Just go to http://soldersmoke.com. On that archive page, just click on the blue hyperlinks and your audio player should play that episode.
http://soldersmoke.com
We've talked many times about the pleasures associated with a rig that is still just a collection of parts and boards, all still spread out on the workbench, unboxed, perhaps held together by clip leads and bits of duct tape. They seem to sound better this way. This is the condition under which we experience that magical moment of "First Signals" (similar to First Light with a new telescope).
We haven't had a concise way of describing this (note my long-winded description above). Well, this morning the Sage of Newbury Park has, on his amazing blog, provided us with the words that we have so long needed:
Al Fresco!
That's it! Perfect. When a new rig is put into operation in this way, we will henceforth say that it is being run "al fresco." Thanks Pete!
Check out the blog post that gave us this wonderful phrase:
Read and heed, or you'll be sorry. The cold weather causes us to spend more time in the shack and to work on new homebrew project. Some of these projects may involve sensitive, delicate, solid-state components that can be instantly wiped out by that little winter spark from your finger... Take a look: http://soldersmoke.blogspot.com/2016/01/an-electro-static-bandaid-to-protect.html
I have to be especially careful this year, because Northern Virginia is now officially in a drought. So that spark-friendly dry winter air is likely to be even dryer this year.
Well, we were talking about it on 40. This just proves that there is more to 40 meter SSB than the never-ending quest for audio "brilliance," "presence," "body" and "sparkle." I was working at the bench yesterday when I heard Frank NC1I telling another fellow about his 35 years of experience with moonbounce. Wow, you don't hear that kind of talk on 40 every day. Frank also said that the contact I was listening to was one of very few HF contacts that he has made in recent years. I just had to jump in to encourage him to get on 40 more regularly. He seemed impressed with my BITX40 Module (which I was using). I warned him of the buffoonery that can be found on the band, but told him not to be deterred by it -- there are a lot of FB hams on 40. Above you can see Frank's amazing antenna farm. The dish is for 23 cm EME. Behind the you can see his 70 cm array. That is 48 (FORTY EIGHT!) end-mounted Yagis, aimed into space. Check out Frank's QRZ.com page: http://www.qrz.com/db/NC1IHe has some great pictures of his shack. In case you are wondering why he has so many rotator control boxes, remember that the dish and the Yagi array need two each (azimuth AND elevation).
Wow! Now THAT is a shack! This morning I heard Butch K0BS and his friends on 40 meter SSB. I knew I was listening to the voices of kindred spirits when I heard them talk about a drifting VFO and the need to heat up the filaments of an ART-13. As the group was shutting down to begin their preparations for Thanksgiving dinners, I gave Bruce a call with my BITX 40 Module. He was on a KWM-2 (the rig that had been drifting a bit) and a homebrew 4-1000 amplifier. I told him that I think a bit of VFO drift is a sign of good character.
You really need to check out the pictures on Bruce's QRZ.com page:
Driving home from work the other day I heard this NPR interview with the woodworking guy from the TV show "Parks and Recreation." I've never seen the show, but I really liked the comments on the benefits of what we would call homebrewing: MCEVERS: I feel like there are a lot of people out there listening who have spent exactly zero days being handy, like, their entire lives. Is there hope for people like this, and does your book provide it? OFFERMAN: I think so. I mean, a lot of my own woodworking education comes from books and periodicals like Fine Woodworking and Popular Woodworking magazines. They're great teachers, but they're very somber. They're very sober. So it was important to me for this book to be really friendly and gentle and fun to let you know that whether you're getting into woodworking or making anything with your hands, it's really important to know going in that you're supposed to make mistakes. You're supposed to screw it up. And not only do I think this is a very friendly introduction to woodworking, but I really have become a little bit of an evangelist to encourage - find something to make. If you make stuff for your house or your loved ones, you're curating your life in a way, saying, I don't have to just limit my choices to what I can buy at Amazon. I can also choose to make a table myself. And even if it looks crappy, it's still so much more charming because you've made that gesture. You can listen to the 6 minute interview (it is funny) by clicking on the "PLAY" arrow in the upper left of this page: http://www.npr.org/2016/11/17/502476216/nick-offerman-shares-his-love-of-woodworking-in-good-clean-fun
Wow, THE RADIO GODS HAVE SPOKEN (TRGHS). Pete gets on 40 with his new-old FPM5 homebrew rig and works homebrew legend Jeff Damm WA7MLH, who was also running a homebrew SSB rig. HB2HB! For those of you who don't know, Jeff is the guy who built many of the inspirationally ugly rigs in Solid State Design for the Radio Amateur. Pete's second QSO was with SolderSmoke podcast listener K7ADD. TRGHS!
