HFU HF Underground
General Category => General Radio Discussion => Topic started by: jordan on September 12, 2014, 0224 UTC
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Here is a recent report of a couple of ham radio operators on the 40m band getting in trouble for not identifying on the air:
http://transition.fcc.gov/eb/AmateurActions/files/Kraje14_08_19_5521.html
But how do they pinpoint a location from so far away? The letter mentions use of long-range direction finding techniques. The FCC agent was in Maryland, and the two ham operators were in South Carolina and Delaware.
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I know the FCC has monitoring stations in various areas of the U.S. They probably have high gain directional antennas, and how closely they can pinpoint a transmission I really don't know.
But there aren't a huge number of hams in the U.S. Some neighborhoods may have one ham on the air, if that. My guess is that if they didn't use local trucks to pinpoint the offending hams, their antennas may be precise enough to pinpoint the neighborhoods in question, and then they just used satellite imagery to spot the house with the antenna -- probably cross referencing the FCC database.
But I'm just guessing here.
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The FCC has remotely controlled HFDF stations. They can dial up any HF signal on a frequency & using 3 stations, triangulate the "offender" with reasonable accuracy.
While the FCC does have "mobile units", they are used for more prioritized cases, like Public Service & governmental ones. I know of a ham who was visited by a mobile unit but it was not active case of jamming. These vehicles have fiberglass roof replacements, allowing multiple antennas to be mounted but concealed. Looking from the driver's seat, the antenna lines are run to various receivers on a control pod mounted on passenger side of the vehicle...
Hope this explains it but it is not that obscure to DF. The techniques were developed during WWII...
Rafman
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If this is the case, then how do all these SW pirates mentioned in the Logging board on this forum manage to not get caught by the FCC?
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"On Tuesday, July 15^th and Wednesday, July 16^th, you were heard by a
Commission employee operating your amateur radio station for 20 minutes
without identifying in a timely manner. The Commission employee used
direction finding equipment and confirmed the transmissions were coming
from your location. The employee recorded the offending transmissions and
provided undersigned counsel with recordings of the incident in question.
Should you desire a copy of the recording, one will be made available to
you.
"This incident constitutes a failure to properly transmit your assigned
call sign in violation of the Commission's rules. Your operation as
described above is contrary to the basis and purpose of the amateur radio
service as set out in Section 97.1 and is a violation of Section 97.119(a)
of the Commission's rules.^ Section 97.119(a) states that "[e]ach amateur
station . . . must transmit its assigned call sign on its transmitting
channel at the end of each communication, and at least every 10 minutes
during a communication . . ." Please be advised that the Commission
expects you to abide by its rules."
The way this reads, the guy may have IDed at some point, but not the required amount of times... in which case the long-range DF would only have been used to confirm that the transmissions originated from the general known location of the licensee in question.
I don't believe the FCC would send a notice like this, based on a long-range DF only, without the operator having IDed at some point. That seems more like a "guess".
"The Commission employee used direction finding equipment and confirmed the transmissions were coming from your location."
Ah-- so that does read as if they had an address from license records, and just used the DF to confirm that the signals originated from that general area.
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FCC does have a nationwide HFDF network:
http://transition.fcc.gov/omd/contracts/pre-award/RFQ11000024.pdf
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My Master's degree work was in using HFDF to locate transmitters using a single receiving site. By using the angle of arrival of signals from known transmitters with known exact locations, the unknown transmitter location could be determined within a few miles. That was in 1975. This is 2014. I have not followed up on technology advances in this area recently, but I imagine equipment has advanced considerably. Also, the FCC has multiple receiving sites, which would increase the accuracy. They would either have to guess the transmitting station's identity from their license records beyond that, or send a mobile unit to verify if they wanted to pursue the violation.
As was discussed in another thread here, the FCC doesn't seem to be too interested in going after SW pirates unless someone complains, and I am guessing that doesn't happen too often.