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
When this ad appeared in 73 Magazine in February 1963 I was 4 years old, living on Manhattan Island. Pete N6QW was in the Navy, heading to Midway Island.
Pete writes:
-------------------
This ad has a tremendous impact on the foundations of our hobby. The SBE-33 was pure genius in its design and implementation.
It is a hybrid rig using Germanium transistors –the transistor was only 15 years old
The Mechanical band switching showed the strong use of mechanical assemblies
The small size was simply amazing
The Bi-lateral circuitry predates any Bitx circuits.
The urban legend was that a team of illuminati were involved in its design (Don Stoner is one name that pops up)
The Japanese were a quick study and the FTdx100 in 1967 is a result, only better.
Many are still around in shacks. I have three
Gonset was well known for innovative designs – the Gooney Box is another example. Look at all of his compact mobile equipment.
The next point – the final owner of SBE was Raytheon thusly the next generation of SDR Radio Equipment for the US Air Force can trace its pedigree to the SBE-33.
This was the appliance box of 1963. I saw my 1st SBE-33 (August 1963) when likely you were in the 2nd Grade and I was headed off to Midway island.
-----------------------
I have an SBE-33 that N6QW sent me. Thanks again Pete!
Also, I'd like to note that W6VR had a very cool name. Faust Gonsett. I just sounds like the name of a real radio guy. Google says this of the given name Faust:
"Faust as a boy's name is of Latin origin, and the meaning of Faust is 'fortunate, enjoying good luck.' Indeed.
SolderSmoke fans have an interest in saving this antenna because it is the site of one of the most amazing RF troubleshooting stories of all time: Wilson and Penzias were trying to track down some noise. At one point they thought it might be the result of bird droppings. Uh, no, it was really the result of the Big Bang! Please sign the petition:
Most of us grew up with the above diagram of how a receiver detects (demodulates) an AM signal. Here is how they say it works:
-- Because of the way the sidebands and the carrier in the transmitted signal interact, we end up with a signal whose "envelope" matches the frequency of modulation. And we just need one side of the envelope.
-- We used a simple diode to rectify the incoming signal.
-- A simple filter gets rid of the RF.
-- We pass the resulting signal through a capacitor and we get audio, which we listen to.
REASONS FOR SCEPTICISM
But recently, a member of my local radio club has questioned this explanation of AM detection. He maintained that "envelope detection" is not real, and that was actually happening was "square law" mixing. I guess there are reasons for skepticism about the envelope detection explanation: The envelope detection explanation does seem very (perhaps overly) simple. This does sound a bit like the kind of "dumbed down" explanation that is sometimes used to explain complex topics (like mixing). Envelope detection does seem consistent with the incorrect insistence from early AMers that "sidebands don't exist." (Of course, they do exist.) All the other detectors we use are really just mixers. We mix a local oscillator the incoming signal to produce audio. Envelope detection (as described in the diagram above) seems oddly different.
Denial of envelope detection can even be found in the ARRL handbook: On page 15.9 of the 2002 edition we find this: "That a diode demodulates an AM signal by allowing its carrier to multiply with its sidebands may jar those long accustomed to seeing diode detection ascribed merely to 'rectification.' But a diode is certainly non-linear. It passes current only in one direction and its output is (within limits) proportional to the square of its input voltage. These non-linearities allow it to multiply."
ISN'T THIS REALLY JUST MIXING, WITH THE CARRIER AS THE LO?
It is, I think, tempting to say -- as the ARRL and my fellow club member do -- that what really happens is that the AM signal's carrier becomes the substitute for the VFO signal in other mixers. Using the non-linearity of the square law portion of the diode's characteristic curve, the sidebands mix with the carrier and -- voila! -- get audio. In this view there is no need for the rectification-based explanation provided above.
But I don't think this "diode as a mixer, not a rectifier" explanation works:
In all of the mixers we work with, the LO (or VFO or PTO) does one of two things:
-- In non-switching mixers it moves the amplifier up and down along the non-linear characteristic curve of the device. This means the operating point of the device is changing as the LO moves through its cycle. A much weaker RF signal then moves through the device, facing a shifting operating point whose shift is set by the LO. This produces the complex repeating periodic wave that contains the sum and difference frequencies.
