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The question might be quite confusing since I'm totally new to electronics world. When I was in school, I had a TV that required a TV Antenna to capture free air channels. So one day when I was just tuning different frequencies in TV Settings, it captured a frequency and started playing video. Later I got to know that frequency was from a DVD player used by my neighbors. So I could literally watch what they were playing in their DVD player on my TV (Without any loss of clarity).

So the question is why DVD player was leaking the frequency? And how my TV was able to capture those frequencies?

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  • \$\begingroup\$ In what country and year did this occur? Radiofrequency emissions standards may vary. \$\endgroup\$ – Aaron Brick Apr 27 '17 at 17:38
  • \$\begingroup\$ India, I guess in between 2005-2009. \$\endgroup\$ – Rakesh Mane Apr 27 '17 at 17:58
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It's hard to be sure what was going on without knowing the exact physical setup and equipment used but random speculation and guessing is always possible.

I'm assuming this was a fairly old DVD (or possibly VHS?) player that had an RF output that allowed you to connect via the antenna input to the TV rather than using composite video, HDMI or some other connection system. Modern players don't have this output because it's lower quality and all newer TVs have other options to connecting but some older players did have it.

Clearly the signal was leaking from their DVD player into your TV. A DVD player is going to output a fairly strong signal, the manufacturers don't want complaints and returns because a customer used a long or low quality cable so they will output towards the upper end of the signal strength range that TVs are designed for. If they weren't using the RF output from the player then the unconnected socket on the back will act as a transmitting antenna. It won't work very well but some signal will get out.

A TV is designed to pick up signals over a very wide range of signal strengths, when you are dealing with radio signals the signal strengths can easily vary by factors of thousands or more. This means that they can pick up some very weak signals, especially if the antenna is pointing roughly at the signal source. If things were physically close enough then your TV could have picked up the signal leaking out of the back of their player.

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    \$\begingroup\$ That, and/or they did hook it up to their DVD-player via RF socket, perhaps via VCR and TV to their antenna or RF-antenna-distribution wireing in their house which leaked some. \$\endgroup\$ – winny Apr 27 '17 at 10:46
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    \$\begingroup\$ True, it could be leaky wiring or it could even be leaking out of their antenna. There is just no way to be sure what is going on. If the player didn't have an RF output then I have no idea what the cause was. RF out on a DVD was virtually unheard of here even for early units but was common on VHS players however I suspect that varies a lot country to country. \$\endgroup\$ – Andrew Apr 27 '17 at 11:07
  • \$\begingroup\$ I just checked my old DVD player, it has RF port. So probably signal was leaking from their DVD players RF port and antenna. I used to get two such signals from two houses, one (Samsun DVD Player) from around 13 meters away (they didn't had TV antenna) and one (Beston DVD Player) from around 25 meters away (they did had TV antenna). I doubt if DVD players still leak the signals. Is there any way to prevent such signal leak? \$\endgroup\$ – Rakesh Mane Apr 27 '17 at 12:22
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    \$\begingroup\$ The "Correct" way would be to terminate the RF output with the appropriate impedance, normally 75 Ohms for TV antennas but it may be 50 Ohms in some areas. In practice putting some metal foil over the port that is held tightly on to the outer ground connection without touching the centre pin will probably work well enough. A plug or short length of cable with the centre pin removed would also significantly reduce the signal levels, they would act as an imperfect shield around the signal pin. \$\endgroup\$ – Andrew Apr 27 '17 at 13:51
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Lots of home electronics used Channels 2/3/4 (60 and 70MHz region) to communicate video to the TV. Wirelessly. The Recoton Company sold lots of those video links. Some, also, at 900MHz.

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    \$\begingroup\$ Can you please elaborate? \$\endgroup\$ – Rakesh Mane Apr 27 '17 at 12:53
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    \$\begingroup\$ Probably some kind of semi-legal low-power VHF transmitter.... \$\endgroup\$ – rackandboneman Apr 27 '17 at 14:14
  • \$\begingroup\$ I was thinking about this "RF modulator" \$\endgroup\$ – analogsystemsrf Apr 28 '17 at 4:04
  • \$\begingroup\$ I was thinking about this "RF modulator" en.wikipedia.org/wiki/RF_modulator Even if wired to the TV, if the TV antenna remains connected that Antenna will radiate the "RF modulator" signal, at whatever channel the RFM used.For a clean picture, NTSC video needs 50dB (or 60db) SNR. Atop the -174dBm noise floor, plus 67dB for 5MHz video bandwidth, the RFM needs to produce -174+67+50 = -57dBm signal into the TV. With 0dBm being 0.632vpp, that -57dBm is 3dB stronger than -60, which is 0.632milliVoltspp \$\endgroup\$ – analogsystemsrf Apr 28 '17 at 4:11
  • \$\begingroup\$ From memory, cableTV signal levels are near 1 millivolt (peak, rms,PP). If your rabbit ears point to their rabbit ears, good picture. \$\endgroup\$ – analogsystemsrf Apr 28 '17 at 13:09

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