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#21
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I've been a SWLer for at least 20 years, have a Ph.D. in EE, have 20+
years of experience in the telecomm industry (uwave, sats, cellular, UWB...) and have taught grad/undergrad comm courses at various U.S. universities. I agree with another poster that the SW8/R8B sync. detectors are among the best ever incorporated into SWL gear. My previous comment about sync. doesn't mean that one cannot achieve similar signall quality without it (e.g., using PBT, but how many portables or low-cost tabletops have PBT these days?), but the convenience of being able to select sidebands in sync mode is a big plus. RK |
#22
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rkhalona wrote: I've been a SWLer for at least 20 years, have a Ph.D. in EE, have 20+ years of experience in the telecomm industry (uwave, sats, cellular, UWB...) and have taught grad/undergrad comm courses at various U.S. universities. I agree with another poster that the SW8/R8B sync. detectors are among the best ever incorporated into SWL gear. My previous comment about sync. doesn't mean that one cannot achieve similar signall quality without it (e.g., using PBT, but how many portables or low-cost tabletops have PBT these days?), but the convenience of being able to select sidebands in sync mode is a big plus. Yep... a newbie. dxAce Michigan USA |
#23
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It's like a girl who is a Quasi Virgin, she's only allowed it in her mou$53!
"Lucky" wrote in message ... Hi guys! I saw this term mentioned in the specs of a radio. What does it mean exactly? That if you hope and listen long enough you can convince yourself it's synchronous? Lucky |
#24
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"rkhalona" ) writes: I've been a SWLer for at least 20 years, have a Ph.D. in EE, have 20+ years of experience in the telecomm industry (uwave, sats, cellular, UWB...) and have taught grad/undergrad comm courses at various U.S. universities. I agree with another poster that the SW8/R8B sync. detectors are among the best ever incorporated into SWL gear. My previous comment about sync. doesn't mean that one cannot achieve similar signall quality without it (e.g., using PBT, but how many portables or low-cost tabletops have PBT these days?), but the convenience of being able to select sidebands in sync mode is a big plus. RK But it seems you are mixing apples and oranges. Sync detection means a locally generated "carrier" is present, so if the signal fades the lack of a strong carrier is not a factor. It does nothing to prevent fading (which I bring up because someone recently said something along those lines here) it merely helps when the signal fades. Selectable sideband really has nothing to do with synchronous detection, other than that using the phasing method it's relatively cheap to implement compared to an expensive IF filter. It's not really like a few extra parts to a synchronous detector will add selective sideband, the added parts may be cheap but it adds complication to the circuit. When Webb wrote about the synchronous detector in CQ Magazine about it, it was the whole shebang. But, that was a time when many receivers had fairly wide IF filters, and lacked product detectors. At the same time, you'd see SSB adaptors that used the phasing method, which added that product detector and reduced the unwanted sideband. Adding synchronous circuitry to those was relatively simple, so once you added the sync circuitry you not only got DSBsc reception, but better SSB reception. What we often see is lower end receivers tossing it in (because the phasing method is a cheap way of knocking out the unwanted sideband, and plus there are ICs that do it all in one package), but it doesn't make up for the lack of a narrow IF filter with steep sides (at least not as implemented in those cheap receivers). It's a means of adding something without a major cost increase. I'm not even sure where we've veered off to. I thought the previous comment was something like synchronous detection wasn't all that important. I'd say that's true, given that people lived without it till it became a feature in relatively recent years. Someone listening to broadcast radio (am or shortwave) that are relatively strong may be the ones to benefit the most, because you can get deep fades where the sidebands are still nice and strong. Signals that you have to strain to hear, it's far less likely to be useful, because they are already below a minimum strength. You'd want to pull in other techniques at that point, and that includes the narrow IF filter that has good slopes. Michael |
#25
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In article .com,
"rkhalona" wrote: I've been a SWLer for at least 20 years, have a Ph.D. in EE, have 20+ years of experience in the telecomm industry (uwave, sats, cellular, UWB...) and have taught grad/undergrad comm courses at various U.S. universities. I agree with another poster that the SW8/R8B sync. detectors are among the best ever incorporated into SWL gear. My previous comment about sync. doesn't mean that one cannot achieve similar signall quality without it (e.g., using PBT, but how many portables or low-cost tabletops have PBT these days?), but the convenience of being able to select sidebands in sync mode is a big plus. This news group has more than it's share of Ph.D.'s and double E's it seems. Where do you think the future of telecom is going? Is it going to be mostly fiber-optic or do you think RF for the last mile to the home or business? Do you think Ethernet is winning over ATM? -- Telamon Ventura, California |
#26
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#27
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On Fri, 03 Jun 2005 02:56:59 GMT, Telamon
