A Double Sideband Transmitter from France -- F4IET's "Master Robert"

The Radio Gods seem to be steering us toward Double Sideband.  A few days ago I got an e-mail from Alain F4IET.   We had him on the SolderSmoke blog two years ago, talking about his French backyard pandemic Field Day.  His recent e-mail reminded me of his very fine homebrew DSB transmitter, which is his only rig and with which he has worked the world. 

The rig is named for the fellow -- Robert F6EUZ -- who is Alain's teacher from the local radio club. 

Alain's rig was shown to the world in the G-QRP club's Winter 2020 issue of SPRAT (SPRAT 185).  Once again, let me note:  If you are not subscribing to SPRAT, you are just WRONG.  Join G-QRP and start receiving SPRAT:  http://www.gqrp.com/join.htm

Alain gives some nice shout-outs to Pete N6QW,  Charlie ZL2CTM, and Basanta VU2NIL, all of whom provided advice and counsel on this project.  So think about it:  the Master Robert rig was built in France under the guidance of a French Elmer, with advice from hams in the U.S., New Zealand, and India, and was featured in journal of the British QRP club.  That, my friends is the International Brotherhood at its best. 

As I read about Alain's rig, I found myself thinking about the Direct Conversion receiver projects underway around the world.   The Vienna Wireless Society's Maker Group, is, for example, building a simple DC receiver.   It would be relatively easy to pair up a rig like the Master Robert with a DC receiver (the VFO could be the only stage common to both transmit and receive) to make a simple phone transceiver.  That kind of rig was my first phone transceiver.  Alain reports that he is currently working on a second version of the Master Robert.  It will be a transmitter-receiver (TRX) and will be used in SOTA operations. 

Alain's description of his transmitter is a lot of fun: http://www.f4iet.fr/mdwiki/#!master_robert.md

I especially liked his comment about how the other phone stations never knew he was on DSB: http://www.f4iet.fr/mdwiki/#!dsb.md I had similar experiences out in the Azores with my DSB rigs.  

Here is Alain's main page: http://www.f4iet.fr/mdwiki/#!index.md

Alain's QRZ.com page:  https://www.qrz.com/db/F4IET

Here is the Master Robert schematic from GQRP: http://www.gqrp.com/Maestro_Robert_Cct.pdf

 

Here is a link to the 76 DSB posts on the SolderSmoke blog (keep scrolling down!): 

https://soldersmoke.blogspot.com/search/label/DSB

SolderSmoke FDIM Interview with Farhan VU2ESE -- The sBITX is Coming!

Bob Crane W8SX --  our correspondent in Dayton/Xenia --  once again collected interview with FDIM presenters. Thanks Bob!  Here is his talk with our friend Farhan:  

http://soldersmoke.com/2022 VU2ESE.mp3

Here is a great post on the sBITX (May 30, 2022) from Farhan's web site: 

https://www.vu2ese.com/index.php/category/uncategorized/

Here is Farhan's amazing presentation on the sBITX at the 2021 FDIM: 

https://soldersmoke.blogspot.com/2021/11/farhans-amazing-knack-story-from.html

"Hobby High" from the Lamarkaan Radio Club and The Hindu magazine

 

https://www.thehindu.com/opinion/open-page/hobby-high/article65375392.ece?fbclid=IwAR01JGwweZuJEH1Pg15rREybZqfqKUjU3ZLbGn-xhOYZVlFPs7yN_FbJoX4

This is a really nice look at hobbies and their role in life. It is very relevant to discussions of The Knack. 

Many of the quotes resonate with me, especially those about how hobbies -- in our case ham radio -- provide an important source of enthusiasm.  I remember an old timer in Rome telling me that at age 85, he jumped out of bed each morning, heading to the radio shack with enthusiasm. 

I'd add that ham radio adds elements of permanence and continuity in our lives. For many of us, we've been working on radios since our early teens.  I have in my shack gear that I've had for almost 50 years! Amidst the vicissitudes of life, it is really nice to have things with this kind of permanence. 

