AVOIDING IMAGE FREQUENCIES
You might discover one of your regular stations on another frequency that is not list- ed. It might be what is known as an image frequency. For example, you might find a service that regularly uses a frequency of 431.975 also on 474.775.
To see if it is an image, do a little math. |
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Note the new frequency. | 474.775 |
Double the intermediate frequency of 21.4 MHz (42.800) |
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and subtract it from the new frequency. | |
If the answer is the regular frequency, | 431.975 |
then you have tuned to an image. |
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Occasionally, you might get interference on a weak or distant channel from a strong broadcast 42.8 MHz below the tuned frequency. This is rare, and the image signal is usually cleared whenever there is a broadcast on the actual frequency.
FREQUENCY CONVERSION
The tuning location of a station can be expressed in frequency (kHz or MHz) or in wavelength (meters). The following information can help you make the necessary conversions.
1 MHz (million) = 1,000 kHz (thousand)
To convert MHz to kHz, multiply the number of megahertz by 1,000: 9.62 (MHz) ⋅ 1000 = 9620 kHz
To convert from kHz to MHz, divide the number of kilohertz by 1,000:
2780 (kHz) ⎟ 1000 = 2.780 MHz
To convert MHz to meters, divide 300 by the number of megahertz:
300 ⎟ 7.1 MHz = 42.25 meters
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