---

Summary:

• Time varying birdies are seen  at 430 and 327 Mhz. At 430 they are seen in the dome, carriage house, and the 430 Mhz yagi. It was 5 times stronger in the 430 yagi than the 430 linefeed.
• At 1 frequency the birdie repeats every 60 seconds.
• The duration of the birides is 2.31 seconds.
• At 430 Mhz there is a pattern of 4 frequencies that are staggered in time. This pattern of 4 frequencies is repeated about every 7 Mhz.  At 327 Mhz it looks like there is a single set of 4 frequencies staggered in time.
• At 430 MHz the 4 birdies occur at : 7.5, 20.5, 33.6, and 41.1 seconds after the minute. Measurements taken in 12feb06 and 29may06 showed the 20.5 second birdie at the same phase of the minute. Whatever is creating the birdie is locked to some clock.
• The frequency separation of the 4 frequencies at 430 differs from that at 327.
• The 327 birdies show an azimuth dependence. (no azimuth swings were done at 430 ). They appear at azimuths 80 thru 180. They are strongest around azimuths 113 and 147 in  the dome 327 receiver. Azimuth dependence means the birdies are coming from outside the dome.
• The birdie power gets up to 5*Tsys in a single 24 Khz channel.

---

29may06/12feb06  430 yagi has large 1 minute glitches

29may06 yagi glitches (.ps)  (.pdf):

• Top: Total power for a single cross versus wall time (from start of observation). The first set is the az strip, the second is the za strip. The red dotted line flags a jump that occurs every 60 seconds.
• Bottom: (Total Power - beam fit) vs AstTime module 60 seconds for all 24 yagi crosses. There is a jump that starts at 20.5 seconds after the minute and lasts for 2.31 seconds. The horizontal scale was blown up to 10-30 seconds, but there were no other visible jumps in the 60 second time span. The jumps are about 15 kelvins.

• Cross #2 for the line feed. The top is versus seconds from start of observation and the bottom is AST time modulo 60 seconds. You can see the jump at 20.5 seconds after the minute in the linefeed data. It is about 5 kelvins.

• The top plot has two crosses plotted versus time from the start of the observation. There are 4 colored dashed lines then align with the first 4 jumps. They are then repeated every 60 seconds. All of the other glitches line up with one of these 4 combs. The bottom plot is power-fit vs ASTseconds modulo 60 seconds. All 10 yagi crosses are shown. There are 4 separate jumps that align with :  7.5, 20.5, 33.6, and  41.1 seconds after the AST minute. The jumps are 20 to 25 kelvins.

• The second cross is plotted vs start of observation (top) , and versus AST seconds modulo 60 (bottom). The 4 60 second combs found in the yagi data are over plotted in the linefeed data. You can see the jumps at 7 seconds and 20 seconds (the other two are on the slopes of the beam and are hard to see). The size of the jump is about 5 kelvins.

Summary:

• The 430 yagi has strong 1 minute glitches.
• On 12feb06 there are 4 separate phases for the 1 minute glitches. The 1 Mhz bandwidth taken about 430 Mhz includes 4 of the 1 minute glitch frequencies found in the dome: 429.89, 430.31, 430.39, 430.48. Each of these had a separate phase.
• The glitches are also seen in the line feed but they are about 5 times weaker.
• The phase of the 1 minute glitches are: 7.5, 20.5, 33.6, and 41.1 seconds after the start of each minute. The phase for the 20.5 glitch was the same on 12feb06 and 29may06 (a span of 3.5 months). Whatever is causing the rfi is stable in time.
• The rfi glitch lasts for 2.31 seconds.

02dec05: birdies at 430 Mhz with 1 minute periods.  (top)

• 25 Mhz bw, 2048 channels, 1 sec dumps, cfr of 430.
• Data was taken for about 2 hours while sitting at az=270, za=10.

