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In article ,
Ralph Mowery wrote: As hams are not reqired to keep the spacing or deviation some areas did go to 20 kHz spacing and 5 kHz deviation. Other areas went to 15 kHz spacing and kept the 5 kHz deviation. If the rigs are not very well up todate and the frequency and deviation set correctly there can be problems with the 15 kHz spacing. Yup. Here in NoCal, some parts of the 2-meter spectrum use 20 kHz spacing, and others use 15 kHz. There was a proposal to move things down to even narrower 12.5 kHz spacings a few years ago, but some experiments (which I helped perform) demonstrated that a lot of the then-available mobile and hand-held radios would suffer some pretty severe adjacent-channel bleed-through - their IF filters aren't sharp/narrow enough to avoid it. Getting people to cut their peak deviation down to 2.5 kHz would also have been difficult (older radios often don't have this available as an option, and those that do are often easy to mis-adjust). The 440 band is still on 20 kHz spacings. Keeping peoples' transmit oscillators accurately centered within 1 kHz or so is harder, up at those higher frequencies, and it pays to make allowance for some amount of drift when doing the frequency planning. |
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