(From The LOWDOWN, August, 1997) "The LF Notebook" The Mailbag, News and Comments About LF Radio, Etc. John H. Davis, Box 367, Warm Springs, GA 31830 - E-mail - longwave@mindspring.com -World Wide Web - http://members.aol.com/lwcanews/ [ TWO PICTURES ACCOMPANY THIS ARTICLE: ] http://frodo.bruderhof.com/longwave/notebook/n53pic1.gif http://frodo.bruderhof.com/longwave/notebook/n53pic2.gif *Summer When It Sizzles. Late in June, while the July column was still in the works, your columnist actually had to use heat one night that week. But no sooner did the column go out than air conditioning became a daily way of life. Our traditional three days of spring arrived and left in June this year, instead of April. At last we're joining the rest of you in heat waves, tropical storms, all the things that make summer the refreshing, restful time that it is. No catastrophes at work this time during column preparation week; at least, if you don't count having to capture and find a home for a young nanny goat. The lack of obvious trouble should have made me nervous, because while I was lulled into a false sense of security, my once- faithful Epson laser printer was conspiring against me. After four and a half years, my toner ran low. It got low enough that I started getting error messages which kept me from printing. At least, I thought that was the reason. Naturally, I installed a new cartridge, and expected the error message to go away. Nope! It got worse instead. After a long night of struggle, I reached the point where I appeared to be printing OK once more, so I got back to work on the column itself...now a last-minute chaotic chore (as usual) instead of the leisurely, well-organized project it started out to be for a change. So, that means a few changes of plan, as we try to persuade something, anything, to come out of the old clunker. I think we'll manage to squeeze most of the material in, but in case we don't, there's always September! Life would be dull if it got too predictable. Little danger of that happening here. *E-mail Advisory. Just a reminder about my recent policy of acknowledging receipt of all e-mail intended for this column. It may only be a short "thanks" or "hi there," but if you don't hear back from me within 48 hours of sending e-mail, you should assume I didn't receive your message and try again. Numerous outages and delays all across the Internet are making it distinctly less than reliable these days. *The Home Page. Not many updates to the Web site in June or July, sorry to say, but we have plenty of files to place there as August progresses. Jacques d'Avignon, for instance, is helping us put together an archive of LF signals that are falling by the wayside as technology marches on. Recent LOWDOWN articles are waiting to be added, as are more interesting links to other sites. Also remember when America Online experiences another of their classic day-long server outages, we'll make the home page and message board available at http://www.mindspring.com/~longwave/ (they're only updated when I'm aware of an AOL outage, so don't depend on that URL as your regular source of information). BPSK Update It's been a while since we heard from Cliff Buttschardt (HDO, K7RR; cbuttsch@slonet.org) with BPSK information, so it was especially great to do so this month. (Sure enough, he was even back at sea briefly.) Even though LF is not the greatest band for DX at this time of year, BPSK has been used extensively on the ham bands. "The most popular frequencies are 3591, 7081, 10141, 14091 and 18091 KHz. The 40 meter frequency looks like a missprint but it is not. We had to move down ten KHz. The standard call up uses MS25 (40 bits/second) and no ET (Error Tolerant mode)which is the default in any of the latest software from Bill DeCarle. Any version past five will not contain any CCW as all the emphasis is on BPSK now." " Another craze using COHERENT is the use of lasers for a transmitter. Especially active is our own AA1A who advocates the use of a subcarrier of 160 to 190 KHz (on the optical "carrier;" see Dave's information later in this column). Nothing wrong with that notion for the LOWFERS." "The HDO(null) beacon remains on 167.65 KHz which is a good place to start if you need a signal on BPSK using MS1000." "Johan Forrer, KC7WW, is the moderator of the HF special interest group for TAPR and has joined us in BPSK experiments. Most of the activity occurs on 7081 at about 0230 UTC. We seem to have North American coverage then (including a pesky Mexican phone station). Johan is very advanced