The antenna may be correctly oriented, but that doesn’t mean anything; its bandwidth and gain must also correspond to the characteristics of the signal, and that may be why the television doesn’t lock on to certain multiplexes, either manually or automatically, as explained multiple times:
TUTORIAL: PARTIAL RECEPTION OR TOTAL NON-RECEPTION OF DTT MULTIPLEXES.
Main research avenues (identification of problems) for locking issues on the appropriate adapter or television for any missing DTT mux containing specific associated channels, regardless of the site or transmitter, but in individual reception mode... RECEIVER PROBLEM?
First of all, partial non-reception may sometimes stem from the television with an integrated DTT tuner or the external adapter that do not manage the frequency offset observed on some DTT transmitters. If, after an unsuccessful automatic search, one or more multiplexes are still missing, it will be necessary to proceed differently by manually entering the coordinates of the 5 channels (frequencies of the mux or multiplex) from your transmitter and adding, if necessary, up to + 498 kHz, or subtracting - 166 kHz, a value to be determined empirically, but always in increments of 166 kHz, if the exact value is unknown.
For example, nominal frequency "602.000 MHz" = standardized channel 37, corrected frequency, "602.166 MHz" or "602.332 MHz" or "602.498 MHz" etc..
Some receivers have a 4-digit display; in the last example, we implement "602.5 MHz", while others have a 5-digit display: "602.50 MHz". Others, particularly integrated DTT televisions, simply indicate the channel number (between 21 and 69) in the installation menu with fine adjustment -/+++. Refer to your user manual.
In principle, one should be able to correct the centering of the frequency; if this is not possible, either perform a new software update or return directly to customer service... It should also be remembered that some adapters (external/integrated) find their frequencies more difficultly than others in automatic search, thus emphasizing the importance of entering them manually one after the other, which requires, of course, knowing the frequency or channel plan, as applicable.
RECEPTION ISSUE
Next, and more generally, problems often stem from the antenna and the cable.
Is the antenna a standard UHF type, meaning for all DTT channels, from channel 21 to channel 69 or from 470 to 860 MHz? Beware, many old antennas for the reception of analog TV only cover half of the UHF band (e.g., 21 to 38) or UHF channel groups... (e.g., 28 to 37) and therefore may no longer be suitable for different, distant digital frequencies (DTT). Problems of non-reception on certain muxes are often encountered solely due to an unsuitable antenna. It must be changed without fail.
Does the antenna have sufficient gain and directivity? It should show at least 13 dB of gain, but 15 dB is sometimes more relevant. The higher the gain, the more directive the antenna is toward the transmitter, reducing interference risks... It should be checked that it is indeed directed toward your regional transmitter and is clear above the rooftops of surrounding buildings in the useful direction. For information, the standard published during planning calls for an antenna to be 10 m above the ground... so beware of poor receptions due to an antenna placed on the façade, in too low an attic, etc... In some regions (e.g., the North), disturbed by other French or foreign transmitters, only antennas with high directivity, like "Trinappe" or Yagi or long Lambda (many elements), should be preferred. "Design" antennas such as shark fin, wing, caravan, compact, or encased planar panel types should be avoided in weak, disturbed, and heterogeneous fields. All these antennas, very trendy, marketed as "special DTT *" have no chance of competing with a so-called traditional optimized and efficient antenna. If in doubt, consult a "real" professional, not the sellers in hypermarkets or DIY stores, nor online sellers, where flashy marketing prevails... However, it should be noted that most DIY stores offer trinappe antennas for weak or disturbed fields.
* There is no such thing as a special DTT antenna; an antenna is an antenna.... always transparent to the nature of analog or digital radio waves, whether black and white or color and mono or stereo...
Now consider the potential issue caused by the coaxial cable; does it fit into the recommended category, meaning triple shielded and low loss? The industrial reference is the mention 17 VATC or 19 VATC (it's written on it or 17 or 19 PATC). If the cable is obviously damaged or oxidized, crushed, too bent, or too old, replace it with a standardized section of a single piece, as short as possible, up to the adapter's entry. Take care with the connectors and avoid coaxial spaghetti... If analog TV accepted slapdash tinkering, digital DTT tolerates it much less = black screen, pixelation, macroblocking freezes....
Is a terrestrial splitter LB (Wide Band = 40/860 MHz) being used, shielded with an F connector, for how many sockets in the house, knowing that the more ports the splitter has (2, 3, 4, 6, or 8 directions), the more losses it introduces, to which coaxial losses must be added (each 10 m - 1.9 m dB). To compensate for the losses (attenuation), an antenna amplifier is installed upstream of the splitter, with its amplification gain varying between 15 dB (if the splitter is 2-way) and 20 dB (3 or 4 ways) or 25 dB, if the splitter is 6 or 8 ways, but everything depends on the strength of the initial signal.
Is the DTT signal received sufficiently strong at the antenna level (in case the transmitter is below the horizon or there is a blocked opening)? It must have a high gain, 17.5 dB, like a trinappe or others. If the signal is already artifacted, freezing, pixelation, mosaic, and sometimes a black screen for a few moments, a UHF mast preamplifier (21 to 69) with very low noise may resolve weak signal problems (at the limit of range, in a dip, screen-building... See this subject treated separately:
https://www.jechange.fr/telecom/internet In conclusion, if you do not receive one, two, three, or four of the five multiplexes (each mux contains six specific channels) of DTT, all the points listed, particularly the antenna one (statistically, needs changing in 30% of cases), should be reviewed. If you are no longer receiving certain or all multiplexes when it was previously fine, it may be an equipment failure (leakage, misalignment, to be checked...) or a reception just on the limit and the slightest minimal signal drop results in malfunctions on your "no margin" installation.
Regarding specifically those near the borders of foreign DTT transmitters, the principle remains the same, although some reception equipment (antennas + accessories) that are suitable and common within France can sometimes be useless at the borders.
Note:
- 1st ensure that you are in a covered area, check the maps, ask neighbors.
- The rule that says if you receive analog well, you will receive digital well is not systematic...
- 2nd: check the connectors.
- It is necessary to check that the installation does not have an accessory that splits the signal in the shape of a molded "T", as this "thing" is prohibited in DTT.
- If there is no reception in a building, see the issue with the antenna technician responsible for the maintenance of the collective antenna and its upgrade.
- Beware of GSM transmitters (telephony) and others that are too close to the DTT receiving antenna, which can interfere with or prevent the reception of DTT TV, as well as electrical impulse noise from industrial and domestic sources (small vehicles, household appliances, machines, networks, etc...).
- Indoor antennas (see this subject treated separately) may only work correctly near a DTT transmitter that should often be visible. Stick antennas (rod or whip) supplied with DTT/USB keys are the least effective in the range of antennas.
See:
https://www.jechange.fr/telecom/internet To know the correspondences between channels and frequencies, see below, knowing that in DTT the standardized frequency is that at the center of the channel:
https://tvignaud.pagesperso-orange.fr/tv/canaux.htm If, after exhausting the standardized technical solutions (except antennas in the attic and reception with indoor antennas or the use of "folklore" antennas like "wing of thing"), you still lack channels (or multiplexes), see:
http://www.csa.fr/upload/publication/demande_enquete_pb_reception3.pdf
.
