摘要:

The paper describes the apparatus and associated techniques developed early in the war for the study of the propagation of centimetre-wave energy through the troposphere. The point-to-point method is employed in which a measured power is transmitted along the path under observation and the signal received at a distant point is recorded by a receiver which is calibrated with a signal generator.The transmitting, receiving, monitoring and calibrating apparatus for the three wavelengths used (9, 6 and 3 cm) is described in some detail, and an outline is given of the method employed to record the signal strength continuously.A short account is given of operating experience, the setting up and maintenance of the equipment and the editing of records. Finally an estimate is made of the probable accuracy of measurement and this is compared with observed results.

DOI:10.1049/ji-3a-1.1946.0230

出版商:IEE    

年代:1946

数据来源: IET

摘要:

Frequencies up to about 50,000 Mc/s can be measured in terms of a standard frequency by means of the apparatus described. The unknown frequency is compared, by the heterodyne process, with that of a harmonic of an auxiliary oscillator, the frequency of which is adjustable about 3 000 Mc/s and measured by means of a frequency-meter previously described. The method is capable of an accuracy of the order of 1 part in 106, but the present sources of frequencies of the order of 104Mc/s are not stable to this degree even with the highest practicable stability of operating voltages. For example, several low-power oscillators with frequencies in the region of 25 000 Mc/s were found to vary in frequency by as much as 1 part in 104during periods of 15 min, even under very stable conditions of power supply and temperature. This instability of the unknown frequency imposes a practical limitation on the narrowness of the band-width of the components used for the detection of the heterodyne frequency. In the present design the accuracy is limited thereby to about 5 parts in 105.The apparatus has been applied to an investigation of an absorption wavemeter of the resonant cavity type, for a similar region of frequency, oscillating in the H11n mode. It was found that although the first half-wavelength may differ by as much as 5% from the value calculated from simple wave-guide theory, the subsequent half-wavelengths agree with this value within the accuracy of measurement. The frequency of resonance may be calculated from the measured value of wavelength with an accuracy of 2 parts in 104, but the same wavemeter can be calibrated in frequency and thereafter used as a single-reading instrument with an accuracy of 3 parts in 105.

DOI:10.1049/ji-3a-1.1946.0231

出版商:IEE    

年代:1946

数据来源: IET

摘要:

This paper presents some theoretical considerations on the effect of using heater wires whose length is comparable with the wavelength of the radiation, and describes methods of using them to measure the output of local oscillators and of signal generators at Wavelengths of 10 and 3 cm. The theoretical treatment is limited to the case of very small power inputs (< 10−4watt) where the differential equations involved have simple solutions. Its interest lies chiefly in the use of lamps for the calibration of signal generators and the measurement of noise factor of a receiver.

DOI:10.1049/ji-3a-1.1946.0232

出版商:IEE    

年代:1946

数据来源: IET

摘要:

A rapid method of measuring the characteristic impedance and attenuation coefficient of cables is described. This method is suitable for the testing of cables in the 10-cm wavelength band for uniformity of characteristic impedance.The results of some series of measurements are quoted.

DOI:10.1049/ji-3a-1.1946.0233

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The design of signal generators for the measurement of receiver noise factors at 10- and 3-cm wavelengths is described, one of the main points being the elimination of connectors which give unreproducible results. To achieve this, the monitor and attenuator are made integral parts of the signal generator; the signal emerges through a length of Pyrotenax cable of over 10 db attenuation, giving a resistive output. The signal generator is calibrated by measurement of the power output when the piston attenuator is set to low attenuation but still obeys the theoretical law. Known power outputs of the order of 10−14W may thus be obtained with an accuracy of ± 1 db. The screening is such that no leakage can be detected with the most sensitive receivers.

DOI:10.1049/ji-3a-1.1946.0234

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper describes apparatus for the measurement of voltage at centimetre wavelengths. The equipment includes a gold-leaf electroscope for establishing a standard of voltage; test connectors by means of which connection is made to the circuit to be measured; broad-band crystal holders by which the voltage is actually measured; and amplifying equipment for use with the crystal holders when small voltages have to be measured. Two sets of equipment are described, one for the range 8.5 to 11.0 cm and the other for the range 3.0 to 3.5 cm.

DOI:10.1049/ji-3a-1.1946.0235

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper describes a new instrument for the measurement of power in rectangular wave guides. The instrument consists essentially of a resistive film, forming one wall of the guide, whose change in resistance, due to the absorption of a small fraction of the power passing through the guide, is used as a measure of that power. The instrument is self calibrating, is extremely broad-banded and can be used for any wavelength for which rectangular guide is employed.

DOI:10.1049/ji-3a-1.1946.0236

出版商:IEE    

年代:1946

数据来源: IET

摘要:

An instrument is described which permits the rapid and accurate plotting of the complete radiation characteristics of directive antennae. The information is presented in the form of a contour map. This gives far more information than can be obtained from a simple polar diagram.The instrument itself is described in Section 2, and an example of the type of record produced is given. Section 3 describes the use of the device in solving a particular production problem and Section 4 gives a method of “balance line” plotting which was developed.

DOI:10.1049/ji-3a-1.1946.0237

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper describes a calorimeter (consisting of a water load and thermocouple unit) designed for the measurement of r.f. power at 3 cm, where the mean power range involved is 5–200 watts.The design and performance of a water load providing a good match to the guide over a wide frequency band (8% in the 3-cm range is given.Details are also given of a satisfactory thermocouple unit which can be used on both 10 and 3 cm, and relevant precautions in manufacture and operation discussed.

DOI:10.1049/ji-3a-1.1946.0238

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The u.h.f. resistance of specimens of wire form is deduced from changes inQof ¾-λ concentric-line resonator in which the specimen forms a ½-λ section of the inner conductor. The apparatus is calibrated with copper and molybdenum specimens of calculated u.h.f. resistance ratio.Qmeasurements are made by a novel method in which the resonator is compared with a standard one. Both resonators are coupled to a frequency-modulated oscillator and the difference in output of crystal detectors in the two resonators is displayed on a cathode-ray tube against the frequency-modulating voltage. A null indication is obtained when a triple balance is secured, (a) of resonant frequencies (b) ofQ's and (c) of peak heights of the resonance curves. The load added to one of the resonators to effect theQbalance is removed and the increase in peak output from its detector gives the (square of) the ratio of the unloadedQ's.Results are given for the effect of different surface treatments on solid copper, for different thicknesses of copper plating on steel, and for similar plated layers fused on the steel in hydrogen. These results are discussed and shown to agree with theory and expectation.

DOI:10.1049/ji-3a-1.1946.0239

出版商:IEE    

年代:1946

数据来源: IET