A characteristic of the radio observatories participating in RadioNet is that they allow to observe the sky in a large range of frequencies. The previous state-of-the-art has been to use different radio receivers optimized for a specific range of frequencies and to switch receivers whenever it was necessary, which sometimes has been time consuming and required trained staff. It also meant that a large number of equipment had to be developed and maintained. Therefore, RadioNet has launched a Joint Research Project “BRAND EVN” (which stands for Broad Band European VLBI Network). BRAND will be a receiver with an unprecedented bandwidth ranging from 1.5GHZ to 15.5 GHz. This frequency range is an order of magnitude larger than any existing single radio receiver. The advantages are evident: due to the larger bandwidth BRAND will increase the sensitivity of a radio observatory enormously. The effort for maintenance will drop significantly and there will be no time losses when changing frequency ranges.
The prototype, which is constructed by a consortium under the lead of Walter Alef at the MPIfR, will be first installed and commissioned at the prime focus of the Effelsberg 100m Telescope. To suppress the strongest radio frequency interference (RFI) and to protect the first amplifier stage from saturation, superconducting filters will be designed and manufactured. The entire 14 GHz wide band will be digitized directly and then processed with powerful FPGAs. The firmware will convert the linear polarization to circular, it will digitally suppress RFI features and calibrate the signals. The processed data of up to 128 Gbps will then be either recorded or transmitted via the Internet to a correlator.
Once the BRAND prototype has passed the commissioning tests, the whole EVN shall be equipped with such receivers to offer new scientific possibilities to the users, like simultaneous maps of radio sources over the whole usable band.