Later after another QSO was called by K7ADD, Ben, and he couldn’t wait to tell me he was a long time SS listener and stated listening to SS made him take a whole new interest in ham radio –especially building stuff.
I've been working with an Arduino today. Seeing this video makes me feel like such an APPLIANCE OPERATOR. FB OM! No store-bought mystery boxes for him! Thanks to Steve N8NM for alerting us to the magnificent project. More details here: http://www.popsci.com/man-builds-huge-megaprocessor
Perhaps this was a reaction to a frustrating morning spent trying to get a 20x4 digital display to work with an Si5351 and an Arduino Uno via an I2C bus (I feel my blood pressure rising just due to the typing of those words). After much digital fiddling, I declared a "BASTA!" and looked around the shack for an antidote for the digital frustration. There on the bench was my fully analog BITX40Module rig, with its homebrew L-C analog VFO. It needed a better frequency readout. And this morning, it got one. The pointer is Sharpie ink on a bit of PC board. It is held in place by superglue, suspended by a piece of wood about 1/4 inch off the chassis (to reduce dial parallax). The numerals are in Dymo tape -- there was not enough room for the "7" but I think I will be able to remember this.
I should have tried this a long time ago. It works great. The power supply that I picked up at the Kempton Park rally many years ago happens to have a 25 volt unregulated output. Coincidence you say? I think not. TRGHS.
Farhan provides a really excellent description of how to do this:
Two things really caught my attention: -- Note how OM Carson, way back in 1915, had figured out how to get rid of the carrier, but needed some way of eliminating the unnecessary sideband. He did it by using his antenna tuner as a filter. FB OM! -- In the early days of SSB, when it was an exciting new technology, hams had regular "sideband dinners." At these events an award was presented. Kind of like an Oscar or an Emmy I guess. The award was the "Sideband Suzy" (see above). Kind of a classic figure... but half of Suzy was missing!
The fan that I installed yesterday was driving me nuts. It was noisy, both acoustically and electrically. And I would occasionally get my fingers in the blades. Not good. While it did seem to keep the IRF510 from getting too hot, I knew that a real heatsink would do better thermally. But how was I going to attach the sink to the transistor? That tab on the IRF510 goes to the collector, so if it touches a grounded heat sink, you get a short. A nylon screw and some mylar between the transistor tab and the heat sink is one option. But I didn't have a nylon screw. So I decided to just keep the heat sink electrically insulated from the chassis. This project required me to refresh my memory on how to tap a 4-40 hole. I went back and watched the short video I made on the tribal knowledge that Pete had shared with me. Out came the Tap and Die gear and the machine oil. The process went very smoothly. Here is what I did to get the heatsink in place: 1) After removing the original heatsink, I gently bent the leads on the IRF510 so that the transistors outer edge would be flush with the edge of the PC board. 2) I put a strip of thick tape (Gorilla Tape) along the lower side of the heat sink. This will keep the heat sink from shorting to the chassis. 3) I placed the heatsink where I wanted it, and carefully marked where the mounting screw (through the transistor's tab) should go. 4) Drill! Tap! (see video)https://www.youtube.com/watch?v=LuqliWT1k5A 5) I applied some heat sink compound (or Desitin!) and then attached the transistor to the heatsink. 6) I put a few drops of glue between the heatsink and the board and the chassis, just to mechanically stabilize it a bit. 7) Bob's your uncle. It seems to work great. The MOSFET stays cool. even after long "old buzzard" transmissions. And I notice no stability problems. It was fun to put to use some tribal knowledge and refresh a mechanical skill.