Thanks to Atanu Dasgupta of the Lamakaan Amateur Radio Club of Hyderabad for alerting me to this article.  OM Atanu wrote: 

My friends, acquaintances and members from my extended family often ask me how I spend my time and keep myself busy throughout the day. When I say I pursue a hobby called Amateur Radio (Ham Radio) and I spend more than 8-10 hours in a day for that purpose, I don’t find many takers. Many of them feel that I must be earning handsomely by devoting my energy and time as seriously as pursuing a regular work-from-home regime for some corporate entity. Sometimes even my domestic help express doubts, albeit in a decent manner, about my devotion to something in life without any financial gain and expect a wage-hike for them against my ‘extra earning’. After all how can a hobby (pastime) can keep someone so engrossed physically, mentally - on the computer, over thick books/ magazines , on the work table at the radio shack, on the floor for some odd metal works, on the rooftop with antennas, over the Radio-on-air, over phone etc - without some pecuniary benefits? Recently a brilliant essay by Himani Datar on ‘hobby’ in the Hindu Magazine (https://www.thehindu.com/.../hobby-high/article65375392.ece ) has been very impressive and appears to be a savior to all concerned like me. The essay brings out all in favour of all hobbies and hobbyists and I feel more confident now about my course of engagement on a long-term basis.   

Atanu's Shack

SolderSpace! N2CQR from Geostationary Orbit

 

Farhan VU2ESE kindly invited us to talk to his Lamakaan Amateur Radio Club.  They did a simulcast through the QO-100 Geostationary Satellite.  This picture shows N2CQR being beamed into India from 22,500 miles.   Note the ET-2 and the Mythbuster on the bench.  This was a lot of fun.  Thanks Farhan! 

My Kind of Chip: A Homebrew Discrete 555 Timer Built on Wooden Boards (video)

This is really beautiful. Radraksha Vegad (Pargrahi) from India built a discrete component version of the venerable 555 timer chip.  He built it on wooden blocks.  This leads to the kind of understanding that even Jean Shepherd would have admired.  No longer is the 555 a little mysterious black box.  No, Pargrahi shows us how it works.   

 I know we could do something similar with the NE602 or the LM386.  But probably not with an Arduino microcontroller or an Si5351.  And that says something about understanding and complexity. 

Thanks Radraksha.  And thanks to Hack-A-Day for alerting us to this: https://hackaday.com/2021/12/20/all-hail-your-new-giant-555-timer-overlord/#more-512230 

The Lamakaan Annual Radio Convention Starts Today!

 

The Lamakaan Amateur Radio Club's annual convention begins today in Hyderabad, India.  This is Farhan's club so it is sure to be a great event.  Presentations are being live streamed on YouTube and on the QO100 geostationary satellite. 

Here is the link to the convention: http://www.larc.in/larc4/

Pete N6QW will be the first presenter and will talk about his new PSSST Rig. He will be speaking at 0430 UTC Saturday 11 December.  That is 11:30 pm on Friday, December 10 on the East Coast of North America.  

I will be speaking at 1130 UTC on Sunday December 12.  That is 0630 Saturday 11 December EST. I'll be talking about the Mythbuster rig and about the ET-2. 

Here is the schedule.  

Here's a time zone converter: https://www.timeanddate.com/worldclock/converter.html?iso=20211211T043000&p1=505&p2=250&p3=137

Here is the Lamakaan Club's YouTube Live Channel.  https://www.youtube.com/watch?v=cRznKwGgvDo

I don't know how we might be able to watch or listen via the QO100 satellite.  The U.S. is not in the footprint of this bird.  But there is a good WEBSDR receiver run by BATC and AMSAT DL: https://eshail.batc.org.uk/

KI4IO in India and Nepal, and Discrete Homebrew Gilbert Cells

Jerry KI4IO is such an amazing homebrewer that he has been dubbed "The Wizard of Warrenton." The picture above shows Jerry during the early 1980s in the shack of Father Moran 9N1MM in Nepal. Jerry was also in India.  (I previously posted the info on Jerry's time in India and Nepal, but I didn't have this picture.  The picture makes it worthwhile to post the story again.)  From Jerry's QRZ.com page: 

-------------------------------

While in India I was licensed at VU2LHO and worked a lot of US hams with a 135' flat-top and open-wire feed. I had the antenna strung between two bamboo towers atop the embassy housing 2nd-story roof-top. I also put up a 3/8 wave vertical on the roof for 10 meters. That little antenna had 110 radials stapled into the roof screen and worked very well! The rig was a HW-101. I was in Kathmandu, Nepal from early 1980 to late 1982. I could not obtain a license there, but became good friends with Father Moran, 9N1MM, and would often spend time up at his place putting his Drake station on CW. Pretty cool being real DX! Back in the states in late 1982.

Here I am at one of my many visits to Father Moran's shack. 

---------------------------------

Check out Jerry's QRZ.com page: https://www.qrz.com/db/KI4IO

I got in touch with Jerry because Pete Eaton reminded me that Jerry had homebrewed a discrete transistor version of the NE602 Gilbert Cell Mixer, a device that I am very interested in. Nick G8INE also built one. 

