[mythtv-users] HDHomerun signal strength required

[Brian Wood]

Roger Heflin wrote:

> I don't believe that they are actually wired in parallel, the RC circuit is
> carefully setup so each of the 4 outs get the same signal, having one
> of the out's be an in would likely get some odd reflections (ie ghosts)
> on the other outs.  Besides like Brian says, you may get some unwanted
> attention from the FCC.

Correct, they are not wired in parallel. In fact, there is an isolation 
spec, any output to any other output, of 30db. This isolation is only 
maintained if all ports are properly terminated in 75 ohms. If you want 
to be sure of isolation even with bad terminations (opens or shorts) you 
need to use a directional coupler, not a hybrid splitter/combiner.

In truth the FCC is not likely to be the first to notice a new channel 3 
transmitter, the local cable company would be (assuming there is one).

Because cable systems utilize frequencies that are not ordinarily used 
for broadcast, a shield failure will result in energy being radiated on 
frequencies used for other services, like two-way radio and in 
particular aeronautical communications and navigation. Because of this, 
cable systems are required to regularly patrol their systems looking for 
leakage, and it's likely they would pick up the signal (and probably go 
nuts looking for the flaw in their system that's creating it, before 
they figured out it was not their doing).

beww