DE2057726C3 - Frequency converter for radiation-tight community antenna systems - Google Patents

Description

214.15 MHz; 221.15 MHz and 228.15 MHz directly into the standardized channels K 10; K 11 and K 12 fall and there lead to picture disturbances. As shown in FIG. 2 shows the coincidence of the species these oscillator fundamental waves with the color carriers and the resulting color disturbances.

A particularly advantageous embodiment of the invention is shown in FIG. 3 shown and in described in more detail below.

The distributor 9 of a communal antenna system is in volume III with the channels K 5; K 6; K 7; K 8; K 9 and the channels KIO 'and K W, which are offset by about +5 MHz, due to the frequency of the conversion oscillator. The oscillator fundamental waves Osz fall here. K6 and Osz. K7, which is on the channels K 5; K 6 and K 7 matched receiver tuners, no longer in the transmission range of channels K 10 '; K 11 'and possibly K 12', but to the beginning or the end of the respective channel, where they are not disturbing

Can have an effect.

Since most receiver tuners have an upper and a lower cut-off frequency for reasons of tolerance, it would be entirely conceivable to also use channel 12 ', especially since a shared antenna system is a radiation-proof, closed cable system. Another advantageous embodiment results when the distributor 9 of a communal antenna system in Volume III with the standardized channels K 8; K 9; K 10; K 11; K 12 and the caused by the oscillator frequency of the respective converter, offset by about -5 MHz, channels K 6 '; K T and possibly K 5 'is fed. Here, too, the oscillator fundamental waves, the receiver tuners tuned to the offset channels, no longer fall within the transmission range of the upper, standardized channels, but rather at their beginning or end. The same applies to the use of channel K 5 'as to channel K 12'.

For this purpose 2 sheets of drawings

Claims (1)

Claim: Frequency converter for radiation-tight community antenna systems for converting television channels into the frequency range of band III in the VHF range, characterized in that when converting to the upper or lower area of band III, this conversion takes place in standard channels and that the conversion takes place in the remaining Area is done so that when a television receiver is tuned to a television channel in the lower range of band III, the associated receiver oscillator frequency comes to lie between the video carrier frequency of a television channel and the audio carrier frequency of the television channel below. 20th The invention relates to a frequency converter for radiation-tight community antenna systems according to the preamble of the claim. It is known that in communal antenna systems, in addition to the usual channel or broadband amplifiers, also use frequency converters. The latter are especially used when, for Avoidance of the relatively large cable attenuation with UHF, a transmitter received in the UHF range in a standardized VHF channel is to be implemented. With the constantly growing number of antenna community systems connected television receiver is for technical and economic reasons the question of the optimal utilization of the transmission channels in the VHF range is becoming more and more urgent. Even now are when transmitting the locally wirelessly received programs and the programs from the Neighboring states largely occupied the channels of the VHF areas via community antenna systems, z. B. by implementing the UHF programs in the VHF areas or by implementing them within the VHF areas because of direct radiation into the receiver. For the distribution of converted from the 12 GHz range or additional received or locally generated programs then hardly any leeway remains, so that looked for technical possibilities to meet the need for transmission channels in Volume III must become. It is possible to use the channels fed into a shared antenna system, e.g. B. by approximately the same level and lowering of the image carrier, so that an adjacent channel operation can take place within the system. In this case, however, only a maximum of five of the eight channels provided can be used in the HI band , since in this band the oscillator fundamental wave of a television receiver operated with the standard IF of 38.9 MHz falls directly into a receiving channel five channel numbers higher Antenna sockets of television sets if the oscillator terminal level of the fundamental oscillation in range III reaches values of up to 1 mV, this also has a disruptive effect on other suspended television sets via the decoupling elements common in antenna community systems. Color television sets are particularly strongly disturbed by a television receiver operated in the HI band by five channel numbers lower, since its oscillator base vibration falls within the range of the color carrier and, if the interfering receiver is only slightly detuned, by around +0.5 MHz directly with the Color carriers of the disturbed receiver would coincide. It can be seen from this that the channels available in Volume III cannot practically be fully used. From the journal Post Office Electrical Engineers Journal 1969, pp. 164-167, a free is known Divide the available frequency band so that all channels are equally spaced 10.5 MHz have from each other. In this case, the receiver oscillator frequencies are - as far as they are still in the Frequency band fall - between the image carrier of one channel and the sound carrier of one below Channel, so that no interference caused by the receiver oscillator is effective. Such a one However, the solution does not lead to optimal utilization of the volume III, since it only allows five channels in Volume III is available and the use of a sixth channel is already available without exceeding the Band limit required. The invention is based on the object of optimal utilization of the HI band in communal antenna systems to achieve. According to the invention, this object is achieved in a frequency converter of the type mentioned above by means of that in the characterizing part of the claim specified measures resolved. The advantages achieved by the invention are in particular that while avoiding the critical channel combinations 5/10; 6/11 and 7/12, at least seven channels in the area of Band III can be transmitted. In this case, a frequency position deviating from the standardized channels within band III is only required for at least two channels. However, since today's receiver tuners are almost exclusively continuously through: immable, coordination with the offset channels is possible due to the closed system without violating the applicable interference radiation regulations. By largely retaining the standard channels, transmissions received in band IH do not have to be converted in the communal antenna system. In FIG. 1, for example, a possible and generally customary arrangement of a communal antenna system is shown schematically. In the channel amplifiers 1 to 8, the antenna signals fed to them are amplified and either connected together directly via a distributor 9 or, if frequency conversion is required, converted into the desired channel using a frequency converter inserted between the channel amplifier and distributor and consisting of an oscillator 10 and a mixer 11 Corresponding frequency converters can also be inserted at the points identified by the reference symbols 12 to 18. In the known converters, the Oszillatorfre frequency of the frequency converter has always been chosen so that the respective implementation in a standardized channel of the *; VHF band took place. '·,. *> F i g. 2 shows the arrangement of the standardized television channels K 5 to K 12 in the VHF band IH. The respective ^r r image carrier, color carrier and sound carrier are provided with the ^ reference characters B, and T. From the arrangement it can be seen that the oscillator fundamental waves Osz. ks; ο _t Osc. Ke and Osz. Κ7 of television receivers operated on channels K 5, K 6 and K 7 ,,, -, ", with a standard? IF -.Λ (picture carrier = 38.9MHzX with its frequencies of