[evlatests] RFI sweep: July 2014

[Emmanuel Momjian]

A RFI sweep spanning the frequency range 1-50 GHz, with a channel
separation of 125 KHz, was carried out on July 2, 2014. The array was in
D-configuration.

 The spectra are now posted on the web (thanks to Heidi) at
https://science.nrao.edu/facilities/vla/docs/manuals/obsguide/modes/rfi
(under the RFI spectral sweeps section).

I report here a list of internal birdies as well as external RFI that are
currently not tabulated on our web site. For narrow features, I give a
single frequency value, while for wide features I provide the frequency
range. Some of these may have already been reported by Rick or others in
the past.

L-band:
- 1400 MHz: ea13 continues to show this birdie.
- 1408 MHz: compared to the past year, more antennas are showing this
birdie. ea08 (N01) and ea28 (E01) have it on many of their baselines. Other
antennas that have some baselines showing this are: ea12 (N09), ea19 (W01),
ea20 (N04), ea21 (E05), ea25 (W03), ea26 (W02).
The above noted two items are already being investigated by the electronics
group (Keith).

- 1450 MHz: only two baselines are showing this: ea05-ea13 (W8-W6) and
ea09-ea13 (W7-W6). The stronger signal is on ea09-ea13. The signal in LL is
stronger than in RR on both baselines.
-1813.25 MHz. This is seen on numerous ea09 baselines, but only in LL.
-1920 MHz. This is the 15th harmonic of 128 MHz. ea08 (N01) has this birdie
on many of its baselines. Other antennas that have some baselines showing
this are: ea28 (E01), ea12 (N09), ea20 (N04), ea25 (W03), ea26 (W02).


S-band:
- 2028-2032 MHz; stronger in LL
- 2706-2711 MHz
- 2808.5-2811.5 MHz
- Several RFI features between 3400 and 3700 MHz. There were less of these
in the two RFI sweeps done in 2013 (the spectra of these are also on the
web in the address given above).


C-band:
- 4401-4409 MHz.
- 5248 MHz. The signal is seen on many of the baselines to the following
antennas: ea04(E2), ea09 (W7), ea13 (W6), ea21(E5). This is the 41st
harmonic of 128 MHz.
- 5290 MHz.
- 5830 MHz.
- 5879.4-5880.1 MHz
- 5888 MHz. Strong. This is the 46th harmonic of 128 MHz. Seen on all
baselines.
- 5931-5960 MHz. Microwave link?
- 6182.5-6212 MHz. Microwave link?
- Note: the microwave link at 6772-6778 is not present even though our RFI
table has it as "Continuous".


X-band:
- 8192 MHz. This is the 64th harmonic of 128 MHz. The majority of the
baselines showing this signal are of: ea02 (N07), ea05 (E08), ea21(E05),
ea27 (N08), ea28 (E01).
- 9708-9714 MHz. This has a main peak and lobes on both sides. The main
peak is between 9709-9711 MHz.
- 9858-9907 MHz: this is a comb with 10 components. They are separated by 5
MHz. Each component has a full width of ~2 MHz at half max.
- 10750.1 MHz. API LO frequency.


Ku-band:
- 12160 MHz. This is the 95th harmonic of 128 MHz. Seen on the majority of
the baselines.
- 13825-14012 MHz. this is a comb with 11 components. They are separated by
18.875 MHz. Each component has a full width of ~0.25 MHz at half max.
- 15524.7-15525.7 MHz (double peak). Very strong on baselines to ea19 (W01)
- 15552.0-15552.6 MHz (double peak). Strongest on baselines to ea25 (W03),
and ea26 (W02). Also seen on almost all baselines to ea01(N03).
- 16873-16874.5 MHz. This is only seen on baselines to ea27 (N08).


Ka-band:
- 26324-26327 MHz (note: the K-band setup ends at 26 GHz in the RFI sweep,
Ka-band starts at 26 GHz, hence this is reported here under Ka-band). This
feature is only seen in RR on baselines to ea24 (W05). During the 48
seconds of the scan the peak of the feature smoothly moves by a few
channels: from channel 656 (26325.875 MHz) in the spw to channel 653
(26325.5 MHz).
- 29440 MHz. This is the 230th harmonic of 128 MHz. Seen on all baselines.


Q-band:
- 48512 MHz. This is the 379th harmonic of 128 MHz. This is seen on
baselines to ea21 (E05) as well as ea22 (N02).
- 48640 MHz. This is the 380th harmonic of 128 MHz. This is seen on
baselines to ea21 (E05) as well as ea22 (N02).
- 48768 MHz. This is the 381st harmonic of 128 MHz. This is seen on
baselines to ea21 (E05) as well as ea22 (N02).
- 48896 MHz. This is the 382nd harmonic of 128 MHz. This is seen on
baselines to ea21 (E05), ea22 (N02), and ea13 (E07).
- 49024 MHz. This is the 383rd harmonic of 128 MHz. This is seen on
baselines to ea21 (E05), ea22 (N02), ea13 (E07), and ea20 (N04).
- 49152 MHz. This is the 384th harmonic of 128 MHz. This is seen on
baselines to ea22 (N02) only.
- 49280 MHz. This is the 385th harmonic of 128 MHz. This is primarily seen
on baselines to ea22 (N02).
- 49408 MHz. This is the 386th harmonic of 128 MHz. This is primarily seen
on baselines to ea22 (N02) and ea21 (E05).
- 49536 MHz. This is the 387th harmonic of 128 MHz. This is seen on
baselines to ea21 (E05), ea22 (N02), ea13 (E07), and ea20 (N04).
- 49920 MHz. This is the 390th harmonic of 128 MHz. This is primarily seen
on baselines to ea21 (E05), ea22 (N02), and to a lesser extent on baselines
to ea13 (E07), and ea20 (N04).


Emmanuel
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