Kurt, an RFI engineer from National Grid, met John, WA1ABI, at Portsmouth’s Glen Park on Friday, September 27 to investigate the RFI issue we previously identified in our RFI hunt at the site. Kurt was armed with a Radar Engineers Model 242 RFI locator receiver and a Radar Engineers Model 250 ultrasonic pinpoint locator. (See photos) The Model 242 locator receiver is an AM receiver covering 500 KHz through 1.0 GHz. Kurt used the 242 receiver in conjunction with a handheld VHF/UHF log periodic antenna. The Model 250 is an ultrasonic detector mounted in a clear parabolic dish equipped with a gun sight. This expensive professional grade RFI locating equipment is not too different from the amateur-grade equipment we used in our amateur RFI hunt two weeks ago.
Although Kurt is a seasoned RFI specialist and he was using designed-for-purpose professional equipment, his RFI location results were very much like ours. He experienced the same inconclusive results when using the 242 RF receiver and directional antenna. The 250 ultrasonic detector led him to the same pole we identified in our amateur RFI hunt. Once again, the loudest noise signature was heard coming from the pine tree adjacent to the suspect pole! Kurt’s best guess was similar to our amateur hypothesis – the ivy growing up the guy and onto the crossarm is probably involved in the RFI equation. The lesson here is that at least some of the time Amateur radio operators can achieve good RFI location results using simple equipment.
Kurt will schedule a line crew next week to service the entire line that runs through Glen Park. He plans to work alongside the line crew to monitor RFI levels. After they clean up the suspect pole, they will then sweep the entire line again to identify and repair any additional noise sources. Kurt promised to keep John informed of the outcome of their repair work.
National Grid RFI Engineer listening for electrical arcs
RFI Receiver at Work
A survey was sent to all our members today to determine how many might be interested in an Upgrade Class to General to be held next spring. So far the survey has been mailed only to NCRC members, but we might open it up to a state-wide audience at a later date.
Please fill in the short form and return it (its an Email thing — just fill in the blanks and press the SUBMIT button at the bottom).
The latest NCRC Technician Class began on Monday September 16, with seven students. Classes will be held for the next five Monday, and an exam will be held on October 28th. As we did last session, students who pass the exam and join NCRC for two years will receive a HT once they receive their license.
Remember that the October NCRC meeting will be held at the VFW Post
This past Field Day saw the GOTA station having difficulty due to horrible RFI at the Glen Park Pavilion. The noise was so bad that it even prevented weak signal satellite work near the power lines on 144/440 MHz. With an upcoming JotA event in October, WA1ABI, John King, offered an instructional class in RFI finding techniques using VHF/UHF AM receivers with directional antennas, a KX3 with a rubber duck antenna, and a ultrasonic leak detector.
The RFI levels were high enough, even on 2 meters, that directional antennas were still yielding multiple peaks, and the lack of a RF gain control on the VHF gear further hindered the process. On the other hand, signal levels were more reasonable at 70 cm, and a rather pronounced peak was observed in the direction of one particular telephone pole.
Other participants were “walking the line” with the KX3 set to 6-meter AM, and independently established a rather strong signal level from the same pole. John King then brought out the mystery weapon — a ultrasonic receiver that detects sounds in the 36-46 KHz range and converts them to audible signals (a hetrodyne receiver operating a ultrasonic frequencies). Sure enough, when John pointed his parabolic dish at the pole, he could easily detect arcing, and he observed ivy was growing up the pole’s guy wire and right into the MV 3-phase lines. Fascinatingly enough, a much stronger arcing noise was actually coming from a pine tree that was growing at the base of the power pole. Moving the guy wire could cause the noise to go away or come back.
National Grid will be called in next week to fix the issue, and a second RFI party will check to see if the noise is improved.
Thanks to John WA1ABI, Willy W1LY, Jack K1JG, Rich N3RWB, Dave KC1AAA, Dirmid KB1ZZY, Rob KB1ZZU, Julian N1UHP, and Bob WB4SON who participated in the hunt.
The “Guilty” Power Pole – Observe the Ivy Growing Up the Guy
Ted Wrobel demonstrated one variety of dual-band “roll-up” high gain antenna for use with HTs during our August meeting.
His antenna came from N9TAX: http://www.2wayelectronix.com/
Another source using smaller coax and twin-lead is from Nelson Antennas on eBay: http://www.ebay.com/usr/nelson_antennas