Why does reception of AM stations get worse after dark? During the day, everything is crystal clear, but at the sun goes down, interference and other stations become more prominent.
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HF radio f
Actually, reception generally gets better after the sun moves across the horizon. At night, we used to consistently listen to WBZ in Boston when we lived in Florida during the winter. As propagation changes at night because of decreased apparent solar activity, the distant stations on adjacent frequencies become stronger.
Actually, reception generally gets better after the sun moves across the horizon. At night, we used to consistently listen to WBZ in Boston when we lived in Florida during the winter. As propagation changes at night because of decreased apparent solar activity, the distant stations on adjacent frequencies become stronger.
AM at night
At night, the atmospherics allow greater range for AM signal (really medium wave, I suppose... AM is just the modulation method)so the FCC requires that stations scale down their transmission strength at sunset, unless they are "clear channel" license holders, meaning they are the only station on that frequency within listening distance. Often these clear channel stations remain at the max FCC commercial wattage, 50,000, day or night. The atmospheric phenomenon is related to the way an upper atmosphere layer reacts to solar radiation. I think the affected layer is either the E or F layer, but it was a long time ago when I studied this. The interference that you hear is in fact a lot of stations sharing frequencies, or nearly so, all operating at low output power. It would be worse without the power shed at sunset. In the 1950's and 60's there were stations on the southern side of the Mexican border that maintained over 100,000 watts, day or night, and really upset the cart in the US. XERA in Del Rio had a show involving a "doctor," John Brinkley, which included a medical questions segment, in which he entertained questions which had been mailed in. Brinkley would read the letters and prescribe pills (by number) to be selected from a Dr. Brinkley pill kit, available for sale by mail. If you had arthritis, he would prescribe pill number 22, or something like that. It appears most, if not all, of Dr. Brinkley's pills were based on goat glands. -Hooper p.s. - The admiral, a holder of the old FCC Third Class license says the layer is called Kennely Heaviside Layer. Heaviside does not refer to the opposite of lighterside. Mr. Heaviside was the physicist who gave us the concepts of impedence, capacitance and inductance Who knew?
At night, the atmospherics allow greater range for AM signal (really medium wave, I suppose... AM is just the modulation method)so the FCC requires that stations scale down their transmission strength at sunset, unless they are "clear channel" license holders, meaning they are the only station on that frequency within listening distance. Often these clear channel stations remain at the max FCC commercial wattage, 50,000, day or night. The atmospheric phenomenon is related to the way an upper atmosphere layer reacts to solar radiation. I think the affected layer is either the E or F layer, but it was a long time ago when I studied this. The interference that you hear is in fact a lot of stations sharing frequencies, or nearly so, all operating at low output power. It would be worse without the power shed at sunset. In the 1950's and 60's there were stations on the southern side of the Mexican border that maintained over 100,000 watts, day or night, and really upset the cart in the US. XERA in Del Rio had a show involving a "doctor," John Brinkley, which included a medical questions segment, in which he entertained questions which had been mailed in. Brinkley would read the letters and prescribe pills (by number) to be selected from a Dr. Brinkley pill kit, available for sale by mail. If you had arthritis, he would prescribe pill number 22, or something like that. It appears most, if not all, of Dr. Brinkley's pills were based on goat glands. -Hooper p.s. - The admiral, a holder of the old FCC Third Class license says the layer is called Kennely Heaviside Layer. Heaviside does not refer to the opposite of lighterside. Mr. Heaviside was the physicist who gave us the concepts of impedence, capacitance and inductance Who knew?
Some stations are requred to
decrease their output to let the larger stations come thru. Lived in Pensacola and would listen to WBZ out of Chicago at night. Jim S/V Java
decrease their output to let the larger stations come thru. Lived in Pensacola and would listen to WBZ out of Chicago at night. Jim S/V Java
In the early sixty's we would listen to Wolf Man
Jack in Tijuana on XRB. He just started again on XM. My man.
Jack in Tijuana on XRB. He just started again on XM. My man.
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