The LF Notebook The Mailbag, News and Comments About LF Radio & Other Experimental Topics John H. Davis, PO Box 367, Warm Springs, GA 31830 -Fax/Voice: (706) 672-0964 -E-mail: johnhdavis@aol.com -Longwave/Part 15 BBS: 706/672-0360 In an old Beatles song, the tax man sang "here's one for you, nineteen for me." Well, I didn't have it quite that bad with Uncle Sam. In fact, I'll eventually get a little back. Not enough to buy any interesting equipment, mind you...in fact, barely enough to cover the tax help and maybe a payment on my car insurance...but anything at all is welcome, even if it doesn't quite justify the time spent working on it! I hope you all survived April 17 reasonably intact, too. It has been hectic enough here, but because I've been trying to start a small sideline business since December, I managed to complicate the paperwork situation further. On top of everything else, Warm Springs received a visit from the President himself on April 12, marking the 50th anniversary of Franklin Roosevelt's death at the Little White House here. The population of the town swelled from several hundred to 5,000 for one day! All normal activity ground to a standstill, I can tell you. When it rains it pours, but then when we reach the time of year that it should rain--it doesn't. If only that translated to low static levels, it would be great, but there have been enough spring storms elsewhere to offset our potential QRN drought. At your columnist's home, the era of moderate QRM may be winding down, too. Rural electric lines are not noted for being quiet, but ours haven't been as bad as most. We had several power interruptions in the last few days, though, and I just found out why. It seems our EMC is upgrading our distribution line from a relatively low voltage to the same voltage they run on the rest of their system. Oh, goody. By the time you read this, the only problem I may have with lightning static is being able to distinguish it from the corona and arcs. Now, I haven't taken much time this year to update you on operation at SEA, so I hope you'll indulge me for a few moments. I hinted once before at the reason for my transmitting antenna being relocated this year. An estate settlement resulted in my landlord splitting some land with his brother, so the far end of my back yard belongs to someone else now, and the cable runs to open areas I once used are a lot longer. That's why I tried suspending the antenna on a span between two trees. A number of our correspondents have had good success with antennas near trees, at least in winter, so I figured it wouldn't hurt to try. I think the sweet gum tree at one end was probably not much of a problem, but there are several pines near the other end, and they may have been fatal to my signal. The drawings here, obviously not to scale, [DOWNLOAD "NOTEBK26.GIF"] show the general arrangement. The antenna is suspended from the trees with small diameter nylon rope. It was placed there by means of bow and arrow, which I used to shoot monofilament fishing line first. The fishing line enabled me to pull nylon twine over the appropriate branches, and the twine was strong enough to drag the rope up. The antenna was assembled on the ground, clipped onto the ropes, and hoisted into position. The first antenna was simply a T of stranded antenna wire, as shown in the vertical plan view. Over the holidays, I replaced the single horizontal top run with a 3-wire top section, using lightweight 1" PVC pipe for spreaders. That made a vast difference in the capacitance of the top hat, but a marginal ground system at this site resulted in very little change in current, as it turned out. The whole winter's operation ended rather suddenly in early April, when my landlord decided the best way to run a water line to another building was right through my side yard, where the transmitter and (admittedly marginal) ground system were. I could put it back in service there, now that the project is done, but it seems rather pointless given the lateness of the season and its performance so far. There has been some talk of removing the sweet gum trees, in which case I could put a really good antenna in the back yard. Otherwise, I may try to relocate it somewhere altogether different next year. My receiving experiments also suffered from the estate settlement. From the present house, a cable to the big lake (a relatively quiet spot for receiving) has to cross a dirt path that runs across the dam of the small pond. I'd started work on a broadband active antenna amplifier, and a floating antenna platform, and was about to dig a shallow trench for running RG-59 in PVC pipe out to the lake. Normally, the worst traffic one has to contend with is a pickup truck once or twice a week. Until this winter. That's when they decided to log some timberland on the back 40, and it's still going on. Guess what road they have to use? Yup, you guessed it...the dirt path across the dam, which is now so wide, it takes another chunk out of my back