What dB for an outdoor TNT antenna?

Hello
40dB sounds a bit far-fetched! I have a twenty-element (Optex Castorama) on my roof, thirty-six kilometers from the 4 kW transmitter; this antenna has an average gain (depending on the frequencies) of 18dB. Do you see what size and especially how many elements a 40dB antenna could have? Mine is 1.80 meters long, and I live by the sea, so it’s a windy country; we also need to be reassured on that technical side!
Go take a look at www.tvnt.net, there’s information about antenna size in relation to the distance from your transmitter, with colored maps and all. So, it's worth reading, and then take a little look up in the sky to see if there’s a recent antenna installed near you (new antennas shine); you’ll see what the “others” have put up, and it will give you an idea of the size to use. Lastly, an old saying goes, “he who can do more can do less,” in other words, you need to ensure you have a sufficient antenna that provides a reserve reception since the power of the received signal in TNT varies greatly depending on the weather. There, we've quickly covered the situation.
Have a nice day!

It is this one that you have chosen because the link does not work. Be careful, it is an (active) antenna with 5-volt power supply and 220-volt mains transformer.

He’s right “40 dB !!!!”, no UHF rabbit ear antenna reaches that gain, 19.5 dBi is the best you can hope for with a triple staggered dipole, 40 dB might be imagined with a 20 dB amplifier behind it, but 20 dB of antenna gain, true, + 20 dB of amplification in RF doesn’t make 40 dB.... again, just a lot of misconceptions.. dB are only additive for increasing levels in distribution.. but the received signal must still be usable, because nothing + 42 dB = nothing, nada, ..

One must understand that these consumer shops are run by salespeople who know nothing at all, or very little... the technical level of the salespeople there is low, contact professionals.

The same goes for the packaging of indoor antennas that claim “42 dB”, if it gives 2 or 3 of useful gain, that’s good..

Hello
don't confuse gain and received signal if a balcony antenna is rated for 20dB it's certainly an electronically amplified antenna but "amplifying what?" if there is no "visibility" to the transmitter it doesn't help much. Glandu said it all you have to try a product and if it doesn't work return it and get a refund. Each reception location remains a special case and sometimes escapes theory
cheers
Standard: received signal in DTT at the antenna between 48 and 56 dB/µV this is measured with a field meter so a professional tool

in TNT reception not necessarily ...

https://fr.wikipedia.org/wiki/Qualit%C3%A9_de_r%C3%A9ception_en_t%C3%A9l%C3%A9vision_terrestre

Stop with the messages, friends, poor Mellie is overwhelmed. The thing is simple: she gets an antenna, plugs it in, and if it doesn’t work, she returns it and gets a refund.

I come across your post, I'm not a specialist, but I'll reply more simply: start by checking around you if the other houses are receiving well, if you are in view of the transmitter, because often too much signal can hinder reception. If you buy the antenna from a supermarket, you can return it and exchange it. Avoid an active antenna, as it requires a permanent power supply.
Also, check the coverage map with the signal strength: https://www.tnt-gratuite.fr/

Hello,
For a good reception, about 55dB is required.

What you need to know now is that the gain of UHF TNT antennas should be mainly focused between channels 21 to 48 or >470 to <700 MHz, the new operational TV band starting in April 2016, the date of the transition of TNT to all MPEG 4... (i.e. renewal of MPEG 2 equipment >>> 4)

The historical TV antenna gain curve refers to between channel 21 and channel 69, bandwidth which was reduced to channel 60 in 2012... This type of tri-band antenna (max gain 17.5 dBi), still sold, which goes up to nearly 900 MHz..... also picks up mobile telephony 3G or 4G, the so-called 700 MHz and 800 MHz bands..

If there is interference, we add an LTE rejector, or if the TNT signals are weak, a mast preamp for useful frequencies < 700 MHz, with anti-telephony filtering.

On the other hand, for free ludo-social applications in ISM 868 MHz (home automation, gate control, wireless weather stations, etc....), these older models, even at 75 Ohms, are highly sought after in certain circles to achieve longer distances or ranges transmitting various digital data via domestic radio beam...

http://img110.xooimage.com/files/b/2/2/courbe-gain-antenne-uhf-tnt-4d77eae.png

(can also pick up the ISM band at 433 MHz, home automation application, but the antenna gain is weaker)

The most marketed UHF TNT antenna for channels 21 to 60 in France is the trinappe, which provides a real peak gain of 17 dBi. (from €35 to €40). New models 21/48 are expected.

Thank you Gil, it is indeed very technical ;-), apparently this type of antenna comes after the rooftop antenna which is the best solution.

But since I can't use a rooftop antenna, I would like to hear from those who have the type of antenna I originally mentioned.

Thank you in advance.

P.S.: Thanks again to Gil for his very detailed link that covers all aspects of DTT, worth checking out.

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It's because the speed of light is faster than the speed of sound that some people appear bright before they look stupid.

Thank you very much to everyone for your help, I was right to ask because it's easy to get fooled by the so-called capabilities of antennas; I'll go back over all the links you've provided and thoroughly study the issue, and possibly consult a professional if I'm not able to figure it out (which is quite likely to be the case ;-))

I'm marking this as resolved and thank you again.

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It's because the speed of light is faster than the speed of sound that some people appear brilliant before they look foolish.

re
you can always consult an antenna technician, a quote is free, if you want to follow his idea it can only be good, but it's possible to do it yourself with a bit of skill (it's not guaranteed because digital terrestrial television, all things considered, is not as easy to receive as one might think), furthermore with the phasing out of analog broadcasting, meaning soon for some channels will be moved (frequency changes so you need to rescan the receivers) and transmitter powers generally increased which could disrupt those who have added amplifiers. There you go, happy reading for the link to tvnt.net, look carefully through it there are treasures of information
Good luck