In the smoothed copy of Itasca's position 2 radio log I see several signals that, if I understand the log entries correctly, seem to suggest that Itasca was hearing transmissions originating from sources other than the Electra:
July 5, around 04:28 (page 16/22 of the pdf of the smoothed position 2 radio log): “HEAR CUPLE RUSSIANS STNS ON ICW CODE- RTM AND RNW- NOTHING ELSE ON 3105”
July 5, Around 21:40 to 21:44 (page 18/22): “HEAR S3 FONE SLITELY HIGHER IN FREQ THAN LAST ONE-ABT 3130 KC- MANS VOICE APPARENTLY TALKING IN FOREIGN TONGUE- CRM BREAKS IT UP SO UNABLE READ”
July 5, At 23:39 (page 18/22): “ …EAR S3 FONE ON 3105 MANS VOICE “AAA FIVE O’CLOCK AAA – VOICE DID NOT (sou)ND EXCITED, BUT NORMAL””
July 5, At about 23:42 (page 19/22): “ HEAR SAME S3 FONE ON 3105 AS AT 2339-VOICE MANS ES SOUNDS PLEASANT- APPARENTLY NOT FROM EARHART PLANE”
July 7, 05:23 (page 22/22): “ICW CODE SIGS ON OR NEAR 3105 KC UNREAD RUSSIAN OR JP CODE”
If these transmissions originated from sources other than the Electra, doesn't this suggest that some of the other, harder to characterize, signals that Itasca received could have originated from sources other than the Electra? If yes, what are the implications for the catalog of credible post loss radio signals?
The Howland radio logs also record foreign receptions on the 3105 kHz frequency. There are four of them:
July 5, 0518: ‘DISTINCT JAPANESE MUSIC ON 3105’
July 8, 0200 : 'WEAK JAPANESE STATION'.
July 10, 0245 : 'MUSIC FROM JAPANESE STATION ON 3105'
July 12, 0330: 'WEAK CW CARRIER FROM JAP STATION’
There are an additional eight receptions listed as ‘WEAK CARRIER’ or some variant of this description, on the 3105 kHz frequency, all received AFTER the Lambrecht flyover, on July 9. Since we know the Electra wasn’t on Nikumaroro after the flyover, these radio signals clear did not originate at Nikumaroro. Here are those eight receptions.
July 9, 2210: ‘WEAK CARRIER 3105’
July 9, 2222: ‘CW SIGS’
July 9, 2238: ‘WEAK CARRIER’
July 10, 2227: ‘WEAK CARRIER’
July 11 0030: ‘WEAK CW CARRIER’
July 11 0215: ‘WEAK CW CARRIER’
July 11, 2349: ‘WEAK CARRIER’
July 12 0515: ‘WEAK CW SIGS (CARRIER)’
July 13, 0300: ‘WEAK CARRIER 3105’
While Itasca and the Electra may have been the only possible central Pacific source of signals on Earhart’s frequency, as stated in the material accompanying the post-loss catalog, the 12 Howland receptions listed here and the Itasca receptions quoted above indicate that listeners in the central Pacific could have, and did, hear radio signals that weren’t from either of these sources.
Notice that these 12 messages were all received during times of darkness. Somewhere in the forum there is a post by Gary LaPook where he pointed out that the post-loss receptions were best thought of as correlating with darkness rather than water levels at Nikumaroro. At night listeners in the Pacific were able to pick up radio transmissions fromgreat distances. LaPook argued that the post-loss receptions were fragments of transmissions from far away rather than fro the Electra, and the Itasca and Howland logs certainly show that those listening for Earhart did receive signals on her frequency from far away places.