SolderSmoke Podcast #148 is available: http://soldersmoke.com/soldersmoke148.mp3 December 30, 2012 SPONSORED BY usedradiomall.com -- Hurricane Follow-up -- Subliminal Mind Control to Encourage Homebrewing (beep-beep) -- The Shortcomings of the All American Five Receiver -- Solid-Stating a Heath SG-6 (with Farhan's circuit) -- VK3YE's Beach DSB Rig -- Tek 'scope connection to frequency counter -- Mod to W7ZOI/W7PUA power meter -- JBOTing my 20 meter DSB Rig -- A Tale of Woe -- LU1AR "The Most Interesting Ham in the World" -- Billy's Raspberry Pi -- Latest QST, SPRAT, Hot Iron -- Videos: Landfillharmonica, Knack in Sierra Leone -- Santa delivered a Soldering Station -- MAILBAG
There is an old saying in Spanish: "No hay mal que por bien no venga." More or less this is the same idea as: "Every dark cloud has a silver lining." Well, the dark cloud was my techno-agony with the parasitic oscillations (see below). The silver lining was the e-mail from Edgardo, LU1AR, in Buenos Aires that helped me get rid of them. Edgardo advised putting a resistor across the primaries of the JBOT amplifier stages. This is an old "lower the Q" trick, the idea being that lowering the Q might help prevent the amp from self-oscillating. I used 680 ohm resistors. First I put one across the primary of Q1. No joy. Then Q2. No luck. Then I put one right across the primary of that big output transformer. That did it! The parasitics disappeared. And I still get a nice 4 watts of output. Thanks Edgardo. I hope to make a contact with this rig today. The real silver lining in this story comes, however, in the form of Edgardo's blog site. Wow, what an inspiring example of Argentinian Knack. Radios, telescopes, auto-giros. This guy is also into homebrew DSB rigs. Wonderful stuff. Check it out. (Google will translate it for you, if necessary, but even if you don't read Spanish, the pictures tell most of the story.) http://www.lu1ar.blogspot.com.ar/ Thanks to all who sent advice and encouragement. Merry Christmas!
I'm building my FOURTH JBOT and this one is giving me more trouble than all the others combined. Here are the details of my tale of woe: 20 meter rig. Double Sideband. The JBOT is fed by a simple two-diode, trifilar toroid singly balanced modulator. NO DIPLEXER TO SPEAK OF. At the output of the balanced modulator there is a 1000 uH choke to ground and a .001 uF cap to the input of the JBOT. AF amp is an LM-386. VXO is a very simple MPF-102 one stage ceramic resonator VXO with no buffer stage. 7 element low pass filter (three coils, four caps). All the transformers are wound on FT-37-43 cores. T3 is four such cores stacked 2X2. The arrangement works beautifully into a 50 ohm dummy load. But as soon as I connect it to an antenna (a dipole out in the yard, fed with 50 ohm coax) the output signal gets ugly. Looking at it on the scope, instead of the nice figure eight pattern (similar to the two tone test pattern of SSB) I get ugly fuzzy outcroppings from the peaks. Looking at the signal more closely I can see that in addition to the 14.2 Mhz signal, there is another LF oscillation at around 250 kHz. I've been struggling with this. I can't get rid of the LF oscillations. The leads are all short and the inputs are far from the outputs. I've beefed up shielding, and decoupling. I've sacrificed a chicken to Papa Legba. Nothing seems to help. I THINK the feedback/oscillation is taking place in the JBOT itself -- not through the audio amp or the balanced modulator or the VXO. I watch the RF and the AF inputs to the balanced modulator to see if there is any difference between the stable situation (with the 50 ohm dummy load) and the unstable situation (with the antenna), I don't see any differences. I even put an antenna tuner between the final and the antenna anb made sure that the antenna looks like 50 ohms non reactive. This seems to help a bit, but the ugly instability is still there. Help me! \
Watch this video and you will see that Limor Fried has The Knack!
She and her company have brought homebrew electronics back to lower Manhattan.
Some kind listener sent me a gift certificate for Ada Fruit. We will put it to good use, probably
with Raspberry Pi and Arduino gear.
Three cheers for Lady Ada!