in most techniques and is attmepting to find a better modulator for BPSK since that modulation scheme is inherently rather broad. Also, I learned that (Bill) DeCarle has been comparing notes with G3PLX in the UK. J.P. Martinez is the father of the AMTOR system now extensivly used. Something good will come of that!" "Back to the TV for more Mars pictures!" Powerhouse of the Rockies, Revisited Last month I asked if anyone was familiar with the Navy FRT-72 transmitter, soon to be used by our friends at WWVB to triple that station's power. Sure enough, David Emsall, a recent addition to the member rolls, had just the sort of information we were looking for. (There's also a letter from him in the Mailbag section.) As it happens, the transmitter was made by Continental, and appears to have been at the height of its popularity in the late Sixties. The data sheets David sent were from NAVSHIPS 0967-420-0013, Directory of Communication Equipment (Supplement 3), dated 1968, which includes a lot of equipment of that era. As he notes, "I don't think you'll be hauling one of these home from the local hamfest in the trunk of the family car." That is, of course, unless you've got the suspension to handle 17,720 pounds! Or, to put it another way, 8.86 tons...or 8050 kg...or just generally a heck of a lot of weight. It's built like--pardon the expression--a battleship. I wish I could reproduce the photo a little larger here, but this was about the most I could manage without Moire patterns. (This one will be a challenge for our printers: a medium-resolution laser printer halftone, from a scan of a photocopy of an image from a 30 year old book!) The unit basically consists of two complete transmitters. The Class AB RF amplifier, power supply, and exciter and control circuitry for transmitter 2 are on the left; followed by the exciter and control circuits, power supply, and RF amplifier for transmitter 1 on the right. The original gear was intended to operate over the range of 30 - 150 kHz. It was designed to supply 50 kW average power for steady carrier, FSK, on-off CW, etc. For AM, carrier power was 25 kW. And for any mode involving single-sideband, dual independent sidebands (telephony, data, or a combination), or other suppressed carrier modes, the gear was rated for 100 kW PEP. Frequency stability was mighty good, too: 1 part in 10^8 over 24 hours! Of course, the oscillator and modulator sections are being replaced with custom gear for NIST purposes. [The transmitter photo is n53pic1.gif.] Beginning To See The Light Last month, we mentioned a unique mode of experimenting that simultaneously involves frequencies from LF to light, currently being practiced by Dave Riley (1A, AA1A; Marshfield, MA; daveaa1a@ssih.com) and other laser enthusiasts. He writes: "Although LowFER has gone away for this summer here, there is work with BPSK Coherent and on laser too. You may read through this message I sent on the laser reflector (the Internet message reflector for the laser special interest group, that is) and see some possible good uses for LowFER Band." Modulating a light beam with what amounts to subcarriers is not new. But Dave has taken to modulating them with the kind of signals we're already familiar with on LF, even using familiar LF gear in the transmission and detection of signals. It's certainly an intriguing concept. I don't really know any better way to present it than in the form Dave sent it beginning this spring. "Well, after the flurry of activity caused by K3PGP et al, I finally finished up a long thought out project...a Laser Transverter that handles Wideband, SSB, CW, Data, ??? After taking a clue from my ham band 10 GHz transverter, I decided what with limited parts on hand and a love for the least common denominator approach, I would try the following (showing the analogy between the 10 GHz and laser transverters): 10 GHz. Transverter = Laser Transverter =================== ================== Antenna 1' dish = 4" lense receive Colimated 5mw diode transmit Receiver Ku Band LNA (reworked) = Pin Photo Diode Mixer sma 10gHz mixer j-fet preamp,Vlf converter I.F. Gasfet preamp into IC-706 into IC-706 receiver any mode.. Transmitter IC-706 @ 146 MHz = IC-706 @ 4.040MHz Mixer same sma and gasfet preamp Attenuator, sampler, DBMixer L.O. is same brick L.O. is same as one above. Output 1/4 watt amp., 1' dish = NPN series modulator into 5mw 650nm laser diode. The thing that makes this fly easier is a RF sensed remote mast mounted type preamplifier. I send +12 volts up the RG-58 in each case to power the RF