I was going to put the BITX40 Module in a box today, but I just couldn't bring myself to do it. That board looks too good to be hidden inside a box. So I put it topside. That's the analog VFO to the right. You can see a fan off to the left -- that is perhaps temporarily in lieu of a large heat sink for the final. You can see the two Gel cells in the background. I am indeed running 24 volts to the final, and am putting out about 20 watts. I had three nice contacts today on 40: WB2RON up on Long Island said I was "20 over". Later I worked W1SJ in N. Vermont -- I was 5-9. Then -- icing on the cake -- DK1NO in Stuttgart. I was 5-8. TRGHS. I kind of like this arrangement -- it has the "three dimensional" feel of an old tube rig. This obviously wouldn't be good for portable operations, but I am not planning on going portable. There is a lot of room under the chassis. I could put a digital VFO in there and put in a switch so that I can easily go from digital to analog.
I blame Pete for this. And Farhan. Pete has been leading us astray with all his talk of high power linear amplifiers ("Two 813s kid, that's all you need!"). And Farhan practically pushed us beyond QRP limits by placing a separate DC power connector for the IRF510 final amplifier on his new BITX 40 Module board. Farhan writes:
There are jump-points from where you can add more modules like the DDS, more bands, better audio amplifier, etc. Imagination is your limit. You can separately increase the power amplifier's supply voltage to 25 volts to be more than 20 watts of power : You will have to add a better heat sink. The mods are on the way!(from hfsigs.com) A while back Chris KD4PBJ sent me some very nice heat sinks -- one of those would fit quite nicely on the PA side of the BITX40 board. And I just happen to have two 12V Gel cell batteries. One will power the board and the two together will power the IRF510. With 20 watts out to my dipole I feel confident that I will WIN the upcoming ARRL Phone Sweepstakes (in my category: Homebrew VFO, Northern Virginia).
When I opened the package from India and saw Farhan's s beautiful board with all those little SMD parts, I immediately worried about frying those parts by accidentally reversing the polarity of the 12 volt DC input. Believe me, this can happen. It is especially likely during the early, enthusiastic testing and experimenting that takes place in the days after the arrival of a new rig. So, my friends: Save yourselves the agony of fried components! Don't let your BITX 40 Module go up in smoke! Install a simple reverse polarity protection circuit BEFORE you start working with your new board. Here is what I did: I just took a diode (a fairly hefty diode) and I soldered it in between the pins of that neat little circular power jack that Farhan sent with the module. Be sure to solder it in so that it does NOT conduct if you have connected the power correctly. The arrow should be pointing to positive terminal. Then put a fuse (3 amp or even a 2 amp) in the line from the connector to the power supply or battery. If you don't have a holder you can try just soldering the fuse into the line. With these two little parts, you can save yourself a lot of grief: If (WHEN!) you connect red to black and black to red, that diode will conduct like crazy and will blow the fuse. You'll just have to replace the fuse (and not the module).
This morning I built a mic/PTT for the BITX 40. I used the little electret element that Farhan sent with the rig. The element sits atop the plastic tube from a pen. For the push-to-talk I used a little push switch that locks down (on) until you push it again (which opens it). This is very convenient -- you don't wear your thumb muscles out on long "old buzzard" transmissions! I used some PVC pipe and some wooden dowel to make the thing a bit ergonomic. It is held together with Gorilla tape. It works great! I put the rig on the air this morning and very quickly worked KD3TB up in Pennsylvania -- Irwin was testing his K3. Then I worked KM4LWP -- James was only a mile or so from me, running 3 watts from a KX3. Then Mario, K2ZGW called in.Everyone said the rig sounds great.
In the picture above you see the rig, the mic and (on the right) the VFO.
That, my friends is an extreme example of what we mean when we use the word "rig."This magnificent machine sent Pete's melodious voice across the mighty Pacific several times during the recent CQ WW contest. Pete wrote to Jun:
Hi Jun,
This weekend is the CQ World Wide SSB contest and I just worked three JA stations on 40 Meters. The time 1400 UTC. I must confess that I was using 600 watts to my droopy dipole but they came back on the first call. So there are paths open and perhaps 600 watts was overkill but the timing seems like it works for a good path to the west coast. Along the way I also worked a station in Hawaii (KH6).
