Category: 40 meters

Videos from Mike AG5VG — His Homebrew BITX Rigs

Here are two great videos from Mike AG5VG showing his two homebrew receivers in action. (The transmitter portions of Farhan’s circuit will come later.) See yesterday’s post for more details.

On the video above (40 meters)
— I love that speaker.
— The enclosure and the reduction drive for the VFO is really great. FB OM.
— Very cool that Mike captures a 40 meter QSO with “Wild Bill” ZS6CCY in South Africa, someone who we’ve spoken to many times, often on the long path, sometimes from Mozambique.
— I like how Mike demonstrates the effect of removing the antenna. You can definitely see what we mean when we say you should be able to “hear the band noise.”
Above you see the 20 meter receiver in action. You can see one of the physical benefits of using a wooden base: You can easily mount connectors, switches and tuning controls using just pieces of copper-clad board screwed into the wood. This is what I am doing with my latest BITX 15-10 rig.

For the tuning of the VFO, it looks to me as if Mike has a large “main tuning” control in the center, with a smaller “fine tuning” or “bandspread” control off to the left. Does that smaller control work with a varactor diode or with a smaller variable cap? Also, to the right of the main tuning control we see a 3 pole switch. Is that switch putting additional L or C into the VFO circuit to move the frequency around? These techniques would all be quite valid; Mike demonstrates that there are many ways to skin a cat (or tune a VFO!)

Mike: Please send more info.

Pine Boards, Analog VFOs, and Homebrew BITX Transceivers — AG5VG’s Magnificent Creations

Click in image for a better view

This is amazingly cool. WE ARE NOT ALONE! There are others out there breaking the tyranny of the Si5351, building BITXs with analog LC VFOs. And using copper clad boards affixed to pine boards. Plywood cabinetry! And medicine bottle coil forms. Really great. And what a wonderful workshop. Thanks Michael.

Good Afternoon Bill,


This is Michael Sahn, AG5VG.

I hope your doing well, all is well here in south Texas. I have recently built a bitx20 receiver and bitx20 for 40 meters receiver.

I built it using the analog VFO and both of mine are stable. What an awesome feeling it is to have a stable homebrew VFO. I have attached pictures .

It’s been a fun journey to get to this step. I have just been enjoying the receiver as Farhan instructed us. Then I’m going to go through the transmit side.

Air core coils are great for VFO. On my bitx40 I used a medicine bottle bottom but I put the VFO in a tin can as you will see in the pictures.

The bitx20 is all out, hand capacitance is a slight issue but it’s all learning experience.
Going to be adjusting the pvc coil bandpass filter inductors, I think the value is a bit off so it’s not as loud as it should be, but everything else is set good.

Just wanted to check in and great job on the videos and podcasts. I really enjoy them

73s
Michael
Click on image for a better view
Click on image for a better view

Scott KQ4AOP Successfully BUILDS a Receiver (Video) — This is the Homebrew Spirit at its Maximum

This is just so cool. Scott KQ4AOP has successfully homebrewed a ham radio receiver. He used the circuit Dean and I developed (with a lot of input from Farhan and others) for the High School receiver project. But Scott has had more success than any of our students. And I think he has had — in a certain sense — more success than any of us. After all, how many of us can say — as Scott can — that he used a homebrew receiver that he made to listen — for the very first time — to amateur radio signals? Scott writes: “Those first sounds were my first time ever hearing any Amateur Radio first hand!”

In the email below, you can see Scott’s deep commitment to homebrew: “I want to build my own gear for 40m. I want to learn morse code. I want my first contact to be on my own gear.” Wow Scott, the building of the receiver is the hard part, and you have already done that. I think you are well on your way.

In the video above you can watch Scott tune the entire 40 meter band and a bit beyond. You hear CW at the low end. Then FT-8. Then SSB. Up just above the top of the band I think you can hear our old nemesis Radio Marti. And this powerful broadcaster is NOT breaking through on the rest of the band. FB Scott. Congratulations.

———————————————-

Bill,


Thank you for the quick response, direction, and pointers. I won’t give up, and I am not in a rush.


I have wanted my amateur radio license since the early-to-mid-80s. I got my Technician and General in May of 2022 and completed my Extra in May 2023. I always wanted to understand how to design circuits, and I wanted to build them. I share that background to say that I have this impractical goal that I am stubborn enough to stick to (all due respect to you and Pete’s advice on the topic of getting on the air). I want to build my own gear for 40m. I want to learn morse code. I want my first contact to be on my own gear. So, your blog and podcast really resonates with me.

I am only teaching myself at this point. It was the perfect project for my goals. I thought that if all these high school kids in Virginia, Canada, and Germany can do it, it was the sweet spot I was looking for.

The only transceiver I have was recently gifted to me. It is a Sommerkamp TS-788DX CB radio that allegedly works on 10m in addition to CB. I haven’t connected it up because I wanted to stay focused on the HSR. I have a mentor who has gear that I can use to test the oscillator. I am not involved with the nearby ham club, but I know they would help if needed.

Thanks again and I will keep you posted,

73 Scott KQ4AOP


KQ4AOPFebruary 2, 2024 at 10:49 PM

Bill and Dean – Thank you for sharing and documenting this receiver. I greatly appreciate you publishing the circuit, class notes, and build videos. That got me 75% to completion.
I feel blessed that both of you chipped in and encouraged me through the troubleshooting to finally getting the receiver to start “breathing RF”.
Those first sounds were my first time ever hearing any Amateur Radio first hand!