switch, Rx/Tx. It makes a remote setup easier and it's nice to be in the car having a QSO just like it was 75 meter AM. Have also used a set-up like this on the LOWFER band 160-190 kHz. Guess you could say the IC-706 is good for D.C. through light. "This was fun and now am ready for some springtime hilltop QSO's. FN42/41/51 anyone? This mode is a GREAT no-code license free ham band eh?" In case you're still a bit baffled by all this, don't be concerned. That's the nature of following exchanges on the Internet when you don't have all the intervening material. If it hadn't been for the current printer difficulties here, I'd planned to try to organize the topic chronologically, and add some notes. But keep reading. It becomes clearer with additional explanatory material Dave posted: "Am currently building a basic universal RF switched transverter for the IC-706 with dual Balanced Modulators that will supply 0-500kHz at 1mw, in any mode, for transmit and likewise receive down into the noise. This is all similar to the last set-up explained in previous messages to the list, only full duplex." "If the LowFER head is plugged into the switcher, then I can receive and transmit 160-190 kHz, any mode, with 1 watt output. An E-Probe on the receive channel and a loaded wire or flat-top for transmit antenna makes portable work easier." "If the LASER head is plugged in, then I receive light from baseband up to 500 kHz+, and transmit with 3mw coherent diode with any mode from the ICOM. With Coherent/BPSK in mind for adding to the above, one can truly say that the ICOM-706 covers DC to light with a few small transverters." "I am planning to use the L.O. out of the ICOM so that 'netting on Coherent' will be a reality. With the optional TXO, things stay nice and stable for Coherent. Even the stock unit is good once the offset is known." "Thanks to VE2IQ for the neat software and ideas. You can get his version 6.0 Coherent BPSK software and other neat helper programs from his site: www.ietc.ca/home/bill/bbs.htm He also has some pre-made sigma- delta A/D boards to make life real easy as far as interfacing your radio to PC." "June 97 Update: The Burr-Brown chips with their trick circuits are doing better than I figured. The first attempt was with 10 MHz RF and it was real hot. The daylight saturated the amp. Al's idea of lower resistance worked well and the feedback op177 sure did make a nice AGC. The dark test will see the s/n differences though. It seems we have the transmit power, receive gain and large enough 'antennas' to do some serious work." "The thing I still find worth some thought is the aiming. With the help of some micrometer X/Y tables from a flea market and some surplus 4X rifle scopes, it seems fairly easy once you find a stable platform (stone wall, rail, etc). I'm looking for some old camera pan/tilt heads to put the laser stuff into. Will try drive belts on the micrometers from some small dc motors or servos. Can hardly wait to try the ccd camera attached to the rifle scope to remote aim/view." "As for the transverter, here is a talk- through of what I did here. Take any ham rig HF through UHF, build a RF power sampler/detector, two way double balanced mixers, a diode modulator, photodiode and associated op-amps, and a local oscillator. Now, there are as many ways to do this as there are readers. Here is how I do it at this end for narrow band subcarrier QSO's/data." "An Icom 706 presently is running as a 4 MHz I.F. which equals 0 Hz; 4020 kHz = 20 kHz, 4067 kHz = 67 kHz etc. I can get sigs up past 500 kHz (4500kHz) but they get dim because of the photodiode bandwidth. The 20, 40, 67 kHz etc. frequencies are fine and you avoid a lot of ambient light and 60/120 Hz noise." "Here is a signal flow from the IC706 in transmit mode then in receive. The transceiver is keyed in any mode at 4 MHz. It delivers 10 watts to a converted mast head VHF pre-amplifier; which, upon detection, puts the relays in the transmit mode, provides a dummy load for the 706, and uses capacitive coupling to deliver 10 mw (+10dbm) to a double balanced mixer that has a 4 MHz xtal oscillator looking into the L.O. port. On the output of this mixer is your original 4 MHz signal plus modulation." "So, I pick 4.020 MHz transmit frequency which will send a milliwatt or so of 20 kHz signal out of the mixer with the same modulation impressed upon it as the original 4020 kHz signal had. This new 20 kHz (say, SSB) signal is now 1 milliwatt, and feeds a simple NPN transistor amplifier set to directly modulate the laser diode." "I pick an