-- In a switching mixer, the device that passes the RF is turned on and off. This is extreme non-linearity. But here is the key: The device is being turned on and off AT THE FREQUENCY OF THE LO. The LO is turning it on and off. The RF is being chopped up at the rate of the LO. This is what produces the complex repeating wave that contains the sum and difference frequencies.
Neither of these things happen in the diode we are discussing. If you try to look at the diode as a non-switching mixer, well, the operating point would be set not by the carrier serving as the LO but by the envelope consisting of the carrier and the sidebands. And if you try to look at is as a switching mixer you see that the switching is being controlled not by the LO but by the envelope formed by the carrier and the sidebands.
Also, this "diode as a mixer" explanation would require the diode to be non-linear. That is the key requirement for mixing. I suppose you could make a good case for the non-linearity of solid state diodes, but the old vacuum tube diodes were quite linear. The rectifying diode mixer model goes back to vacuum tube days. The "diode as rectifier" model worked then. With tubes operating on the linear portion of the curve, the diodes were not -- could not -- have been working as mixers. We have just substituted solid state diodes for the tubes. The increased non-linearity of the solid state diodes does introduce more distortion, but the "detection by rectification" explanation remains valid.
Even in the "square law" region (see diagram below) an AM signal would not really be mixed in the same way as signals are mixed in a product detector. Even in the square law region, the diode would be responding to the envelope. Indeed, the Amateur Radio Encyclopedia defines "Square Law Detector" as "a form of envelope detector." And even in the square law region, the incoming signal would be rectified. It would be moving above and below zero, and only one side of this waveform would be making it through the diode. Indeed the crystal radio experts discuss "rectification in the square law region" (http://www.crystal-radio.eu/endiodes.htm ) So even in the square law region, this diode is a rectifying envelope detector.
Here is what I think is the best proof that the "envelope detection" explanation is real: In this video, we see someone build an envelope detector in a simulator. Watch as he then traces the signals as they move through the diode, the RC filter, and the coupling capacitor. He goes through it cycle-by-cycle. You can clearly see how the rectification of the AM leads to envelope detection.
The rectifying envelope detection model goes way back in radio history, back to when authors did not shy away from complex technical explanations. Terman knew how mixers worked, and his 1943 "Radio Engineers Handbook" went to 1019 pages. Terman presented it as a rectification-based detection of the envelope. I think envelope detection is real, and that Dr. Terman was right.
--------------------------------------
Some links that might help:
Analog Devices has a very good, rigorous site showing how envelope detectors work:
The crystal radio guys have a good take on square law detection (note, they just see it as rectification, but on a lower, more parabolic portion of the curve): http://www.crystal-radio.eu/endiodes.htm
Obviously there is a lot here that it applicable to ham radio. Feynman admonished us to try to deeply understand what we are doing. Do we risk cargo culting when we make use of gear that we really don't know anything about? Or when we use a chip that we don't really understand? (I'm looking at you, Si5351.)
I guess we can't really understand some of this stuff as deeply as Feynman would like -- can anyone describe the signal flow in a CPU chip? I don't think so. And Feynman would be the first to admit that no one really understands quantum mechanics. Still, as the author notes, we should be cognizant of the gaps in our understanding. For there dragons lie. Or opportunities to learn. The comments on the Hack-A-Day post are mostly pretty good.
I've said this before: I just seems so unfair. We just should be able to listen to DSB signals with our beautifully simple homebrew Direct Conversion receivers. I mean, building a DSB transmitter is a natural follow-on to DC receiver construction. And we are using AM shortwave broadcast stations (Radio Marti --I'm looking at you) to test our DC receivers for AM breakthrough. But when we tune these stations in, they sound, well, awful. So unfair! Why? Unfortunately it has to do with laws. Laws of physics and mathematics. Blame Fourier, not me.