wrote: In article .com, "rkhalona" wrote: I've been a SWLer for at least 20 years, have a Ph.D. in EE, have 20+ years of experience in the telecomm industry (uwave, sats, cellular, UWB...) and have taught grad/undergrad comm courses at various U.S. universities. I agree with another poster that the SW8/R8B sync. detectors are among the best ever incorporated into SWL gear. My previous comment about sync. doesn't mean that one cannot achieve similar signall quality without it (e.g., using PBT, but how many portables or low-cost tabletops have PBT these days?), but the convenience of being able to select sidebands in sync mode is a big plus. This news group has more than it's share of Ph.D.'s and double E's it seems. Where do you think the future of telecom is going? Is it going to be mostly fiber-optic or do you think RF for the last mile to the home or business? Do you think Ethernet is winning over ATM? Ermmmm...ATM (asynchronous transfer mode) is a 53-byte packet protocol that travels OVER ethernet (a method of transferring data over coax cable - and wire pairs.). See IEEE standard 802.3. Ethernet is the most widely installed local area network technology. The most commonly installed Ethernet systems are called 10BASE-T, providing transmission speeds up to 10 Mbps. Fast Ethernet LANs, 100BASE-T, provide transmission speeds up to 100 Mbps. ATM is a dedicated-connection switching technology that organizes digital data into 53-byte cell units and transmits them over a physical medium using digital signal technology. Individually, a cell is processed asynchronously relative to other related cells and is queued before being multiplexed over the transmission path. Because ATM is designed to be easily implemented by hardware (rather than software), faster processing and switching speeds are possible. The prespecified bit rates are either 155.520 Mbps or 622.080 Mbps. Speeds on ATM networks can reach 10 Gbps. Regards, Al in CNMI ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#29
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In article ,
Tebojockey wrote: On Fri, 03 Jun 2005 02:56:59 GMT, Telamon wrote: In article .com, "rkhalona" wrote: I've been a SWLer for at least 20 years, have a Ph.D. in EE, have 20+ years of experience in the telecomm industry (uwave, sats, cellular, UWB...) and have taught grad/undergrad comm courses at various U.S. universities. I agree with another poster that the SW8/R8B sync. detectors are among the best ever incorporated into SWL gear. My previous comment about sync. doesn't mean that one cannot achieve similar signall quality without it (e.g., using PBT, but how many portables or low-cost tabletops have PBT these days?), but the convenience of being able to select sidebands in sync mode is a big plus. This news group has more than it's share of Ph.D.'s and double E's it seems. Where do you think the future of telecom is going? Is it going to be mostly fiber-optic or do you think RF for the last mile to the home or business? Do you think Ethernet is winning over ATM? Ermmmm...ATM (asynchronous transfer mode) is a 53-byte packet protocol that travels OVER ethernet (a method of transferring data over coax cable - and wire pairs.). See IEEE standard 802.3. Ethernet is the most widely installed local area network technology. The most commonly installed Ethernet systems are called 10BASE-T, providing transmission speeds up to 10 Mbps. Fast Ethernet LANs, 100BASE-T, provide transmission speeds up to 100 Mbps. I suppose ATM could be stuffed into a ethernet frame but I have not heard of it. In the telecom world it's ATM over SONET that terminates at my DSL modem. The DSL modem is used as a bridge. Between my DSL modem to the computer it's ethernet so I can use the usual routers and or hubs. ATM is a dedicated-connection switching technology that organizes digital data into 53-byte cell units and transmits them over a physical medium using digital signal technology. Individually, a cell is processed asynchronously relative to other related cells and is queued before being multiplexed over the transmission path. Because ATM is designed to be easily implemented by hardware (rather than software), faster processing and switching speeds are possible. The prespecified bit rates are either 155.520 Mbps or 622.080 Mbps. Speeds on ATM networks can reach 10 Gbps. It can go over any of the SONET rates. Maybe I should have been more specific. The question is whether ethernet will take over the local metro area from ATM over SONET. I expect that ATM over SONET will be maintained at higher levels in the network. -- Telamon Ventura, California |
#30
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"Pete KE9OA" wrote in message ... I had one of those. It did have quite a bit of RF gain, but the I.F. strip did not have the gain that the Plessey SL6700 that is used in the HF-150 does. They are not the same receiver, performance wise. If you can find one in the 125 dollar range, it isn't a bad deal. Pete "Lucky" wrote in message ... "John S." wrote in message ups.com... Which radio...haven't heard that term. OK I'm interested in the old Lowe SRX-100 also known as the AKD Target HF3 and now the Nasa Target HF3/p or Nav-fax 200. Check on the very bottom specs under "demodulator: I'm going to buy one. They look cool and seem to have the same Lowe slower rate, faster rate knob. Simple receiver but I seem to like it from what I've read about them. Now this company makes a Nasa Target HF5E that I can only find in Germany. It's supposed to be comparable with the Lowe 150. http://www.pyacht.net/cgi-local/Soft....htm?E+scstore Lucky Pete, I ordered one yesterday and found a dealer in this country who has them. Wasn't easy for sure but I did it. They are much cheaper here then in the UK for sure. Like 1/2 the price. I should be getting it hopefully today or tomorrow! I asked around and one supplier tracked the radio down for me. It's renamed again in the U.S. Can't wait to fool around with it. Have a good day. Lucky |
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