Single coax to roof

[thescannerdude123]

Hello. Can you run a single coax cable to your roof (of a home) and then have a splitter to have multiple antennas? I have a CB, Ham, and scanner radio and would like to put up an antenna for each. But does that mean I need three coax cables? I already have a coax going to the attic (connected to all tv connections in the house). Is there too much degradation to use those?

 

[redbeard]

If your coax is already suitable to transmit with, you could try one of these: Duplexers | Comet Antenna

If you ran TV coax and expect to use it on ham/CB, that's a bad idea for transmitting.

 

[mmckenna]

Hello. Can you run a single coax cable to your roof (of a home) and then have a splitter to have multiple antennas? I have a CB, Ham, and scanner radio and would like to put up an antenna for each. But does that mean I need three coax cables? I already have a coax going to the attic (connected to all tv connections in the house). Is there too much degradation to use those?

It can be done with a diplexer. The problem with that is that they take large chunks of the bands and split them off to specific ports.

So, you might have an HF port, which would be good for your CB radio.
You might have a VHF port, which would be good for your ham radio, but it might do something like 100MHz - 300MHz on that port.
And say you want a dual band ham radio, well, then you need a UHF port, or a port that does 144 all the way through 450MHz.
That's all great, not a problem. You can buy those.

But then, where do you connect your scanner? The VHF and UHF bands are going from your dual band antenna to your dual band ham radio, and all the signal will go between those ports, and none to the scanner.

For a CB radio, a 2 meter/70 centimeter radio, you can buy diplexers that will hand that over one coax.
But the scanner is the issue, if you want to use the full capabilities of it.

So, best you could do would be 2 coax runs. If you are going to do 2, why not do 3 and skip the diplexer. That'll save money, and all diplexers have a bit of loss to them.

 

[Ubbe]

Hello. Can you run a single coax cable to your roof (of a home) and then have a splitter to have multiple antennas?

Are you still going to use that coax for TV reception?
Then you'll have
CB 27MHz
HAM 144/440MHz
TV 500-700MHz (might also be 175-250Mhz or even 50-65MHz)
Scanner 750-950MHz

You'll need one diplexer at the antennas and one more at the radios.
You get SWR1,5:1 equals to 8% loss using a 75 ohm CATV coax with your CB or HAM transmitter, no big deal.
Most diplexers have less than 1dB loss, less than a 20% loss, and many are less than 0,5dB.

Haven't seen any diplexers that still allows you to use TV frequencies, but the other frequencies have displexers that can be used.
They are not cheap, maybe $100, so routing a second coax, and a third, are usually a more suitable alternativ.

/Ubbe

 

[thescannerdude123]

Thank you @mmckenna and @Ubbe for the descriptive replies. To both of your points, I think I'll have to find a way to get a few cables up to the roof. If it were just one I might have been able to sneak it through without it showing outside too much (I have to think about esthetics per my wife). But if I need three or four (might as well have another for TV backup), then I'll need to rethink the route up there.

 

[WB9YBM]

It can be done with a diplexer. The problem with that is that they take large chunks of the bands and split them off to specific ports.

You might have a VHF port, which would be good for your ham radio, but it might do something like 100MHz - 300MHz on that port.
And say you want a dual band ham radio, well, then you need a UHF port, or a port that does 144 all the way through 450MHz.
That's all great, not a problem. You can buy those.

check out triplexers--they're used with tri-band radios (144MHz, 220MHz, & 440MHz) to split three ways. I don't know how much power they'll handle; the local op I talked to about it didn't mention if he's using a tri-band H.T. or a mobile.

 

[mmckenna]

then I'll need to rethink the route up there.

It can be tough, but finding closets that are directly stacked over each other could allow you to run up a back corner. Or, look for plumbing or HVAC ducts that run up to the attic and see if you can run your cable up along with them (not inside them).

Other option is to route them outside. You can buy rain gutter down spouts and just use it as a disguise.

Ultimately running separate coaxial cables that are tailored for your specific needs will work better in the long run.