Author Topic: Medium Wave (AM Radio) Propagation Characteristics  (Read 848 times)

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Offline Halcyon

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Medium Wave (AM Radio) Propagation Characteristics
« on: November 11, 2015, 06:33:44 am »
I often drive between Sydney and Canberra for work and I've noticed this week that many of the AM radio stations I listen to are reaching further than they previously have. We've had a bit of bad weather so I don't know if it's the cloud cover that has had an effect or if the broadcasters have changed something at their transmitter sites.

For example: On 873 kHz, I would normally get a lot of noise and lose any useful signal around 60-100 kilometres from the transmitter site. On two occasions recently, I've been able to pick up a fairly loud and clear signal from ~200 kilometres away (that said, passing under any overhead high voltage transmission lines overwhelmed any AM signal).

Same thing has happened on 576 kHz (ABC Radio National; they use a different transmitter site in Sydney). On ABC especially, I used to have to change between three different frequencies on the drive down to continue listening to that station. This afternoon, I could pick up all three from the Federal Highway.

I should make note that on each occasion, I was driving during the day. I understand that atmospheric conditions at night often increase the range of low frequency broadcasts. How much of an effect does weather have on AM radio broadcasts? Will the cloud cover be reflecting a lot of the signal back down to earth at greater distances?
« Last Edit: November 11, 2015, 06:41:39 am by Halcyon »

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