![]() The first requires what is commonly referred to as a hotstick line sniffer, which is an insulated pole with detectors to find and pinpoint noise sources. LABNATION SMARTSCOPE AMAZON PROFESSIONALThe Last Step Professional RFI investigators typically use one of two methods to locate a noise source on a utility structure. Practically speaking, once the source pole or structure has been identified, some means is needed to identify the actual offending hardware on it. Even a relatively simple utility pole can exhibit a multitude of potential and likely sources. Furthermore, the offending hardware on a structure is seldom obvious by eye. As good as RDFing and signature analysis are for finding structure with the noise, you still haven t located the actual source. 1 Since power line noise is typically caused by arcing, and each source has its own unique pattern when viewed in the time domain, so-called fingerprint or signature analysis can be used to conclusively link specific offending noise sources causing the actual problem. tion finding (RDF) techniques to track the noise down to the source pole or poles, typically using VHF or UHF in AM mode once in range of higher frequencies. This is usually accomplished by using radio direc- Bottom Line The MFJ-5008 ultrasonic receiver is an affordable and useful tool for pinpointing faulty or loose hardware on a utility pole once that pole has been located. Given the difficulty in resolving many of these cases, it isn t surprising that hams attempt to expedite the process by helping their utility find the sources. Even under the best of circumstances, power line noise can often test the patience and resolve of almost any ham. This can be especially true if the noise is more likely to be active at odd times, such as nights or weekends. Since locating a noise is only possible when it s active, attempts by utility RFI investigators can often be a hit or miss proposition. Frequently the noise is intermittent and weatherrelated. Further adding to the frustration, many utilities lack the equipment and expertise to address a complaint in a timely fashion. In fact, we ve seen some cases drag on for more than 10 years without resolution. For a variety of reasons, power line noise is one of the most difficult interference problems to resolve. In the case of power line noise, this is most likely your local utility. If and when interference occurs from an incidental radiator, and in fact most Part 15 devices, the rules place the burden on the operator of the offending device to correct it. In a nutshell, these rules prohibit power lines and related hardware from causing harmful interference to licensed radio services, including Amateur Radio. These are the FCC rules that pertain to unlicensed sources of RF. Power lines and related hardware are classified as incidental radiators under Part 15. The FCC rules regarding power line noise are clear. Typically it is caused by arcing on power lines and utility-related hardware. Wilson, Spencer, K1RO, WA8SME MFJ-5008 Ultrasonic Receiver A useful tool for pinpointing power line noise sources Reviewed by Mike Gruber, W1MG ARRL Laboratory RFI Engineer Without a doubt, power line noise is the single most frequent source of interference reported to the ARRL Lab. ( viewtopic.php?f=76&t=20638&hilit=interrupt+o3&start=25) With a little tweaking the Arduino should be able to go faster still! I haven't tested with the standard optimisations to see how much it impairs performance.2 Product TechnicalReview Mark by Mark J. Note that I used the -o3 compiler optimisations to minimize the interrupt handler time. It displays the frequency if it has changed. The program simply counts the interrupts received on INT1 per 1s (using the interrupt on INT0 from the RTC) The Arduino Micro was just on the board and doesn't do anything here. LABNATION SMARTSCOPE AMAZON GENERATORSQW from RTC connected to d2 (INT0) and output from signal generator connected to GND and D3 (INT1) I'd tweaked the output from the signal generator to be ~5v (using the amplitude adjustment) - worryingly it still seemed able to power the Arduino and display! (Still no harm done?) The setup is straightforward - RTC and oLED are connected to power, gnd and i2c, no need for pullups (built in to RTC) I tested the resulting frequency count using a SmartScope (. Frequency.jpg (58.25 KiB) Viewed 5274 times ![]()
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