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
Pete WB9FLW alerted us to the work of Peter DK7IH, a very talented homebrewer who recently followed the lead of Pete N6QW in building some really small SSB transceivers. Here is his Micro QRP SSB rig:
You can see more of his fine work here: https://radiotransmitter.wordpress.com/ https://www.qrz.com/db/DK7IH Have you guys noticed how many Peters there are among homebrewers, especially among SSB homebrewers? Just from recent mentions on this blog: Pete Juliano N6QW Pete WB9FLW Peter Parker VK3YE Peter DL3PB Peter W1UO Peter GW4ZUA Peter G6GNR Peter VK2EMU Peter VK2TPM Peter HA5RXZ Peter DL3JIN
We had some posts about this kid a few years ago. He is 21 now and was recently interviewed on the TED Radio Hour -- the nine minute interview (above) is worth listening to. Just click on the arrow. Philo Farnsworth would be pleased.An amateur creates a star in a jar.
This is from 2014, but I stumbled upon Wayne Burdick's article just this morning. Great stuff. That picture of Wes had a big impact on many of us. Wayne's article: http://www.elecraft.com/KX1/N6KR_KX1_History.html
I found myself almost cheering out loud as I listened to this wonderful interview, especially at the point where Hans lets it be known that he has NO COMMERCIAL HAM GEAR in his shack! Yes! That's the ticket! You can also hear the story of Hans and Farhan meeting up in Mumbai for dinner. The interview includes discussion of WSPR and QRSS and BITX and crystal ovens and, at the end, a special QSO TODAY overtime session in which Hans describes the little WSPR rigs that fly around the world, carried aloft by half-filled birthday party balloons. Thanks to Eric 4Z1UG and Hans G0UPL for this very nice Christmas present. Listen here: http://www.qsotoday.com/podcasts/g0upl
Some fellow jumped into the BITX20 yahoo group this morning, casting aspersions on our friend Farhan. The fellow alleged that a lot of money was being made on the BITX 40. He seemed deeply unhappy about the shipping materials and found fault with the documentation that came with the boards. Farhan came back with a very gentlemanly and detailed response. He was a lot more patient and temperate than I would have been. And when I think about how Pete would have responded, well, it would likely have involved -- at the very least -- a lot of colorful words from Southern Italy. Anyway, below (unedited) is Farhan's response. I think it provides a lot of very interesting background info on our beloved BITX 40 Module and on the place that these boards come from.
thanks for writing in, I couldn't get your handle from the mail, so do excuse me for improper address! I think you have raised from valid points. I think it is important that everybody understands what tried to do, what we did and where we are now.
this is going to be a long and full of personal details that i didn't consider to be of any interest to the group and hence it was kept out. but i guess, i need to let a few cats out of the bag.
i am retired, early. i had a modestly successful run in a few businesses but i had promised myself to retire from active work, which i did around five years ago. i no longer run any for-profit businesses. most of my investment goes into 'stuff that matters'. i founded a libera cultural space in hyderabad, i am a partner in a strategic venture fund that promotes technologies that are important rather than profitable. neither ehsan nor i are any longer running anything full time. i do mentor some startups now and then but never as an investor.
i would be only too glad if someone else takes over the entire hfsigs approach. the design has been out in the open for more than a decade. apparently, it doesn't make economic sense to make them at $45 dollars a pop. so, there is nothing preventing others 'creaming the market' if they want to. surely, the turnover is modest but it is not profitable.
it is fallacy that India is cheap. In Hyderabad, a modest apartment will cost you over 250K USD. An independent house in a reasonable area goes for a million USD. A gallon of gas will costs you more than 5 dollars. smart people are hired by facebook, google and microsoft. they have a big a presence here as in the valley and seattle. there is no healthcare, all education is privatized and has to be paid. there is no social welfare. the multinationals they pay top dollar and that drives the living index up, not down. a quick indicator is that only 7% of the population of Hyderabad moves in cars and taxis and they account for 85% of the traffic congestion. our purpose is not provide the women who work low wages, but respectable wages. but i am getting ahead of myself...
Two years ago, our local club conducted India's annual hamfest. As a part of the delegates kit, Ehsan and I decided to put free BITX PCBs in the kit. These were done without any commercial interest. At this time, the hamfest was still short of money, so we decided to buy the back page ad of the souvenier to help them with the money. I had to put in something in as text, I decided to put a message in the name of HF signals (which was the name of the wiki that is still up at www.hfsignals.org). We distributed a 1000 PCBs for free. Only a few turned up on Air. It was time to do something.
