Table of contents
- 1. Systems Check
- 1.1.1. RF-over-Fiber to R2DBE
- 1.1.2. GPS/Maser 1PPS
- 1.1.3. LO offsets
- 1.2. R2DBE setup
- 1.3. Control computer setup
- 1.3.1. /etc/dnsmasq.conf
- 1.3.2. /etc/ntp.conf
Temporary page for filling in details on the NOEMA April 2019 setup.
Systems Check
RF-over-Fiber to R2DBE
The RFoF receiver and IF processor unit currently receives Antenna 4, 2 polarizations x IF 4-12 GHz.
The RFoF has an internal dual-LO chain (9.0 GHz +5.4 dBm, 4.0 GHz +16.9 dBm) that splits the RFoF signal into a selected 2 pol x 2 sideband x 2 GHz. In case of April 2019, the RX LSB is mixed LSB(1) LSB(2) so is Net LSB.
R2DBE receives lower 2 GHz from boths pols into if0, if1.
R2DBE power levels were checked to be within +-1 dBm of ideal.
R2DBE 2048 MHz clocking and the dual-LO clocking is somewhat adventurous. Timetech freq dist amp (in: H-maser 5 MHz) in the correlator room, one output sent to a stack of three synthesizers (R&S SMA 100B for 9 GHz, SMA 100A for 4 GHz and 2.048 GHz) with ext.ref. from this 5 MHz line shared by BNC-T. Oscilloscope shows distortion of sine. Spectrum analyzer shows still good phase noise.
GPS/Maser 1PPS
R2DBE : HB_sma <-- GPS 1PPS; 1pps_sma <-- H-maser 1PPS
The R2DBE 1pps monitor returns odd readings of merely +-2 clock cycles. Checking with an oscilloscope, the actual offset is ~ 53.28 milliseconds. Need to ask Andre why R2DBE doesn't work (Dress Rehersal involved a software update on EHT-CC, maybe this feature broke)
LO offsets
On the RFoE receiver side in the correlator room it is clear from the synthesizer settings that there are no LO offsets at that
nd Olivier has
R2DBE setup
Clock 2048 MHz clk, 0 +- 3 dBm 50 ohm
Driven by 5 MHz H-maser locked R&S SMB 100A
HB input from GPS 1PPS
1PPS ref input from Maser 1PPS, to utilize internal counter-comparator in addition to separate external 1PPS GPS-MASER unit
Control computer setup
Enabled ip4 NAT/masquerade to allow Mark6's to use further NTP, and access the internet for installing DiFX for zero baseline tests
Added jwagner as publickey-only auth (/etc/ssh/sshd_config section like "Match User daan").
Reverted back to the R2DBE scripts from SAO-EHT https://github.com/sao-eht rather than Radbout written-from-scratch "vlbicontrol" (we have not tested it, especially not for GMVA, and no earlier experience since neither NOEMA nor APEX were in the EHT dress rehersal)