Jagadish Chandra Bose

Jagadish Chandra Bose

(30 November 1858 – 23 November 1937)

Acharya Sir Jagadish Chandra Bose, was a Bengali polymath, physicist, biologist, botanist, archaeologist, as well as an early writer of science fiction. He pioneered the investigation of radio and microwave optics, made very significant contributions to plant science, and laid the foundations of experimental science in the Indian subcontinent. IEEE named him one of the fathers of radio science. He is also considered the father of Bengali science fiction. He also invented the crescograph.

Born in Bikrampur (present day Munshiganj District near Dhaka in Bangladesh) during the British Raj, Bose graduated from St. Xavier's College, Calcutta. He then went to the University of London to study medicine, but could not pursue studies in medicine due to health problems. Instead, he conducted his research with the Nobel Laureate Lord Rayleigh at Cambridge and returned to India. He then joined the Presidency College of University of Calcutta as a Professor of Physics. There, despite racial discrimination and a lack of funding and equipment, Bose carried on his scientific research. He made remarkable progress in his research of remote wireless signaling and was the first to use semiconductor junctions to detect radio signals. However, instead of trying to gain commercial benefit from this invention, Bose made his inventions public in order to allow others to further develop his research.

Bose subsequently made a number of pioneering discoveries in plant physiology. He used his own invention, the crescograph, to measure plant response to various stimuli, and thereby scientifically proved parallelism between animal and plant tissues. Although Bose filed for a patent for one of his inventions due to peer pressure, his reluctance to any form of patenting was well known. To facilitate his research, he constructed automatic recorders capable of registering extremely slight movements; these instruments produced some striking results, such as Bose's demonstration of an apparent power of feeling in plants, exemplified by the quivering of injured plants. His books include Response in the Living and Non-Living (1902) and The Nervous Mechanism of Plants (1926).

......Bose's education started in a vernacular school, because his father believed that one must know one's own mother tongue before beginning English, and that one should know also one's own people.

Speaking at the Bikrampur Conference in 1915, Bose said:

“At that time, sending children to English schools was an aristocratic status symbol. In the vernacular school, to which I was sent, the son of the Muslim attendant of my father sat on my right side, and the son of a fisherman sat on my left. They were my playmates. I listened spellbound to their stories of birds, animals and aquatic creatures. Perhaps these stories created in my mind a keen interest in investigating the workings of Nature. When I returned home from school accompanied by my school fellows, my mother welcomed and fed all of us without discrimination. Although she was an orthodox old-fashioned lady, she never considered herself guilty of impiety by treating these ‘untouchables’ as her own children. It was because of my childhood friendship with them that I could never feel that there were ‘creatures’ who might be labelled ‘low-caste’. I never realised that there existed a ‘problem’ common to the two communities, Hindus and Muslims.”

Thanks to K.P.S. Kang for alerting us to this.

More on J.C. Bose here:

https://theprint.in/features/j-c-bose-father-of-radio-science-who-was-forgotten-by-west-due-to-his-aversion-to-patents/552556/

And here are some really interesting notes from NRAO sent to us by Drew N7DA:

 https://www.cv.nrao.edu/~demerson/bose/bose.htm

There is a crater on the Moon named for him.

Farhan's Amazing Knack Story: From a Boyhood SW Receiver to the Design of the sBITX SDR

The presentation starts at about the 4 minute point. 

I think if I were only allowed to watch one YouTube video in the next year, I'd make it this one. 

In this amazing RSGB video, Ashhar Farhan VU2ESE takes us back to his earliest days as a radio amateur.  He tells us about his very early desire to build radios, his early projects, and his personal evolution as a designer and builder,  from a simple DC receiver, to the BITX, the Minima, the uBITX and now the hybrid HDR/SDR sBITX.  

There is a lot of  homebrew wisdom and tribal knowledge in this video. And we learn so many hitherto unknown details about the rigs that have become so important to us:  

-- Farhan had the EMRFD book with him on the famous flight from Sweden to India during which the BITX was designed. 

-- We learn about the origins of the BITX oscillator circuits, and that the VFO and BFO are essentially the same.  

-- I was really pleased that Farhan included a picture of my HB BITX17 rig in his presentation. 

-- Farhan discusses the difficulties he faced in obtaining needed parts in India. 

-- We actually see the nylon washers that Farhan used in the original BITX. 

-- Farhan discusses his early system for measuring coil inductance. 

-- In addition the huge contribution of EMRFD,  Farhan talks about how he was helped by Pat Hawker G3VA's writing, and the ARRL's SSB Handbook. 