• Dynamic spectra for 300 seconds, polA (.gif): This image is spectral density (time vs freq). The small dots are the time variable rfi. The short lines at the bottom of the plot are added to show where these birdies occur (some of the weaker periodic birdies were not flagged).
• Time and frequency extent of birdies (.ps) (.pdf): The top plot shows the power in the 429.89 Mhz birdie vs time. It lasts for 3 samples so the time duration of the signal is about 2 seconds. The bottom plot shows a spectral blowup of this same birdie. The freq. resolution (after hanning smoothing) is 24 Khz. The fwhm is about 3.5 channels so the birdie is about 30 khz wide.
• Time periodicity of channels over 1500 seconds (.gif): The spectra from the first 1500 seconds of data was interpolated in time and then  fft'd along the time direction. The image shows periodicity vs Rf frequency. The vertical scale is in milliHz. The horizontal dashed lines are plotted ever 16.66 milliHz (1/60.  seconds). You can see strong periodic combs around 422-423 Mhz, 430 Mhz, and 432.5 Mhz. These channels have birdies that have a 1 minute period. There are also some channels that have a weaker 1 minute periodicity (but do not show up well in this image).
• Birdie power vs time for 140 minutes (.ps)   (.pdf): Thirteen freq. channels with 1 minute periodicity were selected. The power in the channels were averaged over 7 freq. channels and then plotted versus time:
• Fig 1: all 140 minutes. Each color is a different birdie. The top plot is polA while the bottom plot is polB. This data taking session started at about 9 am. You can see that the birdies were stronger at the beginning of the run. Looking at the data toward the end of the run, the periodic birdies were still seen at some of the frequencies. The gaps in the data are where no data was taken (between scans).
• Fig 2: This is a blowup in time of fig 1 showing the first 5 minutes of data. The dotted lines in polA (top) show how the birdies are aligned in time. You can see two groups. The first starts at 422.72 (lower black trace) while the second group starts at 429.89 (light blue middle trace). The nth birdie of each group occurs at the same time.
• Fig 3: (power in periodicity) vs period:  For each birdie, 8500 seconds of data was interpolated and then fft'd. The plot shows the power vs periodicity. There is a comb with 16.6 millihz spacing (1/60 seconds). The width of the comb was 1 channel (about .1 millihz) so the 60 second period is relatively stable.

 

Summary of 430 birdies:

 

period	1 minute
freq. width	about 30 Khz
time Duration	about 2 seconds
birdie groups	4 birdies per group rf spacing: .45,.1 .1 .1 Mhz tm spacing in group: 13,7,26 seconds each group repeats every 60 seconds.
group rf  spacing	7.2 Mhz between groups.
birdie freq.  (strongest)	422.72, 423.18, 423.25, 423.35 grp1 429.89, 430.31, 430.39, 430.48 grp2 432.67
when appeared	looking at the x111 data for oct/nov05 we had: 18oct05 : 2 scans worth of birdies 26nov05: birdies started to appear more regularly


    On 30nov05 A2125 also saw a group of birdies at 432 Mhz. The 7.2 Mhz spacing looks close to the comb that is generated by the alfa motor controller.  The 1 minute birdies are also seen at 327 Mhz (see 327 dynamic spectra of 3rd az swing). The dots around 318.6 are spaced by 1 minute (20 deg azimuth = 1 minute in the plots).These were done with the alfa motor controller turned of.
 

---

28oct05 327 Mhz rcvr azimuth swings show 1 min periods.  (top)

    The az swing dynamic spectra showed some birdies that were coming and going with time. They were centered around 318.6 Mhz and azimuth near 120 degrees (see the az swing dynamic spectra 2,3,4,5). These dynamic spectra were made with polA.  The last 3 azimuth swings in polB turned out to have the strongest    ence of these birdies.

• Dynamic spectra of the last 3 az swings (.gif): These are from polB. 2.5 Mhz was taken from the larger 25 Mhz band.  The spectra show:
• The dots appear for azimuths 80 to 180. The repeatability shows a real az dependence.
• They tend to jump in frequency like the 430 Mhz birdies.
• Plots of the 4 birdie frequencies (.ps) (.pdf) : The power in a single spectral channel was extracted and plotted.
• Fig 1: 60 second periodicity of the birdies. The time of each birdies is plotted modulo  60 seconds. The 3 plots are az swings 3,4,5 (polB). The 4 colors code the 4 frequencies. All of the birdies of the same color line up modulo 60 seconds for the duration of all of the az swings. For each az swing there are only one or two birdies of each frequency that stick up (so it only lasts for 1 or two minutes while the azimuth is moving).
• Fig 2 top: 4 birdies versus time for the last azimuth swing. The colors show the 4 birdies. The dotted lines are spaced by 1 minutes.
• Fig 2 bottom: 4 birdies versus azimuth for the last 3 azswings. There are peaks at az 113 and az 147. The birdies do not appear when we move away from these azimuths.
The 4 birdie frequencies are: 318.41, 318.47, 318.56,  and 318.74 Mhz.

Summary of the 327 birdies:
 

period	1 minute
freq width	about 30 khz
time duration	1-2 secs
birdie frequencies	318.41,318.47,318.56,318.74
az dependence	peaks at az 113 and 147 degrees.