Over the years there has been a lot of handwaving about this problem. From Doug DeMaw, for example:
In his "W1FB's Design Notebook," Doug wrote (p 171): "It is important to be aware that two DSSC (DSB) transmitters and two DC receivers in a single communication channel are unsatisfactory. Either one is suitable, however, when used with a station that is equipped for SSB transmissions or reception. The lack of compatibility between two DSSC (DSB) transmitters and two DC receivers results from the transmitter producing both USB and LSB energy while the DC receiver responds to or copies both sidebands at the same time."
That's correct, but for me, that explanation didn't really explain the situation. I mean we listen to AM signals all the time. They produce two sidebands, and our receivers respond to both sidebands, and the results are entirely satisfactory, right? Why can't we do this with our Direct Conversion receivers? I struggled with this question before: https://soldersmoke.blogspot.com/2015/07/peter-parker-reviews-dsb-kit-and.html You can see in that post that I was not quite sure I had the answer completely correct.
It took some discussion with a fellow Vienna Wireless Society member, and some Googling and Noodling for me to figure it out. But I think I've got it:
Imagine a station transmitting a DSB signal at 7100 kHz with a 1 kHz tone at the AF input. There will be signals at 7101 kHz and at 7099 kHz. Assume the carrier is completely suppressed.
We come along with our DC RX and try to tune in the signal.
Remember that they heart of the DC RX is a product detector, a mixer with the VFO (or PTO) running as close as we can get it to the suppressed carrier frequency (which we can't hear).
Lets assume that we can somehow get our VFO or PTO exactly on 7100 kHz. The incoming signals will mix with the VFO/PTO signal. We are looking for audio, so we will focus on the difference results and ignore the sum results of the mixing.
The difference between 7101 and 7000 is 1 kHz. Great! And the difference between 7099 and 7000 is 1 kHz also. Great again, right? We are getting the desired 1 kHz signal out of our product detector, right? So what's the problem?
Here it is: SIDEBAND INVERSION. Factoring in this part of the problem helps us see the cause of the distortion that plagues DSB-DC communication more clearly.
Remember the Hallas Rule: Whenever you subtract the modulated signal FROM the unmodulated signal, the sidebands invert. So, in this case, we are subtracting that 7099 "lower sideband" signal FROM the 7100 VFO/PTO signal. So it will invert. It will become an upper sideband signal at 1 kHz. We will have two identical 1 kHz signals at the output. Perfect right? Not so fast. Not so PERFECT really.
The perfect outcome described above assumes that our VFO/PTO signal is EXACTLY on 7100 kHz. And exactly in phase with the suppressed carrier of the transmitter. But if it is even SLIGHTLY off, you will end up with two different output frequencies, signals that will move in and out of alignment, causing a wobbling kind of rapid fade-in, fade-out distortion. You can HEAR this happening in this video by Peter Parker VK3YE, starting at 6:28:
And you can see it in this LTSpice simulation.
This LTSpice model just shows two diode ring mixers. The transmitter is on the top, the receiver is on the bottom. The transmitter has RF at 7100 kHz at L1 and audio at 1 kHz at R1. The receiver has the VFO at 7100.001 L7, DSB from the transmitter at L12 with audio appearing at R4. It is instructive to watch the output as you move the VFO frequency. If you move the VFO freq away from the transmit carrier osc frequency you will see the distortion. Here is the netlist for the LTSpice simulation:
On paper, using simple mixer arithmetic, you can tell that it will be there. With the VFO/PTO just 1 Hz (that's ONE cycle per second) off, you will end up with outputs at 1.001 kHz and at .999 kHz. Yuck. That won't sound good. These two different frequencies will be moving in and out of alignment -- you will hear them kind of thumping against each other. And that is with a mere deviation of 1 Hz in the VFO/PTO frequency! We are scornful when the SDR guys claim to be able to detect us being "40 Hz off." And before you start wondering if it would be possible to get EXACTLY on frequency and in phase, take a look at the frequency readout on my PTO.
Now consider what would happen if the incoming signal were SSB, lets say just a tone at 7101 kHz. We'd put our VFO at around 7100 kHz and we'd hear the signal just fine. If we were off a bit we'd hear it a bit higher or lower in tone but there would be no second audio frequency coming in to cause distortion. You can hear this in the VK3YE video: When Peter switches to SINGLE Sideband receiver, the DSB signals sound fine. Because he is receiving only one of the sidebands.
