(From The LOWDOWN, November, 1997) "The LF Notebook" The Mailbag, News and Comments About LF Radio, Etc. John H. Davis, Box 367, Warm Springs, GA 31830 - E-mail - lwcanews@aol.com -Web http://members.aol.com/lwcanews/ [ ONE PICTURE ACCOMPANIES THIS ARTICLE: ] http://frodo.bruderhof.com/longwave/notebook/n56pic1.gif Geezerhood and I are not getting along very amicably at all. My mother, after her hip replacement last month, is getting around better than I am at the moment. My crummy back will surely be better again by the time this gets to you, but for now, sitting up to type is extraordinarily difficult. Stretching the arm far enough to work the mouse is an even touchier proposition. Therefor, it's not likely we'll get to the feature material this time, either, since the mouse is crucial to formatting material on the page. So, please excuse another column that is unexpectedly abbreviated. We'll depend on the Mailbag material for now, and hope for a festive holiday edition next month. Meanwhile, I hope you have a wonderful Thanksgiving celebration! Our family has much to be thankful for this year, so we will be enjoying the occasion with you. On To The Mailbag -Lyle Koehler (LEK, MIN, K0LR; Aitkin, MN; k0lr@emily.net) has been busy this past month in a number of different areas related to digital communication. For one thing, Bill de Carle is now up to Version 7.2 of the popular COHERENT software, available at his Web site (http://w3.ietc.ca/home/bill/bbs.htm). Lyle reports: "I left COHERENT running in the Trace mode last night, monitoring STLMO's MedFER signals with the frame grabber at 6:3 and using the SYNC3 option. The signal apparently faded in and out a number of times. Even if the signal level had been constant, the 1-minute CW transmission during each 2-minute cycle guarantees loss of sync and forces the frame grabber to start over. My word processor says there were 115 exact occurrences of 'STLMO' in the Trace file (lots of partials which I didn't bother to count). Considering the QRN levels, that's a pretty good success ratio. Looks like version 7.2 is another winner!" He also had MedFER beacon MIN transmitting very slow CW for a while. "The speed is approximately 0.1 WPM. My stop watch says the dashes are about 34 seconds long. MIN is transmitting on 1641.998 kHz; the frequency will probably drift a bit during the night." And, Lyle comments on a recent product: "Brian Beezley's 'DSP Blaster' software offers some features that may enhance reception of LowFER CW signals. See 'Improved CW Reception Using "Stereo"' in the Digital Dimension column of the October, 1997 QST, page 97. There is a coherent CW processing feature that can present the audio in such a way that the signal and noise appear to be spatially separated when heard in a pair of stereo headphones." "To run DSP Blaster, you need a 486 or better with math coprocessor, a 16-bit Creative Labs Sound Blaster card and mouse. The software isn't cheap ($125) but there's a demo version available at http://www.megalink.net/~n1rct/db/dbindex.html The demo is fully functional except that you can't save the settings, and it has a limited run time of about five minutes -- long enough to get a good feel for how it performs. I had trouble running it on my 486 computer. It kept giving me a 'not enough memory' message even though the software only requires 50 KBytes. An e-mail inquiry to the author got me a response telling me I apparently had a system software problem. Not very helpful. Finally I tried all the possible command-line parameters and found that it worked if I started the DB.EXE program by typing 'DB R', which has something to do with VGA screen-restore techniques. Whatever works, as they say." "I ran some limited tests of DB while receiving LowFER beacon SAM with the loop oriented for a null so the signal was right at the noise level. I also repeatedly played back (on another computer) Steve McGreevy's Z2-IN-HI.WAV file containing the all-time LowFER DX receiving record of California beacon Z2 in Hawaii (with a Realistic DX-200 receiver and no audio filter!). Did DSP Blaster help? Maybe, maybe not. In both cases, I could detect the beacon ID with or without the "enhancement". However, I already knew exactly what the identifiers sounded like, and might have been able to hear them in a pan of frying bacon. If you have a 'real' Sound Blaster 16 card, the DB demo is definitely worth a try." -Barry Dieser (bdieser@worldnet.att.net) tells us about a cheap and easy direct conversion LF receiver he's been playing with: "I would be very interested if others would try it, and state what results they are getting. This circuit was inspired by a DC receiver for SW that I saw on Harry's Home Brew web site. After thinking about it, I felt the same thing could be done with a center-tapped audio transformer. It seems to operate within the range of 15khz to about 60khz. The transformer is Radio Shack part number 273-1380. Basically, the audio transformer is being used in a LF mixing circuit, making a direct-conversion receiver. (There may be better transformers to use). Tune by varying the AF generator. Below 15khz, you start to hear the AF generator. The 60khz upper limitation seems to be the transformer itself." "The amplitude of the AF generator is critical, you need to play with this. Adding a VLF active