[TriLUG] [OT] HD Antenna suggestions, was: TV Tuner Card suggestion
dave at jamsoft.com
Thu Jan 8 15:20:19 EST 2009
3dB loss per terminal represents a perfect voltage divider. Passive splitters are not 100% efficient and 4-6 dB per terminal isn't uncommon for two way. The splitter itself usually has the loss figure printed on it.
A good receiver front end AGC (built-in amp/attenuator) can accommodate a wide range of input signal levels, so don't worry too much about the loss figure and consider trying a good passive splitter before throwing outboard amplification at the problem. It's only when the receiver AGC runs out of gain than another stage of amplification can help at all, of course adding its own noise. The noise contribution from an amp is far more than any transmission line of which I'm aware.
The extra few $ a wideband splitter costs, e.g. with upper frequency well past 900 MHz, can deliver more consistent results because the UHF-TV channels are in the middle of the passband for which it has presumably been tested vs. close to the top. A bargain splitter can also have goofy phase response across its passband, unpredictably affecting performance.
(Not yet doing OTA digital TV but with actively dabbling in FTA satellite TV and VHF/UHF ham radio)
----- "Randy Barlow" <randy at electronsweatshop.com> wrote:
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> Steve Litt wrote:
> > From what I hear, splitting lowers the signal by 3db each split, or
> > like that, and it requires special hardware.
> 3 dB = 10*log10(2)
> So, if you are cutting 3 dB, you are cutting the signal in half.
> are also cutting the noise received at the antenna in half, though
> the noise received in the lines, which could give a slightly higher
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