-- Farhkan talks about his Tex 465 'scope and his building of a Spectrum Analyzer. 

-- We see his evolution to dual conversion. We see the conceptual birth of the Minima and the birth (thanks Wes!) of the TIA amps.  I didn't know about the HF-1.  Then Farhan designed the uBITX and now the sBITX.  

 -- Farhan talks about his practice of taking the pictures of new rigs with the new rig sitting atop the book that was most important in its design and construction.  FB. 

-- I was really blown away by Farhan's presentation of how the uBITX advertisement was inspired by and in many ways based on the Heathkit ad for an HW-101.  Amazing. 

-- I learned a lot from Farhan's discussion of SDR theory.  I pledge to spend more time with this.  I really like Farhan's hybrid HDR/SDR approach. 

-- But I have a question:  Farhan seems to say that we'd need a big expensive GOOGL computer to do the direct sampling HF SDR.  But doesn't the little RTL-SDR do just that?  Without a GOOGL?  

-- Great to see Wes's AFTIA being used in the sBITX.  

-- Really cool that Farhan has his mind on VHF transverters when designing the sBITX.   I liked use of the TCXO module to free up one of the Si5351 clock outputs.   FB.  And great to include an idea from Hans in this rig. 

Thanks very much to Farhan (who stayed up until 3 am to do this!) and to the RSGB for hosting.

The SST QRP Transceiver

 

Click on the schematic for a better view

Bob KD4EBM recently sent me an amazing package of radio goodies.  Included was a little metal box not much larger than a deck of cards.  It is a 20 meter SST transceiver designed by Wayne Burdick N6KR during the late 1990s.  This transceiver is built around three NE602 Gilbert Cell mixer chips.  It arrived in my shack as I was struggling to understand the Gilbert Cell.  TRGHS.  It also put me back on the path of QRP CW righteousness.    Thanks Bob.  Thanks Wayne. 

I e-mailed Wayne Burdick (now of Elecraft fame) to tell him I was now using the rig he had designed so long ago.  Wayne e-mailed back, saying that the SST was the smallest "real" radio that he had ever designed.  SST stands for Simple Superhet Transceiver. 

I've been using the SST every day for the last week or so.  It is a pleasure to operate.  I'm using it with the key from India that Farhan brought for me.   It is truly QSK -- the receiver stays on when I transmit.  I've never used a QSK rig before and I can now see the big advantage that this provides:   When I am responding to a CQ, I can immediately hear if the other guy put out another CQ or respond to someone else -- I can stop calling at that point.  My first contact with it was with F6EJN.  Again, TRGHS. 

I made two small mods to the SST:  I added 1 uH to the RFC in the VXO; it  now tunes 14.053 -- 14.063.   And I took out a noise blanker that had been installed. Removing the noise blanker left an ugly hole in the front panel which I promptly filled with a completely cosmetic machine screw. 

Here's the manual:

https://qrpbuilder.com/wp-content/uploads/2017/04/sst_manual_042217.pdf

Help India's Makers Build Oxygen Concentrators for COVID Victims-- The M-19 Oxikit Initiative

Why building oxygen concentrators is NOT rocket science. 

To make a donation: 

https://www.ketto.org/fundraiser/m19-oxygen-concentrators-make-in-india

Hack-A-Day Article: 

https://hackaday.com/2021/05/10/building-an-oxygen-concentrator-it-isnt-rocket-science/

Hyderabad Field Day

Hams in Hyderabad, India held a Field Day this week.  That looks like a uBITX next to that HT.  FB! 

More info here: 

http://telanganatoday.com/hyderabad-hams-organise-field-day

HP8640B Internal Frequency Counter Fixed (More Repairs Pending)

 

The HP8640B is a complicated machine.  Above you see just one sub-assembly, and the page from the manual that describes it.  This is what I've been working on.  The little spring "tine" fell out of one of those discs behind the two control knobs.  So I had to open this thing up, find the spot from which the tine had fallen, and glue it back in.   

I used Gorilla Super Glue, followed 24 hours later by a dab of JB Weld "minute weld" dual epoxy. One of the other tines was about to fall out, so I went ahead and gave all the tines in this assembly the glue treatment.  ( I bought some "Weld On" acrylic cement but the warnings on the label were quite sobering.  So I left that can sealed up.) 

This morning I put the thing back together.  This is not easy.  At one point a spring popped and a tiny metal part that is probably irreplaceable seemed to fly away into the black hole that is the shack's carpet.   I had just about given up hope when I found the thing sitting right in front of me on the bench.  TRGHS. 

