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#1
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#2
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On 8 Jul 2006 20:22:18 -0700, "Steve" wrote:
The last couple of nights I've heard a very faint broadcast station on 4050, but I don't see anything listed for that frequency on the EIBI schedule. Anyone happen to know what it is? I heard it at around 01:30 or so. Steve 3rd harmonic 1350? |
#3
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![]() David wrote: On 8 Jul 2006 20:22:18 -0700, "Steve" wrote: The last couple of nights I've heard a very faint broadcast station on 4050, but I don't see anything listed for that frequency on the EIBI schedule. Anyone happen to know what it is? I heard it at around 01:30 or so. Steve 3rd harmonic 1350? wh..? |
#4
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On 9 Jul 2006 06:33:19 -0700, "Steve" wrote:
David wrote: On 8 Jul 2006 20:22:18 -0700, "Steve" wrote: The last couple of nights I've heard a very faint broadcast station on 4050, but I don't see anything listed for that frequency on the EIBI schedule. Anyone happen to know what it is? I heard it at around 01:30 or so. Steve 3rd harmonic 1350? wh..? THE ULTIMATE CHALLENGE: DXING MEDIUM WAVE HARMONICS By Don Moore This article was originally published in The Journal of the North American Shortwave Association. If you've been reading NASWA very long, you've noticed by now that shortwave broadcasters aren't the only broadcast stations using the shortwave bands. On occasion loggings of mediumwave (AM) "harmonics" creep in. But, although some mediumwave stations broadcast on shortwave at times, usually when they do they don't even know it! And that's just part of what makes DXing mediumwave harmonics such a challenge. WHAT ARE HARMONICS? All radio transmitters naturally put out harmonics, which are multiples of the fundamental frequency. For example, a station on 1400 kHz will transmit harmonics on 2800, 4200, 5600, etc. Twice the fundamental frequency, e.g. 2800 khz, is called the second harmonic; three times it, e.g. 4200 khz, is called the third harmonic, etc. The first harmonic, or one times the fundamental frequency, is the fundamental itself. Harmonics should not be confused with images, which are generated internally in a receiver, and are usually received plus or minus 910 kHz or 1000 kHz of a frequency, depending on the receiver, or receiver mixing products that cause exceptionally strong stations to appear where they don't belong. Harmonics are produced at the transmitter, not the receiver. Harmonics may seem like a free way for a small AM station to become an international broadcaster, but AM stations don't want to intentionally transmit harmonics, as any power that goes into a harmonic frequency is not being used for their fundamental frequency, which means a less powerful signal for their main audience. In addition, harmonic transmissions are prohibited by law as these unintentional broadcasts on higher frequencies may interfere with other stations which are licensed to use those frequencies. To prevent these problems, station engineers suppress harmonics below a maximum level allowed by the FCC or their nation's equivalent agency, although enforcement may vary (especially in Third World countries). But, not all stations have competent technical help watching over the equipment, or even if they do, mistakes can happen. Sometimes something gets maladjusted or whatever and suddenly there is maybe fifty or a hundred watts going into a harmonic instead of half a watt or a watt. Usually the problem is so small that it won't be noticed until the engineer does a regular check-up on the transmitter, or someone hears the harmonic and tells the station about it. In the meantime, it's happy harmonic hunting for DXers! |
#5
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![]() Steve wrote: The last couple of nights I've heard a very faint broadcast station on 4050, but I don't see anything listed for that frequency on the EIBI schedule. Anyone happen to know what it is? I heard it at around 01:30 or so. Steve I heard it again tonight and it is indeed Radio Verdad. It sounded best on the humble Lowe HF-150. Steve |
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