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======= List of problems found =======

=== Active general issues ===

None\\


===== 2019 Session 3 =====

=== L - Band ===
**Jodrell Bank (Lovell)**: 

There is no ANTABFS files produced from station for any of the Lovell L band observations, due to a new 
source of RFI identified at Jodrell Bank which it appears has had very deleterious effects on all the Lovell L band observations for this session. This new RFI is approximately 30 dB above the noise and 20 Mega Hertz wide, spanning 1472 - 1492 Mega Hertz.

The RFI is believed to be for a 4G+ mobile phone service which will bridge the gap between 4G and 5G. It is thought that the signal provides coverage to the Manchester metropolitan area, and this is seen at Pickmere and Darnall too.

This signal was first observed in September / October 2019 and they are still devising methods to mitigate its effects. \\

===== 2019 Session 2 =====

=== L - Band ===
**Tianma**: Recorded linear polarization (eg.user experiments - EG100C-D and EH036A-F).\\

===== 2019 Session 1 =====

**Urumqi**: No ANTAB files produced (invalid TPI values recorded for all experiments).\\
**Tianma**: In this session they have fixed the high leakage observed in the last year.\\
**Jodrell Bank**: Wiggles in LCP across the band since ~2017 session 2 from unknown origin. It is visible in NMEs or spectral line experiments, although in continuum ones the wiggles are smeared out and only a larger scatter is visible.

Last checks from Eskil point to: "One of the receiver boards in one optical-to-RF converter used for Mk2 VLBI seems to be suboptimal. With very high input power, it works, but when decreasing the power to usual or weaker than normal observing level, the jagged bandpass appears. We'll investigate buying a replacement model. In the mean time, we'll use the identical Lovell hardware which appears to suffer less from this problem."
**Solved for 2019 Session 2.**


=== L - Band ===
**Sardinia**: LL signal in Subband 8 much lower than RR signal.\\
**Svetloe**: LCP is broken (at least in the NME).\\
**Urumqi**: recorded linear polarization (in the NME and also in the user experiments, eg. EP106E, EP106F and EP106G).\\
**Tianma**: recorded linear polarization (in the NME and also in the user experiments, eg. EP106F and EP106G).

=== C - band ===

**Svetloe**: LCP is broken (at least in the NME).\\


=== K - band ===
**KVN**: high invalid data percentage (~7%).\\
**Sardinia**: No LL signal in subband 7 (and bad sampler stats there too).\\

=== M - band ===
**Torun**: large cross hand amplitude noticed (~30%).\\

===== 2018 Session 3 =====

=== General ===

**Tianma** high leakage between cross and direct polarizations. They should fix that.\\
They also had recording problems: again they overwrite part of the diskpacks.\\
**e-MERLIN**: recording issues. But good fringes and data obtained during several experiments.


=== L - Band ===
**Sardinia** LL signal in Subband 8 much lower than RR signal.\\
**Urumqi** Observed with linear polarizations.\\
**Westerbork**: high leakage between polarizations.


=== C - Band ===

**Noto**: Out in many experiments due to receiver problems.\\
**Kunming**: Fringes only appear in prat of the observations, not full time range. Antenna problems?


===== 2018 Session 2 =====

=== General ===


=== C - Band ===

=== L - Band ===
**Westerbork** issues finding fringes in NME -> found 7s offset in fila10g. fila10g time seems to be jumping out of sync very quickly (1s/half hour).\\
**Sardinia** LL signal in Subband 8 much lower than RR signal.\\
**Zelenchukskaya** Tsys values high for Subbands R1 and L1 caused by RFI.

=== S/X - Band ===
**Westerbork** issues with fila10g during NME. Would only send 1 packet per scan. Fixed for first user exp.\\
**Effelsberg** issues with fila10g during NME. Would only send 1 packet per scan. Fixed by first user exp.\\
**Noto** fringes very weak.

=== K band ===

**Noto** fringes very weak.

===== 2018 Session 1 =====


=== General ===

**All EVN** Major issue with E-series firmware -> amplitude calibration very difficult as slope/jumps across band.


=== C band ===

**Onsala** Broken chip in antenna control unit.


=== L band ===

**Westerbork** L-band receiver problems (no fringes found, unclear reasons).\\
**Tianma** recorded a single linear polarization. Fixed for the e-EVN in 7 Feb 2018.\\



===== 2018 e-EVNs =====

**Westerbork** (2018/04/06) the maser broke.\\
**Tianma** (2018/02/07, L-band) recorded linear polarizations instead of circulars (continuation of the problem observed in 2017 Session 2). Fixed with Martí-Vidal's program.\\
**Noto** (2018/04/04, K-band) had a communication problem between the computers in the control room and was impossible to perform the experiment.\\

===== 2017 Session 3 =====

=== General: ===
Large amplitude issues across band with E-series firmware.\\
Zc tsys bad. Almost always 999s.\\
**Hartebeesthoek** encoder issues (continued).\\

===L band: ===
**Jodrell Bank** had a warm receiver.\\
**Tianma** sent one linear polarisation only initially, then linears.\\
**Urumqui** sent linears.\\
**Torun** no fringes ea058b. Unknown reason.\\
**Irbene** low power LCP.
**Jodrell Bank** warm receiver.\\
**Westebork** had some issues with setting incorrect mark5 mask.\\
**Svetloe** missed a few scans due to antenna control issues.

===S/X band:===
**Onsala6** had a warm receiver.\\
**Urumqui** reported receiver fault. Also formatter failure.\\
**Kunming** issues with maser.

