A note from the Pacific Section Manager.

We had a report of an AM broadcast  intruder on our 40-meter band that
appears to be a spurious signal from a Honolulu broadcast station. Tom
(NH6Y) was the first to report it from Maui on 7.040 MHz.  Further
reports from Oahu and Big Island stations confirmed it, some with S7
signal strength.

Our ARRL ASM on Maui, Alan (AD6E/KH6TU) followed up with the Northern
California Contest Club (NCCC).  Several of their members identified the
offending AM station causing the spurious signal. N6IE (Ron) gave us a
detailed analysis of possible intermods that proved to be the cause!  He
even offered a possible location of the signal based on recent FCC
filings. Great engineering detective work!

Merv (K9FD) monitored the signal on Molokai.  He confirmed receipt and
offered an engineering contact that might be able to help.  He had
previous experience with signals caused by intermods from Honolulu
broadcast stations.

Following up with Merv’s contact, we got in touch with  the contract
engineer who confirmed Ron’s analysis.  It turns out the station had
to move its tower out of the way of the Honolulu rail project but could
not complete the transfer in time for the start of rail construction.
They moved the antenna to a temporary tower just out of the way of
construction.  He acknowledge the spurious signal on 7.040 MHz is the
result of a temporary antenna combiner and amplifier.

The short story is that they may try use of a low pass filter to reduce
the signal that may see improvement by December.  The station plans to
move to their permanent tower with a new amplifier and combiner in
January.

The ARRL RFI Lab is aware of the report and is monitoring the actions to
resolve the situation.

Hawaii hams can help by monitoring 7.040 MHz and sending us reports.

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Follow the Pacific Section on social media for other reports on Hawaii
Amateur Radio.

http://hawaiiarrl.info/stories/2018/ARRLHawaii-SocialMedia.pdf

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ARRL Pacific Section
Section Manager: Joseph Speroni, AH0A
ah0a@arrl.org

 

ASM = Assistant Section Manager

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