The rig I was using is shown below. The mainboard came from a Hallicrafters FPM 300 (late 1960) to which I added the Rx Tx Mixer (SBL-1), my stock 2N3904 bi-directional amp board, the 2N2222 + BD139 driver stage using the EMRFD circuit and a 2SC2075 final which gives about 3 watts. This in turn drives an intermediate SS amp to 100 watts and then the SB200 to 600 watts. The FPM 300 used a 9.0 MHz IF frequency.
Of course no rig today from N6QW would be complete without a Si5351 and the color TFT display. Rounding this out is an LM386 audio amp stage. Cosmetically the rig doesn’t look pretty but sure works well.
73’s
Pete N6QW
(The comments about the 813s are kind of SHOCKING, coming from a member of the QRP Hall of Fame!)
I am having a lot of fun with Farhan's new BITX 40 Module. I think I'm doing exactly what Farhan intended people to do with this rig: work on it, modify it, improve it.
I've been working on frequency stability. I was, I admit, skeptical from the start about the stability of a thumb-sized, SMD, varactor-tuned VFO with a ferrite or iron powder toroidal coil. Don't get me wrong -- it worked. But it drifted. It seems to me that it would be asking too much to expect a VFO like this to be drift-free. (But I may be wrong -- are there any SMD, varactor-tuned VFOs out there that DON'T drift?)
First I thought it might be the 9 uH metallic core toroid. So I replaced that with a 10uH choke -- no ferrite or iron powder in there. That seemed to help a bit, but SSB QSOs would still quickly drift into Donald Duck chatter. Then I thought it might be the varactor diode. I let it warm up. A lot. Still, it drifted. Then I thought it might be the trimmer cap, so I took it off the board. No change. During this process I noticed that even slight pressure on the board caused the rig to shift frequency. I began to suspect that the drift was just structural -- a consequence of the physical characteristics of the SMD parts and the board. To get VFOs stable I've had to build them big: 10 X 10pf NP0 caps to make one 100 pf cap, large air-core coils, and big sturdy variable caps. I'd isolate the frequency determining elements in a box separate from the powered components. This little VFO just looked too small to be stable.
So faced with drift, at first I asked myself, "What would Pete do?" I took an AD9850/Arduino combination off the shelf and plugged the output into the "DDS" jack Farhan had placed on the board. I removed the 10uH choke. Viola! With the DDS tuned to 4.7 - 5 MHz, the receiver worked great. I briefly tried to updated the Arduino code to take into account the 12 MHz IF (so I could get an accurate frequency readout), but ran into the old painful Arduino IDE problems: Now it is claiming there are library problems. Not wanting to suffer through another round of digi-agony, I left well-enough alone. I used the DDS with the old code for one day.
But of course, I was not satisfied. Attaching a DDS or PLL synthesizer to the BITX 40 Module just didn't seem right. Heck, it was kind of like just hooking up my FeelTech Chinese sig gen to the DDS jack. Farhan's rig is simple, beautiful and ANALOG. The parts are small, but you can see them. You can put your scope probe on the collector of Q7 and see what is going on. DDS or PLL. It is a REAL HARDWARE-DEFINED RIG. So I decided to build a VFO. Pete calls VFO's "grief machines" but for me, the grief machines are those little Arduino beasts. To each his own.
When I build a VFO, I start with the variable capacitor and the reduction drive. I found a nice one (with reduction drive) in my junk box. I tunes from 40 pf to 56 pf. I decided to use the super-simple Hartley circuit presented by Wes Hayward W7ZOI in SSDRA (page 34, fig 7).
I went with a 4.4 uH air core coil (wound on a cardboard tube from a coat hanger). Consultation with on-line resonant frequency calculators showed that I'd need to put about 180 pf in parallel with the variable cap. For this, I used a bunch (maybe 10?) of small value NP0 caps in parallel. This really helps keep the VFO stable.
As I did with my HROish receiver, I put the coil and the caps in one box, with the MPF-102 and associated parts in an attached Altoids tin. Everything was glued and bolted down very solidly.
