll see things that look very much like splitters, and some that are labeled splitter/combiners. It can be very confusing to try to find what you’re looking for. Here’s a quick tutorial:
This is as simple as a combiner can get. This Channel Plus combiner can also be used as a splitter. It’s a very simple device that doesn’t discriminate in any way about what sort of signals are going into or out of it. You can feed a signal in and split it equally between the outputs, or it can take two signals from two different sources and combine them on a single line.
A combiner like this is perfect if you are pointing two antennas in two totally different directions. What you’ll get is one line that contains both signals. There’s no attempt to balance the incoming signals, so it’s up to you to make sure that all the signals are different, because when you have the same signal on two lines and try to combine them, the result is usually worse than either of the incoming signals, because the two interfere with each other.
Band Separating Combiners
A combiner like this Blonder Tongue model does a little more for you. This specific combiner is designed to let you take two antennas and use one for UHF only and one for VHF only. This is very useful if you find that all your signals come from the same location but your old yagi-style antenna isn’t quite picking up all your UHF signals. You can still use it for VHF but add a new, more powerful UHF antenna that does a better job with distant UHF signals. Older antennas just didn’t put a lot of emphasis on UHF, but today’s digital signals are almost all UHF.
To use a combiner like this one, connect the VHF end to your old-school antenna and the UHF end to the newer antenna. The combiner will block the unwanted signals from each antenna so you can have them pointing in the right direction and still avoid interference.
Here’s something you probably won’t use at home. This Holland combiner is designed to work with commercial setups. It lets you combine 12 inputs from modulators into a single cable. When you’re setting up a system like you’d typically find in a hotel, there is a modulator for each channel, and each modulator is tuned to a channel on an off-air antenna or satellite TV source. Combining all these modulator outputs on a single cable lets you use the TV’s tuner to change channels.
A combiner like this is designed to accept 12 inputs that have all been carefully tuned to the same output power and are clean enough so that they all output only the signal they should, without any interference from each other.
It’s very easy to confuse a diplexer like this one with a combiner since they essentially do the same thing. There’s a lot more to a diplexer and even though it’s really basically a very fancy combiner, it brings a lot more precision to the table.
Diplexers are designed to very carefully and cleanly allow two completely different sets of signals to exist on the same cable. In this particular case, this diplexer is used in commercial installations to add antenna signals to cable and satellite ones, or to allow DIRECTV commercial installations to work with a shared internet signal. One port passes signals precisely between 25 and 806MHz and the other passes signals between 0 and 5MHz as well as 950-2150MHz. There is also additional circuitry to make sure the strong cable or satellite signal doesn’t completely overwhelm the relatively weak antenna signal, and you’ll notice that some frequencies aren’t passed through at all.
What about power passing?
Power passing is used in splitters and combiners to let you power devices like satellite dishes and amplifiers. While signals are coming down the line, DC power is going up the line. This is perfectly fine because of a peculiar quality of signals — they only travel on the outside of the wire while power travels throughout the entire wire. They don’t interfere with each other.
This combiner looks just like the one above, but this is model 2512 while the other is model 2532. This model will pass power through it, but the other one blocks the passing of power. For the most part, it’s safer to block power from passing through splitters, as it stops power surges that can damage equipment. It’s not a huge deal if you need a power passing combiner but if you don’t, then don’t use one, simple as that. In the world of antennas, you’d only really need one to power a pre-amplifier and it’s pretty likely that you’d put the pre-amplifier after the combiner (in other words, you combine the antennas and then run the one line into the amp.) If you did need to power an amplifier that was only being used for one antenna, you could use a power-passing combiner to pass power through one port and a DC Block (or voltage blocking coupler) on the other.