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#1
October 22nd 04, 12:05 PM
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DRM 3995
The past few evenings I've tuned up to the top of the 75 meter band to see what
effect DRM on 3995 has on the band and it's atrocious. DRM = QRM dxAce Michigan USA |
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#2
October 23rd 04, 05:23 AM
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In article , dxAce
wrote: The past few evenings I've tuned up to the top of the 75 meter band to see what effect DRM on 3995 has on the band and it's atrocious. DRM = QRM That's one of the neat things about technology is predictability. DRM claims about better audio in the same bandwidth is BS as are the non adjacent channel interference clams. -- Telamon Ventura, California |
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#3
October 23rd 04, 06:53 AM
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Telamon wrote: In article , dxAce wrote: The past few evenings I've tuned up to the top of the 75 meter band to see what effect DRM on 3995 has on the band and it's atrocious. DRM = QRM That's one of the neat things about technology is predictability. DRM claims about better audio in the same bandwidth is BS as are the non adjacent channel interference clams. Yep, I just checked the signal a few minutes ago on 3995 and it wipes out at least the top 10 kHz of the band. dxAce Michigan USA |
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#4
October 23rd 04, 07:09 AM
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In article , dxAce
wrote: Telamon wrote: In article , dxAce wrote: The past few evenings I've tuned up to the top of the 75 meter band to see what effect DRM on 3995 has on the band and it's atrocious. DRM = QRM That's one of the neat things about technology is predictability. DRM claims about better audio in the same bandwidth is BS as are the non adjacent channel interference clams. Yep, I just checked the signal a few minutes ago on 3995 and it wipes out at least the top 10 kHz of the band. How about below? The upper harmonics are a sure thing but I expect the DRM signal to spread out as far below the frequency transmitted on. Digital signals spread out above and below the frequency they are on. Upper frequency spread is from multiple carrier mixing products and higher frequency harmonics of the fast switching edges and phase noise or random jitter. The low frequency spread is from data dependent effects or data dependent jitter and the data mixing with the carriers. -- Telamon Ventura, California |
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#5
October 23rd 04, 07:15 AM
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Telamon wrote: In article , dxAce wrote: Telamon wrote: In article , dxAce wrote: The past few evenings I've tuned up to the top of the 75 meter band to see what effect DRM on 3995 has on the band and it's atrocious. DRM = QRM That's one of the neat things about technology is predictability. DRM claims about better audio in the same bandwidth is BS as are the non adjacent channel interference clams. Yep, I just checked the signal a few minutes ago on 3995 and it wipes out at least the top 10 kHz of the band. How about below? The upper harmonics are a sure thing but I expect the DRM signal to spread out as far below the frequency transmitted on. Digital signals spread out above and below the frequency they are on. Upper frequency spread is from multiple carrier mixing products and higher frequency harmonics of the fast switching edges and phase noise or random jitter. The low frequency spread is from data dependent effects or data dependent jitter and the data mixing with the carriers. Well I did mention the top 10 kHz of the band. Apparently the signal is centered on 3995, and it is certainly audible both above and below that point. In the few times I've checked recently I've not noticed any amateur use of that range when the DRM signal is on. It's a mess! dxAce Michigan USA |
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#6
October 23rd 04, 07:25 PM
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In article ,
Telamon wrote: How about below? The upper harmonics are a sure thing but I expect the DRM signal to spread out as far below the frequency transmitted on. Digital signals spread out above and below the frequency they are on. Upper frequency spread is from multiple carrier mixing products and higher frequency harmonics of the fast switching edges and phase noise or random jitter. The low frequency spread is from data dependent effects or data dependent jitter and the data mixing with the carriers. Huh? There're no fast edges. It's a COFDM signal that consists of hundreds of closely spaced subcarriers modulated as some slow baud rate (around 30-50 Hz). It shouldn't slop over much, but it'll fill up all the spectrum it's using. It's very similar to a FDM telegraph (Droning DC-3) signal, only about 5-20 times as wide. Mark Zenier Washington State resident |
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#8
October 25th 04, 03:43 PM
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dxAce wrote in message ...
The past few evenings I've tuned up to the top of the 75 meter band to see what effect DRM on 3995 has on the band and it's atrocious. DRM = QRM dxAce Michigan USA What is DRM?? Some kind of digital communications?? Steve P.S. sorry if this is a dumn question. |
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#9
October 25th 04, 03:53 PM
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Steve wrote: dxAce wrote in message ... The past few evenings I've tuned up to the top of the 75 meter band to see what effect DRM on 3995 has on the band and it's atrocious. DRM = QRM dxAce Michigan USA What is DRM?? Some kind of digital communications?? Yes, it is radio transmitted digitally. Give a listen up on 3995 in our North American evenings and listen to the QRM. And then try and imagine what that sort of thing will do to the other shortwave broadcasting bands. dxAce Michigan USA |
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#10
October 25th 04, 07:18 PM
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Ok, yeah, I used to talk with a group on 3985 in the evenings and I
always noticed that from about 3995 on up it the band was trashed.. Steve dxAce wrote in message ... Steve wrote: dxAce wrote in message ... The past few evenings I've tuned up to the top of the 75 meter band to see what effect DRM on 3995 has on the band and it's atrocious. DRM = QRM dxAce Michigan USA What is DRM?? Some kind of digital communications?? Yes, it is radio transmitted digitally. Give a listen up on 3995 in our North American evenings and listen to the QRM. And then try and imagine what that sort of thing will do to the other shortwave broadcasting bands. dxAce Michigan USA |
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