I only built the actual oscillator stage -- I decided to use the buffer amps on Farhan's board.
The oscillator started right up. I had to add and then take away some turns on the coil to get it to run in the desired range. Then I plugged it into the DDS jack -- the receiver was working immediately.
I noticed, however, that it seemed a bit less sensitive than it had been with the AD9850 DDS. And when I grabbed the wire going into the DDS connector, audio output jumped dramatically. It took me a few minutes to figure that out: I think the output from my VFO was not adequately turning on the diodes in the diode ring. When I grabbed the wire, I was putting a lot of noise into the mixer port, probably turning the diodes more fully on (but also letting a lot of noise through).
Fixing this problem part was fun: Looking at the BITX 40 schematic, I saw that the two 1000pf feedback caps in the original oscillator were still in the circuit. I figured those caps would be sending a lot of my VFO energy to ground. So I fired up my hot air rework station and deftly removed C91, the 1000 pf cap that is connected to the base of Q9. Instantly the receiver started inhaling as it had with the DDS VFO. That was a very satisfying fix.
This whole VFO project was very satisfying. It was all done in one day, and all the parts came out of my junk box. I think I ended up with an LO frequency source that matches up in a pleasing way with the analog circuitry in Farhan's rig. And here is bonus that I think is just what Farhan had in mind: this kind of circuit adds a definite homebrew element to the module rig.
I found that this external VFO improved stability significantly. I don't know if it is as stable as the DDS, but with the external VFO the receiver no longer drifts away as I listen to SSB signals.
Finally the Mate for the Mighty Midget is finished, just in time for the G-QRP Valve Day 12-13th of November.
Got the LO fixed for 40m by lowering the parallel capacitor from 150 pF to 100 pF.
Also the 68 pF series capacitor was lowered to 33 pF for some more band spread on 40m.
It now receives from about 7.0 to 7.4 MHz and from 3.45 to 4.0 MHz
Had to exchange C1 in the end, the one used initially quit every now and then.
I only had a large 3 section variable in the junk box covering 10-550 pF, which works fine now. For the lower end of 80m I had to add additional 47 pF next to the 47 pF trimmer caps, so there it is about 600-650 pF max!
At the high end of 40, it is also just not too much.
The meter was used as a position indicator for C1.
Tried several ideas, but with no separate tube for AGC, I couldn’t get it to work as a S- meter
Read something about audio derived AGC, maybe this is worth a try.
The BFO can be switched off for AM reception.
Simultaneously the input on the mixer side of the crystals is disconnected but still coupled by some capacitance of the switch wires.
AM reception is possible, but not very good.
Need to find a better solution which doesn’t degrade the crystal filter properties to much.
(By the way, the detector regen. control ads about 4 dB to the AM sensitivity)
The receiver will mainly be used for CW/SSB reception, so maybe it stays this way for a while J
I hooked it up to the W1TS transmitter, which was very loud.
Didn’t foresee a T/R relay (learned a lot from this project ;-) ), so added this one between the front plates next to the RF and audio gain control.
The quit down everything a little, the RF gain pot is lifted of ground as suggested by James, N2EY at QRZ.com.
It helped a lot, but was still too loud if tuned exactly in the bandpass of the crystals.
The T/R relay now also switches an adjustable potentiometer at the input of the audio pre-amplifier.
The dial cord has no lag, and works very well for fine tuning.
Unfortunately the reduction drive went from 1:19 to 1:9…, the tuning capacitor only has a 180 deg. span.
Something to remember for the next receiver.
It’s a nice little receiver and quite stable after warm-up.
The only extra luxury a next receiver will have, is AGC.
But with no AGC it’s easier to tune the antenna tuner by ear J
There’s now a complete homebrew station here, antenna, feeder, tuner, receiver, transmitter, power supply, al home made J
About the Mystery Hole….
If you haven’t guessed it by now, or Pete hasn’t told you, it is revealed in one of the pictures below.
"SolderSmoke -- Global Adventures in Wireless Electronics" is now available as an e-book for Amazon's Kindle.
Here's the site:
http://www.amazon.com/dp/B004V9FIVW
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