On a more practical level, don't overlook the older Sadelco and Wavetek meters.
You would have to do a lot of work with DTV to recover this investment. Of course, it commands a big price at about $4000.
It can also display an SD version of the DTV broadcast on its internal monitor screen. It is the only mobile device that will display BER and MER as well as average power for ATSC modulation formats. Promax makes DVB-T analyzers for other part of the world and introduced the Explorer line about nearly 5 years ago.
Sedelco display master tv#
If you have more bucks to spend, the Promax TV Explorer (for North America) is the most advanced istrument for ATSC. I find it to be a very compact and effective DTV service instrument. It's not cheap at nearly $1400 list but if you can find a refurbished one, you will have a useful tool that is more than just a meter. The channel flatness display can identify issues with the antenna and/or the presence of multiplath. To anyone considering a meter for DTV, the Sadelco is perhpas the most affordable, near-spectrum-analyzer-like display that can tell you a lot about the signal.
The actual correction factor depends upon the calibration accuracy of the individual meter in question. If you want to know the correction factor for meters that measure analog and digital signals, Sadelco says to add 6.8 dB to the analog reading when measuring a digital signal.
Sedelco display master pdf#
pdf p 21 of 53, p 4 of 36 of the attachment The required NTIA sensitivity for CECBs is -83.0 dBm (-34.2 dBmV):Ĭlick on Digital Converter Box Report which should take you to: I have made some tests and have found that a good tuner can maintain lock on a good quality (low BER.bit error rate) weak signal down to about -30 to -35 dBmV the limiting factor then becomes the SNR (signal to noise ratio) which needs to be at least 15.5 to 16 dB to maintain lock:ĪVS Forum - View Single Post - The Official AVS Antenna Topic! If it has to deal with errors caused by mulitpath or ambient noise in the reception area, then a stronger signal is needed to maintain lock. Its ability to correct errors is limited. How weak a signal can be, and still have good reception depends upon how much work the FEC (forward error correction) has to do, and the quality of the tuner and its chipset (5th generation.6th generation). Sencore says that the signal should be between +15 dBmV and -15 dBmV: The linearity can easily be checked by inserting the 20 dB attenuator to see if the new reading is 20 dB lower.Īctually, I prefer to use the needle of an analog panel meter to the digital readout meter when aiming an antenna.Ĭlick to expand.I'm pretty sure that the CM SLM was made by Sadelco after looking at a 7277D. Old TV field strength meter any good? - AVS Forumīut, when comparing antennas, aiming an antenna, or finding the best location for an antenna the absolute calibration is not as important as the linearity of the meter when making comparisons. I have compared a Sadelco 719E analog meter with a Sadelco DisplayMax 800 designed for analog and digital signals and they are, by chance, fairly close: How closely to two meters agree depends upon the individual calibration of each meter. If you read the Aussie DTV forums (they have had a longer experience with their DVB-T digital, especially with many antennas in the outback) you will see it said that you shouldn't hire an antenna installer unless he uses a BER meter to aim your antenna. This is another example of signal quality (related to BER) being just as important as signal strength with digital signals. I often also have my Apex DT502 CECB connected with a splitter and watch the signal QUALITY bar when aiming an antenna because the best quality signal isn't always at the same azimuth as max signal strength because of multipath reflections. The digital signal nearly fills the whole 6 MHz channel, but I fine tune the meter to about 1/3 or 1/2 the channel width up from the bottom to avoid the pilot carrier at the lower end, which would give a false reading. Its a rushing noise that sounds like white noise (or intercarrier noise between FM stations if the tuner does not mute). When I use my Sadelco 719E meter to measure a digital signal I turn on the audio to listen to the carrier. The meter for digital signals is designed to measure the average value of the digital signal. The reading of a digital signal on an old FSM will not be exactly the same as the reading on a signal level meter designed for digital signals, because the analog meter is designed to measure the peak value of the signal. The newer models are called a signal level meter (SLM). I have found that an old TV field strength meter can be very useful when comparing antennas. Glad to hear that you like Salvati's book it's one of my favorites.
0 kommentar(er)
