Posted: 10/31/2009 11:28:15 AM EDT
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What causes that out of phase/square wave sort of sound with SSB audio? I'm not sure how to describe it, so here's an example of what I'm talking about:
link to audio file Just curious and I've not yet been able to find an explanation of why it happens. Thanks! |
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I can't listen to the file because apparently I am missing some codec your recording requires. However, the sound you describe is from your receiver being slightly off the frequency being transmitted.
Do not assume the that the station you are listening to is supposed to be dead on an even kilohertz frequency, that is, say, for 20 meters, do not assume the station would be dead on 14.195 mhz. Particular for contesting, the station may be on the half kilohertz, 14.195.5, or even a 1/4 or 1/3, such as 14.194.75 mhz, or 14.195.3 mhz. If you tune to the even khz you will never get the sound right. You can change the tuning increment. For example, on my radio it would say 14.195 mhz. I can change that to read 14.195.0 or 14.195.00 which allows me to tune to finer increments. Or his radio or yours may be off frequency slightly, not unusual. If you are both supposed to be transmitting on 14.195 mhz, for example, and you want your radio to transmit on that frequency, but want to dial in the other station better, you can use the "clarify" knob (or other names), which allow you to slightly adjust the receive frequency up or down without changing your transmit frequency. (Edit to add) I could not get the file to work in Windows Media Player so I dropped it into a recording program I use, Goldwave, which instantly opened it. I can play it from Goldwave. Yes, that is from being off frequency. A male voice may sound like a distorted female voice, or if tuned the other way, very low and mechanical. Or squawky, "Donald Duck". Fine tune the frequency until the voice sounds natural. And sometimes it IS a female voice. |
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You have a couple of different things going on there...
First, the frequency is not correct. With SSB, the audio is reconstituted by mixing the received signal with a carrier supplied by the radio - so if your receive freq is off, the audio will sound unusually high or low pitched and with a strange quality. It takes a little experience to get the hang of tuning into voice SSB signals and get the freq just right even though you don't know what the voice sounds like. Second and on a related note, either the person operating the radio is adjusting the receive frequency or else you have some serious receiver drift, thats what is causing the audio to go from high pitched to low pitched. Lastly, you have some fading in that audio clip... the peculiarities of HF/shortwave propagation are such that signal sometimes go from strong to weak and back over a period of a few to several seconds. That's why the audio fades away into noise and then back. |
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Quoted:
You have a couple of different things going on there... First, the frequency is not correct. With SSB, the audio is reconstituted by mixing the received signal with a carrier supplied by the radio - so if your receive freq is off, the audio will sound unusually high or low pitched and with a strange quality. It takes a little experience to get the hang of tuning into voice SSB signals and get the freq just right even though you don't know what the voice sounds like. Second and on a related note, either the person operating the radio is adjusting the receive frequency or else you have some serious receiver drift, thats what is causing the audio to go from high pitched to low pitched. Lastly, you have some fading in that audio clip... the peculiarities of HF/shortwave propagation are such that signal sometimes go from strong to weak and back over a period of a few to several seconds. That's why the audio fades away into noise and then back. Thanks! |