Very cool: Japanese students sent up a small satellite. One of its capabilities is to flash Morse code messages in the visible light range using LEDs. Prepare to peg your geek meter: http://www.fit.ac.jp/~tanaka/fitsat.shtml
Billy alerted me to this TED Talk presentation on an MIT Media Labs project that used new "femto photography" techniques that allow us to watch -- in VERY slow motion -- a light beam pass through a bottle. Amazing. Makes me think about Einstein's old thought experiment about running alongside a light wave (but of course here they are slowing down time...)
I think I said before that Paul, NA5N, has one of those "dream jobs" for a radio amateur. Confirmation of this came in a message he posted to QRP-L today: We're running a special experiment today using the VLA antennas to observe at 74 MHz (a protected radio astronomy band) and at 327 MHz. We've hung dipoles just below the antenna subreflectors, acting as a virtual ground, and of course the 88ft dia. dishes to illuminate the dipoles. Picks up a lot more power from the sky than I would have thought (about 30dB gain over the same dipoles in free space). Anyway, about 0830 MST, suddenly the system temperature climbed about 200 deg. K. Our switched power calibration injected into the LNAs showed no shift, meaning the jump in power came from the sky, not from the electronics. The power plot looked just like a solar flare. Checked the NOAA site, and sure enough, we had an M4 solar flare from region 1618 ... about smack in the center of the sun. About 1530UTC=0830MST=1030EST, Wed. Nov. 21. NOAA has since measured the shock wave from the CME at 1918 km/sec. This is a fairly strong shock wave, and coming from the center of the sun means planet earth will be pretty close to the bulls eye. The first time in my life I witnessed a major solar flare in real time watching the "sky power" plots. Pretty neat. First time the astronomers involved in this experiment have witnessed a solar flare as well real time. Region 1618 has produced numerous C- and M-class flares past couple of days with high potentials of future activity. This will ionize our E/F layer for elevated MUF and weak signal reflection. Check the bands if you're not at work. This 1918 km/sec. shock wave headed for us will almost assuredly trigger a major geomagnetic storm in a couple of days. If it hits Friday evening, it will trigger likely aurora over northern U.S. It may hit Saturday. I'll check the NOAA predictions later today and post as to the expected shock wave arrival. 72, Paul NA5N Socorro, NM Currently inside of VLA antenna #5, west arm. http://www.vla.nrao.edu/
A short e-mail from across the pond. Thanks for sharing the VK3YE link, so impressed I was that I have built one.
It receives great and puts out a nice looking dsb signal, looking forward to some good qso's, ready to improve on it as we speak and looking to make a top band and 18m version also, love the site and keep up the good work...Ian
Peter Parker's amazing 8 transistor DSB rig (featured in an equally amazing YouTube video -- see earlier blog post) has sparked a worldwide resurgence of QRP minimalism. There is now a lot more activity on the "Minimalist QRP Transceivers" Yahoo group (be there or be square). Steve "Snort Rosin" Smith WB6TNL is minimalist mentoring to the max -- with his help it looks like more VK3YE transceivers will soon be on the air. Steve was kind enough to take the info from Peter's video and turn it into a .pdf schematic (see above). It is in the file section at the Minimalist QRP Transceivers group. I was, of course, pleased to see the inclusion of a robust 7 element low pass filter. Michigan Mighty Mites are also tickling the ether. I may pull out my single MPF-102 Yingling 80 meter rig. You can join the Minimalist group here: http://groups.yahoo.com/group/Minimalist_QRP_Transceivers/
We have kind of half a holiday today -- I have the day off, but the kids went to school. I made use of the additional shack time to test the feasibility Farhan-izing my old, not-so-beloved Heathkit SG-6 signal generator. I did a quick Manhattan build of the oscillator section from Farhan's sig generator (link in yesterday's post). Using an idea from an old 73 Magazine article on a similar project (thanks Clint!), I smashed the tube (appropriate, don't you think?) and connected (using the glass stump!) Farhan's oscillator directly to the pins that lead to the switchable coils and the variable cap of the SG-6. I just wanted to see if it would oscillate, and see if there was a big change in SG-6 dial calibration. Wow, it worked great! It oscillates very nicely on all but the upper frequency band setting (20-50 MHz). I feel confident that I'll get it to oscillate at least up to 30 MHz. Next I'll build Farhan's buffer and amplifier stages. The SG-6 had a switchable attenuator -- I want to include that feature in the solid state version. I'll have to give some thought to the audio modulation feature (nice for aligning AM receivers).
I've recently become acutely aware of the shortcomings of my signal generator. It is a Heathkit SG-6. It is really old. It has a selenium rectifier in it. It has one of those old mic connectors on it for the output. The output is very low. But I like the cabinet and there is a nice switchable coil/variable capacitor LC circuit in there (see above). In 2008 in Hyderabad, India Farhan went to McDonalds with his kids and went home with some straws. Soon the straws are chopped up and turned into coil forms for a signal source: http://www.phonestack.com/farhan/siggen.html
So here is my idea: de-tube the SG-6. Turn the selenium over to the HAZMAT authorities. Save the coils and the cap and most of what George Dobbs would call "the socketry." Use an MPF-102 for the oscillator, then make use of the buffer and feedback amp from Farhan's soda straw circuit. What do you guys think?
Another brilliant rig from DSB guru Peter Parker, VK3YE. I really liked this one.
I loved his drawing of the circuit diagram -- right there on the beach! Lots to be learned from this video. Thanks Peter!
In SolderSmoke 147 I mentioned that I had found some old pictures of AA1TJ's underground hamshack and workshop. People wrote in asking me to post them. Here they are. I still can't find the shot of the door surrounded by snow.
People have been asking about the DC to AC inverter that I have been using during the now frequent power outages (5 in the last two years, two of them since July 2012). With it I can easily keep the lights on in the house and even run the TV. Not bad for $69. Here it is:
SolderSmoke Podcast 147 is available for downloading: http://soldersmoke.com/soldersmoke147.mp3 October 29/30 2012 Hurricane Sandy on the way Thanks for birthday wishes Einstein -- a very nice fellow with a bit of the Knack Rocket project update 808 key chain cameras (thanks for the Amazon support!) Audio output transformer for Barbados Barebones RX Mighty Midget RX -- breaking it, fixing it (with help from friends) Freq counter connection to Tek scope Halli S-38E -- How to avoid electrocution? The HQ-100's anti-drift alarm clock Book Review: "Instruments of Amplification" by H.P. Friedrichs (5 Soldering Irons!) BANDSWEEP: 20 meter SSB via DC receiver on hurricane day Report on outcome of the hurricane -- inverter saves the day (really the night) MAILBAG (a big one).
Hurricane Sandy went through here yesterday. We had a lot of water and wind. Power went out at about 7 pm, giving me the opportunity to display my technological prowess by deploying my 1.1 kilowatt DC/AC inverter. It worked very well -- we had lights and TV, and were the envy of the neighborhood. We all went to sleep on the ground floor -- trees are the real hazard here. We were very pleased to be awakened by the lights coming back on at 1:20 am. Three cheers for Dominion Power! I hope listeners in the storm's path had it as easy as we did. Podcast #147 will be a special Hurricane Sandy edition. I should have it out in a day or so.
That vortex off North Carolina is Hurricane Sandy, and it is heading right for us. It should make landfall tomorrow, perhaps in Southern New Jersey, perhaps closer to us (the location of the landfall of the eye doesn't matter much -- the wind field has a radius of 300 miles!) It could really mess things up --- lots of water, lots of wind, and it will collide with a cold front moving in from the west. Yuck. There is a good chance we will lose power. I have pulled out my trusty Heathkit HW-8 and my solar-charged gel cell battery, so I am ready to go. Good luck to all those in the storm's path.
OM Carlo Consoli, IK0YGJ, has produced a nice book on radio telegraphy. Very much in the spirit of the International Brotherhood of Electronic Wizards, he has made it available in Italian, English, French and German. I have started a refresher language course in Italian and intend to use Carlo's book as reading material for the course (my instructor will be sympathetic because her son is a radio amateur). Who knows, I may be able to improve my Italian and my CW at the same time!
The stop-action film Frankenweenie is hitting the theaters here. Its mad scientist/workshop theme seems to have some Knack relevance. This morning I found this five minute film called "The Maker." I thought you guys would like it. I also liked the video (below) about some of the homebrew gear that they used to make The Maker.
Now THAT'S a ham shack! My Mighty Midget receiver allowed me to listen in this morning to Al, W1UX, and friends on 75 meter SSB. One of Al's AM operating positions appears above. Note the DX-100. And the R-390 (want one). And the Tek 465. I've been a big fan for years. Check out Al's boatanchor web site: http://www.tinyradio.com/boatanchor01.html
3 October from AA1TJ: Here's an admittedly late reminder that the Sputnik Party begins tomorrow (4 October). I've been preoccupied with non-hobby concerns in recent months but I did manage to throw something together for the event. My transmitter follows the lines of the 10mW, battery-powered, RF beacon that was carried into orbit in 1958 by "Vanguard 1." You may recall this is the one Premier Nikita Khrushchev characterized as "the grapefruit satellite." My present build uses essentially the same circuitry and componentry as did an earlier, 20m version; details of which can be found at http://aa1tj.blogspot.com/2012/06/vanguard-1-satellite-transmitter.html The 15m version drives a 44m end-fed wire with 30milliWatts. The receiver that I built for the event is essentially a "Q-multiplier -> detector" type regenerative job. However, the Q-multiplication is accomplished by a parametric amplification using a quartz-crystal controlled pump. I thought it would be historically appropriate given that parametric amplifiers were all the rage in the late 1950's. I put together the keying and R/T changeover circuitry this morning. When it appeared that "all systems were go" I began sending CQs on 21.060MHz. The band, or at least that portion of the band (the receiver only tunes from 21.060 to 21.064MHz), seemed rather quiet, but my 6th call netted a "dit dit dah dah dit dit." Resending my call, I was very pleased to hear HB9DCL come back to me from just outside of Zurich. The reports were 579/339. Frank was running 5W to a log periodic antenna. I sure hope this is a sign of things to come! I hope to be at the key by 1300Z tomorrow. Although my little "grapefruit" only puts out 30mW, folks running "Sputniks" made from ex-Soviet subminiature "rod tubes" should be at least two S-units stronger. A number of European stations will be operating this year and at least one station that I know of will be QRV from Japan. Just listen for the beeps and give them a call! Thank you, Mike, AA1TJ .......................
04/10/12 ( first day)
dear friends &Sputnikers
today a Belgian "sputnik clone" crossed the pond
15:22 with N0UR a 2 x sputnik "solid" QSO
Jim wrote: Thanks QSO, here is how you sounded in MN
( in attach)
16:00 second hit with AA1TJ , Mike "the inventor of all this Sputnik madness" hix 3
this time a bit more difficult but at last we could manage to exchange reports,
between the QRM and noise at last got confirmation ,
Mike's sigs here where 339 but still copyable
all OK with my 559 sigs then suddenly some other sputnikers came on the scene and I lost Mike
with my 60 years again excited as a young boy
as we made some history today hi x 3
will take a picture
for the moment a complete mess as the DC/DC invertor inside the sputnik broke down
lost the very early contact with UA1CEG suddenly no more power in the SPUTNIK-cabine LOL
had to drag my new testbench power supply (still under construction )
or lot of things to fix for those lausy 700 milliwatts hahahaha
73 to all
News flash...Sputnik worked Vanguard across the pond. I just sent this letter to some of the guys Dear Friends I won't forget this morning's QSO with ON6WJ anytime soon! As he beeped/called CQ I could hear him riding on waves of QSB. I kept hoping he would end on the top of the wave. It happened one time and Jos sent "AA1TJ?" but by the time I re-sent my call we were back in the trough of the wave. He started calling again and once again I crossed my fingers. Finally it happened, he ended on top of a particularly strong peak...and sure enough, he copied my callsign. It took more effort to exchange the reports but we eventually did it! He confirmed my 559 and I did the same for my 339 report. It must be true that anything worthwhile doesn't come easy, because the more difficult the QSO the more I seem to enjoy it! I copied Jos' info: "SPUTNIK PWR 700mW = ANT 3EL YAGI" perfectly on my tiny receiver. Just as amazing, he copied my 30mW transmitter made from one PNP Germanium transistor dating from September of 1959. Needless to say, I'm a happy camper today. Merci Beaucoup, Jos. Just above my operating frequency I heard PA0PJE sending "CQ Sputnik." You had a beautiful signal here, PJ! It was easily S6 on the peaks. My transmitter frequency trimmer adjustment is buried in a rat's nest of wires which I didn't dare stick my hand in so early in the day. However, if I hear you again I will definitely risk it. Thanks Carlo/IZ4KBS and congratulations on your Russian QSO. Any contact all with this simple stuff is reason for a celebration! ...and now back to the Hobbit Hole for another dose of QRPp. 73/72, Mike, AA1TJ
OK gang, it is time for us to do what we can to help a worthy Short Wave Listener transition into the world of amateur radio. Chris will be facing the Irish radio examiners on October 4. So please try to send some positive vibes in the direction of Ireland. Cross your fingers (especially the ones with the soldering iron scars!) Maybe melt some sacrificial solder. C.F. Rockey might suggest sacrificing a chicken to Papa Legba. Say a prayer if you are so inclined. Good luck Chris!
Just wanted to say thanks for the great podcast and keep up the good work.
I’ve been listening for a good while now and following your subscriptions advice on things like Tim’s “Hot Iron” Constructors club and QRP/Sprat magazine.
I’ve got my Amateur Radio licence test in 2 days time (4th Oct) over here in Ireland (Dublin’s Comreg Offices) so please give all the candidates a mention and wish us luck.
Great book as well…When I’ve had my fill of studying I switch over to your book for a while to relax a bit and read your thoughts on getting to grips with it all.
There’s only one licence here in Ireland so it’s Full or nothingso it’s going to be tough!My brain is well and truly fried!!
I’m determined not to be a (can’t even remember what you call them in your book ha ha) “User” and go out and buy everything I need so I’m looking forward to lots ofconstruction projects when (IF!) I get my licence J
Best Regards (I don’t think I’ve earned my right to use 73’s yet),
Continuing with our workshop inspiration theme, I spotted this in the BITX-20 mailing list this morning. The response is from Farhan:
i would suggest a different route. a long and winding one, that will finally lead to a bitx.
the idea is to learn. you do this by understanding what you build and building what you understand. by 'understand', i specifically mean, being able to measure. here is what i suggest, buy yourself a bunch of 2N3904s from the local radio shack and some resistors and caps. then build this :
this is an oscillator. if you plug a coil between the open ends, it will become a vfo, if u plug a crystal, it becomes a crystal oscillator. you can use your frequency oscillator to check the frequency it is oscillating at, etc.
with this, you would have mastered the first of the three blocks that make up almost every radio circuit. but next, you must make another test instrument. a power meter. most of us ham start out with a simple RF probe. while that was fine and dandy for its day, now we can do much much better. we can make a very accurate power meter that enable you to measure things as finely as anybody in this business. W7ZOI has designed a super simple power meter. it is available as a kit. read about the power meter here : http://www.kangaus.com/Documentation%20files/Power%20Meter%20Documentation%20May%202011.pdf you can purchase the kit at www.kangaus.com (I have no business interest with kanga or any other kit manufacturer)
with the power meter in place, you can now measure the power levels coming out of any circuit with great accuracy.
now, you can build a single stage feedback amplifer (there are six of them used in the bitx) on a copper clad board. using the test oscillator as an input, you can measure how much gain the amplifer has (measure the oscillator output, then connect the oscillator to the amp and ,measure the amp output. the, amp output - oscillator output = amp gain).
of course, while building both these blocks, you will discover what voltages to expect at which junction of components in both these blocks.
finally, you can build a simple signal generator like this : http://www.phonestack.com/farhan/siggen.html . this will allow you change frequencies and measure what a circuit does at different frequencies. you can use this to test how the filters are doing and get them to 'spot' where you want them to.
so, there it is, a signal generator, a power meter, step attenuator, test oscillator. four, very simple test instruments that you can build yourself. they will give you one helluva education in radio. and within weeks, you will understand and start building on your own!!
- farhan > Quoting bfabman : > > Hello Everyone, I have been watching the group for a few months now > with interest. I have no electronic experience to speak of, but I have > a burning desire to make one of these, and I am wondering what all of > you think of someone like myself building one as my first real radio > project, to be used for qrp mountain topping. I don't have any > electronic test equipment for the final alignment, other than a > standard DIG vom meter. (I am willing to buy some equipment if > necessary) I think that this would be an awesome winter project just > don't know if it would be over my head. If I got it all built, could I > actually get it aligned and working properly. I did make a Norcal > frequency counter project last year and it turned out very well. Thanks > for your opinions before I spend the money. Blake > > Paul Daulton K5WMS > beacon WMS 185.302 khz qrss30/slow 24/7 > Jacksonville,Ar 72076 > em34wu
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