1. EVN Performance and Reliability Jun Yang, JIVE 4 Dec, 2009
TOG Meeting – Bonn December 4, Jun Yang, JIVE

2. TOG Meeting – Bonn December 4, 2009 Jun Yang, JIVE
Outline
Sampler statitistics
FTP fringe tests
Session reports
Highlights
Summary
TOG Meeting – Bonn December 4, Jun Yang, JIVE

3. TOG Meeting – Bonn December 4, 2009 Jun Yang, JIVE
Sampler statistics
An example:
6cm 1Gbps experiment EP064H
Auto-corr. =
High-bit fraction * 2.747
Ideal: Amp ~ 1
High-bit fraction ~ 36.4%
** Higher is better than lower.
** Imperfect sampler distribution:
Jb, Nt, & Tr.
** Ur used 1bit sampling.
TOG Meeting – Bonn December 4, Jun Yang, JIVE

4. Sampler distribution was significantly affected by RFI at Tr and Wb.
18cm Gbps experiment EP064F
Sampler distribution was significantly affected by RFI at Tr and Wb.
Could dBBC solve the problem?
TOG Meeting – Bonn December 4, Jun Yang, JIVE

5. TOG Meeting – Bonn December 4, 2009 Jun Yang, JIVE
Sampler should be monitored via systests samplestat procedure & Mk4 decoder samples command to check for potential problems in analog or digital domain.
Ideal distribution
Deviation from the ideal may indicate
# # Attention set too high/low.
# # Impedance mismatch in VC/BBC formatter cable.
# # No input to sampler.
# # VC/BBC AGC circuit not working properly. ……
(Himwich, Corey, & Smythe 2007, 4th IVS TOW）
Sampler
– – – + ++
Voltage (mv)
<-200
0-200
0200
>200
Mk4 Formatter 01 00 10 11
Fraction
18.2%
31.8%
TOG Meeting – Bonn December 4, Jun Yang, JIVE

6. ---- Very useful for station to quickly check system setup.
Ftp-Fringe Tests
---- Very useful for station to quickly check system setup.
Problem with “scan_set” at Nt, Mc, & Ur and network connection. Please update MK5 SDK, firmware, and OS.
Problem with MERLIN out stations. JIVE needs to know their setup before the experiment to create the vex file for correlation, and fast response via Skype group chat.
512/1024 Mbps bit rate is required to check more BBCs for wide-band user experiments.
TOG Meeting – Bonn December 4, Jun Yang, JIVE

7. Session 3/2009 ---- detected from ftp-fringe tests and feedback
No “preob” in the FS log files of Mc, Tr, & Mc in N09M3.
Bits missing reported by “scan_check” at Ef, Wb, Tr, On, Mc, Jb & Ur in 1Gbps experiment. The problem was also reported in Session 1-2/2009.
Problem with a disk pack at Nt in EM077A, Mc in EC029A, and Tr in GF015B.
Mc: instable H-maser in ES062A and other experiments of Session 2.
Sh: the 2nd head connection between formatter and Mk5a on VLBA connection instead of MK4 resulting in no valid headers. Found and solved after F09C2.
On: a strange problem with the noise diode.
Cm: replaced by Da and Kn.
TOG Meeting – Bonn December 4, Jun Yang, JIVE

8. TOG Meeting – Bonn December 4, 2009 Jun Yang, JIVE
Session 2/2009
Ur: No fringes in the Gbps experiments EM072A and EP064E due to the over-rate recording. Later, 1 bit sampling was used.
Cm & Kn: The 14 MHz signal was not fed into one subband in 16 MHz/subband experiment, Session 1-2 /2009.
Ys: H-maser failure in the last four experiments.
On: Problem with setting the correct LO in ES060A.
Mc: Incorrect LO in EG040D and show some tiny phase jumps due to an instability of the H-maser.
Tr: No fringes in EB040B.
Jb1: Suffered a wheel casualty in EP063A and was then replaced by Jb2.
No “tpicd” monitoring messages at Tr and Mc due to missing the "datavalid=" command.
TOG Meeting – Bonn December 4, Jun Yang, JIVE

9. TOG Meeting – Bonn December 4, 2009 Jun Yang, JIVE
Session 1/2009
Ur: Over-rate recording in the 5 Gpbs experiments (and at Mh in N09K2?).
Jb2: Low (<0.1) sampler statistics in LCP in the 6cm experiments.
Jb1: Replaced by Jb2 in 18cm experiments.
Ys: Correlation amplitude had a fluctuation in the K band experiments due to a broken RG-58 cable.
TOG Meeting – Bonn December 4, Jun Yang, JIVE

10. TOG Meeting – Bonn December 4, 2009 Jun Yang, JIVE
Highlights
The Yebes 40m radio telescope started to perform the 5cm EVN observations.
First EVN fringes to the Kunming 40m and Miyun 50m radio telescopes.
The Nt 22GHz RCP LNA was fixed before session 2.
TOG Meeting – Bonn December 4, Jun Yang, JIVE

11. TOG Meeting – Bonn December 4, 2009 Jun Yang, JIVE
Summary
Problems with
## MK5: bits missing, over-rate, & scan_set,
## FS: no “preob”, & missing “tipcd” output.
## BBCs: mismatch LO, bad sampling, & low correlation amplitude (see calibration report),
## H-maser: instable at Mc, & failure at Yebes,
## Antenna: a wheel casualty at Jb1.
No problems with receiver and formatter in session 1-2/2009.
TOG Meeting – Bonn December 4, Jun Yang, JIVE