Originally Posted by rxheaven
Long cable.. I'd say yes since it must be about 100 ft. But I use a PRE-amp, outside next to the tower. No amp inside, just a regular splitter.
Thanks for this technical explanation. Although, the poor soul that I am still doesn't understand that this process would allow me to pick up a channel that's got a lower DB rate than the one it makes me lose. According to tvfool that is.
Thanks for trying it out
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I wonder if anyone who has the newer 53x models would care to try it. Some people alledged these tuners are "better".
ok... i just looked at tvfool to get an idea of your reference to DB rate (?) ... there are 2 references...
the first is NM or ' noise margin ' .. this number is a measure of the ' margin ' between a given signal at your location
and the ' noise floor ' ... the greater the number, the more usable a signal is... it must be above 0 in order to be
detectable from the noise floor... the number represents a theoretical value that may or may not actually exist,
depending upon any number of external factors, including things like broadband noise at your locale, other
non-tv stations in your immediate area, etc...
the 2nd is the signal strength expressed in -dBm ... this would be an actual measure of the signal level that SHOULD be
arriving at your antenna, given whatever parameters you made for your particular location... again, this is theoretical, and is
affected by things such as terrain, buildings ( even if they are not directly in the path of the signals you are trying to receive ),
and other strong RF sources not necessarily associated with the frequency bands that our tuner is used for.
for the sake of argument, lets use the following figures as an example :
in the normal connect configuration -
1 - actual noise floor at the point of detection inside the tuner = -63dbm
2 - station X with a signal level of -55dbm at the same point ( noise margin = 8db )
3 - station Y with a signal level of -66dbm at the same point ( noise margin = -3db )
in the above scenario, station X works, while station Y is below the noise floor, and does not work.
in the reverse connect configuration -
1 - actual noise floor is reduced by 8db and is now -71dbm
2 - station X signal level is reduced by 10db and is now -65dbm ( noise margin = 6db )
3 - station Y signal level is reduced by 1db and is now -67dbm ( noise margin = 4db )
the differences in the amounts of attenuation can be due to non-linearity across the bandwidth of the tuner,
especially given a reverse connection. it can also be due to reflections and impedence bumps created
by pumping a pair of output stages into each other, albeit separated by 100ft of feedline.
so in the reverse scenario, both stations are now ' above ' the noise floor, and with noise margins within 2db
of each other. both signals would theoretically be usable, but would have different characteristics than those
noted with a normal connect configuration. this would be due to how well the tuner itself was designed, as well
as possible bit error rate differences that might determine successful or failed station recovery and memorization.
again, these numbers are just random for purposes of the example. depending on the amount of noise margin
for each station, as well as the ' relative ' margins between the 2 stations in question, and along with how 1 or more
other uninvolved stations are affected in terms of their levels and margins, it all might be affecting the tuner's
ability to recover and use either of the 2 stations' signals.. indeed, the weaker station might prove more usable
than the stronger, or vice versa.
not really an exact science, here. having a spectrum analyzer would more than likely provide an accurate answer.
none of this even considers the effects of oxidized dissimilar metals close by or on the antenna structure, or feedline
condition. both of these can use incoming RF to create either broadband noise, or noise at a specific region in the
it also doesn't consider the effects of having a powered output stage ( your DVR tuner output ) feeding another output
stage ( your pre-amp's output stage at the other end of your 100ft cable run ) . you could be setting up various
reflections and impedence bumps along that whole route, some of which might produce ' adding ' or ' cancelling '
hopefully, this helps and does not confuse the issue moreso...
in essence, i don't really think you are observing something extraordinary, but rather the random anomolies associated
with the backwards connection setup...