The Arcminute Microkelvin Imager is a pair of interferometer arrays operating with six frequency channels spanning 13.9-18.2 GHz, for observations on angular scales of 30 arcsec-10 arcmin and for declinations greater than −15 • ; the Small Array has a sensitivity of 30 mJy s −1/2 and the Large Array has a sensitivity of 3 mJy s −1/2 . The telescope is aimed principally at Sunyaev-Zel'dovich imaging of clusters of galaxies. We discuss the design of the telescope and describe and explain its electronic and mechanical systems.

We present observations between 14.2 and 17.9 GHz of 16 Galactic H ii regions made with the Arcminute Microkelvin Imager. In conjunction with data from the literature at lower radio frequencies we investigate the possibility of a spinning dust component in the spectra of these objects. We conclude that there is no significant evidence for spinning dust towards these sources and measure an average spectral index of α= 0.15 ± 0.07 (where S∝ν−α) between 1.4 and 17.9 GHz for the sample.

Aims. We describe a 6-12 GHz analogue correlator that has been developed for use in radio interferometers. Methods. We use a lag-correlator technique to synthesis eight complex spectral channels. Two schemes were considered for sampling the cross-correlation function, using either real or complex correlations, and we developed prototypes for both of them. We opted for the "add and square" detection scheme using Schottky diodes over the more commonly used active multipliers because the stability of the device is less critical. Results. We encountered an unexpected problem, in that there were errors in the lag spacings of up to ten percent of the unit spacing. To overcome this, we developed a calibration method using astronomical sources which corrects the effects of the non-uniform sampling as well as gain error and dispersion in the correlator.

We present observations between 14.2 and 17.9 GHz of 12 reported supernova remnants (SNRs) made with the Arcminute Microkelvin Imager Small Array (AMI SA). In conjunction with data from the literature at lower radio frequencies, we determine spectra of these objects. For well-studied SNRs (Cas A, Tycho's SNR, 3C 58 and the Crab Nebula), the results are in good agreement with spectra based on previous results. For the less well-studied remnants, the AMI SA observations provide higher-frequency radio observations than previously available, and better constrain their radio spectra. The AMI SA results confirm a spectral turnover at 11 GHz for the filled-centre remnant G74.9+1.2. We also see a possible steepening of the spectrum of the filled-centre remnant G54.1+0.3 within the AMI SA frequency band compared with lower frequencies. We confirm that G84.9+0.5, which had previously been identified as a SNR, is rather an H II region and has a flat radio spectrum. ) that 'shell' type remnants, which typically have α in the range 0.3-0.7, show spectral flattening at higher frequencies.However, the detection of small changes in spectral index over a limited range of frequencies is not easy (see e.g. Green 2007), and observations over a wider range of frequencies are an advantage in such studies. Finally, possible excess 'anomalous' emissionwhich may be from spinning dust -has been reported in the case of one Galactic SNR (3C 396; AMI Consortium: Scaife et al. 2007). These AMI SA observations provide additional constraints on any similar emission associated with the observed remnants. T H E T E L E S C O P EThe AMI SA is situated at the Mullard Radio Astronomy Observatory, Cambridge. It consists of ten 3.7-m-diameter equatorially mounted dishes with a baseline range of 5-20 m. The telescope observes in the band 12-18 GHz with cryogenically cooled indiumphosphide High Electron Mobility Transistor (HEMT) front-end amplifiers. The system temperature is typically about 25 K. The astronomical signal is mixed with a 24-GHz local-oscillator signal to produce an intermediate-frequency signal of 6-12 GHz. The