The tuning range of the 3mm receivers, nominally 80 - 115.5 GHz,
has been slightly extended toward lower frequencies. Test with B100 fed
by an alternate local oscillator showed that this receiver works correctly in SSB
and high USB rejection down to 77 GHz. Below this frequency, the USB rejection
progressively weakens, until the mixer becomes fully DSB near 72 GHz. At
still lower fequencies, however, the tuning behavior is very irregular, and
high USB gain (
) makes the receiver very noisy and
calibration difficult. Faulty responses of the receiver at higher frequencies
(due to mixing products with harmonics of the LO) were, however, not detected.
Corresponding tests with A100 will be made in May.
Applications for frequencies down to 
GHz will be considered. Requests
for frequencies below 77 GHz should describe the precision of the calibration
needed. Due to their special LO hardware requirements the accepted proposals
will be scheduled together in one block.
Proposers should use the time estimator which will include the correct receiver temperature at the low frequencies and an extra overhead for calibration.
The second polarization module of HERA is planned to be installed this March. Given the risk involved in this upgrade and the fact that most observational parameters are not yet precisely know for the full dual polarization array, we request HERA proposers to still use the parameters of the present single polarization array when estimating integration times.
The upgraded HERA, dubbed HERA-2, makes necessary an expansion of the IF distribution system. A whole new set of the 100m long IF cables has been installed together with switching units, which permit flexible connections to continuum detectors, attenuators, and the increasing complement of backends.
A new broadband autocorrelator, WILMA (Wideband Line Multiple Autocorrelator), has been shipped to Pico Veleta. This autocorrelator, designed for use with the dual polarization HERA frontend, consists of 18 units each of which handles the full 1 GHz IF band of one HERA detector. Each WILMA band has 512 spectral channels with a spacing of 2 MHz. Most of the acquisition software is ready, and the instrument is currently undergoing extensive tests. WILMA is expected to be available when HERA-2 is operational.
The 117 pixel bolometer array MAMBO-2 which still has a slightly inferior point source sensitivity compared to MAMBO-1 (37 pixels), will be shipped to the MPIfR, probably in May, for several minor upgrades. MAMBO-2 is expected to be available again in autumn when the bulk of the accepted bolometer proposals will be scheduled. During summer MAMBO-1 is available for time critical observations and other technical work.
Zero spacing observations needed for a proposed PdB Interferometer observation no longer require a parallel proposal for the 30m telescope. It is sufficient to mark ``zero spacing'' on the interferometer proposal form and give the necessary scientific and technical information in an additional paragraph of the Bure proposal. We strongly recommend to use the 30m time estimator.
When the need for zero spacing data becomes obvious only after the reduction of the Bure observations, we still request a separate and self-contained proposal for the 30m telescope.