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In article ,
Larry W4CSC wrote: Most ham radios can tell when your local AM stations are out of tolerance, now...(c; My Yaesu FT-990 with the high stability master oscillator doesn't vary off WWV on 15 Mhz over a couple of cycles in a year! This has absolulty nothing to do with the IMD Spec for Type Acceptance. IMD is not Frequency Stability. Like I stated before Frequency Stability hasn't been the probelm for 15 years. Bruce in alaska -- add a 2 before @ |
#2
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On Mon, 07 Feb 2005 19:40:33 GMT, Bruce in Alaska
wrote: This has absolulty nothing to do with the IMD Spec for Type Acceptance. IMD is not Frequency Stability. ===================================== Bruce, does the IMD spec speak to audio clarity, off channel interference or both? |
#3
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In article ,
Wayne.B wrote: On Mon, 07 Feb 2005 19:40:33 GMT, Bruce in Alaska wrote: This has absolulty nothing to do with the IMD Spec for Type Acceptance. IMD is not Frequency Stability. ===================================== Bruce, does the IMD spec speak to audio clarity, off channel interference or both? IMD = Intermodulation Distortion A Spec for Transmitters, and it is a very HARD Spec to design for, and PROVE, via Type Acceptance Testing for General Coverage (1.8 - 30 Mhz) transmitters. There is a significant variation in parts used in the post Power Amplifier Filtering Systems, of these radios, and to get the required IMD Spec, for all these various filters and bands, for all the production radios isn't an easy trick, especially for the radios that you MUST submit to the FCC Lab for Type Acceptance. Bruce in alaska -- add a 2 before @ |
#4
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On Tue, 08 Feb 2005 19:50:19 GMT, Bruce in Alaska
wrote: In article , Wayne.B wrote: On Mon, 07 Feb 2005 19:40:33 GMT, Bruce in Alaska wrote: This has absolulty nothing to do with the IMD Spec for Type Acceptance. IMD is not Frequency Stability. ===================================== Bruce, does the IMD spec speak to audio clarity, off channel interference or both? IMD = Intermodulation Distortion A Spec for Transmitters, and it is a very HARD Spec to design for, and PROVE, via Type Acceptance Testing for General Coverage (1.8 - 30 Mhz) transmitters. There is a significant variation in parts used in the post Power Amplifier Filtering Systems, of these radios, and to get the required IMD Spec, for all these various filters and bands, for all the production radios isn't an easy trick, especially for the radios that you MUST submit to the FCC Lab for Type Acceptance. Bruce in alaska A little clarification: Intermod distortion is usually refered to as unwanted inband products produced by the mixing of different rf frequencies that are closely spaced (audio produced). Mixing together that produce unwanted signals within the audio pass band and in adjacent channels. The main contributor to this type of distortion is non linearity in one or more RF power amplifier stages. This type of distortion can cause rough sounding audio on a signal. The bigger problem is that it causes splatter on adjacent channels. The post amplifier filters do nothing for this type of intermod reduction. They do however reduce second and third harmonics of the wanted signal which is another strict requirement of commercial type accepted radios. There can also be other unwanted mixing products produced in a radio as the result of other types of intermod. These are commonly referred to as spurious signals. These usually result from non linear stages mixing signals to produce signals significantly removed from the wanted signal. The output filter may or may not help with this type of unwanted product depending on where it falls. These can be tough to get rid of at times. The spec for commercial type accepted radios is tougher on this also. Regards Gary |
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