[mythtv-users] Pre-amp for Hauppauge 1600

[Brian Wood]

On Monday 26 April 2010 10:32:48 am Joseph Fry wrote:
> > The best tool I have for aiming antennas is the HDHomeRun Config tool
> > that shows signal strength, signal quality, and symbol quality.
> 
> Check out the HDHomeRun_Config_GUI package
> http://www.silicondust.com/downloads/linux
> 
> I take my laptop up on my roof with me and use the gui tool to adjust my
> antenna.
> 
> As far as amplification is concerned, it is highly dependent upon your
> particular setup.  Amps are really only suitable for overcoming loss due to
> splitters or long cable runs, not for reception issues.  I put my HDHR's as
> close to the antenna as I could, and used some good splitters to keep loss
> at a minimum... this prevented any need for amplification.
> 
> If you must amplify, I recommend a good mast mount amplifier as close to
>  the antenna as possible.  Make sure it is adjustable and only amplify as
>  much as is necessary to overcome the DB loss from the cable and splitters.
>  Alternately, if your splitters are less than 20 feet from the antenna, you
>  could replace them with a good distribution amp instead of using a mast
>  mount to get about the same performance.  I would never recommend more
>  than one amplifier as each amp will hurt your SNR (Signal-to-Noise ratio)
>  and eventually make for a strong, but very noisy and worthless signal.
> 
> Research the amp you buy... they vary widely in quality and cost... pay
> particular attention to SNR vs Gain.  A high gain amp is worthless if it is
> very noisy.  Also, try and calculate how much amplification you really need
> as the higher the gain, the higher the noise (typically).  Figure 1 DB per
> 15ft of coax plus whatever loss you get from splitters (they are usually
> marked).  A loss of 4-5 DB is usually acceptable without amplification...
>  if you can't get a signal after 4-5DB of loss... then it's likely a
>  reception issue that cannot be fixed with amplification alone (antenna,
>  aiming, multipath, etc.)

Something important about amplifiers:

You want all of the signals going through the amp to be pretty close to the 
same level. Using an antenna amplifier for 5 or 6 distant stations when you 
have a local station or two means that you will have some signals of a much 
higher level than the desired ones, probably overloading the amplifier and 
causing beat products.

The same is true of local FM stations, they fall within the passband of the 
amplifier and will also cause overload.

Any two-way radio transmitters close to your antenna might also fall within 
the amplifier's passband, and will also cause problems. You may need a specific 
frequency filter to deal with such situations.

You can get a filter that will drop the entire FM band, and/or specific channel 
filters or adjustable filters to drop the level of any local TV stations.

Unless all of the signals going into the amplifier are about the same level you 
will not get the best results, and the amplifier will appear to actually make 
things worse.

There is a maximum level that a channel can be without overloading the amp, 
and a minimum level before the amplifier noise is higher than the desired 
channel level.

Ideally all the signals going into the amp will fall between these two 
limiting values.

Often your best bet is to speak with a local technician who is experienced 
with the particular signal environment in your area.