The HP8640B fired up right away without trouble and the internal frequency counter is working fine. 

As I noted in the last SolderSmoke podcast, a very nice community devoted to the HP8640B has developed around the world.  Here are some of the notable participants: 

Bill at Electronics Revisited is a very nice fellow with lots of experience on the HP8640B.  He offered to sell me a replacement unit for the assembly pictured above.  If you have an ailing HP8640B and are looking for someone to work on it for you, Bill is the guy you should talk to:  http://www.electronicsrevisited.com/  He also very kindly offers to answer any questions you may have about the HP8640B. 

Here is the e-bay page of the fellow in Bangalore who makes the brass gears.  Mine are on the way! 

https://www.ebay.com/usr/engineeringideas?_trksid=p2047675.l2559

Marcus VE7CA has a great site devoted to the HP8640B: https://www.ve7ca.net/TstH86.htm

BH1RBG in China has a nice site describing his adventures with the HP8640B: https://sites.google.com/site/linuxdigitallab/home/hp8640b-20v-power-supply-down

K6JCA has a good blog post about fixing the tines and the gears: 

http://k6jca.blogspot.com/2018/09/repair-log-hp-8640b-rotary-switches-and.html

Steve Silverman (who gave me this HP8640B) found a really useful  history of the device: 

http://hpmemoryproject.org/timeline/bob_devries/some_memories_05.htm#part_05_chapt_09

And of course special thanks to Dave VE3EAC who alerted me to the falling tine problem and put me on the path to a successful repair.  

The gears should be here in a few weeks, so that will be another opportunity to work on this HP8640B.  Also there are some tines in the attenuator assemby that might reinforce with the glue treatment. 

Global Collaboration: The uSDX -- A Multi-Mode QCX

Bill:

There is a new open source, home brew, multi band, multi mode QRP transceiver that grew out of the QRP Labs QCX. Through some serious magic it retains an efficient class E RF amplifier for sideband and digital modes. It crams impressive SDR capabilities into an Arduino. More info at https://groups.io/g/ucx/topics

The basic work appears to have been accomplished by Guido Ten Dolle PE1NNZ. It uses pulse width modulation of the PA supply voltage to transmit  modes other than CW while retaining class E efficiency and uses a direct conversion SDR receiver.

 https://github.com/threeme3/QCX-SSB .

There are several variants by different developers. I built a variant designed by Barbaros Asuroglu WB2CBA  

https://antrak.org.tr/blog/projeler/usdx-an-arduino-based-sdr-all-mode-hf-transceiver-pcb-iteration-v1-02/ that uses through hole components (mostly) and I'm pleased with it's performance. I also designed and 3D printed a case.

This has an interesting development process with contributions by many, including the usual gang of suspects: Hans Summers, Ashhar Farhan, Manuel DL2MAN, Kees K2BCQ, Allison KB1GMX and Miguel Angelo Bartie PY2OHH. I apologize to the many others whose names I didn't list.

The band switch multiband version by DL2MAN is even smaller, but with SMD components which I wasn't ready to tackle yet.

BTW - your podcast encouraged me to go in this direction. I built a BITX 40, a uBITX (sent you a pix of it in an old Heathkit Twoer case), U3S, QCX and now my first step from kits to built from plans.

73

Bob   KD8CGH

https://antrak.org.tr/blog/projeler/usdx-an-arduino-based-sdr-all-mode-hf-transceiver-pcb-iteration-v1-02/

Presence (Absence?) and Direct Conversion Receivers (with wise comments from Farhan)

Hello Bill,

    I was reading an online article by Wes Hayward, W7ZO  from 1968  about the history of direct conversion receivers (http://w7zoi.net/dcrx68a.pdf)  .  It was linked in an email in qrptech.    It recounts how he had first build a dc receiver with a single diode for the detector, and how microphonic it was, and dissatisfying an experience.   This was in the early days of solid state devices, and so they were hard to come by.   He describes meeting another ham engineer at work Dick Bingham, W7WKR who immediately recognized that what he needed was a diode ring mixer.    The story goes on to describe their experiments, and success at this design.   

  They decided to write up the design for QST.   I won't bore you with the details...the article is well worth reading about how Wes mailed the radio and the design to ARRL, and how it ended up in the hands of a new person on their staff there, Doug DeMaw, W1CER (later W1FB.).  Here is an excerpt from the article describing Doug's reaction to the receiver:

"This was the epiphany, the moment when Doug realized that solid-state technology had produce a new way to build a simple receiver. Doug tuned the receiver higher in the band and found some SSB. Again it was like nothing he had ever heard. It was as if the voice came from the same room. Doug used the term presence in his description."

