The cycling lights are High Preasure Sodium (HPS) type and if cycling only at
night the photo cell is functioning properly. If the light cycles 24/7 the
photocell is also bad. It's more common to be 24/7. The defective photocell
causes the lights to fail earlier than normal.
HPS bulbs are a common source of rfi for 40 & 80 meters and is represented by a
single spike when using a scope.
The cycling is caused by the element in the bulb opening when it gets hot.
During the noise cycle the bulbs usually illuminate. This makes them easier to
locate in the dark.
Mike Martin
RFI Services
240.508.3760
Sent from my pocket office!
"Frank N. Haas KB4T" <utility.rfi.pro@gmail.com> wrote:
>As a Utility Interference Investigator, I run into bad street lights all
>the time. The most common failures are cycling and constant "invisible"
>RFI.
>
>The cycling failure is fascinating. The photocell senses that darkness has
>fallen. The light begins the process of coming on. The bulb will begin to
>illuminate dimly and its brightness will increase slowly over about a
>minute. At the end of the minute the bulb reaches full brightness and stays
>lit at full brightness for about 10 seconds. After 10 seconds at full
>brightness, the bulb goes dark. The light stays dark for about 30 seconds
>or so and the process repeats.
>
>Listening with a radio tuned to a quiet spot (or 1710) on the broadcast
>band, you can usually hear the repetitive street light symphony. Sometimes
>the RFI produced by these failed cycling lights can be heard as high as 325
>MHz.
>
>In my region, the cycling street lights can produce the following sounds in
>a receiver. As the bulb first dimly lights, the RFI begins. In the receiver
>a broadband buzzing modulation can be heard that seems to have a low pitch.
>As the street light bulb increases in brightness, the pitch of the
>modulated RFI increases in lock step with the bulb's brightness. At full
>brightness the RFI's modulation reaches its highest pitch and greatest
>loudness. When the bulb goes out 10 seconds later, the RFI stops. In 30
>seconds to a minute, the process repeats. The process continues non-stop
>until daylight comes. I have never actually determined what causes this
>behavior in street lights. It sounds to me light the photocell's electronic
>switch has failed and as the current through it increases, RFI is produced.
>The only other likely source would be the ballast.
>
>When a street light produces constant, unchanging RFI, it can be heard
>strongest at low frequencies. Only 50% of the time have I been able to
>detect a street light producing constant RFI at frequencies above 50 MHz.
>The light DOES NOT need to be illuminated to produce this constant RFI.
>However, it's usually very easy to pinpoint the offending light. Here
>again, either the photocell or ballast are bad.
>
>When I report a bad street light, they get fixed without my being present
>for the repair. I never know if a contractor will make the repairs or one
>of our troublemen. I've spoken to some troublemen who have done street
>light repairs but have never gotten definitive answers as to which failure
>causes which problem. Sometimes the entire lighthead is replaced and
>shipped to an inhouse shop for rebuilding. Sometimes the head is rebuilt on
>the spot. I am never told which repair method will be used or when the work
>will be done (so I can observe and learn!!)
>
>Like any other RFI source, finding a bad street light requires a
>portable/mobile receiver with RF Gain control, signal level indicator and
>directional antenna (or sensible technique based on signal strength). Not
>all street light RFI manifests itself as visible light. However, it can
>always be heard. Good DFing tools and technique will get the problem
>located promptly so repairs can be ordered.
>
>Good luck!
>
>Frank N. Haas KB4T
>Utility RFI Investigator
>Florida
>
>-----Original Message-----
>
>From: RFI [mailto:rfi-bounces@contesting.com <rfi-bounces@contesting.com>]
>On Behalf Of N1BUG
>
>Sent: Sunday, November 24, 2013 6:17 AM
>
>To: RFI@contesting.com
>
>Subject: [RFI] Street lights
>
>I'm wondering about noisy street lights - specifically the pattern where
>noise is present for a couple of minutes, then goes away for a similar
>period of time. It has been said the noise is due to the light trying to
>restart after going out. Is it a reasonably safe bet that any street light
>making this on/off RFI will be visibly going out and restarting?
>
>I'm wondering if I really need to drag all the RFI tools out with me on a
>street light hunt. If the light is visibly going off/on I should be able to
>find it visibly and confirm it's the one by listening to audio from my home
>receiver via some wireless link, correlating to cycles of the light. No?
>Just wondering here.
>
>73, Paul
>
>--
>
>Paul Kelley, N1BUG
>
>RFI Committee chair,
>
>Piscataquis Amateur Radio Club
>
>http://www.k1pq.org
>
>_______________________________________________
>
>RFI mailing list
>
>RFI@contesting.com
>
>http://lists.contesting.com/mailman/listinfo/rfi
>
>
>On Sun, Nov 24, 2013 at 6:16 AM, N1BUG <paul@n1bug.com> wrote:
>
>> I'm wondering about noisy street lights - specifically the pattern where
>> noise is present for a couple of minutes, then goes away for a similar
>> period of time. It has been said the noise is due to the light trying to
>> restart after going out. Is it a reasonably safe bet that any street light
>> making this on/off RFI will be visibly going out and restarting?
>>
>> I'm wondering if I really need to drag all the RFI tools out with me on a
>> street light hunt. If the light is visibly going off/on I should be able to
>> find it visibly and confirm it's the one by listening to audio from my home
>> receiver via some wireless link, correlating to cycles of the light. No?
>> Just wondering here.
>>
>> 73, Paul
>>
>> --
>> Paul Kelley, N1BUG
>> RFI Committee chair,
>> Piscataquis Amateur Radio Club
>> http://www.k1pq.org
>> _______________________________________________
>> RFI mailing list
>> RFI@contesting.com
>> http://lists.contesting.com/mailman/listinfo/rfi
>>
>
>
>
>--
>Frank N. Haas KB4T
>Utility Interference Investigator
>Florida
>_______________________________________________
>RFI mailing list
>RFI@contesting.com
>http://lists.contesting.com/mailman/listinfo/rfi
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