yard. The activity also makes our Canada geese nervous, so they aren't as sociable with me as last year. (These are the ones that "migrate" a whole 2 - 3 miles from another nearby lake for nesting each year.) None the less, they've managed to produce five little fuzzy, yellow offspring so far, and there may be more to come. My MedFER activity fared better this year, but is still suffering from my own lack of time and/or organization to make proper repairs to the January lightning damage. It should remain on the air most of the summer, barring further mishaps. Shrinking boundaries, lightning strikes, new power lines, logging trucks, all at the same time. If that's not incentive to move to the wilderness, I don't know what is. But have no fear! If LF weren't challenging, we wouldn't be doing it. Would we? As the saying goes, "enough about me." We've got more important fish to fry... Reviews and Previews. Looking over the season past, I find I've gotten farther behind on letters and phone calls than usual. My apologies to all to whom this applies. Next month, I hope at last to begin our series on digital signal processing. It will commence with a general review of filters, move to discrete-time signals, and finally we'll apply it all to DSP in a basic way. Just a little light summer reading.... Powerful Tool, Attractive Price Whistler hunters, communications enthusiasts, amateur sleuths! For quite a while, now, those of us with PC-clone computers envied our Macintosh brethren the sophisticated spectrum analysis tools that were available for their machines from time immemorial. In the last couple of years, such programs became available to the rest of us, too, but at a price. Granted, that price has come down. And with versatile software such as Bill de Carle's COHERENT package, the price of digital signal processing technology is virtually negligible. This month, I'm pleased to announce availability of software dedicated to producing detailed spectrograms, at the best price of all. Free! The program is available on the Longwave/Part 15 BBS. It was written by R. S. Horne, and was sent to us by Glenn Jolly, who describes it thus: "The spectrogram program GRAM is a Windows 3.1 program useful for natural radio data analysis. It supports both 8 and 16 bit sound files. I've used it with data recorded on tape and then digitized via a Sound- Blaster Pro card. Although the GRAM program has a record feature, I've used the VREC program to produce '.voc' files and then converted them off-line with the VOC2WAV utility distributed with the SoundBlaster cards." "For natural radio recordings I record at 22050 Hz, which will reveal 0-11 kHz events faithfully. Since whistlers and other phenomena are distributed through a tremendous dynamic range (approx. 50dB according to Mideke), I would recommend the use of a 16 bit sound card. This helps greatly if you are needing to filter out unwanted 60 Hz harmonics with other utilities before running the spectrogram." Your columnist has tried the program under Windows 3.1, Windows for Workgroups 3.11, and Windows 95, and it works well with all of them. There appears to be no reason why you couldn't run it under Windows NT, assuming you have a suitable driver for your sound card. The more memory you have, the longer the files that you'll be able to analyze, and to greater resolution. The quality of the sound card will make some difference, and when you digitize your audio recordings, you'll want to save them as PCM (uncompressed) .WAV files. That uses more space, but the program only processes uncompressed files. Here is a sample screen from a test run I made with the program. The traces may look a little lighter than they did on-screen because of the various translations the image went through to end up in printed form. (In real life, you can display the result in black and white or color, and save a BMP picture of just the display area.) This particular spectrogram was made from a recording of Mike Mideke's. It exhibits fairly sharp roll-off above 8 kHz. Several whistlers are visible, mostly of the two-hop variety. It was an extremely tweaky day, too; most of the static crashes have noticeable dispersion around 2 kHz. The upper part of the display depicts the envelope of the digitized waveform, distinctly showing the amplitude of the static crashes that correspond with the spectrum display below. The denser an area of the spectral display, the more energy was present at that frequency and time. I used a 22.05 kHz sampling rate and 16 bit resolution. The scan was done with a 512-point Fast Fourier Transform, but 1,024 and 2,048 points are available for extreme resolution. The horizontal scale was 8 milliseconds per line, though one can also choose 2, 4, or 16 ms intervals. Parameter setting is quick and easy. A short but thorough "readme.txt" file accompanies the program, and is recreated when you unzip the distribution file. (This requires PK Zip 1.10 or higher.) I've had some slight success so far at visually