The Chelsea repeater (WD8IEL), since this trustee assumed its maintenance responsibilities in 2022, has demonstrated an attribute of performance suggesting desensitization. That is, the background RF noise has a magnitude greater than the receiver’s sensitivity. The effect is that the repeater can be heard at a much greater distance than it can be worked.
BACKGROUND ELECTRO-MAGNETIC FIELD QUANTIFIED
The collective background electromagnetic field for the area measured from the parking lot of the Taco Bell restaurant was -66dBi based on a 50 Ohm impedance. This translates into 12u Volts which represents a very great limitation for any radio receiver in its vicinity.
APPLICABILITY TO THE CHELSEA REPEATER
The Chelsea Amateur Radio repeater (WD8IEL) is located in the water tower behind McDonalds and the Coney Island restaurant on M-52 which is in the immediate vicinity of this measured RF background noise. Because the repeater receiver is specified to have a sensitivity of 0.2u Volts, this background EM noise represents a very great limitation for the repeater. Any RF signals reaching the repeater having frequencies of 144.850 MHz (the repeater input) must have magnitudes greater than whatever the background EM radiation is.
Are you beginning to see the dilemma? Only very strong incoming signals will be able to be recognized by the repeater receiver. However, this does not affect how far away the repeater may be heard. The overall effect, therefore, is that the repeater may be heard at distances far greater than it may be worked.
A POSSIBLE SOURCE OF THE EM BACKGROUND RADIATION
On June 17th, with the help of George Byrkit (K9TRV), I was able to measure the EM background radiation present in the parking lot of the Taco Bell restaurant on M-52 in Chelsea. This location is situated directly across from where the Chelsea Water Tower is which houses the Chelsea Repeater operating on an output frequency of 145.450 MHz. As noted above, we saw -66 dBi representing 12 u Volts. If that is all that we knew about the EM radiation, then we would be toast with no alternatives other than to find another site for the repeater if the intent is to optimize the amateur experience.
WHAT ABOUT THE DTE UTILITY POLE IN FRONT OF CONEY ISLAND?
With some directional AM equipment, we were able to identify a broadband EM noise signal emanating from the power pole in front of the Coney Island restaurant on M-52. The offending power pole can be seen in the background in the picture shown on the right. A close-up of its transformer for ID is shown below that.
Such background radiation is not normal for a transformer and indicates that it is in need of attention. The nature of the EM radiation is broadband indicating arcing within the transformer.
It is particularly important that the responsible utility company address this issue since the FCC regulates such EM as excessive.
WHAT IS BEING DONE
The responsible utility company is being advised of this anomaly and is expected to address the matter in a timely fashion. It appears that the jurisdiction for the telephone pole is Consumers Energy (www.ConsumersEnergy.com, Lansing, Michigan). Calling them, I got nowhere with no suggestions offered on what alternatives may exist to get a remedy.
ALTERNATIVES FOR THE REPEATER
If the offending background EM radiation cannot be remedied, the only option is to find another site for the repeater, assuming optimal performance is required. There are many opportunities for alternative sites to choose from.