June 22, 2018
- JR For the SNAPs wrote a program “getdetpams” that gets the current value of the PAM detectors (x and y) and the PAM db settings.
- Jack is continuing to perfect his SNAP program. Data gatheres on/off the Sun, moon and quasars. The data is being looked at.
- Received the fieldfox spectrum analyzer. See details at fieldfox
Franklin's question on slack: “I presume that “on” and “off” refer to pointing, not electronics, and that the vertical scale is linear, and that's total power, ie all polarizations. Am I close? What do the different graphs represent? Different samples? Different antennas?”
Dave M's answer:
We tuned the 6.667 GHz methanol maser line to the lower half of the IF band, then used a spectrum analyzer to average the IF output of the RFCB for the Y-pol of 8 different antennas. We then used the low half of each spectrum as the “ON” spectrum and the high half of each spectrum as the “OFF” spectrum. This is a sort of poor-man's frequency switching technique. ON-OFF gives the extra flux from the source, but in arbitrary units so we then divide by OFF to get a the increase in power levels relative to the OFF. By comparing this to the known flux, one can derive the SEFD, but I think that's a little tricky to do on a maser because it has a fair bit of spectral structure that can complicate the comparison to known fluxes. The more meaningful SEFD calculation will come from ON-OFF position switching on quasars, which have very well known fluxes and relatively flat spectra. The individual plots correspond to antennas:
1H 2A 2B 2E 2J 3D 3L 4J