The same thing happens when we try to tune in an AM station using a Direct Conversion receiver: Radio Marti sounds awful on my DC RX, but SSB stations sound great.
My Drake 2-B allows another opportunity to explore the problem. I can set the bandwidth at 3.6 kHz on the 2-B, and set the passband so that I will be getting BOTH the upper and the lower sidebands of an AM signal. With the Product Detector and the BFO on, even with the carrier at zero beat AM sounds terrible. It sounds distorted. But -- with the Product Detector and BFO still on -- if I set the 2-B's passband to only allow ONE of the sidebands through, I can zero beat the carrier by ear, and the audio sounds fine.
There are solutions to this problem: If you REALLY want to listen to DSB with a DC receiver, build yourself a synchronous detector that gets the your receivers VFO EXACTLY on frequency and in phase with the transmitter's oscillator. But the synchronizing circuitry will be far more complex than the rest of the DC receiver.
For AM, you could just use a different kind of detector. That will be the subject of an upcoming blog post.
Please let me know if you think I've gotten any of this wrong. I'm not an expert -- I'm just a ham trying to understand the circuitry.
Above is the screenshot of the LTSpice model of the 40 meter Direct Conversion receiver that Dean KK4DAS and I have been working on. I will post a larger scale version of the picture below. Click on the images for a better view. Comments welcome. Please let us know if you find any errors or mistakes. Realize that we wanted to keep this all simple, discrete, and entirely analog.
Here (I hope!) is the net list for the LTSpice model:
First, one of the surprising things about the LTSpice model: IT IS ALIVE! I never had a VFO or PTO actually turn on for me in LTSpice. This one did! So I just connected the PTO to the Mixer and the receiver works in LTSpice. I just put an RF signal at the receiver input, and you can see the resulting AF across the 8 ohm resistor at the audio amp output. I was even able to calculate the precise frequency of the PTO: 7078 kHz. As in the real world, in an effort to stabilize the frequency, I changed the capacitors to NP0 in LTSpice. Very cool. Dean joked that all we need is a way to get RF in and audio out and we will have made an SDR receiver.
About the receiver:
-- Four stages that will be built by students Manhattan-style on four copper clad boards: Bandpass filter, diode ring mixer, Permeability Tuned Oscillator (PTO), AF Amplifier.
-- The bandpass filter is a simple dual-tuned circuit device based on the info on the QRP Labs site. (Thanks Hans!) We out a 10k pot as an RF gain control between the antenna and the filter.
-- The mixer is a standard diode ring. We included a diplexer at the output using a circuit from the famous W7EL Optimized transceiver. (Thanks Roy!)
-- The Permeability Tuned Oscillator is a very simple and very stable Colpitts design developed by Farhan VU2ESE. We added a simple FET buffer using the circuit in Farhan's Daylight Again rig. (Thanks Farhan!)
-- The AF amp is a very simple three transistor amplifier based loosely on designs from Forrest Mims and from the Herring Aid 5 receiver. Both these designs use just two stages -- we added a third and put an AF gain pot between the first and the second stages. There is an impedance mismatch between the diode ring and the AF amp, but we found that most of the proposed solutions were more trouble than they were worth, so we left it as is.
--Thanks to Wes W7ZOI for his November 1968 QST article on the solid-state DC receiver. Wes's article inspired our efforts.
Dean and I have both built these receivers. They work very well. Dean has even decoded FT-8 with his. We used Radio Marti at 7355 kHz to test for AM breakthrough -- with the diode ring, the diplexer, and the RF gain control we were able to bring the AM breakthrough down to acceptable levels. You can see many videos of my receiver in action over on my YouTube channel: (355) SolderSmoke - YouTube
Here is a larger image of the schematic (click for a full view):
And here is a nicer schematic done by our friend Walter KA4KXX:
The above video popped up on the BBC channel a few days ago. Three cheers for the Beeb for doing this, but I'd like to point out that we have been building Trivial Electric Motors for at least 16 years. We were inspired by Alan Yates VK2ZAY W7ZAY.
Below is a video from 2006:
And there are several links (and a video) about Alan and the Trivial Electric Motor here:
The improved resolution could be useful -- we may now be able to see the sidebands coming out of a mixer that is producing AF out (as in a DC receiver).
The bigger screen is nice.
Looks like Dean and I will not have to modify our TinySAs for audio out. We will just upgrade to Ultra so we can listen in style to Vatican Radio and Radio Marti.
I recently commented that I was building a discrete LM386 for a Direct Conversion receiver. I think I was exaggerating my project. In fact I just built a very ordinary push-pull amplifier using a 2N3904 and a 2N3906 as a complementary pair AF amplifier. This is part of an LM386, but there is much more inside that little chip. Dave went much further. His schematic is above.
Please find enclosed the LT spice circuit for the small audio amp that I developed. I have included numerous notes on the schematic as to component function, suggested values to tweak, etc.
My intention was to come up with a relatively low parts-count design while adhering to the classic three-stage topology [diff pair / voltage amp / voltage follower] that has been used as the basis for so many audio power amplifiers for decades. I'm sure some of the parts could be eliminated at the risk of possible stability issues, but a lot of that also depends on proper layout, length of speaker leads, speaker load impedance, etc.
In any case I thought it would be great if someone wanted to build up this design to see if it works in real life or whether any serious mods are needed to get it to behave (I have no illusion that the spice models are entirely accurate, nor is my analysis thorough).
It should be capable of at least 500mW into an 8 ohm load at 9VDC supply, and over a watt at 12VDC. It should handle a 4 ohm load although at reduced voltage swing on the output, and with increased output transistor heat dissipation requirements.
The output stage is a complimentary compound ("sziklai") pair which should, in theory, maximize voltage swing from a low supply voltage (as compared to the more traditional complimentary Darlington configuration.
The bias current is set by a fixed pair of resistors and could be quite different from the simulated value, so I would be careful on initial power-up to monitor the quiescent current draw. I would guess it need not be more than a few mA or so, and definitely less than 40mA or so. This can be made adjustable if desired.
Regards,
Dave
-----------------
So, does anyone out there want to give this a try? You could be helping to save generations of homebrewers from the indignity of using an integrated circuit!
November 18, 2022 1244 UTC. I was using a TinySA spectrum analyzer to look at noise levels on the 40 meter ham radio band. I also wanted to take a look slightly above the band (in frequency) to see Radio Marti at 7355 kHz. As I was doing this I remembered that Vatican Radio was on the air at 7305 kHz from 1230 UTC to 1245 UTC. So was just going to catch the last moments of that day's transmissions. Sure enough, I caught it, and watched it disappear from the TinySA screen. See the video above.
Radio Marti continued on. In the morning we can hear the rooster recordings from that station. We are using it to test how well our homebrew Direct Conversion receivers avoid AM detection. In the video I mistakenly said these two transmitters were on the air with 250 megawatts. The correct power is 250 kilowatts. Both transmit from Greenville NC. I think the signal from Vatican Radio is stronger here because they are using a different antenna pattern -- Radio Marti is aimed at Cuba.
This reminds me of a cool project I have not yet done: modifying the TinySA to allow the user to listen to the station: https://soldersmoke.blogspot.com/2021/10/how-to-listen-with-your-tinysa.html I notice that Dean KK4DAS (my colleague in DC receiver design) was the only commenter on the blog post describing the TinySA mod. TRGHS. We need to to do this.
Here are the reports showing when Vatican Radio and Radio Marti were on the air on November 18, 2022:
In April 1966, Lewis Fitch W4VRV of Columbus, Ohio built a Permeability Tuned Oscillator. It is remarkably similar to the devices we are building today.
Lewis opened his article with this:
Clearly, this guy was one of us!
His article is filled with good practical advice on VFO construction, with a special focus on PTOs. I was intrigued by the way his PTO mechanism allowed for the use of a reduction drive. This would help us avoid the indignity of attaching a digital frequency counter to such a quintessentially analog device.
Thanks to Michael (VE2BVW ?) for suggesting that I dig up some old 73 Magazine articles on PTOs. A quick search revealed that there weren't many. If anyone out there knows of good PTO articles in the ham or EE literature, please let me know.
