CS212869B1 - Method of equalizing low-frequency broadcast circuits - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a method of equalizing low-frequency radio circuits transmitted by a cable provided with radio-pairs intended for high-quality stereo operation, thereby ensuring that the desired crosstalk attenuation and crosstalk spacing limits are achieved. Recently, new types of cables have been produced that contain low-frequency radio-pairs. Assemble ae and pimple step 915 m with inductance 3.2 mH. The installation of these cables makes it very difficult to achieve the required crosstalk attenuation and crosstalk spacing limits required for operation in the highest quality class. The fundamental problem is that e-crosstalk self-alignment has not yet been performed and was not considered possible. After the assembly of several lines, which contained cables with radioparas, there were always certain combinations that did not meet the required limits.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of mounting and electrical alignment which, while maintaining cable values, ensures that the required values of the crosstalk attenuation and crosstalk spacing limits are maintained. The principle of the method according to the invention is that the alignment is carried out in two steps, of which the first is to select radiogroups with the same direction of transmission and to cross them so as to minimize the permissible imbalance of the radiogroup itself against shielding. and in the second step, the capacitance unbalance against the radiopairs with the closest imbalance value of own ra212 869 is equalized for pairs above the limit of imbalance of its own radiopairs against the shielding of these radiopairs.

212,869 to a shielding pair by connecting a cable capacitor between the cores of the two selected radiopairs to eliminate the capacitive imbalance between the selected radiopters.

The main advantages of the invention are that ee eliminates inadmissible attenuation and crosstalk spacing values. The pupin section is aligned in only one, the middle junction. The sprinkling section consists of two lengths of 460 m each. The unidirectional combined coaxial cable group consists of only three radiopairs. If this equalization does not reach values equal to or less than 400 pF, a second equalization step is required. A radiopar that exceeds the 400 pF limit, along with another radiopar that exhibits the second highest value in the group, is measured for the Kg imbalance, i.e., the capacitance imbalance between adjacent pairs. In case the excess value is higher than 10 pF, we make a simple equalization using a capacitor, which is connected in such a way that the Kg imbalance is reduced to the lowest possible value, but safely below 10 pF. If the Kg imbalance does not exceed 10 pF, we do not need to perform the equalization because the crosstalk limits are not compromised.

Currently, the construction of cables and radiocouples, which are designed for the best quality transmission of radio programs. Radioparas are pupinated by an inductance of 3.2 mH and a 917 m pupic step. These radioparas are either assembled into separate special cables that contain only radioparas or are in combination cables. E.g. cable with six coaxial pairs and six radiopairs. When transmitting the last two events, it was found that in some cases radiopairs do not meet the required limits for attenuation and crosstalk spacing. To overcome this drawback, improvements were made to crosstalk values in the umbilical coils. However, this is not sufficient to provide the required limits. The design of the solution consists in additional alignment of radioparas during assembly so that the resulting values for the whole amplification section are observed.

Calculation of the limit Both for the non-asymmetry of radiopairs against shielding and for Kg values They are derived and calculated in the Annexes.

This solution will enable the use of the above mentioned radio cables for the operation of radiopairs and the highest quality.

The invention is explained in the following with reference to the drawing.

FIG. 1 schematically illustrates the crossing of radioparas in the alignment coupling; and FIG. 2 schematically illustrates a cross section of the alignment pupin section.

The following is a general example of calculating the limit for radiopar non-symmetry against shielding for a length of 915 m.

We calculate from the basic relations:

and.

(2) l ² tu ² . R _k . and ² . OF

212 8G9 ^β 1 .2 2 ¹ µ (la)

12.4. 10 ³ Vf _e- 1, k5.10

Vf (2) where:

e is the basis of natural logariths, is the mean value of the crosstalk to amplitude, the segment in Np, is the length of the amplifiers, the segment in km,

W is the 2f ring frequency,

R ^ is the shielding coupling resistance, e ^ is the capacitive coupling of the radiopar to the shielding to 915 m in F,

Z is the radiopair impedance and f is the frequency in Hz

The initial assumptions are chosen so that the attenuation of the radioparas is the same, the amplification section has a attenuation greater than 10 dB and the mean values of the radioparads against shielding are the same in all pupp areas.