Here I present the earliest use, that I know of, of presence being used to describe a receiver.    I have to say when I read it, I immediately thought of you guys, and decided to share.

Thanks for all you guys do.

   dave    /nt1u

----------------------------------------------------------

Bill replied:

Thanks Dave.   Yea, that's the 1968 article that launched the use of DC receivers.  I had forgotten about DeMaw's early use of "presence." 

Just to cause trouble, perhaps we should start commenting on "absence"  i.e.  "I dunno OM, I think your rig lacks a bit of absence in the mid-range... turn menu item 63b to ELEVEN!"  

:-)

73 Bill 

----------------------------------------------------------

 

Farhan wrote: 

Mon, Aug 3 at 3:22 PM

When I got my license, my friend Anil SM0MFC was living in Hyderabad. He lent me his HW-8.  I stringed up a 40 meter dipole with a lamp cord and worked with it. Somehow, the combination of the lamp cord length and the 40 meter inverted V made it resonate on 20 m as well. The HW-8 had a nominal antenna tuner and I worked pretty good DX.

Till date, it remains the best receiver that I have used for regular contacts. The only trouble it had was the the MC1496 was a nominal detector, it overloaded heavily with shortwave broadcast stations. There was an unnecessary RF amplifier in the front-end that they could have done without.

I made several direct conversion receivers, but never managed to hang on to any. This makes me want to build one, one of these evenings. I even have a KK7B R1 kit. but real men solder on without any PCBs or even circuit diagram!

A 7/14/21 direct conversion radio that puts out 3 watts of power is what my ideal setup would be. I am not too bothered with the images on CW. I just tune them out in my head. Real soon now, at the moment, i am trying to finish a radio that has been in the works for years.  Finally, I am making some headway.

-f

---------------------------------------------

Farhan of course is no slouch in the DC receiver area.  Years ago he wrote a wonderful post about building a DC receiver with his cousin for her class project: 

 https://web.archive.org/web/20171109081542/http://www.phonestack.com/farhan/dc40.html

Included in this post was a passage that I included in my book  SolderSmoke -- Global Adventures in Wireless Electonics: 

--------------------------

Why build a receiver?

    Why do you want to build it? These are available at the Dubai Duty Free asked Harish, an old friend, when he spotted us struggling over the DC40 one evening. I didn't have an answer to this question and considering the amount of work piled this quarter, it appeared to be a sensible thing to ask.

    I think this question is answered by us all in different ways. My personal answer would be because we human beings are fundamentally tool builders. We have an opposable thumb that allows us to grip the soldering iron.

    For an engineer (by the word ‘engineer', I don't just mean those who have a degree, but anyone who applies technical knowledge to build things) the act of building a receiver is a fundamental proof of her competence and capability. It is much easier to put out 1 watt signal than it is to receive a 1 watt signal.

    A simple definition of a good receiver is that a good receiver consistently, clearly receives only the intended signal, such a definition hides a wide range of requirements. The receiver has to be sensitive enough to pick up the weakest signal imaginable (note: clearly), it has to be selective enough to eliminate other signals (only), it has to be stable enough (consistently).

    For a ham or an engineer, building a usable receiver is a personal landmark. It establishes a personal competency to be able to understand the very fundamental operation of the radio and mastery over it.

--------------------

Bill:  OM Ryan Flowers did a 5 part series on building the DC40.  If you are want to build one, I suggest you use the schematics on Ryan's site.  There was an error in Farhan's original schematic -- Farhan corrected it but some of the incorrect schematics are still floating around the internet.  Here is part one of Ryan's series: 

 https://miscdotgeek.com/building-direct-conversion-receiver-part-1/ 

Farhan's DC40

QSO Today -- Episode 300 -- Panel Discussion

Congratulations to Eric Guth, 4Z1UG for reaching episode #300 on his QSO Today podcast.  To commemorate the event, Eric organized a panel discussion.   It was a real pleasure and honor to participate.   

Listen to it here:  https://www.qsotoday.com/podcasts/300

Thanks again Eric! 

Farhan's New uBITX Version 6!

I'm currently reviving my "version 3" uBITX and putting it on CW.  It sounds and works great, but when I saw this I realized that I am falling behind.    

Farhan wrote: 

Here is what it looks like :

https://www.youtube.com/watch?v=XdnXn5oibpg

And of course, yoiu can buy it on hfsignals.com. The shipping will happen from Tuesday onwards. We have a limited supply of the first 200 boards. The rest is for after christmas.

The most important thing about this revision is that the  Radio circuitry is almost unchanged. We have incorporated the connectors on the PCBs. So, this kit needs none of the confusing soldering. You snap in the TFT Raduino onto the main board, plug the power and antenna from the back, snap on headphones, plug in the mic (supplied with the kit) and off you go!

It is offered in two kits now : The basic kit (150 USD) is without the box (like old times) but with a microphone and two acrylic templates for the front and back panels. 

The Full kit (199 USD) has the box with speaker, mounting hardware etc. Both are described on the website. 

Now, about the TFT display: 

For those who are using the 16x2 display and you would like to upgrade, you will have to do three things:

1. Add a heatsink to the 7805 of the raduino

2. Buy https://www.aliexpress.com/item/32815224002.html?spm=a2g0o.productlist.0.0.3b9548336X8T43 and hook it up as per http://www.hfsignals.com/wp-content/uploads/2019/12/raduino_tft.pdf

3. Grab the new Arduino sketch from https://github.com/afarhan/ubitxv6

Background : 

I have been hacking away at adding a TFT display for the Arduino for sometime. Finally, I managed to do this with a really inexpensive 2.8 inch TFT display that uses a controller called the ILI9341. The display update is slow but, clever guy that I am, the display very usable. it uses the same pins that earlier connected to the 16x2 LCD display. This display is available everywhere for a few dollars. 

_._,_._,_

VU3JVX's Beautiful Homebrew Scratch-built uBITX

When Farhan announced that BITX40 Module boards would no longer be produced,  my first thought was that it is, of course, still possible to homebrew a BITX.  Anthony VU3JVX proves that in his wonderful description of his uBITX scratch-built homebrew project.  Anthony obviously learned a lot  -- perhaps the most important lesson for new homebrewers is what Anthony did when he couldn't get the receiver to work: HE TOOK A BREAK and went back after a few days.  That is very important. 

I also liked very much the fact that Anthony did what Farhan did when the receiver came to life -- he stopped building the transmitter and just listened to the receiver that he had built. FB OM.  

And three cheers for Anthony's XYL -- she was very wise to suggest that he take on a project like this when he found himself out of work.  

Anthony VU3JVX wrote: 

I would like to share my journey of building ubitx from scratch, I would also like to dedicate this to Farhan (hope he will read this sometime) as he has always motivated to homebrew stuff.

I got my license 'VU3JVX' on March 2017. Passing the exam and getting on HF bands is still two different things. Yes, I started to transmit to local VHF repeater with cheap Chinese Bafong radio, I believe the most economical way to start the ham operator experience. However, I knew that I am missing something since I was not able to operate on HF bands.Coincidentally I saw that bitx40 became available as kit from HF Signals during the same time. I was happy to try it and that's how I made my first HF rig. Then I came to know about the BITX20 forum and joined the same, one of the best thing I did after buying bitx40. I have learned a lot from all the great people caring and sharing information. I will try to contribute whatever way possible from my side in coming days.

I was already thinking of building bitx40 for other band (because the way Farhan Sir has drawn the schematic it becomes so tempting for DIY) and then ubitx happened and it changed everything. I started studying the ubitx circuit and collecting all the required components, even ordered the exact toroid from W8DIZ website (during my good days and travel to US) but I was not having enough time to put things together on the bench as I am by profession a computer network & security engineer.  I was not sure what to do next, during this time my XYL suggested me that why don't I focus on something which I always wanted to do. And that's how my journey started to build the ubitx from scratch.

Honestly, I was not sure if this was the right time to start this project. So I started to work on building the receiver segment of ubitx only. I had my challenges during this time and at one point I thought I made a wrong choice of building ubitx, instead I should had tried the bitx40 circuit first. I was almost on the verge to pack up and shelf the project because I was not able to hear anything from the receiver itself forget about building the transmitter. Then took a break for few days and then started troubleshooting each segment one by one. Finally I found it after reading through the bitx20 forum that my Q70 to be defective then I also came to know that is it better to replace it with audio type transistor 2sc945.

I believe during this process I have read most of the content on bitx20 forum. Some name which repeatedly comes to my mind are Raj (vu2zap), Allison, Jerry and thanks to all other hams out there. I had all the version schematics but started my work based on V5 and wanted to get the best out of all the version so I kept the build approach modular and laying them almost like the schematic for easy troubleshooting (you can see those pic on my qrz page).