This is really an amazing project. Way back in 1967 (that's 55 years ago) John Aggers W5ETT of Ponca City, Oklahoma decided to homebrew a solid state version of our beloved Drake 2-B receiver. Triple conversion. No crystal filters. Twenty two discrete transistors and no ICs. Tuned circuits at 50 kHz to provide most of the selectivity. And he did it. Just look at the picture above. It even LOOKS like a Drake 2-B.
I sent this to our friend Dale Parfitt, W4OP who more recently built a receiver like this. He too was amazed by this project.
The article by John Aggers is very clear and provides a lot of good information on how he designed and built this receiver using the technology of 1967 and junk box parts. I was struck by the lack of diode ring mixers. And I was somewhat taken aback by his use of plug-in socketed transistors. The AF amplifier is our still-familiar transformer-less push-pull complementary pair design. John did a wonderful job on the mechanical tuning and slide rule mechanism.
Three cheers for John Aggers W5ETT. This article is a reminder of the great benefit to the hobby of writing up a project and putting out there in the world. Here we are, more than half a century later, reading John's article and learning from it. FB OM.
I sometimes hear hams claim that our efforts to build simple direct conversion receivers are "very relevant" to modern technology and are "directly applicable" to today's communications techniques. These hams will say that direct conversion receivers are at the heart of modern rigs.
That's a nice thought, and it might have been true in the past, but I don't think it is true anymore.
I think the future is what you see written on the black box (!) that encloses the receiver in the above video: "DIRECT SAMPLING RECEIVER." In the recent past we did have two direct conversion receivers in the front end of SDR receiving systems. These receivers produced I and Q signals that were fed into the computer (often via the sound card). That was nice.
But the writing has been on the wall for a long time. There is no longer a need for all that direct conversion and I and Q. Just put a fast Analog-to-Digital converter chip at the front end, convert the entire HF spectrum to a digital stream, and send that stream to your computer. Or to another part of your "rig." As in the ubiquitous 7300.
I don't mean to be a Luddite here. That big waterfall is very nice. The receiver sounds great. But I am a homebrewer and I prefer to build my own gear. Ordering this black box on my phone, having it delivered by Bezos to my front step, and then updating the driver, is not what I consider homebrew radio.
A couple of things I spotted: The Si5351 chip in the box -- at least one part was recognizable. And the completely vertical skirts on all the SSB signals -- lots of 7300s out there.
Hey, to each his own, YMMV, whatever floats your boat. Just don't kid yourself into thinking that our beloved DC receivers are still somehow being used in these modern black boxes.
This is a really excellent description of how a Direct Conversion receiver works. But more importantly Nick really captures the joy of building one of these receivers using discrete, analog components, including a Permeability Tuned Oscillator made from our beloved Glue Sticks.
Extra mojo comes in the form of a mixer designed by Pete Juliano using J310s to simulate a 40673 dual gate MOSFET. Fantastic. Icing on the cake comes from a W8DIZ AF amp out of SPRAT magazine.
There is a grand finale. I won't spoil it. Watch the video. Suffice it to say that Farhan would be pleased with this.
There is really great info on this page, and even more in the links at the bottom of it. While the page is about PTOs, the links often discuss their use in Direct Conversion Receivers. I really liked the Tin Ear receiver. And it was great to again come across the work of Alan Yates VK2ZAY. Alan very admirably admits that laziness caused him to use an LM386 audio amplifier in place of a more virtuous discrete transistor design.
I bought one of the qrpbuilder PTO kits and I will soon put it together. I have been having good results with a Glue Stick PTO and with a brass screw PTO form designed by Farhan and 3D printed for me by Dean KK4DAS.
Jack Welch AI4SV has been an important member of the SolderSmoke community for many years. I remember fondly our Straight Key Night CW contact in which he told me that my HT-37 had "presence" even on CW. His thoughtful (!) piece on time crystals was also quite memorable. Jack has finally settled down (a bit) after a string of foreign assignments. He has landed happily in France, in a villa, on a vineyard, surrounded by wild boar and hunters. FB OM.
Hi Bill & Pete,
I've packed up the shack and moved from Cyprus to France, so no more 5B4APL. To obtain a French callsign, you have to submit proof that you've lived in France for three months, so I'm F/AI4SV until December and then we'll see.
I'm not sure how long we will be here, but probably a few years at least. Since we know next to nothing about French real estate, we are renting for the first couple years -- a château on the outskirts of Bordeaux. Before you think that I've come down with delusions of grandeur, I should point out that in that area, château means an old, stone house that is hard to heat in the winter -- and particularly difficult to run wiring around. Antennas and grounding are going to be particularly challenging. The selling point for the house was not so much my hobby as its location in wine country. In fact, there is a Sauterne my house's name on it (although I have nothing to do with production of the wine, that's in professional hands).
Back in the early days of Soldersmoke, Bill used to occasionally mention the dreaded Italian wild boar, the cinghiale. I didn't think that would ever be terribly relevant to me, but it is. A couple days after arriving in the Bordeaux suburbs, a sanglier (French cousin of the cinghiale) strolled across a road as I came around a bend. We almost had a month-long supply of bacon, but I managed to steer around him.
Since it will be a while before all our belongings arrive and even longer to set up a proper station, I have focused on operating QRP in the field and activating SOTA summits. That has gone well, but I aborted my most recent attempt when I ran into a bunch of orange-clad rifle-toting hunters who were combing the mountain in search of sanglier. Apparently it's a big thing here. I decided to survive to activate the peak on another day.
Finally, I have attached a journal article, which at first glance doesn't seem to have a lot to do with radio, but kind of does. It turns out that both the human ear and violins have non-linear characteristics that cause them to function as audio frequency mixers. Looking through the article, you'll find some familiar looking formulas about mixing products, harmonics and resonance. If Bill wants to get away from ICs, perhaps his next rig could include a 17th Century Italian violin as a mixing stage.
Cheers & 73,
Jack F/AI4SV
----------------------
Hello Jack:
Great to hear from you. Wow, France! You are rivaling my string of nice-to-go assignments. FB OM. Have fun.
Yes, the Cingales. Hunting season was always a bit of an uneasy time. We used to dress the kids up in reflective vests. One time we found a very drunk Italian hunter wandering around with a shotgun (that was kind of scary). We would know when hunting season started by the sound of gunfire in the morning. Kind of reminded me of other places!
In retirement I have gotten back into VWS. We are having a lot of fun. Just yesterday 30 students at the Thomas Jefferson High School got their Technician licenses. They will soon build Direct Conversion receivers.
As for mixing, what you sent reminded me of my early confusion on this subject. In the SS book I describe the "Terzo Suono" -- it is really just an additive heterodyne. I confused it
with a true mixing product. But it was an educational confusion.
Please keep in touch and let us know how things are going at the Villa!
Here is another update on Direct Conversion receiver construction. In Northern Virginia we get very strong signals from the Radio Marti transmitter in Greenville NC. During the morning hours it is just above the 40 meter band at 7335 kHz. In the evening it is a bit higher in frequency at 7435 KHz. (in the video above I mistakenly give the morning frequency, when in fact they were on the higher evening frequency). In either case, Radio Marti has been a big source of unwanted AM breakthrough in our simple DC receivers. It now serves as something of a test of our bandpass filters and mixers.
The following morning, I tested the mixer with Radio Marti (in fact) on 7335 kHz. By adjusting the VFO signal input to the minimum value needed to turn on the diodes, I was able to bring Radio Marti AM breakthrough to minimal levels. But I could still hear it (weakly) in the background. Putting a very simple diplexer at the audio output of the mixer (just a .1uF capacitor in series with a 47 ohm resistor to ground) helped a lot.
I could also hear break through from Spanish-language broadcasts from Vatican Radio on 7305 kHz (using the 250 kW transmitter in Greenville NC) from 11:30-11:45. Perhaps most surprisingly, I was also getting AM breakthrough from 40 meter FT8!
Here is a short video showing the simple two-diode mixer in action during the morning hours:
I also tried out the more common two diode mixer with trifilar toroid. (In this one, the VFO turns both diodes on, then turns both of them off). The results were similar to what I got with the other two diode mixer.
We are trying to develop four circuits -- bandpass filter, mixer, variable frequency oscillator, and audio amplifier -- that will be simple enough for construction by high school students, but not so simple as to compromise performance. We want the receiver to work well.
So far, my conclusion is that the best results come from the diode rig mixer with two trifilar toroids. Here is a short video showing the diode ring in action on the morning of November 9, 2022:
"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
The Mansfield strainer knot for fence wire
-
Rob Clark from Mansfield in a video by Tim Thomson demonstrated a strainer
knot for fence wire. Rob called it his “Everyday Knot”, Tim thought it
needed a ...
Re: Cath-O-Drive
-
Same here Bill. I have a T-471 that I am also looking for the info on.
Thought it would be fun to experiment with. Hopefully, a data sheet, is in
an atti...
Six Weeks and 7300 Miles: Activating on the Road
-
Many thanks to Brian (K3ES) who shares the following guest post: Six Weeks
and 7300 Miles: Activating on the Road by Brian (K3ES) This article gives
an ov...
VIDEO: Solar Cycle 25 update by Carl, K9LA
-
In November of 2024, Carl, K9LA gave a presentation titled "Review of
Propagation in the First Half of Cycle 25, and forecast for the Second Half
of Sola...
Tried Apple Vision Pro - a glimpse of the future
-
The Apple Vision Pro is a product they've been working towards for many
years. The software progress has been public, in the form of ARKit, and the
hardwar...
WA7GIL
-
Episode 523 - Ron Taylor - WA7GIL Ron Taylor WA7GIL, while having a love
for HF CW, boat anchor restoration, and kit building, still stays current
with hom...
A Few Free Swapmeet Finds
-
Every year in the summer, The California Historical Radio Society (CHRS) in
Alameda, CA host their annual “Radio Day by The Bay”. If you live in the
area, ...
Hollow-State Design, 3rd Edition
-
Hollow-State Design, 3rd Edition is available from: Lulu Press:
tinyurl.com/hollowstatedesign3 eBay: search for “hollow-state design”
Electric Radio bookst...
I Finally Bought My Dream Airplane
-
Aviation has been a love of mine since I was a very little person. Living
in Nevada, seeing posters and ads for the Reno Air Races, specifically the
Texa...
2000 47pF Caps ...
-
An unexpectged package arrive in the mail today. Did you ever wonder what
2000 47pF NP0 capacitors look like? Thanks to John, AB2XT I will never run ...
Broadcast Band AM Radio
-
See the YouTube series for more information:
http://www.youtube.com/c/CharlieMorrisZL2CTM
Buffer Amplifier
Low Pass Filter
IF Ampli...
New QRP Cluster From OM0ET and OM6APN
-
By DX EXPLORER
DX EXPLORER
Paul OM0ET and Peter OM6APN recently launched a new cluster dedicated to
QRP operations. Have a look and I hope you will enjoy...
3D printed project boxes
-
I have been busy with some other things that have kept me away from
electronics projects for quite a while. Now I can get back to them, but
realize I n...
Daylight Again – An all Analog Radio
-
What’s all this? In 10 seconds, A high performance, 7MHz, 5 watt SSB rig
Draws just 24 mA of current 90 dB dynamic range, 80 dB close-in dynamic
range 3D ...
Adding Enclosure to your sBitx Boards Order
-
The early buyers of the sBitx board set who bought it for $270 USD might
want to also add the enclosure (box) for in the kit. What you will now get
is a f...
Digi-chirp! Digital synthesis of ‘nostalgic’ CW
-
The bottom ends of 80, 40 and 20m are not what they used to be. For
starters, the busiest part is the digital segment where computers talk to
computers – l...
-
A Simple Speech Processor
(For QRP/SSB Homebrew Transceivers )
Over the last few weeks I had been thinking to build a small AF speech
processor to add to...
A New Look for your uBitx!
-
Adding a "Cool Blue" Display to your uBitx!
The standard "green background" with black lettering frequently reminds me
that I suffer from Chronic seasickn...
Posts