Later, in 2015, I decided to conduct a workshop to help those interested in assembling the PCBs. asked them to get the components off the local shops and we settled down to do it. i discovered that a seemingly simply job of scrapping the enamel off a copper wire would take them hours and often they'd end up doing it the wrong way. the PCBs were badly designed too. we aborted the attempt. i had learnt something : homebrewing cant be taught in a day. first fail.
i also figured that it might be easier to begin with something that is already working and then start modifying it. something that happens in open source all the time. so,i sat down and designed a new single side pcb .. with through-holes, on Express Pcb. we turned up 100 boards, found a group of five young girls who were laid off after the unit where they worked to assemble TVs had closed down. showed them how to assemble the boards. they made quite a few mistakes. the transformer windings got mixed up, resistors got swapped, the transistors were inverted, etc. each board was an adventure. you can probably see some pictures of these boards floating around. they were cheap to produce. the actual component cost of the bitx is ridiculously low. it cost us about 1000 rupees in components, another two hundred for the assembly and testing and a hundred bucks to ship it. we rounded it off to Rs.1500. About 100 of them were sold. it gave me nightmares. each board took an hour or more to fix. i decided not to do it at all. we rolled up the operations after a while. second time, fail.
by now, i had given up on doing anything with bitx boards. but a conversation with convinced me that SMD might be the way to go. we looked around and found a local SMD shop that agreed to do small runs for us. the smd components are much more expensive in india. we decided to keep the more expensive components like crystals, electrolytics in through hole format. i had to learn kicad. the women were now retrained to do the windings, insertion of through hole components and two rounds of testing. the component cost was at Rs.1500, another Rs.200 to the SMD insertion machine, Rs.200 for through hole insertion, testing. add another Rs.100 for packing and Rs.100 for local posting. we were selling these for Rs.2400 inside india and 45 dollars (a few hundred more to cover the additional expense of international postage) outside.
now, we come to the packing and shipping saga. the DHL/Speed Post quoted above Rs.1500 for shipping it internationally. that would be nearly 60% of the board's sale price. instead, we looked at the ordinary postal service. so, we bought some amazon shipping cartons, assuming that these must be good enough for us as well and shipped some boards to friends around the world. we shipped five of them with the boards in bubble wrap. all fo them arrived in good shape. we rolled with this. WE USED BUBBLE WRAP. When we started actual shipping, we realized that the bubble wrap wouldn't prevent the carton from collapsing. the coils were getting damaged. we needed some kind of a stiff roof over the board so the box's sides wouldn't collapse down. That's when we started using the foam plate over the board. The foam provides a physical shield for the coils. The foam + the amazon cartons worked for a while. Then, we ran out of cartons.
Diwali is the christmas equivalent in India, the packing materials just disappeared from the market. we looked around and bought some other cardboard gift box. we sent them out as gifts to another set of people, they reported no problems, so we continued with those. after a while, we started getting complains about those boxes as well. then, we started looking around for something else.
we found these plastic boxes to be sturdy. we tossed them around, shipped them to a few volunteers around the globe and finally agreed that these were holding up. so we continued with these boxes. these boxes are costly. they are not 'cheap'. i am personally averse to using plastic, but we thought that these were the best for the purpose. if anyone has a better idea, do test it out and let us know. we are always glad to accept anything better.
we buy our toroids from w8diz. these are genuine micrometal parts. the pcb is of high quality made to ISO-9000 standards. we import components from mouser. the only thing that we do on the 'cheap' is that we use microprocessor grade crystals that we sort out manually.
What's the current serial numbering up to as of December. Anyone know? It was #465 in early December. 465 units multiplied by $45 USD is about $21,000 USD. That converted to INR has the purchasing power in India of $70,000 USD here in the US. That's a lot of bread.
we have shipped 1000 boards. we got 45,000 dollars in revenue and we have not yet recovered our expenses. i have provided you with the figures. add them up. as i said above there are far easier ways to follow to make money than bother with these boards. that's why no one else is doing it. the design is in open source anyway.
What's my point?
Seems like with that kind of wealth in play:
1.) The product could be double-boxed and well bubble-wrapped so it arrives undamaged after it's 12,500+ km trip from Hyderabad. Old candy boxes or scraps of waste paper taped together just isn't doing the job. Broken product means unhappy customers and a bad reputation.
as i said, bubble wrap didn't work. there will be enough people here to vouch for that. we did try it.
