eHam.net - Amateur Radio (Ham Radio) Community

Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net



[Articles Home]  [Add Article]  

CO Ham Tracks,Resolves Interference from Pot Cultivators' 'Grow Lights':

from The ARRL Letter on June 12, 2014
Website: http://www.arrl.org/
Add a comment about this article!

Colorado Ham Tracks Down, Resolves Interference from Pot Cultivators' 'Grow Lights':

The ARRL already has complained http://www.arrl.org/news/arrl-to-fcc-grow-light-ballast-causes-hf-interference-violates-rules to the FCC that so-called "grow light" ballasts can generate severe interference on the HF bands. According to a recent article in The Coloradoan, retired electrical engineer Tom Thompson, W0IVJ, first noticed interference on 40 meters at his location in Boulder a couple of years ago. So, he coupled his own portable receiving loop http://tomthompson.com/radio/ReceivingLoop/loop.html with a direct-conversion receiver that he could use to walk around his neighborhood and pin down noise sources. In at least one instance, the problem emanated from a domestic marijuana-growing operation -- a "grow house."

"With the increase in legalized medical and recreational marijuana comes an increase in RFI due to electronic grow light ballasts," Thompson explained http://tomthompson.com/radio/GrowLight/GrowLightBallastFilter.html on his website, where he describes how he constructed a filter that considerably reduced interference from the devices. "These ballasts are usually switching power supplies, capable of lighting 600 to 1000 W high-pressure sodium or metal halide lamps," Thompson said. "The switching frequency is usually 50 to 70 kHz and is rich in harmonics."

Thompson said that because the light fixture is separated from the ballast by about 25 or 30 feet of wire -- approximately a quarterwave on 40 meters -- the RFI may be strongest on that band. "I have heard radiations from these systems up to about one-half mile away," he said. "When the [marijuana] plants are young, the lights are on 24/7. After about 2 weeks, the lamps are on for 12 hours, and off for 12 hours." Thompson said that since most systems are on a timer, it's possible to predict when the RFI will start, once you have determined the initial "on" time.

Thompson said one of the interfering growers was nice enough to loan him a lamp ballast for testing, and he was able to get a used lamp for free from a local grow shop. He gives away the common-mode choke filters to owners of offending lighting systems.

As the article in The Coloradoan pointed out, with 22 states and the District of Columbia now allowing medical marijuana, and Colorado and Washington permitting its recreational use, "there's been an explosion in the number of people growing their own pot, much of it indoors." The noise problems are reported to be worst in Colorado and California.

Thompson told The Coloradoan, "If I can track this down, anybody can track this down. If I listen long enough, I can tell when they turn the lights off...you can tell exactly when the harvest is."

Thompson has written an article on the topic of tracking down and resolving such interference. It is scheduled to appear this fall in QST.

Source:

The ARRL Letter

There are no comments on this article: Post One

Email Subscription
My Subscriptions
Subscriptions Help

Other News Articles
Thousands Expected at Weekend's Hamfest:
Propagation Forecast Bulletin #35 de K7RA:
2014 Arizona QSO Party Announcement!
Fontana Students Talk to Space Station Astronaut via Ham Radio:
ARNewsline Report 1933 -- August 29 2014: