K7JEB AM Log: 02 Aug 2006 - 01 Sept 2006 Summer doldrums - QRN, QRM, crummy band condx and busy work sked - stretch this out to a month of logbook entries. 08/02/Wed Run across Ken, K6CJA, and friends KA9UDA and WA6MTZ on 3880 in a kind of pre-AMI-net get-together at 5pm. Go down to 3870 for the AMI net hosted by Skip, K6LGL (Little Green Light), on his Globe King 400 (I think). 08/03/Thu Early-morning chatter on 75M SSB nets. Consistently impressed with how well Frank, KB7SWQ, does with his 200-ft longwire stretched out into a empty area next to his mobile-home park and fed against a chain-link- fence counterpoise. 08/04/Fri 7293 offers a rare opening for short skip. AE8O is on with his Valiant and bemoans the tendency for the wafer switch in that rig that is used as a plate loading control to switch in fixed capacitors to get chewed up by operators switching them "hot" - while on the air with the transmitter. Ted, WA6TJN, envisions some kind of scheme to blank the RF output when the switch shaft is turned to prevent this chronic damage. Another Valiant mod, replacing the fused, two-conductor line cord with a three-conductor one and moving the fuses to chassis-mount fixtures, prompts Damon, W7MD to relate some "interesting" experiences with the old arrangement. The big sticking point seems to be drilling the holes in the chassis for the two fuse-holders. Everyone in the Phoenix Metro area is breathing a little easier with the apprehension this morning of two individuals believed responsible for a string of sniper shootings. 08/05/Sat Listening on 160, George, W8QBG, is heard on 1885 giving his Bauer 707 its on-the-air maiden voyage using an external driver in the form of a Yaesu 900 transceiver. Sounds good over here in West Phoenix, but audio is a bit rough without the Shark processor in-line. One thing at a time. 3855 has a very respectable turnout of 10 stations between 0611 and 0822 local time. Ted, WA6TJN, advises he is revamping an old project of his for display at a local museum - a plasma speaker. Dubbed the "Singing Arc", it sounds like one of those things that has to be seen to be believed. And it demonstrates some interesting principles of physics as well. George, W8QBG, fills us in on the Bauer progress. Next step is to "critter-proof" it by installing the front door and bottom screen -- very important given its location in George's 'Studio-B' garage. The other Ted (Arizona Ted??), WA8ULG, bemoans the difficulty in checking into the AMI Net on 3870 using his vintage Hallicrafters SX-28 receiver and trying to hear NCS through the "Southern Moss" SSB QRM. He also reports a real "find" at the Williams hamfest - a 3-band professional audio processor for $25. W7MD, Damon, reports working the designer of the Multi-Elmac series of transmitters (AF-67, AF-68), Evangelo Diamantoni, W8ERN, and sending him the now-semi-famous ER picture of the W7MD/7 mountain hideaway operation using one of Evangelo's AF-67's. Len, W7PLR, checks in from Tucson with his "miracle antenna", another long-wire fed against a chain-link-fence ground. AL0F, Tim from Arivaca, reports that Wes, W7UO is on the road in the Western US with his motorhome. Art, KB7LOQ, is on with a TS-850 acquired at Williams and sounding good. He advises that Bill, K7VZP, is in the process of moving to a house in Sun City from his long-time QTH in North Phoenix. Looking forward to hearing the KW-1 on from out there in golfcart land. WA7LYO, Greg, is on with a bright-sounding B&W 5100 acquired at Williams. 08/06/Sun More listening on 160. Hear W8QBG testing the Bauer at two power levels - 'A' and 'B'. Hmmmmm. Wonder what 'B' reads on the wattmeter. Seeing some positive carrier shift on the S-meter from him, but it could be selective fading. More talk about getting just the right shade of enamel from that smelly emporium of coatings, Space-Age Paints. 3855 - Shep, W5EOE, advises that his daughter is joining the Coast Guard to be involved in search-and-rescue operations (and not radio comms??). He also mentions that he has purchased a riding lawnmower and is cautioned not to break any speed-limit laws with it. Can't get over how well Shep's fixed, wire yagi antenna works in putting a signal across Phoenix on 75 meters. Doesn't do too well hitting the folks in Colorado or Idaho however. More discussion on making it reversible. K6EC, Bill in Riverside, checks in with his homebrew transmitter that runs a pair of 813's modulated by a pair of triode-connected 813's. Good signal strength and modulation depth but audio response is a bit bassy. WA6TJN concurs with this, but EC-Bill is encouraged to check in again and not pay too much attention to the 'golden ears' on frequency. John, WA6JUS, continues to pursue his bluegrass muse and is off to church this Sunday. 08/08/Tues Nite 144.45 Mc AM Net - W8QBG has repainted the Bauer door and mounted it. Next: put the Behringer 'Shark' mic. preamp/limiter in-line. George has also mounted a crystal socket on the front of the massive internal vertical chassis/panel that holds the Bauer circuitry. Stock Bauer configuration had the crystals accessible only through the rear door. George plans to use the Bauer's oscillator/buffer/driver chain to drive the finals as well as an external exciter. Jim, K7SC and Lock, W1ZD compare audio on some of K7SC's collection of 2M, vacuum-tube transceivers and conclude that the Clegg 22er has the best audio by far. 08/12/Sat 3855 - W8QBG says the Bauer is stable at 375 watts on 160. His audio chain is coming together, but "helpful" suggestions abound -- including that George needs a classic 'Elvis' microphonium (Shure 55SH) to croon into. Some discussion of off-frequency operation on the "AM Channels" of 3880 and 3870. Crystal-control is nice. Also discussed is the always-interesting phenomenon of having the chassis of various radio equipment at different ground potentials due to leaky (or large) bypass capacitors on the AC power lines. More on WA6TJN's 'Speaking Spark'. I really gotta see/hear this gadget sometime. An overnight rainfall of 1.5" gives some relief in the water-bill department and prompts an extended discussion about experiences with malfunctioning and failed water meters. Bob, NA7RH, mentions he is thinking about backing his 6DQ5 Xmtr with a linear amplifier for those difficult propagation times on 3870 and 7293. QRP is an honorable, pure pursuit, but sometimes on AM a guy's gotta do what a guy's gotta do. Later in the morning run into Jim, WA9JMU, in Fry's Electronics in Tempe. He is over from his home in Elephant Butte, NM and is doing some hi-tech window shopping with the XYL. About this same time I pick up an 11-CD set of Mozart piano concertos for what I think is $39 but which turns out to be $139 and suffer near-fatal sticker shock at the cash register. Gotta get new glasses. 8/13/Sun Shep, W5EOE, is on 3855 with his ART-13 and 3-element, fixed, wire yagi from Delores, CO. Big, big signal here. Was the Collins AN/ART-13 ever used in commercial airline service? K7JEB recalls seeing an ad in a QST of immediate postwar vintage advertising a commercial version and is vaguely aware of an outfit in Van Nuys that converted them to crystal control. Another vague recollection is seeing one in the racks behind the cockpit in a display of the front end of a DC-6 in the Smithsonian Air and Space Museum in DC. George, W8QBG, completes 'critter-proofing' the Bauer with the installation of a screen in the base of the transmitter. Gary, W6GY, now in Boise, Idaho, checks in with a very decent signal from an Apache and a large loop antenna -- and promises to have *his* Bauer on from up there "real soon now". Question: Does asymetrical modulation, higher positive peaks than negative ones, make an AM signal more prone to distortion due to selective fading? A lot of "loud" signals do seem to have that problem, as do some AM signals from SSB transceivers where it is quite possible to have the sidebands 'outrun' the carrier. 8/15/Tues nite 144.45 AM Net - Another update from QBG on the Bauer -- now have MOV's on the primary power, cover fabricated and installed for the big contactor and septic tank pumped out to the olfactory disgust of the neighborhood. Larry, KO6SM, battles heat and humidity to check in from his garage, but calls it quits earlier than usual. Ah, summertime! 8/19/Sat Glendale police call me up three times last night on my landline with an Amber Alert about a kidnapping that happened a mile away. Dunno whether I really like being *that* involved in law enforcement activities. BTW, if you hang up on the automated message before it's done, it calls you back again and again. 3855 - K6CJA makes an early appearance, discusses Corvette rebuilding and ammo reloading. W6GY is on from Idaho again. Copies everyone but Shep, W5EOE, who is beaming his signal into Phoenix. WA6TJN wonders aloud whether the MP3 audio format, protocol, whatever is really hi-fi. It sounds lo-fi to him. Probably so, but I remark to Ted that one really doesn't want to ship uncompressed .WAV files around or store them in an iPod. TJN and I then get into this involved discussion, that we continue off the air, about how one could write a piece of PDA application software to assist a learning-disabled person to make change from an ordinary commercial transaction - how many dollars, quarters, dimes, nickels and pennies to return. This for one of Ted's literacy students who has this particular hangup. My conclusion is that the easiest path to program functionality would be to use a PDA version of the spreadsheet program Excel and write code for a limited number of cells to do this. I think Ted was looking for a stand-alone .EXE file. W8QBG reports he is now using the Shark in his audio chain for the Bauer on 160. 8/22/Tues nite 144.45 - I miss the 3855 roundtable on Sunday and, I am told by W8QBG, Max, K7CAX, on the air with the B&W 5100 he traded to Greg, WA7LYO, for an SP-600 receiver. This is the same xmtr that sounds so good every time Greg shows up on 3855. I think Max got a very nice deal out of that and am sorry I didn't hear it on the air. George, W8QBG, gets crystals for the Bauer on the usual, well-trod AM frequencies. This so that he can use the Bauer stand-alone with its internal oscillator/buffer/driver. Weirdness has arisen in the Bauer. The grid tuning on the final amplifier changes when the rig is on the air. As if this isn't enough to keep QBG busy, he is also recapping an SX-100 receiver and sweeping water out of 'Studio B' from the recent rain. 8/23/Wed 7293 - Final grid tuning shift on the Bauer continues to bedevil W8QBG. Lock, W1ZD, tells me that 'Drake Ron', WA0KDS, was on 40 yesterday with a recently raised 40-meter beam. 8/26/Sat 3855 - Max, K7CAX, is on with his 'new' B&W 5100 and George has the Bauer on 3855 for the first time. Both are sounding great. I patch my TS-850 receive audio into the computer soundcard's line input and lay down a 15-minute audio track that gets a sample from everyone on the air (except me). This compresses down nicely to a 4.7 Meg MP3 file which I upload to the Arizona-AM website: http://www.arizona-am.net/test/26aug06.mp3 This is definitely a milestone for George's Bauer, making power at frequencies a stock broadcast rig can't reach and doing it with hi-fi audio. I think it is a tribute to George's diligence in designing the conversion using parts he had on hand and thinking-through the mechanical layout to get everything in the existing space behind the final tubes. I really need to get over to George's place to document this with digital images. 8/27/Sun 3855 - Max wants a recorded comparison of the various mikes he has on the 5100 and I oblige. WA9JMU checks in from New Mexico and I grab his audio as well. A little bit of slicing and dicing with the Audigy program gives me a couple of MP3 audio clips I can e-mail out to Max and Jim. K7JWA and I have a longish discussion about mobile automatic antenna tuners wherein I lay out my philosophy on the subject, to wit: One still needs a big loading coil to knock out most of the capacitive reactance of the short whip on the low bands. And that loading coil has to cancel- out almost all of the reactance, it has to be very close to resonance, on the band of operation for the autotuner to have any chance of operating efficiently. So one is stuck with manipulating taps on 'bugcatcher' coils, or cranking 'screwdriver-antenna' loading coils up and down. The only thing the autotuner does is gives one the ability to QSY up and down the band without having to mess with the loading coil. My SGC-230 will tune-up into an 8-ft whip with no loading coil, but 90% of the transmitted power will be dissipated in that rather expensive assemblage of relays and toroids. 8/28/Mon 7293 - George has the Bauer on 40! Band condx. keep me from hearing more than just the minimum necessary for copy, but it does sound strong. And he has bottomed-out on the final input detuning problem, tracing the fault to the bypass capacitor on the so-called 'cold' end of the grid RF Choke. 8/29/Tue 7293 - Band condx continue poor, but hear a nice, strong signal from W7HB up near Provo, UT running a Valiant. 144.45 - Larry, W0OGH, and Ron, KD7FGY, check-in from Gilbert but I don't hear either one of them. There must be a mountain in the way. I can't work Larry direct on six meters either. 8/30/Wed 3870 - Really hard getting into the AMI Net tonight due to QRN and QRM. K6IRD perseveres, pulls me and NA7RH out of the junk, and relays our check-ins up to Vic, K6IC, in the Bay Area. Thanks, Sharon. 8/31/Thu 7293 - Another strong signal from W7HB. Bill has had a great deal of experience in HF Comms in his career in the USAF as well as some interesting encounters with broadcasting during his growing-up years. The military/commercial HF part is particularly interesting to Larry, W0OGH, with his collection of TMC equipment and involvement with radioteletype. AE8O, Tom, out in Rio Rancho, continues to have problems with his Ranger. The latest is a broken, insulated coupling on the VFO tuning shaft. W0OGH thinks he may have a replacement for Tom somewhere. I happened to run across the figure of 186 mV/m as the field strength generated by a kilowatt transmitter feeding a short, vertical monopole against a perfect ground at a distance of one mile. I've seen this number bandied around in various publications, so decided to see if I could derive it myself from first principles. The result is appended at the end of this write-up. Where the hell did August go? AM HONOR ROLL... (stations logged this period) AE8O _______ AL0F _______ K0ETD ______ K6CJA K6EC _______ K6IRD ______ K6LGL ______ K7CAX K7JWA ______ K7SC _______ KA9UDA _____ KB7LOQ KD7FGY _____ KO6SM ______ NA7RH ______ W0OGH W1ZD ______ W5EOE ______ W6GY _______ W7GMK W7HB _______ W7MD _______ W7PLR ______ W7SVJ W8QBG ______ WA6JUS _____ WA6MTZ _____ WA6TJN WA7LYO _____ WA8ULG ADDENDUM: Field Strength at 1 Mile from a Short Monopole Antenna. I happened to be going through "Reference Data for Radio Engineers", the old ITT Handbook, and began wondering how that standard value of 186mV/m at 1 mile for 1 kilowatt into a short vertical monopole came about. (A short monopole is something like an inverted-L or Marconi T-top, assumed fed against a perfect ground). I went through the following derivation (using K7JEB BASIC): Radiation from an isotropic source is spread out uniformly on the surface of a sphere centered at the source and having a radius R. The surface area of that sphere is: As = 4 * pi * R^2 ' R in meters, As in square meters Power received (Pr) on one square meter of the sphere's surface from a transmitted power of Pt is: Pr = Pt / As = Pt / ( 4 * pi * R^2 ) Adapting the power formula (P=V^2/R) to free space with a characteristic impedance of Zo=377 ohms gives Pr in terms of Er, the electric field across the one-meter square: Pr = ( Er^2 ) / Zo solving for Er: Er = SQRT( Pr * Zo ) Substituting for Pr: Er = SQRT( ( Pt / (4 * pi * R^2) ) * Zo) However, the geometry of the situation is actually a half-sphere over perfectly conducting, flat ground. This doubles the received power on the one-square-meter of the receive "antenna". Call the revised E-field Erh: Erh = SQRT( 2 * ( Pt / (4 * pi * R^2) ) * Zo) Now, the transmitting antenna, a short monopole with uniform current distribution, has a power gain (of 1.5) over the isotropic in the preferred horizontal direction, which is where the one-square-meter "receive antenna" is (now) located. Call that gain Gt. This gives the final E-field value Erhg: Erhg = SQRT( Gt * ( 2 * (Pt / ( 4 * pi * R^2 ) ) * Zo ) ) Plugging in the numbers: R = 1 mile = 1609.3 meters Pt = 1000 watts Zo = 377 ohms Gt = 1.5 Erhg = SQRT(1.5 * 2 * 1000 * 377 / (4 * 3.14159 * 1609.3 * 1609.3) Erhg = 0.1864 volts across 1 meter or 186.4 mV/m Now, after coming up with the above pretty much on my own, I opened another reference, my copy of the 5th edition of the NAB Engineering Handbook (edited by A. Prose Walker, W4BW {SK - now nearer to God than ever before} ), and found an identical derivation in Section 2 (Antennas, Towers and Wave Propagation). So much for reinventing the wheel. I had to do something with this crap, so you guys are getting it free of charge.... jeb