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Alteration of an old antenna for digital television


I still have an antenna from an old TV from a foreign company, bought in the 90s of the last century. It is interesting that a circuit diagram was attached to the TV set, with which I successfully repaired the TV a couple of times. Now in the new 20th century, electrical circuits complete with goods are not offered. I wondered if this antenna can be used to receive the digital signal of modern television.


Fig. 1. Antenna from an old TV of a foreign company.
The object for modernization is an antenna of the type “symmetrical vibrator with matching transformer”, with two parallel wires in the dielectric, located at the same distance, and a connector for connecting to the antenna jack of the TV or set-top box.


Fig. 2. Close-up matching transformer.


Fig. 3. Close-up plug.

The symmetric vibrator is model from the field of theory, it consists of two conductive segments, each of which is equal to 1/4 wavelength (1/4 λ), and its total length is 1/2 wavelength (1/2 λ). λ is the designation of the wavelength in physics.


Fig. 4. Total antenna length.
The length of my antenna in the shortest form, that is, in the form for taking the shortest wavelength for this antenna, was 50 centimeters.


Fig. 5. Measuring the length of the antenna.


Fig. 6. Enlarged image of the caliper scale.

Using a calculator to calculate the dipole and pin (symmetric vibrator) on the substitution method, I determined that with the highest efficiency my antenna will receive a signal with a frequency of 284 MHz. So it should be, since this is a meter-long antenna.


Fig. 7. Print screen calculator for calculating dipole and pin.

The broadcast frequency of digital television has become more high-frequency. I found out the frequency of broadcasting in my city on the website of the Russian television and radio broadcasting network. The broadcasting frequency of digital television in the city of Buzuluk for the first package of television channels is 610 MHz, and for the second package - 626 MHz.


Fig. No. 8. Print screen of the interactive map of DEC.

So, we have an antenna with the maximum efficiency of receiving a television signal at a frequency of 284 MHz, and we need an antenna at a frequency of 610 MHz, that is, we need to shorten our old meter antenna.

To determine how much to shorten the antenna, I used a calculator to calculate the dipole and pin.


Rice number 9.Print screen calculator for calculating dipole and pin.


Fig. 10. Print screen calculator for calculating dipole and pin.

For effective reception of the first package of TV channels, the total antenna length should be 23.33 cm. But I decided to play it safe and shortened the antenna to 30 cm.


Fig. 11. The total length of the shortened antenna.

Before shortening the antenna, I tested its effectiveness with a digital set-top box. The signal intensity was 73% and there was no television reception. After shortening the antenna and checking its operation, the signal intensity was 78%, 100% quality and reliable reception of television programs appeared.


Fig. 12. The setup screen when operating a TV with an entire antenna.


Fig. No. 13. TV setup screen and antenna (total antenna length 30 cm.).


Fig. 14. TV setup screen and antenna (total antenna length 29.3 cm.)

Shortening the “horns” of the antenna, I decided to enter the results in the table:



After bringing the total length of the antenna to 23.3 cm. I was alarmed by the results. I also decided to reduce the length of the "horns." As a result of locksmith work, it turned out to reduce the total length of the antenna to 19.4 cm. And further refine the antenna to smoothly change its length. Results in the table.


Fig. 15. Details of the sliding contact of the "horns" of the antenna.


Fig. 16. Modified antenna.

Somewhere on the Internet, I read that the transmitter power for a package of RTRS-2 TV channels is less than the transmitter power for a package of RTRS-1 TV channels.

As a result of the work done, I came to the following conclusions:
- a redesigned antenna can be used in my conditions to receive a package of RTRS-1 TV channels on TVK 38;
- in the manufacture of home-made small-sized antennas for digital television, it is necessary to use an antenna amplifier.

I hope that what I wrote will be interesting to someone.

Good luck
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40 comments
pogranec,
Eh, no clues from Ivan_Pokhmelev , you’ll have to fully reveal the secret of this Korean spiral microwave coaster. I know its frequency 2450 MHz (standard for domestic microwave ovens). I’ll translate it into wavelength and compare it with the turns of this spiral. boss

P. S. It’s not so simple in fact, because the coils are welded to the legs at different radii.
New Standard,
No, mercury is heavy metal, the vapor should, in theory, be below. But it can lift it with a stream of air.
In general, I was really afraid then to connect a low-power transmitter. A powerful one had to figure out how to align it with a mirror xaxa And then the output stage would instantly fly out ...

