EVN Calculator

Observing band & data rate [Mbit/s]
On-source integration time [min]







































A simple guide:

- one station: SEFD
- two stations: baseline sensitivity
- more stations: image thermal noise

- field of view and EVN MkIV correlator limitations
are given below

Number of spectral channels, integration time [s], and maximum baseline length
Number of polarizations, subbands per polarizations, and bandwidth of a subband [MHz]

Please select an array (N>2) and an observing band.

Current EVN MkIV Correlator limitations:

- Npol*Nsb <= 16
- using 1/8s integration time, only half of the correlator capacity is available




A couple of comments:

- Your datarate [Mbit/s] = bandwidth/polarization [MHz] * Npol * Nbit (1 or 2 bit sampling) * 2.
- See the list of the two-letter station codes.
- VLA: phased array; your target source will probably contribute significantly to the noise.
For arrays including the VLA, or any of the big dishes (like Arecibo, Effelsberg, Lovell Telescope,
Westerbork etc.) the above noise estimates are realistic only for weak target sources.
- For bright sources (~Jy) dynamic range limitations dominate, not the thermal noise.
- Some stations have only 1 polarization, this is not included here (see the EVN Status Tables)
- Not all stations can record at 512 and 1024 Mbit/s, this is not checked in the calculator.
- The noise is higher for globals if VLBA and EVN observes together only in a limited timerange.
- Only zenith SEFDs used, no gaincurve corrections applied. The 3mm SEFDs are given assuming
typical weather conditions and a mean elevation of 30 degrees (see note below).
- The formula for calculating the thermal noise is below (the VLBI efficiency factor eta is 0.7):



Recent changes:

- Yebes 40m telescope code is now Ys, K-band SEFD added on 30 June, X-band on 19 Aug 2008.

- VLBA 22 GHz SEFDs were changed to 500 Jy on NRAO request, 9 June 2008.

- TIGO added; e-EVN now includes the 100m Effelsberg telescope (22 May 2008).

- VLBA 22 GHz SEFDs were changed from 888 to 350 Jy on 25 January 2008 (after K-band upgrade).

- Added 3mm band on 12-16 November 2007, as well as Pico Veleta (Pv) and Plato de Bure (Pb) telescopes;
approximate SEFDs for non-VLBA telescopes (Ef,Mh,On,Pb,Pv) from Thomas Krichbaum.
These assume an opacity of 0.1 and mean elevation of 30 degrees.

- Use an efficiency factor of 1/0.7 from 5 July 2007, and corrected the formula

- Updated EVN SEFDs on 23 January 2006

- Added narrow baseband filters; Telescopes: W1 included, Yb (old 14m) replaced by Yb40 (3 Aug. 2005)

- VLBA telescopes may be selected one-by-one, and the VLBA sensitivity was also updated;
sensitivity calculation vs. observing setup data rates checked for consistency (4 May 2005)

- GBT SEFDs updated, U-band and Q-band receivers added (25 May 2004)

- EVN MkIV Correlator capacity calculations and field-of-view estimations added (25 Feb. 2004)

- SEFD values were corrected for the VLA (both Y27 and Y1 made available),
and the VLBA SEFDs were also updated; the 2cm band was added (28 Jan. 2004)

- Lovell was made available in the C-band. Estimated SEFD was 34 Jy. (26 Nov. 2003)

- the weighting was changed, it is now real natural weighting (since 24 Sep. 2003)
(in the previous version the weight was inversely proportional to the noise,
now it is inversely proportional to the square of the noise)

- 1024 Mbps data rate was added. This will be available from session 2/2004 at some EVN stations,
using Mk5 recorders (see the EVN Mk5 status)


Comments/suggestions to Zsolt Paragi