On 2002 January 31 observations of several bright radio sources were performed with the GBT Prime Focus 1 receiver at 600 MHz. Here the raw uncalibrated spectra near source 3C48 are presented to show the radio frequency interference (RFI) environment.

The GBT autocorrelation spectrometer (ACS) was used in the 50 MHz wide, dual linear polarization mode. A total of 8 IF inputs were supplied to the ACS simultaniously. The data were organized in 4 pairs of dual linearly circularized signals; one pair in each of 4 spectral bands. The spectral bands were spaced by 40 MHz to give overlapping spectral coverage over the entire frequency range accessible using the PF1 600 MHz feed.

The data were taken in 5 minute scans consisting of 29 or 30 ten second integrations. Below the RFI in the 600 MHz band is shown in a series of plots of the Y polarization linear intensity versus observing frequency. The spectra are processed in two ways below. To show the brightest RFI features, the average of all integrations is shown in the first of the pairs of plots. To show the gains of the system and the weaker RFI features a second plot is shown where the brightest RFI features are set to zero.

The 600 MHz band is particularly rich in RFI and UHF TV stations are important contributors. The Roanoak stations are particularly strong and a selection of features are noted below:

• 477.25 and 481.75 MHz are picture and sound for Channel 15.
• 549.25 and 553.75 MHz are picture and sound for Channel 27.
• 561.25 and 565.75 MHz are picture and sound for Channel 29.
• 608 to 614 MHz (Channel 37) is assigned to Radio Astronomy.
• 627.25 and 631.75 MHz are picture and sound for Channel 40.
• 687.25 and 691.75 MHz are picture and sound for Channel 50.
• 711.25 and 715.75 MHz are picture and sound for Channel 54.
• 741.25 and 745.75 MHz are picture and sound for Channel 59.
• Channels 60 to 69 are being re-assigned to Land Mobile Services.

• The 50 MHz band with the weakest peak RFI features was centered on 690 MHz sky frequency.

	3C48: 9; OffOn 1/2 Samplers 1,5 of 8, Ave of 30 Int. Ascii Data (2002_02_01_02:47:26A.0.log) All data averaged.
	3C48: 9; OffOn 1/2 Samplers 1,5 of 8, Ave of 30 Int. Ascii Data (2002_02_01_02:47:26A.1.log) Bright RFI zeroed.
	3C48: 9; OffOn 1/2 Samplers 2,6 of 8, Ave of 30 Int. Ascii Data (2002_02_01_02:47:26A.2.log) All data averaged.
	3C48: 9; OffOn 1/2 Samplers 2,6 of 8, Ave of 30 Int. Ascii Data (2002_02_01_02:47:26A.3.log) Bright RFI zeroed.
	3C48: 9; OffOn 1/2 Samplers 3,7 of 8, Ave of 30 Int. Ascii Data (2002_02_01_02:47:26A.4.log) All data averaged.
	3C48: 9; OffOn 1/2 Samplers 3,7 of 8, Ave of 30 Int. Ascii Data (2002_02_01_02:47:26A.5.log) Bright RFI zeroed.
	3C48: 9; OffOn 1/2 Samplers 4,8 of 8, Ave of 30 Int. Ascii Data (2002_02_01_02:47:26A.6.log) All data averaged.
	3C48: 9; OffOn 1/2 Samplers 4,8 of 8, Ave of 30 Int. Ascii Data (2002_02_01_02:47:26A.7.log) Bright RFI zeroed.
	3C48: 36; OffOn 1/2 Samplers 1,5 of 8, Ave of 29 Int. Ascii Data (2002_02_01_04:10:12A.11.log) All data averaged.
	3C48: 36; OffOn 1/2 Samplers 1,5 of 8, Ave of 29 Int. Ascii Data (2002_02_01_04:10:12A.12.log) Bright RFI zeroed.
	3C48: 36; OffOn 1/2 Samplers 2,6 of 8, Ave of 29 Int. Ascii Data (2002_02_01_04:10:12A.13.log) All data averaged.
	3C48: 36; OffOn 1/2 Samplers 2,6 of 8, Ave of 29 Int. Ascii Data (2002_02_01_04:10:12A.14.log) Bright RFI zeroed.
	3C48: 36; OffOn 1/2 Samplers 3,7 of 8, Ave of 29 Int. Ascii Data (2002_02_01_04:10:12A.15.log) All data averaged.
	3C48: 36; OffOn 1/2 Samplers 3,7 of 8, Ave of 29 Int. Ascii Data (2002_02_01_04:10:12A.16.log) Bright RFI zeroed.
	3C48: 36; OffOn 1/2 Samplers 4,8 of 8, Ave of 29 Int. Ascii Data (2002_02_01_04:10:12A.17.log) All data averaged.
	3C48: 36; OffOn 1/2 Samplers 4,8 of 8, Ave of 29 Int. Ascii Data (2002_02_01_04:10:12A.18.log) Bright RFI zeroed.

The GBT is a facility of the National Science Foundation

glangsto -at- nrao.edu ----- last modified on: 2002MAR12