Two coax runs needed??

[Mighty Favog]

Got a question about antennas:

I currently have a Magnum-Dynalab ST-2 antenna mounted in my attic with a single 35'-40’ piece of RG-6 Quad Shield coax being run to my Mac MR-85.

I also have the TV (Sony 40” XBR9) in the same set-up as the tuner and the rest of the stereo and being fed via Direct TV (SD w/DVR). As a temporary set-up I put an amplified (+12db – Terk TV5) HD antenna along with another TV-signal amp I had lying around for years that adds another +24db to the signal, on top of my turntable to get HD signals of my “local” stations.

Now if I decide to drop Direct TV, not order their HD package and go with local stations, can I just mount a non-amplified antenna in my attic too and use the same coax run with a splitter for both the TV AND the MR-85, or does it have to be two different runs? I would keep the +24db amp going to the TV. This all assuming I would have to insert two splitters (one in the attic an one at the system) for a total signal loss of 1.2db for 4 connections.

My attic does not have any electric running through it and I'm not having any put up there.

[Masterlu]

You can do this with one coax run.

[jdandy]

Mighty Favog.......I'm not sure how you calculated the 1.2 dB signal loss for four connections, but let me see if I can help you.

Every splitter has insertion loss. How many times a signal is split determines the total insertion loss. This loss is always there, whether a television or a tuner is turned on or off. The average insertion loss of a 2-way splitter is 3.7 dB, a 3-way splitter is 7.5 dB, a 4-way splitter is 7.5 dB, and a 6-way splitter is 13 dB.

Coaxial cable, typically RG6, has a loss of 2.5 dB for every 50 feet. That signal strength loss is added to the splitter insertion loss when determining the total drop in signal strength from the antenna.

RF amplifiers are helpful in recovering from insertion loss through splitters, and signal strength loss through the total length of your coax runs, although the typical RF amplifier will amplify noise and multipath right along with the signal you are trying to boost. Sometimes the boost in noise can prove to be annoying, and can ultimately degrade the overall quality of the received signal. Where your RF amplifier is located impacts the quality of the signal. The closer to the antenna the better because that is where the signal can be amplified before signal line loss occurs.

I hope this information helps you get the best from your installation.