Many thanks to SWLing Post contributor, Dennis Dure, who shares the following item from Radio World:
NRSC Studies RF Noise on Various Roadway Types (Radio World)
Radio World asked Cris Alexander to read the report and comment
The National Radio Systems Committee recently published the results of a study on AM band noise.
The report, principally authored by John Kean, is titled NRSC-R102, “Measurement of AM Band RF Noise Levels and Station Signal Attenuation.” It was released in January.
The study consisted of several measurement series conducted along roadways both in urban and rural areas, measuring the signal strength of three different Baltimore/Washington 50 kW AM stations as well as the RF noise on three different unoccupied AM band frequencies.
Measurements were made across five environments: rural, rural-suburban, suburban, urban and dense urban. The results were mostly as one would expect, but there were a few surprises. [Continue reading…]
Thank you for posting a link to that report.
Here are a few thoughts:
The FCC maps show ground conductivity values averaged over large distances, but in my 68 years I have noted that 2 weeks of dry weather, or 2 days of wet weather, make obvious AM and SW groundwave reception differences.
Internal vehicle RFI has changed “by several orders of magnitude” from 1970 to today.
If a vehicle drives within 400 feet of a Panasonic Plasma HDTV – forget AM band reception below 1300.
Even in very rural mountain areas, DSL internet noice from telephone lines alongside the road covers the weak AM stations. Look for cemeteries 200 yards or more away from telephone lines. Ghosts so like AM radio they listen quietly.
In 1995 several Ham friends were so impressed with the near absence of RFI inside 1994-1995 Dodge Rams with Cummins I-6 Diesel all mechanical fuel injection systems that they bought their first pickup truck. It stood out two ways: low RFI – but extremely high acoustic noise clack-clack-clack, especially at idle.
My 1995 gasoline Dodge Ram’s stock AM radio was quite good, and further improved with aftermarket Magnecor spiral wound sparkplug wires, then an aftermarket Becker Mexico 2340 AM/FM/SW radio, and finally with a loop antenna hidden beneath a rigid fiberglass pickup bed “tonneau cover”. Hurricane Wilma “ate” that tonneau cover but left the rest of the truck alone. I guess the cover was not designed for 120 mph “side winds.”
A Ham friend who was an AM station manager later told me that his 2005 Mitsubishi had “best AM reception he had ever had in a automobile.“ His story about decades ago picking up a distant 5000 Watt AM station in that Mitsu recently led me to drive to the same spot with a Qodosen DX-286, turn off the vehicle, and found that the Qodosen connected to a Selec-A-Tenna Model 541 in a large church parking lot with buried electric wires could pick up the station, but which now transmits at 1000 Watts.
I hear from others that Toyotas and Subarus still have acceptable AM radio reception.
I hear from others that the BHI noise cancelling speaker can also do impressive reception improvement in an automobile.
My grandfather was trained as an
“US Army Air Corps Artillery Ballon Observer” in early 1918.
In WW-I such “Ballon Observers” had a 90% death rate.
Luckily WW-I ended just as my grandfather was on the dock waiting for the boat to take him to Europe.
About 2 years after KDKA went on the air in 1920, my grandfather built a crystal set and was able to just make out the signal from over 140 miles away.
Hard to believe the any RFI whatsoever would allow that.
The only local RFI back then was from a steam engine powered DC electric generating station at a nearby coal mine. My grandfather helped build that electric generating station, from the its very beginning. His first paid job as a 13 year old was to crawl into the insides of a boiler being constructed. Outside the unfinished boiler workers would heat up a steel rivet to “red hot” and toss it to him to catch with gloves, Then he would stick the hot rivet outward through a hole in the boiler, then push hard as he could against it with a big hammer. Another pair of workers outside the boiler would alternately hit the exposed shank of this hot rivet to “mushroom it” into a tight head to create a permanent clamp.
Very noisy first job.
As “The big boss’s kid” his fellow workers failed to inform him “at the quiet beginning of the job” that he needed to put cotton in his ears before going in the boiler. He ended up cutting pieces from his socks to put in his ears.
As more and more hot rivets got installed, it also got plenty hot inside that boiler before lunchtime.
Later this grandfather did another construction job “for fun” – he bought by mail order a newly offered “Motorola” kit from the Elgin Manufacturing Co.
§ 15.103 Exempted devices.
Except as provided in paragraph (j) of this section, the following devices are subject only to the general conditions of operation in §§ 15.5 and 15.29, and are exempt from the specific technical standards and other requirements contained in this part. The operator of the exempted device shall be required to stop operating the device upon a finding by the Commission or its representative that the device is causing harmful interference. Operation shall not resume until the condition causing the harmful interference has been corrected. Although not mandatory, it is strongly recommended that the manufacturer of an exempted device endeavor to have the device meet the specific technical standards in this part.
(a) A digital device utilized exclusively in any transportation vehicle including motor vehicles and aircraft.
https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15/subpart-B