antenna to the front end of this makes a big difference. I have a quick and dirty FET one I have used. You can extend the range of this circuit much lower by using a low-pass filter of some kind on the output. In my case, using a DSP 59Y proved quite effective at allowing me to tune down much further. Again, I would be interested to see if anyone else gets results with this." The schematic is N56PIC1.GIF . -Bill de Carle (VE2IQ, St Adolphe d'Howard, QC; bill@ietc.ca) had good results with his COHERENT software this month (actually Ver. 7.3 by the time he wrote), and offers some observations on computer-related noise levels when using digital modes. Logically, if software can detect signals that are below the apparent noise level, it can detect noise that's not readily apparent to the ear, also. "I set the trap for STLMO again last night and this morning my TRACE.LOG had lots of copies of STLMO - I was using COHERENT v.7.3a - there is a slight improvement in the SYNC code, I now synchronize the start of a sync period with the start of an ET1 frame, so all the bits in the frame are in the same 30-second period. Dunno if this accounts for the better performance or not." "Couple of comments regarding sniffing out ultra weak ones on medfer band... "1. Any computer you use will put out *lots* of RF on the medfer band. You may not be able to hear anything directly by listening to the radio, but you will probably be able to detect an increase in the noise floor whenever a computer is operating (or sometimes just plugged in!)." "2. In my experience laptops put out less RFI than desktops, so I use a laptop when trying to log STLMO on 1690.798 Khz. The Pentium-based Compaq is so bad I cannot use it at all on that band. It's not so much the computer itself, it's the mains power supply - whenever it's plugged in there is a subtle increase in the noise floor all through the medfer band - Compaq seems to have found a way to reduce the noise on any particular spot frequency by spreading it around evenly." "3. For medfer snooping, I use an older laptop from Radio Shack. But I had to get rid of its (switching) supply and replace it with a homebrew linear supply with lots of ferrite beads and bypass caps." "4. The LCD on laptops will emit lots of RFI - if it is anywhere within range of your antenna you will be picking it up. I found that the RFI can be nearly eliminated completely by turning the laptop for minimum noise, and then by closing the cover so the LCD is horizontal. When the cover is open at 90 degrees (normal reading position) - the RFI from the display seems to be at its maximum. My pickup antenna was a long wire (horizontal)." "5. The general idea is to make sure your radio is responding to what comes in from the antenna site, not stuff coming in via the AC power cord or leaking into the coax from strong noise sources inside the shack. It helps if your antenna is far away from the shack. It won't make any difference to the strength of the DX signals you want to receive (they've already travelled a thousand miles anyway so another couple hundred feet isn't going to matter much) - but it will attenuate the "local" RFI from your computer a lot because those fields fall off rapidly with distance from the source." "6. Don't assume just because the 1690.798 frequency sounds "quiet" that you aren't polluting it with noise from your own shack. You can check it easily with the FFTZZ program in integrate mode. Also look out for weak carriers you can't really hear but are near-by. One such is a signal radiated from the S-D board itself. Shield that board, and use a good shielded cable to carry the RS232 signal into your computer's COM port. If not you will hear every byte that goes through it!" "When you have a really quiet frequency and a narrow filter it's amazing what weak DX can be copied." And, as this column was being readied for printing, Bill sent a nice summary of changes in his MeFER beacon, which should make it easier to copy this year: "I just finished installing MedFER beacon 2IQ up on the mountain and it is now operating under its own power (solar panel plus a bank of wet ni-cad cells, suitable for our minus -40 degrees winters, HI). The old 2IQ on 1606.25 has been de-commissioned. Here are the details on the new beacon: Frequency - 1690.591 Khz; Mode - BPSK MS50 ET2 - run length 16 characters; Operation - Continuous." -Donald Moth (MPK, W2MPK; Chittenango, NY) checks in to say his MedFER beacon continues on 1641.5 kHz, and that his LowFER should be back on, using 177.9 kHz, soon. "I am installing more radials and improving the antenna," he notes. "Have heard RGQ on 1703 several times so far this fall. Looks like it may be a good year." Don reports Howard Mortimer's ZWI is still on 178.6, about 20 miles from Don's QTH, but says he hasn't been hearing SVZ, which is only 5 miles away. -Pierre Thompson (RI, KA2QPG; Rifton, NY; pthomson@bruderhof.com) considered potential problems from the Icelandic LF broadcaster, and decides he's not pessimistic about it. " We have a few defenses: "- Loop antennas - good ones can provide 30 dB nulls. "- Filtering - with a good tight filter tuned to TH, you'll only hear the 360 Hz portion of the Icelandic program; sometimes there will be very little energy right there. "- Propagation variations - Iceland is often within the aurora