picking Morse signals out of noisy recordings with this program. It should be good for amateur "voice prints," and the usefulness in natural radio pursuits should be readily apparent. If you want to download the file, it is GRAM22.ZIP on the Longwave BBS (phone number at the head of this column). The board supports up to 9600 baud. If you're not into modems, I can copy the file onto your BLANK floppy disk (5.25" 1.2 M, or 3.5" 720K or 1.44M sizes only), if you'll send the disk in a sturdy mailer, and include return postage and a readable return address. Thanks again to Glenn for bringing this fascinating program to our attention! On To The Mailbag... - Ed Phillips (IZJ, San Gabriel, CA) and Bill Lake (SB, Santa Barbara) report hearing a new beacon signing AA in Southern California last month. At this point, I believe Dave Curry (PLI) may also have heard it, and I gather Frank Cathell may have more information for us, though that hasn't been confirmed at deadline. Bill noted the frequency as 169.68, though Ed logged it as 170.393 on April 9 at 1655Z, with a "strong" signal. Latest word from Ed is that "apparently this beacon is in Adelanto, CA, about 50 miles from here. Still continues to be a 'boomer' here." - Robert Laney (RL, WB7PZU, Herndon, VA ) reports an antenna mishap at RL that has caused some down time since the first week of April: "Strong winds took a dislike to RL's telescoping 40-foot vertical antenna. The upper half is bent over about 30 degrees from vertical. The results of my 'trial and error' engineering would indicate that I should have had an additional guy rope on the side that generally receives the strongest winds." Initially he planned to be on all summer, except for thunderstorms, but the damage was worse than it seemed. A later message indicates: "We took down the entire mast this past weekend. The lower two sections are salvageable for a MedFER antenna, but the rest of the mast will be used for support for pole beans or will be recycled. Because the thunderstorm season is upon us, I have decided to give the LowFER antenna a lower priority and concentrate on improving my reception and constructing more efficient loading coils for a new RL beacon that I will have erected later this summer to early fall. Besides, I want to put a little more thought into constructing a stronger vertical antenna." - Stan Wilson (ALF, AK0B; St. Charles, MO) sends word of his new LowFER beacon, plus amateur interest in advanced communications modes in the St. Louis area. "I have been interested in LowFER activity for many years and enjoy your articles in Lowdown. Several years ago made a half- hearted effort to do some LF work, but was not successful. Well, this time it is a major effort with a CCW/BPSK beacon in the works. I have chosen 187.400 kHz with an ID of ALF. I have VE2IQ's circuit board and COHERENT software, and ordered the necessary parts to build up Max Carter's Super Slow receiver. I have heard that Max has a new receiver front end (see April issue), but have not seen a circuit diagram yet." "We have a ham QRP club here in St. Louis that is building or has built up about 15 of Bill de Carle's boards. So expect some activity at least on the local level. My goal is a good solid signal at 1000 miles." "I have been involved in packet for many years. Run 9.6 kbaud on both UHF and VHF. TCP/IP (JNOS) software. The ham stuff was written by KA9Q for TCP/IP. Phil is writing again, FEC (forward error correction) software, and like his TCP/IP is releasing the source code. So I expect some day in the future to be able to use it with BPSK on 175 kHz." Stan can be reached by e-mail at: randyw@crl.com. - Robert J. Fear (IA; 225 N. Boots, Marion, Indiana 46952; e-mail: rjfear@iquest.net) sends news that he has remedied the signal strength problems at IA. "I recently redesigned my antenna tuner and antenna. Looks like it took care of the awful output levels. IA is again active on 184.32KHz. I am testing some interfaces with my computer and will be running short ASCII and Baudot transmissions of test data, FSK 170Hz, at 50, 100, and 300 baud. I'll let you know if the test schedule changes. I would love to know if I'm getting out anywhere." Robert has been conducting some unusual antenna experiments lately, too. "I recently built a stacked loop antenna as shown in some old Tesla references and patents. As the articles showed, the antenna is placed (or should I say hung) below ground, preferably in water. I hung the antenna in an old cistern, basically an old water storage tank under the house. I am receiving some (what I think might be ) carriers. If any other LowFERs are using buried or below ground antennas please let me know. I would love to run some transmission tests." Although he didn't mention it, I hear from other sources that Robert may be the editor of a newsletter for AM DXers. You can ask him about it the address above, or at his own BBS: (317) 255-0066. - Jerry Peters has been working with fellow ham Pete Smith, who