The values of the actual embodiment are? _Q = 97 dB (11.2 Np), 1 = 65 km, = 9.42. 10 ^{4 4} , Z and 380 Ohm and F = 15,000 Hz, where the initial conditions are met, so from formula (2) we get:

R _k χ 1.32 Ohm and finally from (la) θ _χ = 2.9. 10 ¹⁰ p = 290 pF

Since the calculation was made from the mean value of the crosstalk spacing, it is possible to allow the value of _βι and 400 pF as a limit on the pupinal section

We calculate the limit of capacitance imbalance Kg between radiopairs from the following relations:

and _Ql = a _Q + 10 log N (3) ^and omin = a _Q - 3 θ ', _and -------------------------- Z . eu. e ^{0,115 and} omin (4) (5) where:

and _Q is the permissible mean value of the crosstalk spacing h and the whole amplification section in dB, ^and ol is the mean value of the crosstalk spacing converted to 1 pupin section in dB,

N is the number of pupin sections in pieces, ^and omin Is the minimum crosstalk spacing to the pupin section in dB,

6 * is the variance of the values in dB,

212 869 kg is the variance of the values in dB,

Z is the impedance of the unpupped radiopair in Ohm, <jU is 2f is the circular frequency and e is the basis of natural logarithms.

With practical values and _Q = 80 dB, N = 70, d = 3 dB, Z = 150 Ohm, uj = 9.42. 1θ \ fs 15 000 Hz we get from equation (3) and _Ql = 98,4 dB, from equation (4) and _omln = _89,4 dB and finally from equation (5) kg = 19.1O “^ F = 19 _p p .

Since this value was calculated from the minimum values of crosstalk spacing we choose the limit rounded to a lower value ie kg - 10 pF.

The following is a real use example:

The method of aligning the cable β by radio pairs e by a step of 915 m and the cable lengths of 460 m. The following values were measured in the equalizing connection environment: left length: first radiopar L 1: e ₁ = - 600 pF second radiopar L 2: e ^ = + 540 pF third radiopar L 3: e ^ = - 180 pF right length: first radiopar P 1: e ^ = + 50 pF second radiopar P 2: e- ^ = + 200 pF third radiopar P 3: = + 90 pF

Based on the measured values, we design the crossing of radiopairs in the coupling according to Fig. 1.

The resulting imbalance per pupil section in the right cable length numbering is as follows:

first radiopár 1, that is the second radiopár L2 left longitude and first radiopár PI right length: _β Σ = 540-50 = 490 pF, the second radiopár 2 _t that is the third radiopár L3 left longitude and second radiopár P2 right length: _β χ = - 180 + 200 = 20 pF, the third radiopair is the first left-hand radiopar L1 and the right-hand third P3: eL -600 + 90 -510 pF.

The e ^ values for the first and third radiopairs exceed the limit. We measure the capacitance of kg between these radiopairs:

kg »+16 pF, this is a value exceeding the limit for kg.

This is done by connecting a 10 pF capacitor 8 between the vein and the first radiopar L2, P1 and the vein b of the third radiopar L1, P3. as shown in FIG. 2

Claims (1)

A method of equalizing low-frequency radio circuits transmitted by a cable provided with radio-pairs, which are intended for stereo operation of the highest quality, thereby achieving the desired crosstalk attenuation and crosstalk separation limits, characterized in that the equalization is performed in two steps, and e select ra5 212 069 diopars of the same direction of transmission and crossing them to reduce the acceptable imbalance of their own radiopar against the shielding of this radiopar, and in pairs above the limit of imbalance of the radiopar against the shielding of the radiopar, imbalance of own radiopar against shielding by connection of cable condenser between veins of these two selected radiopairs to reduce capacitance imbalance between these selected radiopairs