Most of this work was done in September. I thought this stuff was going into one über PEM injection report, but I'll post it here for now. Pieces of this have already been posted in other locations, where relevant. Summary: the only frequency where we have observed coupling from external RF to the interferometer is 45MHz, where the SNR would need to be over 100 in the PEM channel before it shows up in darm.

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We injected RF at specific frequencies where coupling to the interferometer was thought possible. The injections were done using dipole antennas and RF amplifier located by the water tank on site (site chosen for easy access and because its 'far away'). For those injections the 9 MHz and 45 MHz injections were picked up by the PEM radio channels in the corner station electronics bay ~1000x louder than the background. Of the frequencies chosen only the 45MHz injection showed up in the gravitational wave channel.

For the 45MHz injection we saw a PEM antenna SNR of ~1000 and a small peak in darm with an SNR of ~4 when viewed at a ~0.1 Hz resolution. From this we can say that an SNR of 200 in the auxiliary channel would be necessary to produce an SNR of 1 in DARM.

The frequencies chosen are posted at the bottom of the report (in most cases we performed the actual injection at the frequency of interest +100Hz, then looked in DARM for a beat frequency at 100Hz).

Figure 1 shows the 45Mhz injection that appeared in darm. Figures 2 and 3 show a later followup from Oct 23 with a better oscillator source but similar results (at 45 and 9 MHz). The final attachment (pdf) has a summary with more plots.

Future work will include repeat injections with a higher power amplifier and more stable oscillator source.

RF Frequency List (MHz)

9.100230
10.000000
21.500000
24.078360
35.500000
45.501150
71.000001
79.200000
80.000000