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LSB Reverse?
- Thread starter Se7en
- Start date
757GX2
i guess i was using it on something lastnight and i just got home to play with the radio this afternoon and i was tripping out why everyone on LSB sounded like crap and on USB everyone sounded fine....thought maybe i missed out on a shift change....:glare: nvm me Cloud 22 here
Quality.
sounds like he's trying to resolve an AM signal on sideband, but i may be wrong as double dutch isn't one of my strongest languages.
Naaah....he is just trying to listen to an SSB signal that is moved partially outside the receiver's passband. This will make signals sound extremely tinny and ringing. IF shift is used to move a nearby interfering signal just outside the passband while leaving the desired signal inside. Audio quality is altered a bit to the desired signal but the signal/interference ratio is increased.
yeah i know how passband tuning and if shift works and the effect the radios filters have on the rx when the wanted signal is moved closer to the skirt of the filter or the filter passband is narrowed, i just wasn't getting his description of what was happening, and being its within the cb band where AM is used i wondered if he was trying to resolve the sidebands of an AM signal whilst on ssb.
Thanks just learned what it does by your post. The manual doesn't talk a whole lot about shift or notch and I still don't use notch cause it makes the audio sound like crap....its probably me not knowing how to use that either.
Was listening to 27.385lsb and I had the shift too far to the right !..doh ! I dont listen to AM unless I am below 21mhz, or above 310mhz.
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The notch filter is useful for blocking out heterodynes. If you tune in an AM signal on SSB and tune a little off frequency, you'll hear a loud single frequency tone. You can also hear this on AM when two stations key up together and they're a bit off frequency from each other (the frequency of the tone will be equal to the difference in frequency of the two carriers, so if one carrier is on 28.400.000 and the other is on 28.401.000, the difference is 1.000Khz, so you'll hear a 1000hz tone).
The notch filter produces a very narrow and very deep zone of attenuation, i.e. a notch in the receiver's passband. You can set the frequency range that's attenuated by adjusting the notch control knob. When you hear a single tone in the receiver that annoys you, turn on the notch filter switch and slowly sweep the notch control knob back and forth a few times. When you get the notch right on the same frequency as the tone, it should disappear (or at least be drastically reduced). This can be a little tricky depending on the shape of the filter and the coarseness of the control.
This does have an effect on the audio of the person you're trying to listen to because you're "notching out" a part of their audio envelope too, but if the filter is designed well, the notch should be narrow enough to reduce or eliminate the unwanted tone without hurting the intelligibility of the other guy's audio too badly. What you sacrifice in audio quality may be worth it to get that damn screeching out of your ears.
Some radios have audio notch filters while some have IF-level notch filters instead. And some have automatic heterodyne blockers that you don't even need to tune manually. (You can also buy or make an external audio-level notch filter for rigs that don't have them built in.)
The notch filter is most useful for tones that are close to the middle of your passband. Unwanted signals at the edges of the passband can often be masked using the IF shift control, or by selecting a narrower filter (if your rig has one).
Basically, the radio gives you the tools, and you get to pick the best one for the job.
-Bill
The notch filter produces a very narrow and very deep zone of attenuation, i.e. a notch in the receiver's passband. You can set the frequency range that's attenuated by adjusting the notch control knob. When you hear a single tone in the receiver that annoys you, turn on the notch filter switch and slowly sweep the notch control knob back and forth a few times. When you get the notch right on the same frequency as the tone, it should disappear (or at least be drastically reduced). This can be a little tricky depending on the shape of the filter and the coarseness of the control.
This does have an effect on the audio of the person you're trying to listen to because you're "notching out" a part of their audio envelope too, but if the filter is designed well, the notch should be narrow enough to reduce or eliminate the unwanted tone without hurting the intelligibility of the other guy's audio too badly. What you sacrifice in audio quality may be worth it to get that damn screeching out of your ears.
Some radios have audio notch filters while some have IF-level notch filters instead. And some have automatic heterodyne blockers that you don't even need to tune manually. (You can also buy or make an external audio-level notch filter for rigs that don't have them built in.)
The notch filter is most useful for tones that are close to the middle of your passband. Unwanted signals at the edges of the passband can often be masked using the IF shift control, or by selecting a narrower filter (if your rig has one).
Basically, the radio gives you the tools, and you get to pick the best one for the job.
-Bill