New Standard,
Then I abandoned these experiments for a long time, then I met with a major and he talked about a radio amateur (his friend). He sort of assembled this antenna, cut the transmitter down and there it was, well, all the connection was gone. All good. In short, they took him. Fun, huh?
R555,
In ancient times, those who made mirrors of mercury went crazy with its fumes. If the mercury evaporates, then its vapors, according to the idea, should rise high, and can act as a metal sheet on the radio signal, that's what the repeater is not, although over time everything will blow away with the wind
Valery,
So I thought that they would start writing about red mercury. Read the wiki. boss

Valery,
And to me 20 years ago, a major radio amateur said. Do not mess with the mirrors! Arrested. This refers to the old large mirrors, where the reflective layer was from mercury amalgam. We used them as a receiving antenna.

R555,
And he said, well, you understand that at least you work for reception, and the local oscillator of your fucking receiver gives a weak, but a signal to the receiving antenna ...

Valery,
I don’t know due to what, maybe because of the area of ​​the mirror (which is unlikely), but the reception was excellent.
And the major said. Do not even try to steal here even your weakest transmitter!
Quote: ino53
Well then, remember the red mercury ...

And a film of the same color ...
Quote: R555
... the time to discuss the so-called mercury antenna. Of course, everyone will now begin to shout that this is a myth. Well, yes, I think so too ... maybe I don't think so xaxa

Well then, remember the red mercury ...
pogranec,
Still, you have to wait for what he writes about this Ivan_Pokhmelev.
R555,
With North Korea or something, she is so radically struggling with smoking in the kitchen, apparently smelling the smoke. The rotation changes as you cook, cool, you can see it smells like it analyzes, well, then Koreans. Here in YouTube, where it’s not for children, they said that if you twist a spiral in a certain field, you can jump in time))
R555, here I picked from the Internet

There is no special material - there is a wavelength and a length of the conductor, the thicker the conductor - the less it will heat up (if it coincides with the wavelength --- therefore, special supports are made so that the length of the conductive surface does not coincide with the wavelength and is thick.
New Standard,
I have a Korean microwave in my kitchen, it’s from this spiral. Her rotation can automatically change. So it has nothing to do with it. The spiral is not grounded as you write. She stands on a glass pallet (he rotates). And sparks or what will be worse when you turn on the empty one, but at full power and go out to smoke xaxa
R555,
You intrigued this spiral in the microwave, and what if it really is, there is some trick. And in which direction does the stand rotate? Although I think it doesn’t matter, it can be seen just grounded on the case. Sparks in the microwave will not only come from the foil, but also if you take out the glass stand
R555,
I know about HF, on HF we even received radio programs from Ecuador (Voice of the Andes)! And he is on the other side of the Earth 20,000 km! And here it was FM (64-108 MHz), I remember Finnish stations that I managed to catch, Albanian. I didn’t receive the stereo signal, there was no decoder at hand
New Standard,
You write a little wrong. This is not FM, but HF, and yes they can even 2000 km with reflection. And VHF is the rarest cases of this, but not for 2000. As for quality, I remember when I was at school, I made recordings of foreign groups from the receiver on short waves at night. It is clear that not stereo and not with CD quality xaxa

Korolev,
It's time to discuss the topic of so-called mercury antenna. Of course, everyone will now begin to shout that this is a myth. Well, yes, I think so too ... maybe I don't think so xaxa
R555,
I once experimented with an antenna and frequency filters and caught on an empty frequency scale an FM station from Israel, or even 2000 km. Moreover, the quality was excellent, but then it seemed to float away. Probably the ionosphere then successfully reflected. At the expense of a spiral with metal. Well, I don’t know, maybe there was a grill mode there? Then the waves somehow disintegrate ... But stop there 3 legs are welded, it’s not quite a spiral
Ivan_Pokhmelev,
I have a question, at first sight not related to antennas. In front of you is a metal stand placed on a rotating microwave tray

We all know that plates, mugs, and other utensils with conductive rims, patterns, and metal objects placed in the chamber of a microwave oven cause fireworks and the magnetron to fail. But how does this stand work properly in the microwave?

