[mythtv-users] Best place to insert a CATV amp

Brian Wood beww at beww.org
Fri Jan 26 22:20:41 UTC 2007

On Jan 26, 2007, at 2:54 PM, Boleslaw Ciesielski wrote:

> Brian Wood wrote:
>> Without a signal level meter you really have no idea what the levels
>> of the incoming channels are, and those are expensive items not owned
>> by most consumers
> A lot of cable modems have some kind of signal level meter built- 
> in. On
> my Motorola SB-4200 it is accessible via 
> signal.htm
> It displays power level in dBmV and SNR in dB. On broadbandreports.com
> one can find out that cable modems want something like between -15 and
> +15 dBmV (ideally -10 to +10). Is there a similar range for TVs? My
> understanding is that TVs require stronger signal than cable  
> modems? If
> so, one could measure the signal by connecting the cable modem in
> various places...

I didn't know about that feature, but it probably only shows the  
level at a certain frequency, helpful perhaps but it won't show  
"tilt" problems or help in setting an equalizer in an amp.
Moving it around might be a problem if you were to try and put if  
after a splitter that didn't have a reverse path, but the SLM feature  
might work even if the modem wasn't locked up.

The FCC spec for minimum level into a TV set is 0 dBmV but most sets  
are happier at 10dBmV, much above that and you can get beats in the  
signal caused by overloading the frontend (RF amp or mixer) but it is  
somewhat dependent on the number of channels.

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