idle current of 50ma on these diodes of the 3-5 mw variety. Modulate them at the most linear setting since the diode output is not very linear or pure by itself. Now you have transmitted your HF or VHF rig out onto a light beam that is coherent. (Pick your own I.F. and L.O.)" "OK, someone picks you up with the same setup, and here is how the signal looks coming back. A beam of light is shining onto the Photo Diode, amp, and output is a 20 kHz signal with upper sideband attached. So the original VHF amp is replaced by a DB mixer and it's L.O. is the same 4 MHz as in the receiver.. Now there is no RF to key my former mast head pre-amp, so the 20 kHz signal goes through the receive side of the mast/amp. The mixer spits out 4020 kHz, with sideband just like what came out of the transmitter originally." "The next generation baseband transverter will be 10 MHz, by taking the 30MHz very accurate oscillator in the IC706 via a source follower, delivering 30 MHz to a divide-by-3, and deriving 10 MHz for L.O. for baseband." "The reason for this is the Integrity of the L.O. in the 706 is plenty good enough to 2x BPSK work on HF with VE2IQ, K7RR, K0LR etc. Believe me, watching a screen print good data while hearing only white noise in the speaker is spooky." "So you want wideband for TV or Data?? Use a Gunnplexer (non-radiating) and watch the bandwidth grow, but we are into DX here with the least effort approach for mileage. An E-Probe Antenna (10kHz -500 kHz) applied to the modulator sends that band across your light beam and comes out at the I.F. frequency, thus giving you a free LowFER converter. (Go ahead and transmit on 160-190 kHz while you're at it.) Also using Coherent (BPSK or CW) sigs for another several DB's in case you really like WEAK SIGNAL DXing." On To The Mailbag - John L. Sielke (N4JS; e-mail: n4js@amsat.org) is a new member. "I joined up, and just got my July Lowdown. Very interesting. I also ordered the Curry Electronics CW Transceiver, so come cool weather, should be ready to go. (I enjoy putting stuff together). I have a spare Autek QF1 to use with it. May even think about beaconing on 184.4 KHz." "Anyway, new fields are the spice of this radio hobby. I really would like to make some two-way contacts on LowFER, if there is anyone around South Jersey, Delaware, Maryland or Pennsylvania who wants to try." - David Emsall (156 Sunset Ave., Amherst, MA 01002) furnished the technical data on the "new" WWVB transmitter that we published earlier in the column. He apparently has quite a collection of manuals for gear back to pre-WW II times. "I've been a member of the LWCA for just a few months," he writes. "I find the Lowdown informative, far and away the best publication of the clubs I am familiar with. The active members really contribute solid material to the magazine: loggings, technical articles, and correspondence, all of which helps one keep in touch with the hobby and feel a part of it. Consider just the labor of love that is Ken Stryker's beacon directory!" "I'm slowly putting up more and better antennas (you can never have enough), and rigging up a nice shack and workshop after a long vacation from hamming and monitoring. Priority #1 now is clearing branches away to make way for the wire. I hadn't noticed there were so many trees out there before." "By the way, the latest Arcron Zeit ad shows their little table model (WWVB-controlled clock) at a new price of $100, quite affordable. Neat stuff." David hopes to be an active contributor to the club and to the LOWDOWN, which will be most welcome. It's member participation that keeps things interesting. And we certainly thank him for his timely data on the AN/FRT-72A gear, too. - Lyle Koehler (LEK, MIN, K0LR; Aitkin, MN; k0lr@emily.net) reports this month that "LowFER beacon MIN is off the air and will remain off indefinitely. LEK and MedFER MIN are still operating continuously, except for brief shutdowns during thunderstorms." "I'm currently in the process of trying to sell the hobby farm. If I'm successful in selling the farm, it will undoubtedly have an impact on my future LF activities. No takers on the farm so far, though. There don't seem to be many buyers who are impressed with the fact that this is a great longwave DX listening site." We certainly hope that if Lyle does sell the farm, he will be able to find another good LF site. His contributions to the hobby are far too valuable to lose for lack of a QRM-free QTH. (I told him I'd be interested in buying the farm for its electrical quietness, if he could ship it to a warmer