2.) The single schematic that represents the functionality of the product could be up-to-date and error-free.
this is the schematic that was used to produce the PCB. where are the errors?
And for totally optional bonus points: A section by section Theory of Operation write-up that explains exactly how all the sections operate and how to troubleshoot. If a template is needed, look at vintage HP test instrument manuals or Heathkit ham radio transceiver manuals. Hint: Saying that, "It's all been explained many times before on many forums, Google it." does not get any points.
surely, it could be done. probably it is already done. bitx happens to be most well documented radio now. it is a community effort. look at http://golddredgervideo.com/kc0wox/ and soldersmoke and arv's work and the large amount of stuff in the file section of the bitx group and you will realize that more people know, understand and write about bitx than a proprietory manual might contain. if you think it is lacking, go ahead and write some more documentation.
oh, btw, Ehsan is not an Ayn Rand supporter. He is a radically liberal guy who is more at home with the socialists at lamakaan than the suits of the software gang.
A very nice Christmas present from Farhan in Hyderabad! An Si5351/Arduino Nano VFO for the ALREADY AWESOME BITX 40 Module. I'm really glad Farhan kept the digital stuff on a separate board -- it just seems like the right way to do it. Details on http://hfsigs.com
There is a lot of radio history in this shortwave transmitting station. I came across it tonight with my BITX DIGI-TIA rig. It was on 7.215 MHz transmitting in Indian (South Asian) languages. But alas, the signals were not from distant India (home of the BITX!). Instead -- as often happens these days -- the signals were from a relay station. In this case they came from relatively nearby Germany, from the Nauen transmitter site. Check out the Wikipedia page: https://en.wikipedia.org/wiki/Nauen_Transmitter_Station
Jim AB3CV reminded me this morning about the work of Eric NO3M. Jim was pointing out that breadboard construction need not be ugly and that Eric's work is the proof of that. Indeed.
Almost one year ago, I worked Eric on 160 meters. He was using one of his beautiful breadboard rigs:
Jim's reminder sent me once again to Eric's site. I see he has been melting a lot of solder, and to very good effect. In just three weeks he built the magnificent 1934 QST "Single Signal Superhet" pictured here.
Eric has a great series of articles on this project, with excellent pictures and videos:
As the proud owner of what has to be one of the world's UGLIEST BITX 40 Modules. I feel somehow qualified to declare Pete's version of this rig to be one of the world's most beautiful. His is resplendent in Juliano Blue -- mine has no paint at all. His features glowing numerals -- mine has nothing but Dymo stickers and an arrow drawn with a Sharpie marker. Bravo Pete!
This week Eric 4Z1UG has a really nice interview with Jim Veatch WA2EUJ. Jim is the three time winner of the ARRL Homebrew Challenge. There is a very interesting discussion of Arduinos, SDR, the technology behind automatic antenna tuners, and even some Raspberry Pi. Jim's first receiver was a Halli S38 and his first rig was a Heath HW-7. Listen here: http://www.qsotoday.com/podcasts/WA2EUJ
I'm not crazy about chips, but I've come to like the LM386. It is not really a little black mystery box -- as the article points out, the internal circuitry is simple and completely understandable. So you shouldn't feel any appliance-op angst when you use one of these.
In the BITX20 yahoo group, Farhan responded to a question about the BFO and the crystal filter in the BITX 40 Modules. In his response we learn more about the work of the members of the women's collective. Uma is the name of the lady who has the job of sorting the crystals. She sorts 1000 a day:
Farhan writes:
There is a longer explanation to this. The crystals we use in the BITX are microprocessor grade. This means that they are not very precise. Uma is the crystal sorter. She takes a bunch of 1000 crystals a day and sorts them by their frequency into different bags. Each board takes its five crystals from any one bag. Hence, the central frequency of each board will be slightly different from another board.
The central frequency of the ladder filter moves down from the oscillating frequency of the same crystal. That is why, in a set of matched crystals, one can be directly used as the carrier/beat frequency oscillator without needing any trimmer : it directly sits on the higher side skirt of the filter.
The BITX40 board's BFO usually ranges from 11.990.0 to 11.997.0, though in almost all cases it is very close to 11.998.0. The best way to determine the BFO frequency is to take it another ham's shack, tune in the BFO to zero beat on USB or LSB and note the frequency. I use the Rigol scope's built-in frequency counter to measure it off the modulator transformer's primary.