zone so it will not always be booming in. Also the sun rises (and the D-layer absorption kicks in) hours earlier in Iceland than here. "Also, aren't the channels 9 KHz apart, like 162-171-180-189? That might leave a little gap around 184-185 free. That's right where my RI beacon is (184.320), so listen for it!" He also passes along this update on RI: "It's October 1, and the RI beacon is running again. The frequency is 184.320 KHz and the CCW speed is 6 wpm (100 ms), though that is subject to change. I am getting about 6 dB improvement over last year's radiated signal, due to a better loading coil and reduced near-field foliage. I still hope to squeeze a few more dB out by increasing the ground system and further cutting back the vegetation close to the tower. Thanks to Bill Bowers (OK) for the coil materials and the neat antenna current sampling circuit. It sure makes tuning easier if you know what the current is doing!" "I drove about 10 miles out this afternoon, and still heard the beacon clearly on a Zenith Trans-Oceanic, using the built-in rod antenna. With a good LF receiving setup, it should be audible much farther away. Maybe this season I'll get a reception report ?!?! 73 & good listening." -Jim Mandaville (Tucson, AZ; email: zygo@azstarnet.com) checks in after several months' absence with some excellent notes on whistler listening in the desert. "I'm been settled in southern Arizona since March 1995 after leaving Saudi Arabia and several years of natural radio observing there. Last month (16-21 August) I finally unpacked my trusty Bill Forgey design (Mark III) whistler receiver and gave it its first whiff of North American ether during a camping trip up into that part of northwestern Arizona known as 'The Strip.'" "This is still one of the most remote parts of the State, with access from the south cut off by the Grand Canyon. As I had hoped, it turned out to be very quiet in the natural radio part of the spectrum. Some high- voltage power lines run across the northern part of the area paralleling the Utah border, but for the most part, the few scattered ranches in this district are still without commercial power." "I certainly missed the feedback shielding of my old aluminum-bodied LandRover, but found reception in my new non-metal pickup shell possible with care. Antennas tried included ham band verticals mounted on the truck roof (which worked fairly well), and a 20-foot horizontal from the ham mount out to a 12-foot pole (which considerably increased the signal- to-noise ratio)." "And results proved that summer need not be whistler-barren. I heard at least a few whistlers every night except one, where camp was in a rather deep canyon. Sunday morning, 17 August, brought long swishers before dawn, without causative sferics. On Monday, 18 August, there were long, low swishers 45 minutes before sunset. Each of these followed a very strong and distinct sferic that stood out from the other background noise." "On 20 August, just after 6 p.m. local time there were several very discrete and clear (if not very strong) whistlers, one of which I caught on tape. Manmade noise in this area was virtually non-existent, although one night I heard intermittent tones of about 800 Hz (each about one second long, at about 10-second intervals). These I assumed were Omega signals beating against some other carrier to bring them down into my personal audible range, which hardly exists above 2000 Hz!" "I'm afraid the whistler bug is biting again, and I look forward to the winter season, other trips, and hopefully some coordinated listening with other observers." - Speaking of Omega signals, Stephen P. McGreevy (vlfradio@triax.com) describes the shutdown of the Omega system, which occured on schedule, September 30. He also has additional interesting whistler observations. "I got a nice recording of Omega's last beeps and also two nights of nice whistlers too, especially this morning, 01 October, between 1100-1330 UT. There was also some intermittant dawn chorus starting at about 1230 UT and going until after 1500 UT - I had not yet caught chorus this summer or full until now, so I was really glad to hear some chorus even though it was not very strong, and overall a really nice 2 days of whistler listening. Many whistlers this morning (October 01) had echoes too! The whistlers seemed to be generated by fairly nearby lightning - not too local but within 1000 miles." "I have found that indeed (and this is shown in a more recent book on magnetospheric physics), whistlers don't follow exact paths and congugate points at all! Often, loud whistlers at any locale may be generated by lightning somewhat far away (1000-2000 miles perhaps) while more closeby lightning is NOT generating the loudest whistlers (which may be loud 1000 miles away somewhere else!) Listening since mid-august has given me quite a bit of observation in this regard and countless examples on tape. I mentioned this somewhat subjectively in my VLF Story I wrote a few years back and I'm even more sure of this. Sooo, Mexican or Montanan lightning may make LOUD California whistlers, and at the same time California lightning may make for loud whistlers in Colorado or even Kansas (to use a scenario). Certainly, there are times when nearby lightning does make for the loudest whistlers, but this is more infrequent in