location. So far, his usual ingenuity hasn't come up with a solution, though.) - Pierre Thomson (RI; Rifton, NY; pthomson@bruderhof.com) has been taking advantage of the summer to prepare for the next beacon season. "The RI beacon (184.320 KHz, grid FN21) is nearly ready for testing. However, it will only go on the air continuously on October 1, after the thunderstorms have diminished. We had one here last week that would have fried the beacon for sure. The hill where the antenna is located was struck twice, causing damage to phones, computers, and other electronics in a quarter mile radius. I was glad the RI transmitter was disconnected and sitting on my workbench at the time!" - Robert Laney (RL; RLLaney@aol.com) says, "Wish I had a lot of good stuff to report on my Lowfer activities. Unfortunately, RL has been off the air more than it has been on since the thunderstorm season began. However, last weekend I got the last of the rotted pressure-treated posts replaced that are attached to the antenna guys. So, I guess that is some news. I was shocked how rotted that wood can get. A good T-storm puff and the whole thing could have come crashing down. Haven't had all that many storms, mainly potential threats. In fact, our lawn is getting pretty dry in places and could use some summer rains. Hope to report more later in the summer." - George Griffiths (Sutton West, ON, Canada) used computer simulation and some toroid inductors from switching power supplies this past winter, to devise a sferics receiver that shows promise of being usable in a residential area. It's no easy feat, of course, considering the hum levels involved, but a strong front end with brute-force filtering of 60 and 120 Hz just might help. I wanted to bring you details of his work in progress during the spring. But I'm embarrassed to report that the software crash in May resulted in the notes he sent --which I only had in electronic form by then-- apparently being lost forever. I've been able to recover George's diagram, though, and it is fairly self-explanatory. The first version of the circuit was mounted (if I recall correctly) with a whip antenna, located atop a TV antenna mast. Hum harmonics up to 3500 Hz or so can still be significant, but various types of sferics were present as well. By powering the unit from indoors, and using a stereo audio frequency equalizer, one can try sferic hunting in relative comfort. The same technique could presumably be applied in the field, with the antenna/preamp/filter at some electrically good location, while the observer retreats to a bit more creature comforts. [The diagram is n53pic2.gif.] Footnotes. If you are reading this, it must mean we managed to coax all the pages out of the ol' Epson in time to get to the Post Office after all. I don't know if that's a great relief to all concerned, but it certainly will be to me! In case you wonder why it sometimes sounds as if the introduction to this column is the last thing written, instead of these conclusions, that's because it's often really the way things work out. I assemble the rough structure of the column...individual e-mail and postal messages, news items, feature material...into the file as the month progresses. But it's all usually random. During column preparation week, I do overall formatting, summarize some passages, reorganize material, etc. Right before printing it out, I write the introduction, then do a final tweaking of how material fits on the pages. These farewell greetings are sometimes the last thing written, if there are a few awkward extra lines to account for, or material unexpectedly has to get bumped; otherwise, they are actually next-to-last. (This month, part was written before the intro and part was added after. For instance, I had to bump the CONSOL material from Don Schimmel one more month, so I'm also postponing a letter from Greg Hardison dealing with the same subject. We'll try in a future edition.) A personal note, at risk of not being very humble for a moment: On June 27, Mr. Answer Guy won third place for Humorous Column in our division at the Georgia Press Association Better Newspapers Contest. As many entries as there were this year, I'm pretty happy about that. (I've got mixed feelings, though, about professional entertainers that same month who "borrowed" four jokes that appeared on the Mr. Answer Guy web page. In a way, it's flattery. But still....) At any rate, I'm very pleased by the GPA results. Shows they have good taste in bad humor. Enjoy your summer, and let us hear from you soon. 73. - - -