7160 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ken Sent: Friday, April 03, 2009 7:26 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] 7160 tonight: Suggestion
what freq ----- Original Message ----- From: "Tom Prohigh" <[email protected]> To: "'Discussion of AM Radio in the Amateur Service'" <[email protected]> Sent: Friday, April 03, 2009 7:24 PM Subject: Re: [AMRadio] 7160 tonight: Suggestion Right now Timtron doing DX AM with Germany! -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of D. Chester Sent: Friday, April 03, 2009 1:52 PM To: [email protected] Subject: Re: [AMRadio] 7160 tonight: Suggestion > From: "Todd, KA1KAQ" <[email protected]> > On Thu, Apr 2, 2009 at 1:45 PM, D. Chester <[email protected]> wrote: >> One suggestion. We need to be more careful about zero beating each other > on >> the 40m frequency. At times in the QSO, stations are so scattered out >> over >> a 1-2 kHz range, that my sync detector won't stay locked when one station >> turns it over to another. But the real problem is that this frequency >> scattering is bound to be generating unnecessary hostility from the SSB >> DX'ers, and will likely to result in deliberate QRM and other hostile >> actions against the AM'ers > When has that ever bothered you before, Don? To borrow your own words > on such matters, 'strap and ignore', 'turn up the wick' etc. I'd agree > with you if folks were scattered out over 4-5 kcs or more, but 1-2 > seems m ore related to sync detectors not locking up than to offending > any SSB ops. After all, it's been one of the ways to discourage > anti-AM SSB types from crowding in close to a QSO in progress. I have ALWAYS, ever since the early 60's, advocated operating zero-beat with the other station whenever possible. One exception might be when two or more stations are xtal controlled, and some of the older VFOs do drift. But failure to zero-beat when it is easily possible and convenient is just plain sloppy operating. This is an example of the difference between necessary bandwidth and occupied bandwidth. If you are running audio out to 5 kHz, 10 kHz is the NECESSARY bandwidth of the signal. But if two stations in the QSO are 3 kHz apart, then the OCCUPIED bandwidth of the QSO becomes 13 kHz. There is no rule that says all stations in a QSO have to be on the same frequency. Hell, DX'ers routinely take up two whole SSB communications channels for one QSO by working split frequency (and these are often the very same self-righteous kilocycle kops who gripe the loudest about all that "bandwidth" that AM and ESSB signals take up). Nevertheless, conspicuous sloppiness about zero-beating just unnecessarily gives the slopbucketeer lunatic fringe more ammunition to use against AM. Another often-overlooked advantage of carefully zero-beating (whenever practicable) is that a "breaking" station attempting to enter into the QSO is less disruptive. If you can hear his audio underneath the transmitting station, and at most, the puttering sound of a nearly zero-beat carrier, this is far less disruptive to the conversation, than a loud 1-2 kHz squeal of an off-frequency carrier, which garbles up the sidebands of both signals. You often miss what the transmitting station was saying, while at the same time, missing the callsign of the breaking station. It is not unusual that "breakers" into a QSO are ignored for this very reason. But older transmitters with drifty VFO's are not the only problem. Some of the worst offenders are using modern transceivers on AM. Even if the audio level and carrier level are adjusted properly, so that a good, undistorted, plate-modulated quality AM signal is generated, many transceivers lack any kind of frequency spotting function. In AM mode the received signal is clearly audible as long as it lies within the transceiver's passband. So it is easy to tune in the signal on the receiver and then transmit, and end up with a carrier 1.5 kHz or more off frequency. If everyone is using a wide bandpass at the receiver and there is little congestion on nearby frequencies, this is no big deal and no-one may even notice. But if the band is crowded and many stations in the QSO are operating with the receiver in narrow bandpass, with heavy QRM off to both sides, some people in the QSO may miss the call entirely. I have seen modifications to transceivers that allow a spotting function for zero-beating purposes. Depending on the circuit design, this may be very easy with minimal alteration of the circuitry, while on others it simply isn't practical. Lacking a spotting function, the easiest method would be to put the rig in SSB/CW mode and zero-beat the AM carrier, then switch back to AM. But on some rigs, this automatically produces a frequency error, because there is a built-in frequency offset when switching between modes. In that case, you have to note the digital display frequency, and retune back to that frequency in AM mode. Even then, there may also be an offset in the digital display reading that must be taken into account. It is a matter of figuring out exactly what works with a particular ricebox and getting into the habit of using it. One factor that hinders proper zero-beating with any receiver is space-shuttle quality, so-called "communications grade" audio, that cuts off everything below about 500 Hz. That makes it nearly impossible to hear two carriers approach zero-beat, if the audio drops out once they are within 300-500 Hz of each other. One more reason to have good low frequency response at the receiver, working into a decent speaker or headphones. While it may be poor operating practice to intentionally operate on scattered frequencies just to discourage SSB stations, that doesn't mean you should hesitate to go into the "SBE" mode when SSB stations intentionally zero in and try to piggy-back ride the AM carrier. Then, to use a Timtron expression, it may be time to "exit stage left" and move about 1.5 kHz down into the LSB passband, and for each station in the QSO to operate a little off frequency to make it necessary for the offending parasites to keep changing frequency to keep up with you. But this should be used only as a defensive tactic in the presence of deliberate QRM, not as a preventive measure. When the QRM finally goes away, then everyone should re-zero beat. Something that I have experienced many many times, is for the offending slopbucketeers to zero-beat, so I exit stage left. The other AM station in QSO zero-beats me. Then the SSB'ers re-zero beat to ride the carrier. So we exit stage left once again. This continues for several more transmissions, until we are 5-6 kHz down from the original frequency. Then, without fanfare, we move back up to the original frequency. Sometimes the SSB QSO stays down below, and we all co-exist peacefully. At other times the slopbucketeers move back up to zero-beat us. When that happens, they have clearly demonstrated that the interference is intentional. Once, someone from an FCC monitoring station (remember those?) explained that if one amateur station merely transmits on top of another, it is not considered deliberate and no "pink slip" will be issued, because amateur radio operates on an interference-expected basis. But if the operators in the original QSO move frequency, and the interfering station follows them to the new frequency to continue causing interference, the FCC considers that to be deliberate. But rather than getting into a pissing contest with jammers, it is sometimes better to just pretend they don't exist and ignore them. "Strap softly and turn up the wick." All said, careful zero-beating is even more essential in the 7125-7200 segment during prime time after-work hours, which just happens to simultaneously be prime time for cross-country propagation AND for European grey-line DX propagation. Because of the outmoded subband restrictions that presently exist on 40m in continental US, the overlap between the new privileges enjoyed by European and other DX stations, and US phone privileges, is only 75 kHz. One AM QSO occupying 7.5 kHz, about the minimum actual bandwidth occupied by a real-world AM signal, is fully 10% of the entire segment, while ZILLIONS of the "Hello-g'bye, ur five-nine, pse QSL, 73, QRZ?" DX'er types are just getting home from work to play a little radio before dinner, or are getting in some last minute DX before bedtime in Europe. Sloppily operating in a manner such that we occupy 15-20% of the segment for one round-table will do nothing but attract the massive wholesale wrath of this element, which will eventually generate unwanted anti-AM sentiment within the greater amateur community, and possible lobbying efforts and FCC petitions to restrict or downright outlaw AM. To repeat a cliché, we need to keep our ducks in a row while using the 7160 frequency. Don k4kyv _______________________________________________________________ This message was typed using the DVORAK keyboard layout. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/ ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.285 / Virus Database: 270.11.37/2036 - Release Date: 04/03/09 06:19:00 No virus found in this outgoing message. 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