=== C band: ===
**Urumqi** has an odd pattern in its TSYS, first four ~20, last four ~100-150.\\
**Onsala** Broken chip in antenna control unit.\\
**Jodrell Bank MkII** pointing issues. Appear time/elevation dependant.\\
**Effelsberg** FS computer froze.\\
**Yebes** reported FS problem.
**Medicina and Westerbork** both reported Fila10g loss of sync.


===== 2017 Session 2 =====

=== General: ===
Torun record pointer jumping back to 0 -> overwriting experiments.\\

=== C band: ===
**Noto** first four subbands, widely different clock LCP (weak phases).\\
**Westerbork** bad weights ~ 0.6 in EG098B EJ019D (these are back to back)\\
** Zelenchukskaya** Consistently has less power in one of the bands (I think RCP). Some phasejumps seen in EG088B also...\\

=== L band: ===
**Urumqi** bad subband 2 (0 counting) LCP\\
**Tianma** - poor polarisation performance. They recorded only one linear polarization and transmitted as RR/LL.\\
**Tianma** receiver malfunctioned needed to be repaired and warmed up. Missed some experiments.\\
**Torun** recorder skipped back to 0 -> overwrote scans 1-208 in EG098A\\



===== 2017 Session 1 =====

=== General: ===
**Noto** had a warm receiver in the Q-band NME.\\
**KVN Ulsan** has consistently had issues transferring data for FTP tests.\\

**Yebes** had a broken maser, didn't affect observations directly, the resulting change in DBBC caused a change in fringe amplitude accross the band.\\
  the above is unedited what Jay wrote -- the effect in fringe amp may
  be because of vector averaging in time with a higher phase(t) slope --
  in the March and April e-VLBI runs, we've noticed that the sign convention
  of the daily GPS may have changed again compared to what we had been doing:
  clock searches there suggested a rate adjustement that effectively changed
  the sign of the rate.  In the e-VLBI, this was a net rate change of ~8 ps/s,
  or about a radian in about 4s, which could lead to de-correlation in a
  vector-averaged amp(freq) or amp(lag) plot




===== 2016 Session 3 =====

=== General: ===
The whole session after the initial two 5cm observations ran with DBBC firmware v105E.\\
**Irbene** showed what appears to be large packet loss to the recorder resulting in poor data being recorded.  The first disk-pack proved unusable.\\
Sub-band 5 (BBC 5,13 LSB) had a dip in the center of the band, seen in auto- and cross-correlations.\\
**Urumqi** had antenna gear-box maintenance, only observed K band.\\
No fringes to **e-MERLIN** stations in NME ftp fringe-tests. JBO still working on obtaining local fringes via their SFXC before sending us the full out-station data (have correlated 3 of 4 user experiments that had out-stations -- they seem to have most hope for the last one EM122B, which  we're holding to last).\\
**Kunming** (thus not yet "EVN") had fringes in 6cm, 5cm, 3.6cm NMEs.May have had a maser problem in 5cm NME (much increased phase noise).

=== M band: ===
**Effelsberg** had a broken amplifier in LCP for the NME resulting in significantly lower power in LCP  channels than in RCP ones.  Fixed by the immediately following C-band session.\\

=== C band: ===
**Hartebeesthoek** had a warm receiver in ER045A (cryo failure); also HA encoder jumping intermittently (but not a large problem).\\
**Jodrell** had no fringes in EM121B and EP099A, which were 1Gbps observations immediately following the first 2Gbps observation.  Another 2Gbps observation followed these two, then another 1Gbps one, and then a series of 2 or 1Gbps ones -- all of these subsequent ones were good.\\
**Noto** showed its typical falling-off in amplitude in the upper LCP channels(BBCs 13,15 in DBBC firmware v105E, but this has also occurred the "normal" firmware in which it was BBCs 7,8).\\
**Torun** had a issue with a pack in which the record-pointer went back to zero after some experiments had already been recorded -- cost 4.5 experiments at C- and L-band.\\
**Yebes** receiver fault in ER045A (fixed during experiment).\\
**Zelenchukskaya** had consistently low power in RCP channels throughout, and  a warm receiver in EM126A.
**Robledo** used a new version of their DVP back-end that enables recording fewer than 32 channels, but no fringes in any observation (correlating a single Ro channel against all channels elsewhere showed some response in the wrong place, but with a null amplitude and a 90-deg phase jump in the middle of the band, suggesting that there was an extra transform going from complex to dual-sideband real "BBCs").

=== L band: ===
**Irbene** had an NTP error in EM123B that prevented recording.\\
**Jodrell Bank** had a problem seemingly limited to L-band observations after the NME in which the fringe walked away in jumps of 512 lags every 10-14s. One difference between the NMEs and user experiments was that the former had 8MHz subbands and the latter 16MHz ones (where 512 lags = 32us).\\

=== K band: ===
**Noto cryo** failure during NME.\\
**KVN Yonsei** did not participate in this session due to re-alignment of antenna panels.\\
**KVN Tamna** had a hexapod failure in EP099B.

=== X band: ===
**Noto** had mark5 problems in EP099C



===== 2016 Session 2 =====

=== General: ===

**Noto** several times has RCP at half the power of LCP.\\
**Torun** BBC5/USB had a different delay (phase vs. freq) for all experiments this session.

=== C band: ===
**Westerbork** broken hybrid - no good circular pols.\\
Several telescopes reporting FS crashes.

=== K band: ===
**Urumqi** receiver failure.\\
**Effelsberg** swapped pols.\\
Several telescopes (**Hh**, **Ef**, **Sr**, **O8**) reported issues with v105E firmware giving bad tsys and bit statistics for several BBCs. Fixed by DBBC re-program. \\