announced plans for beacon Z at Layton, UT, last month. "We have constructed what we would like to think is an antenna for 180 kHz. It is a 3' diameter coil of wire 10 feet long with 1/2" spacing. There is almost 1/2 mile of electric fence wire on this thing. It is constructed of four 3' circles of plywood mounted to a length of Rohn 25 tower. The circles are interconnected by eight lengths of 1' PVC pipe spaced around the circle. The wire is set in saw slots in the PVC pipe 1/2" apart and anchored with hot glue. The tower was set up vertically and the base of it is insulated from ground. The transmitter is a Curry model CW-893. Our problem is matching the antenna to the transmitter." In his message, Jerry asked about test equipment for matching to the antenna, and would appreciate suggestions in that regard, although this particular antenna turned out to be a valiant but not too fruitful effort. (See Pete Smith's letter below.) Jerry's catching the longwave bug himself, it seems. "For now I only listen a bit with a Kenwood TS-440S and a long wire. Haven't heard much of anything. Some airport beacons up 200-400 range. Very interesting band though." - Pete Smith (Z, K7ZTM; Layton, UT 84041) says they are now installing a more conventional antenna for Z. He sent a picture of the first attempt (not available on the BBS at this time), with the assessment, "the antenna turned out to be for the birds," pointing out that a bird is, in fact, perched on a rung of the tower section, inside the coil windings. The attempt was a learning experience, and may give some of us ideas for constructing large tuning or loading coils in the future. (Just speculation on my part, but I'd suspect the tower section in the coil had a pretty drastic effect on inductance, and would probably also cause an increase in distributed capacitance. Also, there's no substitute for all the height one can legally get. Something like this structure, but ideally with non-metallic supports, might do well for loading at the bottom or even top of a tower.) - Lyle Koehler (LEK, K0LR; Route 1 Box 659, Aitkin, MN 56431) says that, as of April 7, "We're still waiting for Spring. You can send it along any time you're ready. The return of QRN (did it ever quit last winter?) has shut down my LowFER reception except for BK, 0KVL and SAM. Whatever Sam (Eastey) did to fix his harmonic problem sure improved his signal. BK and I still exchange messages and have an occasional QSO on weekends. The 36th QSO of the season between XJ and LEK was made back on February 12th. We probably could have made a few more contacts, but I was battling an infection for a couple of weeks and then left on a three-week van trip to Arizona. That pretty well wiped out the LowFER season." "I took along a home-brew LF receiver and a portable loop antenna on the trip to Arizona. Unfortunately my route of travel didn't take me within ground-wave range of any LowFER stations, and the night-time QRN from the West Coast storms wiped out any skywave reception. LEK was readable and BK was still detectable out to 260 miles with my 30-inch loop. A bigger loop would have helped, but the bicycles, dog, luggage and camping gear pretty well filled up our Astro van." (No doubt an example of misplaced priori- ties. - JHD) Lyle has put the Universal Preamp article, mentioned in his recent article on loop experiments, on hold for the time being. "That will give me time to incorporate some recent circuit improvements and maybe run some field tests. In the meantime, I'll be glad to send a copy of the article to anyone who wants it but can't take advantage of the version available on your BBS." - Phillip C. Taylor (G0VSJ; 133 Beech Drive, Schifnal, Shropshire TF11 8HZ England) renewed recently, and has busy with tests that resulted in a full class amateur radio license. He says issues of The Lowdown "are received with delight. The articles are very interesting and informative. They help me to broaden my thinking in MF and down. There seems to be some rising interest here in VLF and ELF with regard to underground caving location and communication research. I am hoping this will continue, and perhaps one day we will be allocated a frequency, or better still, a band slot to experiment in." "I am about to start building a coax loop with L/C tuning and a preamp as an experimental starting point." His plans for the year include more building, participating in radio club activities, and attending a hamfest at Stafford in August. Phillip mentions a recent TV program on electrical storm activity that he found "totally absorbing." It reflected some points pertaining to natural radio, sprites and blue jets, photographing lightning strikes, and such. Footnotes: I had planned to fit in Rick Wright's LF proximity detector project this time, but I think we'll hold off until June. Enjoy the rest of the springtime, and don't forget to send your news, ideas, tips and suggestions! - - - ____________________________________________________________________