my observations than the scenario above." "Anyway, back to Omega's shutdown. I started recording at 0257 UT 9/30. I made a WWV time check at 0259 on the tape and then let it run with the WR-4b whistler receiver set to high-pass--lots of Omega into the tape recorder. At about 0259:30, Omega D (North Dakota) shut down, leaving Omege-C Hawaii going for about 4 more of its cycles. About 0300 (or within a few seconds) and after its first of two 11.8 kHz beeps, Omega C went off. Both D and C did not shut off abruptly, but did a sort of 'fade-out' over a 1-2 second period. Interestingly, going over the tape in slow motion revealed a third Omega station running on until a minute or so later - the 10.2 kHz beep was noticed. Probably H-Japan, the next strongest station here in CA usually. By 0301 UT, all that was left was the Russian Alpha system - short beeps in clusters of three beeps, a pause, then three beeps again in downward frequency steps. Russian Alpha is much weaker and higher up in frequency (up to 14.1 khz) then Omega was and has a far lower duty-cycle, and so the natural radio band is really MUCH cleaner sounding suddenly! It's also fun to observe Alpha propagation - I guess the strongest one I get is from Siberia--it is stronger toward sunrise than at any other time of the day by 3-6 dB or so." "There are supposedly three stations in the Alpha chain. Do any of you fellows know of info on the Russian Alpha system - locations, frequencies and format? Certainly, Alpha is going to continue for a while and it is going to be noticed by some listeners even though it is fairly weak. I'd like to put Alpha information into the VLF Listening Guide replacing the Omega info." Be sure to check out Steve's Web site: http://www.triax.com/vlfradio/index.htm . -John T. Reed (jtreed@poncacity.net) reports, "This morning (Sept. 30) I heard the first MedFER of the fall 97 season. MIN was heard clearly on 1641.95 at 1127 UTC. Reception was on a Harris RF-590 with 150 Hz filter. I traded my Watkins-Johnson for a pair of Harris receivers, an RF-590 and RF-550. The digital noise and filter tests as outlined in Part II of my series on receivers convinced me that an analog filtered receiver is superior. The 590 seems to be an excellent receiver. No spurious responses and it is quiet and sensitive. I installed the 150 Hz filter. Measurement of the weak signal performance on this combination comes out to -86 dB. That's the best rating yet on all receivers I've tested." -Jack Sippel (Lenexa, KS) sent information and pictures this month on the Maple Hill, KS, GWEN site. These should make for a most interesting article later, and will probably appear in some form or another on the Web site. He also passed along word that version 4.1.2 of the famous Spectrogram program (this one optimized for Windows 95) has been uploaded by its author, Richard Horne, at: http://www.simtel.net/pub/simtelnet/win95/sound/gram412.zip or its FTP alternative, ftp://ftp.simtel.net/pub/simtelnet/win95/sound/gram412.zip. It may also be made available to us in the Longwave Home Page file library. (By the way, Jack's amateur call sign is now KU0KU. You might suspect that he is a big fan of the University of Kansas Jayhawks, just up the road in Lawrence.) -Darwin Long IV (DJL; djl4loons@aol.com) announces: "I finally got my web site up and running, on which I have included a section about my beacon DJL. Anyone logging on will be able to see pictures of the transmitter and antenna system, listen to .wav files of the beacon's signal, and leave reception reports for QSL. It works best to use a browser like Netscape Navigator, to prevent the pictures from blurring. The address is: http://members.aol.com/DJL4loons/DJLhome.html". -Shawn Axelrod (saxelrod@hydro.mb.ca) draws our attention to an interesting article on the Internet this month: "A set of plans to build a four foot unamplified box loop is posted at: ftp://bbs.ks-huseby.no/html/loopant.zip.html Although made for the AM broadcast band by adding a couple windings it will easily work on Longwave." Shawn is the antenna's designer. -Bart Prater (VA, N4ZV; n4zv@aol.com) advises that both his LowFER and MedFER beacons are alive and well, running 24 hours a day, seven days a week. "So far, very little time to listen...though I have logged Todd's ABC off and on through the summer. I just finished a new longwave loop, using 12 pair telephone cable inside a 4-foot square PVC frame. Seems hot, and I'm in the process of mounting in it on a rotor on my boat dock. This should help reject Iceland and other ever-increasing QRM here at the lake." Also note Bart's new e-mail address. -Bill Bowers (OK; Davenport, OK 74026; okbill@brightok.net) asks if anyone has the name and address of who put out the SNB 1288 Noise Blanker kit. "I bought this kit a year or so ago, but am just now getting around to putting it togather.. It looks like an excellent circuit and in general a first class kit. There is an very complete set of assembly and operating instructions ( 18 pages ), but no place in the instructions is shown who put out the kit, phone number, or address? I no longer have the box it came in so I do not know where it came from." Footnotes. Thanks to all who made a fairly good size column possible this time, despite your columnist's temporary feebleness. Til next time, 73. - - -