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I really want to try GroundUrMast's suggestion this evening, to remove the splitter, as it is incredibly easy to implement. Would get back to you when I'll have new information, do not want to start another fire. Thanks again! |
Allow me to ask a dumb question: should I rescan after a / any change in antenna's direction? I've only performed this step after significant changes in the overall setup (e.g. added the preamp or splitter). Does a change in direction warrant a full channel rescan? Thanks!
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Most TV's seem to prevent the user from directly tuning the real channel number... a feature the cable companies would like outlawed I suspect. Hopefully your TV allows scanning for additional channels. Some sets force you to rescan, loosing all previous channels (the cable company's preferred feature set because it make OTA reception more difficult). |
Sorry for not being explicit enough. I have Fox in the list from previous scan, however current level is 0 while peak level is 98. Status reads Unlock, SNR (dB) is 0 and AGC (%) is 62. Since the channel is in the list, do I need a rescan? Thanks again!
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But sometimes, after trying everything else... |
Calculate absolute Signal Power level (dBm) from TVFR
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Start from the absolute Signal Power level (dBm) on your TVFR, e.g. WDIV-TV on 4.1 virtual channel at -23.3 dBm - this is the signal level at the antenna input (in the air at your location). Add your antenna gain for that channel / frequency (or a conservative average gain if not known), let's assume +10 dBi (it looks like you do not need to translate from dBi to dBm): you should have -13.3 dBm signal level at your antenna output. Assuming you factor in a preamp, -13.3 dBm is what your preamp receives in input. Add the preamp gain if you have one (e.g. 12 dB) to that figure to get your signal power at the preamp output: -1.3 dBm in this case (again, it seems that you do not need to convert from dB to dBm). From GroundUrMast calculation, it seems that the preamp noise only affects NM and not signal level. Subtract total signal losses (cable, splitters, misc), e.g. 10 dB and you get signal level at the tuner input, -11.3 dBm. Let me know if you notice differences versus Tower Guy's calculations. |
TV Fool uses a dipole reference. Antenna gain is assumed to be specified in dBd.
dBi - 2.15 = dBd If you start with a TVFR NM value, you can add the antenna gain (dBd) . The sum will be 'net NM' at the antenna terminals. Amplifier gain will not affect net NM. Amplifier noise figure will subtract from the net NM. Passive losses such as cable and splitters will not affect net NM. A stable net NM of +10 or better should offer reliable viewing with most tuners. (Multipath, noise, adjacent and co-channel interference all work to reduce or destabilize the net NM.) |
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