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Sony CMT-NEZ30

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  • Sony CMT-NEZ30

    I just bought this radio at goodwill for $10 (pretty good deal, it's almost $200 on Amazon) for dxing. I've got a cheap loop antenna hooked up to it, and I was playing around with it last night on the AM band. To be honest, I was a bit disappointed. I'm not sure if it's my antenna or the tuner, but I could hardly get anything. WGN, WJR, WBBM, and WSCR all came in, but I couldn't find a single new log. My local WCCO and KSTP were also able to be heard on every station on the 800 khz range and 1500 khz respectively. Even the lower powered WREY 630 was able to be heard all the way up on 660, crowding out WBHR, which I can easily get at night. I thought I had a new log on 600, it was a sports station, which I thought was WKYH Paintsville, KY. But when ToH ID came up, it goes "you're listening to 1500 ESPN, KSTP, Minneapolis-St. Paul". How does 1500 end up on 600? I know KSTP is a clear channel at 50kw, but that shouldn't happen, right? Should I return the radio or try to improve the antenna?

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  • #2
    The Amazon price is high because its out of production and the only sellers are third party sellers asking way too much. If you want a better idea what its worth, search it on eBay and then filter by sold listings to see what people are actually paying. This system complete with speakers has sold for around $60 to $80 on eBay, so I'd say you got a good deal even without speakers. Although its probably not going to be a good AM DX radio. From my experience AM radio quality went downhill fast on consumer grade equipment in the 2000s. The older tuners were better but were often analog tuned which isn't ideal for DXing. This unit is from around 2006 based on my Google searching. By then AM was considered an afterthought and people were buying units like yours in order to play their CDs and MP3s. Radios like the XDR-F1HD are an exception because they were designed for HD Radio which requires a good tuner and they were sold as a tuner only, so the tuner better be good or nobody would buy it. Hearing a strong local on random parts of the band usually means the tuner is being overloaded, which happens easily on lower end tuners.
    DX Radios:
    Sony XDR-F1HD
    Sony XDR-S10HDiP
    Tecsun PL-390

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    • #3
      Overload could cause 1500 to also be heard with the radio tuned to 600, but I suspect, in this case, the culprit is superheterodyne image .

      In most AM radio circuits before 2012, the radio takes any signal you tune it to and converts it to 455kHz*.

      When you tune to KSTP (1500kHz) itself, an oscillator in your radio produces a carrier at 1955kHz, the two signals mix to form an intermediate frequency of 455kHz, which is amplified and detected to produce the audio.

      When you tune to 590 (or, in your case, 600), the local oscillator is at 1050 or 1055kHz. While the front end is trying to suppress the strong signal from KSTP, a little gets through, mixes with the oscillator, and feeds it at 455kHz through the IF section thus played on the radio.

      **it would not surprise me if, for some reason, Sony chose to use 450kHz instead of the standard 455 when they designed the receiver.
      Comparing Sporadic-E skip to skip on the AM and shortwave bands is like comparing apples and oranges.

      Comparing tropo to skip is like comparing apples and bacon cheeseburgers.

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