I started repairing microwave ovens when they first started appearing with us.I also carried out some work to study their impact on ... Therefore, I know about them even more than expected. boss But I do not have an exact answer to the above question, though there is 1 version. It would be interesting to know the opinion of knowledgeable people. This question is for everyone in the topic.

P.S. And the attitude to antennas is this. If you understand why the metal stand does not heat up at 800 watts microwave, then you will make a good antenna good
Khatul Madan,
what kind of decoder is on the TV
No, it’s choking on overload there. At home and on TVs and on a samopal: DVB-T2 set-top box + HDMI to VGA converter + monitor. And at work a similar homemade. yes
Valery,
When I listened to air on HF last night last year (I hope not everyone forgot why at night smile ), there the German host spoke German))) about modern means of communication. But, guess, guys, they called them in the studio. About how they call us on the radio, order a song. But then the wave swam away, and German I already vaguely remember ... But interestingly, Who called the radio in shortwave? help
Alexey himself,
For the sake of sports interest, I want to check whether TV shows go on the air. But I am reluctant to knock down the settings of my TV sets, and then return them back. If I turn on the stationary computer, I have a TV tuner in it. I’ll look through it and see what’s going on the air there.

I’ll say along the way. Last year I decided to listen to all broadcasting ranges. And he was disappointed. (Except FM) On HF at night you can still hear something like Deutsche Welle, BBC. In short, the ether bends.
Alexey himself,
Do you have an analogue on the “air” (in the sense of an antenna)? .. Since the 15th year, only some cable operators have had an analogue for them. On the antenna - only digital. Officially warned then for a long time about the transition, and then immediately turned off the analog.

Quote: Khatul Madan
In general, I already "burned out" with satellite television about ten years ago and I was not interested, anyway there is nothing to watch there, and my wife and the first ten channels are enough.

The same story. It’s also not relevant because now there is IPTV everywhere. I don’t like the ether, or the cable - “from the telephone cable” you can remove a hundred other channels.)))) .. Yes, and the Internet is now good enough for the telly to find the channels there ...
Khatul Madan,
Analog, I haven’t tried a number, because so far there’s nothing, the telly in the country house are ancient ..
Buy Nuno, do not want to sculpt homemade.
Korolev,
some channels “brake” due to input overload.
Perhaps this is so, I just thought that the AGC system should cope with a high signal level. And yet, you will need to see what kind of decoder is on the TV, DVB-T for terrestrial, or DVB-C for cable.
In general, I already "burned out" with satellite television about ten years ago and I was not interested, anyway there is nothing to watch there, and my wife and the first ten channels are enough.
Khatul Madan,
the signal is either there or not
I have another problem, some channels are “slowing down” due to input overload. level / quality - 100% / 100%, but this is because baboutthe lower number is impossible to show, you have to twist the antenna from the television center, weaken (not to be confused with the girlfriend of a donkey!) signal! yes
Quote: Khatul Madan
We have the same, but the digital signal is rather weak - the picture "crumbles".

And not vice versa? ))))
We have had cable from the very appearance of the “number” in the “two forms” .. And at first there were “squares” and “hangs” ... But already in the 13th - 14th years everything was fine. I remember that in the 13th I bought a new TV (the first one with "smart TV" and "3D", which is why I remembered it well) and, after running the channels, I did not select the "analogue". He wrote down only the number ... And I left it that way, I didn’t even look for an analog, because the quality of the analog was significantly worse then. And, when the analogue was removed in the 15th, everyone was afraid that the cable men would turn it off too. But have not shut down so far.Although, the "figure" is hundreds of one and a half channels, and all (or almost all) in the "HD quality". And by analogy - channels 40-50. (In my basement, an old kinescope self-propelled gun stands)))). So, analog ones often go bad, and digital ones are always excellent.
R555,
As far as I can see the head and cables, it is dual-band.
There are really two ranges of satellite television: C and Ku, but most likely it is a converter (head) with two independent outputs (for two receivers, there are more) of the Ku range, because for the range C the plate needs a huge one and you can put it only on the roof (the most modest diameter is 2.5 meters),
But cable TV worked for us, and it works. Maybe they receive the signal already in digital, and they give us "the old fashioned way", in the analogue.
Indeed, the cable TV transmitting center is like this: on the roof there are several satellite dishes of both ranges (it all depends on the number of "free" channels for which you do not have to pay), the room with receivers is separate for each channel, and modulators, respectively on each channel (if the receiver does not already have built-in), then the adder and amplifier. The heat in the room from the equipment is such that some, not particularly greedy, have to install air-conditioning fans.