So, the IF offset should ideally set to the measured BFO's frequency. These are however, very subjective choices. Given that 2.2 KHz is not an ideal passband, 3 KHz is more like it, setting the BFO will determine how you would like to hear the receiver. Setting it close to the passband will make it bassy, setting it away will make it tinny. Setting it a few hundred hertz away will make it hollow. You get to choose which way you want to make your radio sound bad (harr! harr!)
The "al fresco" phase has ended for my HRO receiver project. As has happened with homebrew projects around the world, this rig was literally pushed aside on the workbench to make room for BITX-40 Module Mania. I began to worry that the circuitry of the HRO receiver might suffer damage from the various kinds of electronic construction mayhem that take place on our workbenches. Also, I wanted to see what it would look like in the nice big metal box that Tim Sutton had sent me (thanks again Tim.) And I was hoping that the box would help with the AM broadcast breakthrough that I sometimes hear with this receiver. So, as you can see, I have good excuses for declaring Basta! on the HRO Al Fresco. I think it looks great. Black on silver is very cool. It sounds great. I'm listening to 40 right now. Thanks to Armand WA1UQO for the very cool HRO dial that got this all started.
I was flying solo last night. Everyone else in the house was out. So I turned to ham radio for some company. And I was rewarded.
I called CQ with my BITX DIGI-TIA rig and was immediately answered by Doc AC7M in far-off Twin Peaks, Idaho. Doc was running a K3 to a homebrew solid state full gallon amp. And get this -- Doc had also homebrewed the 3 kw switching power supply. I looked at my store-bought supply and felt like an appliance operator. I hang my head in shame.
As we discussed solid state amplifiers, we were joined by another builder of silicon after-burners: Don K9AQ, who called in from a beautiful cabin in rural Wisconsin. Don's amp is based on the venerable EB-104 design. Both Don and Doc talked about the work of W6PQL. He has a really amazing site devoted to homebrew solid stat amps, and he is selling lots of great boards and parts for this kind of project: http://www.w6pql.com/ As I finishing up with Don and Doc, I got a very welcome call from an old friend from the SolderSmoke community: Dino KL0S. He as booming in from Williamsburg, Va. Dino has an amazing workshop. He is building a serious vertical antenna for 160 meters. Dino is going for the DX.
Dino's Bench
At this point Mike WA3O in Pittsburgh called in. And get this: Mike heard me on his new BITX 40 Module. The Radio Gods Have Spoken! (TRGHS!). We switched up to 7.285 MHz where I fired up my BITX 40 Module for a BITX40-BITX40 QSO (albeit not at QRP levels). We should definitely make more use of 7.285 for BITX40 and other HB QRP SSB QSOs. 1930 EST (0030 Z) seems like a good time.
Finally, just when I was thinking that things couldn't get any better, they did: Armand WA1UQO called in from Richmond. Armand and I collaborate on parts acquisition at Virginia hamfests. We specialize in the contents of the musty cardboard boxes found under the tables. We discussed the DISRUPTIVE influence of Farhan's BITX 40: All around the world, other homebrew projects are being literally pushed aside on workbenches to make room for that fantastic little module from Hyderabad. I was very pleased to hear that Armand is building an analog VFO for his module, using a coil in the 4 uH range, wound on a piece of cardboard tube from a coathanger. The inspiration for this kind of coil (which I now have in THREE rigs) came from Farhan, who used sipping straws from fast-food restaurants as coil forms in a sig generator that he built years ago. This week, seeing a Facebook picture of my daughter and me in a restaurant with drinking glasses in front of us, Farhan asked if I had brought home the straws.
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!
Hi Bill,
Was on 40M yesterday with the FPM5 rig and after finishing a QSO was called by WA7MLH (Jeff Damm –the road kill guy and protégé of Wes Hayward). Jeff was operating portable 7 in NW Montana running a homebrew 40 Watt SSB transceiver off of batteries being charged by a solar panel. Now that is real radio. I thanked him once again for sending me a goodie box about 5 years ago and am still using those parts.
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
Bill's OTHER Book (Warning: Not About Radio)
Click on the image to learn more
Where are the readers of SolderSmoke Daily News?
Pete Juliano N6QW
SolderSmoke Co-Host and Master Homebrewer
Dean Souleles KK4DAS
With beret and with a Michigan Mighty Mite in hand
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