|Summary of recent updates||Radio Activity Log||Latest ToDo List|
Pat Ross's presentation to LARC in 2009 describing his experiences finding major interference at his home
Doug's presentation to LARC in December, 2020, on his interference experience. Includes maps and radio waterfall captures.
I separate the interference into 2 categories: general, and frequency-specific. General interference is found all across one of more bands, and is often called the noise floor. This is by far the most troublesome, because it can't be avoided, and reduces my ability to communicate with weak stations. frequency-specific interference (FSI) is annoying, but generally tolerable. However, it's worth investigating because there may be one phenomenon that causes both general and frequency-specific interference.
The noise floor at my QTH is now about S4.5 or -99 dBm on 20 meters, measured at the quietest part of the ham band, with no ham radio activity. At one point, it was S7. I would like it to be S1, but I'd be happy with S2 or S3. I tend to measure noise in dBm because it's more accurate, and because by Flex 3000 gives a direct digital readout in dBm rather than a line on an S scale that I have to judge. There are times when the noise floor is oscillating, across the whole band (Doug, find the video of this) but it's normally stable.
Here's a summary of various forms of FSI that I've encountered
|My name||Characteristics||Investigation Status||Example|
|Fuzzy Fluttering Drapes||soft meandering pattern on 20 M, audible on AM radio, 22KHz repeat interval, copies are identical||Resolved when daughter & family moved out to Toronto from temporarily staying with us. Suspect it was a battery driven baby monitor they used.|
|The big block||solid interference block covering a portion of 20 and 40 m bands. Intermittent||Unknown cause. rarely reoccurs|
|The Striped Tease||Parallel frequency lines, 18 KHz separation, All act identically, and occasionally disappear briefly, or change shape||Caused by furnace. Powering it off completely removes this interference, but the cold gets my wife upset.|
|RFRF||Radio Frequency with Radiated Flatulence. Strong signal with periodic bursts of digital transmission.||Related to Home network monitoring done by a raspberry pi. Could be Pi, Internet modem/router, UTP cabling, or 10/100 Mbit switch.|
|Drapes||similar to Fuzzy Fluttering drapes. Intermittent. Repeated with separation of 70 KHz||Unknown cause. Reappeared Feb 23 after being absent for a while|
|Medium Line||Thick line than wanders around 20 meters, with copies||Attributed to Roger box that interfaces home landline to cable network.|
|Waves||smooth pattern of gradually increasing and then decreasing noise across the repetition interval, which is 55 KHz||Unknown cause|
|Digital Stripes (Digs)||vertical stripes with spacing of 10 KHz. Alternate between 2 frequencies 1 KHz apart. All copies are identical. First seen Feb 23||Appeared when temperature got above freezing?|
Tracking various tests and changes I've done, particularly to allow correlation with power monitoring instrumentation London Hydro installed at my house on Feb 17. Some updates described in the radio activity log as well. Link: Recent updates.
Radio performance including background noise level readings and interference observations, with timestamps. I try to make an entry at least one a day.
Here's a link to the Latest Radio Activity Log.
Identifying and recording things to be done before Doug forgets about them. Also some things that London Hydro could do, recognizing that this is a low priority for them compared to outages, etc.
Here's a link to the Latest ToDo List.