Ivan_Pokhmelev,
We have the same, but the digital signal is rather weak - the picture "crumbles".
I have a cable and a digit transmitted, and an analogue.
Khatul Madan,
it’s equal to saying “be a little pregnant”
On the bus there is a grandmother: “Girl, give your grandmother a place”, “Or maybe I’m pregnant?”, “Yes, you can’t see”, “But how will you see in half an hour?” xaxa
Khatul Madan,
Speak correctly. Digital TV either has a picture or not. So, with a weak signal in an analogue TV you can see in noise, and in digital ... of 3 letters. So the input signal level must be taken care of. Personally, it works for me on a piece of wire 25 cm long. But I also have a tower in direct line of sight at a distance of 10 kilometers.

Khatul Madan,
And they turned off the analogue or not, I do not know. The air did not check. But cable TV worked for us, and it works. Maybe they receive the signal already in digital, and they give us "the old fashioned way", in the analogue. fool Delirium is not delirium, and grannies cannot be deprived of television.

And also here Rostelecom offers interactive TV (there are a huge number of channels) using the same optics as the Internet and landline telephone. They for me ... tormented me with this proposal, they also offer to put video surveillance into the same cable. Yeah, and they will watch what is happening here with me. xaxa

Ivan_Pokhmelev,
And my neighbors put a satellite dish (dish) a floor above last summer. As far as I can see the head and cables, it is dual-band. I wonder what they look there? tongue I haven’t watched a TV set for half a year already;
Alexey himself,
bad catches in the country .... 2 ... 3 channels ..
An analog? So they promised to turn him off altogether, and not talk about him. The number? So there are 10 channels in the packet, and the signal is either there or not. The packet is transmitted at a specific frequency and it cannot be that only part of it is received, this is equal to saying "to be a little pregnant."
fav,
If only at a small distance from the telecentre ...
bad catches in the country .... 2 ... 3 channels ..
fav
complete nonsense.
This is a smart antenna for receiving numbers. And he doesn’t need any alteration.
Smartly catches the DM, which is an analogue, that the figure
Alexey himself, of course. An antenna doesn’t care which signal is digital or analog. All that is called an “antenna for digital TV” is actually a decimeter wave antenna of a TV broadcast.
Ivan_Pokhmelev,
But then, do you still need a converter for old TVs?
Even with the proposed remake of the antenna ..
Alexey himself, somehow you ask so strangely. ((
For an antenna, it does not matter what signal is transmitted, digital or analog. Only the frequency range is important. The digital TV signal is transmitted at the same decimeter band frequencies as the analog TV. Therefore, tuning the antenna to the center frequency of the range of received signals does not depend on which signal is transmitted.
Ivan_Pokhmelev,
I try not to explain what I don’t understand very well, but I think it’s better to ask ...
Alexey himself, what relation
Converter ... or whatever they call it ..
has to the antenna?
I’ll ask you again: try to explain what is the difference between the digital TV signal and the analog TV signal in the DMV range for the antenna. )))
Ivan_Pokhmelev,
Converter ... or whatever they call it ..
Alexey himself, try to explain what is the difference between the digital television signal and the analogue TV signal in the UHF band for the antenna. )))

Quote: Alexey himself
Why buy then ..
Why buy then what?
Quote: Ivan_Pokhmelev
But just did not try to reduce the angle between the "mustache"?

So what ? Reduced the angle between the mustache and this antenna, will immediately begin to take a "number"?
It's that simple ... Why buy then ..
Guest Gennady
maintaining
But just did not try to reduce the angle between the "mustache"?
The broadcast frequency of digital television has become more high-frequency.
The frequency cannot be higher, it can be higher. ;)
in the manufacture of home-made small-sized antennas for digital television, it is necessary to use an antenna amplifier.
Only if the antenna cable is long.

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