lbw 1200 MHz tone
- The 1200 Mhz birdie is
coming from the allen osborne associates gps
antenna/box that is on top of build1. It is the
large square box. This is probably the original gps time
transfer receiver. Looking at the user manul, the first lo
is 1500 Mhz, so i don't see where the 1200 Mhz tone would
reported a narrow band rfi spike at 1200 MHz. Looking back
through the data from "the fractional occurrence of rfi seen
through the telescope", it looks like this birdie has been
present since at least 2001.
01apr13: a2761 position
a2761 did 300 second on,off
position switching using the wapps.
The power from the channel with the
1200MHz tone was plotted for the position on and position off
- The 12.5 MHz band was centered at 1201.7694MHz. The bin
width was 3 Khz.
- Black is polA, red is polB. Linear polarization was used.
- The vertical scale is in units of Tsys.
- Top: polA tone power vs time
- Middle:polB tone power vs time.
- bottom: (polA+polB)/2 tone power vs time.
The tone is coming in through the
horn since the tone amplitude for the on Position and off
position overlay each other.
07may13: high resolution spectra of the tone:
On 07may13 time domain data was taken with
the mock spectrometers to try and resolve the tone. The setup
- The dome was sitting at az=285, za=2 deg.
- lbw centered at 1200.05 MHz was used. The if/lo used the
10Ghz up converter.
- The mock spectrometer ran with:
- 16 bit time domain sampling
- 172.032 MHz clock with x100 decimation (bw=1.72032 MHz).
- PolA and polB were recorded for 80 seconds.
At 20 second stretch of data was transformed and the spectral
density computed. This gave .05 Hz resolution
The plots show the tone
using the time domain data (.ps)
- Black is polA, red is polB
- The data has been plotted about 1200MHz.
- The horizontal scale is in units of Hz.
- The + on the plot show the .05 Hz resolution.
- the tone has not been resolved in .05 Hz.
- It sits at 1200MHz.
- A tone at 1200 MHz has been present since at least 2001.
- the tone is not resolved at .05 Hz resolution
- 1200e6Hz/.05Hz = 2.4e10 this stability is pushing
the stability of a "normal" oscillator
- The tone is probably locked to our maser.