Yebes has developed several low noise cryogenic amplifiers at S, C, X, and Ka bands that were allocated to equip VLBI receivers at Yebes Observatory, Azores, Ishioka (Japan) and Wettzell (BKG, Germany). To cover the VGOS band: 2 to 14 GHz band, there are two approaches: an MMIC-based version and a hybrid amplifier. The first hybrid units produced were tested with different transistors in the first stage.
The best results, obtained with NGST transistors, yield average noise temperatures of 7.5 K.