Next challenge was trying to be too good student and follow everything the master said (pun intended). I made a cocktail of 12 Mhz with 11.059 Mhz crystal filter (Farhan Sir I believe the schematic is still showing X7 as 12 Mhz) and after changing the X7 to 11.059 Mhz I was able to see the radio signal making it through the crystal filter, then came the next hurdle of fine tuning the USB and LSB and fiddling with the software for the right value. After the receiver started working I took a break from building the radio and started enjoying the receiver and checking all bands. One evening I narrowly missed Farhan ji on air but anyway I would not have been able to communicate with him since my ubitx transmitter was not ready.

After that day I thought of building the ubitx transmitter soon. I was quiet confident about the transmitter build by this time and thought it should be straight forward. Logically yes it should had been that way but I was so wrong. Following all the recommendation from the forum about harmonic issue and how to avoid them I started building the BPF. Then I started to work on the PA section then came tuning the IRF510 current (I call it "Bell the cat moment") luckily I never blew any IRF510. However, the output watt on 40 M was hardly 2-3 Watts and other higher band less than 1 Watt. I knew something was wrong with those MOSFET but out of circuit the test look normal. I had some other stock from different source even those performed the same. Played around with different PA transformer settings and checking/tracing the RF signal. Everything looked normal till IRF510. Chances of fake IRF510 is less (as debated on the forum) as it is not an expensive RF part like RD16HHF1. Now I was confused, I had some spare new RD16HHF1 which I got online, which I was not very hopeful thinking that it might be fake. I thought of giving it a try (pin layout configuration was easy for me as I have taken the island cutting approach on single side copper board).

Voila ! I got a whopping 10+ Watt 40M, 5W on 20, 10W on 17M, 10W on 15M, 5W on 12M and 10M. Yes there are lot of fake IRF510 out there. Now it was time to test the homebrew rig on air, checked in at evening into All India Net and got 59 report and the net controller thought I am using commercial rig. Finally during these difficult time in my personal life I was able to smile and sleep well that day. The icing on the cake was installing the Nextion 3.5 display (If I remember correctly this is single most expensive component in the radio and thankfully it is optional).

Does that mean everything is 100% with my home brew ubitx ? Nope, I am still trying to figure out the feedback issue from the speaker during transmit. I traced the issue and found the audio leaking from emitter of Q6. I would like to mention that I tried all the audio circuit and finally settle for TDA2822 circuit. However, the issue is still there during transmit so I have made the audio circuit offline during transmit, I know this will impact my CW listening while transmitting when I upgrade my license . I have exhausted all solutions from Bitx20 forum but still no luck. I would be happy is someone can point me to the right direction. I would be also happy to share any information related to my build or the software settings/tuning, yes I like programming especially 'C' so I am comfortable with Arduino programs. I am thinking of building another PA module with IRF510, I personally feel IRF510 (I got the original finally) has made the home brewing so interesting. 

Anthony VU3JVX

4 Elements on 40 Meters at VU2OT (video)

Farhan Visits Northern Virginia and SolderSmoke HQ

 

Our good friend Farhan came to Northern Virginia last week for the 50th Anniversary Symposium of AMSAT.   We were really delighted that he also came to SolderSmoke HQ.  Elisa and I gave him a lightning tour of Washington DC (including a quick visit to The Air and Space museum) and then we headed back to the shack from some radio work. 

In the picture above you can see my BITX-20 (that Farhan designed) off his right shoulder.  Off his left shoulder you sits my ET-2 rig.  I really wanted to show Farhan how well the N0WVA regen performs -- he was impressed, especially when we started listening to SSB contacts. It was really amazing that we were doing this with just one J-310 FET.  This was great fun.  Farhan tells me that he will soon take up the "two transistor challenge."

When he was here in 2017, I tried to demonstrate my version of Rick Campbell's R2 Direct Conversion receiver.  Unfortunately, when I tried to show off the "single signal" capability that is the whole purpose for this receiver, it was NOT producing a single signal output -- you could hear the signal on both sides of zero beat.   One of the small AF chokes I had used had gone open, knocking our one of the two DC receivers.  This time I had the problem fixed and single signal reception was successfully demonstrated.  

Farhan brought me two pieces of test gear that I have needed for a long time:  A step attenuator and a two tone generator.  Paired with his Antuino, these devices will bring about a big increase in capability on my bench. 

It was really great to have Farhan in the shack.  We had a great time talking about ham radio and homebrewing.  Elisa and I both really enjoyed hearing from Farhan about his travels and about his life in India.  We are all really lucky to be in the same hobby as Ashhar Farhan. Thanks for the visit Farhan.

Here is a quick video of Farhan tuning the BITX 20.