Happy New Year! Straight Key Night at N2CQR (video)

As you know, here at SolderSmoke East HQ we are all about TRADITION. So last night (New Year’s eve) I fired up my venerable HT-37 / Drake 2-B combo and made a few Straight Key Night (SKN) contacts on 40 meter CW. I was indeed using my straight key. Video above.

Also, be sure to check out CuriousMarc’s very cool New Year’s clock video: https://www.youtube.com/watch?v=YZmEz-Y1FFM

Happy New Year to all. May you make good progress on your homebrew projects, and may the radio gods act favorably on your behalf.

73 es HNY de N2CQR

South African Homebrew: ZS4L’s “Griffin” 40 Meter SSB Transceiver

That’s William, now ZL4L, and his homebrew 40 meter SSB transceiver. He has given the rig a wonderful name from Greek mythology: The Griffin (see below). I talked to William this morning on 10 meter SSB. I mentioned my homebrew rig and to my surprise (this doesn’t happen much) he asked for more info. Then he told me about his own homebrew creation, The Griffin. FB William!

——————-

From William’s QRZ.com page (https://www.qrz.com/db/ZS4L):

I have always wanted to build a homebrew transceiver-and recently I completed my pride and joy-a 40m SSB/MCW transceiver-I call it the ZS5WC “Griffin”..

“Griffin”..-well –if you know greek mythology you will find that it defeated much greater adversaries in battle.(to cut a long story short..)
The parallel I am getting at is..Big commercial rigs can be taken on by a rig constructed at home-and with great success!.
Sure, it does not have the bells and whistles of a 1000mp-but the TX audio is good, the RX is great , and the SMILE factor-even with all the little quirks is off the scale!..
Basically it is a single conversion superhet-4 tuned BPF stages,ATT, Gain control stage ahead of 1st Rec. Mixer/Bal. mod (NE612) , Xtal 10mhz homebrew filter,2 transistor feedback amp, second gain control stage,2nd mixer/BFO (NE612)-On TX to PA board-4 transistor pre-amp, IRF510 mosfet PA, LPF and RX /TX relay. ON RX to TL072 audio pre-amp, Spits to AGC/S-meter amp-(741 and BC107’s) and audio amp TBA820m.
ALC is done on AGC board as well with BC107 back to back to AGC bc107.
The S-meter drive is developed in the emitter leg of the AGC BC107-simple series pot to calibrate-no zero pot is required..(Works great!)
There is a volt control PCB too, with RX/TX switching.
On the main PCB there is a phase shift osc. for MCW and sidetone. Alc is adjustable from front panel from 1/2 watt to 5 watt.Rit is included in the Hartley osc. circuit and readout is done with a pic and two line LCD disp.(from AADE.com..)
Freq. drift from warm is 200Hz down in frequency then swings round and stabilises close to start freq.
Rit is good for around 5Khz swing.
Amp keying is available on the back panel, as well as an aux. 12 supply-(To run a homebrew noise squasher and amp..)


An Antenna for the High-School Direct Conversion Receiver (and Next Steps in the Project)

We have reached the point where we have to decide on an antenna for the high-school direct conversion receiver. It needs to be simple and easy. It needs to be something that students can easily install from a bedroom window in an apartment or a town house.

We thought about an End Fed Half Wave, but 66 feet of wire seemed to be too much, and the EFHW would require both coax and the construction of a transformer. That seemed like too much.

So here is what happens with just 33 feet of wire (1/4 wave on 40 meters), with another 33 feet as a counterpoise. I found that the counterpoise worked just as well spread out on the bedroom floor as it did hanging out the window along the outside of the building. As you can see in the video, the counterpoise is really necessary with this kind of antenna. It makes a big difference.

We know that the students could have dispensed with the counterpoise by connecting the copper clad boards to a cold water pipe, but that might be difficult for them. So we went with the counterpoise.

After the antenna demonstration I ramble on a bit about the high-school construction project, and where the students could go from here.

The Islander — A Homebrew DSB Rig from Cuba

This article, the pictures, and the comments are all so cool. They really capture the spirit of homebrew. Obviously we still need more information on the Islander and the Jaguey. If you have it, please send it to me and I will disseminate it via this blog.


I’ve been in touch by e-mail with Jose Campos CO6EC (the guy in the picture above). He sent me this partial schematic of the Islander (we still need the VFO circuit and the RF amplifier) . Thanks Jose!

Views: 2274
Comments: 6

Remembering

By José de Jesús Enríquez Campos (CO6EC)

Next 2019 will be the 30th anniversary of the first convention of radio amateurs in the province of Villa Clara, in Campismo de Ganuza, municipality of Corralillo, on the North coast, about 100 kilometers from Santa Clara, the provincial capital.

This convention was held on a national basis and colleagues from all the country’s provinces participated at that time. We did not reach a thousand members throughout the national territory and most of the radio amateurs worked in the 40-meter Band in Amplitude Modulation Then the Lateral Side Band (SSB) was the privilege of a few and the 2 meters was something rare, which did not yet exist in our environment.

At that meeting, a project for a Tube Transceiver was presented, quite simple, with just six vacuum tubes and a BF310 transistor. It was possible to work in HF in Double Sideband, achieving a greater efficiency than the transmission in Modulated Amplitude (AM). This project became known as the Islander.

In only two printed plates, one for the VFO and another for the TX and RX part, which by the way were printed for distribution, in a company in Villa Clara, due to their easy construction and acquisition of the components (almost all of them came out of a Krin-218 TV), a large number of such equipment were manufactured by radio amateurs from all over the country. Like everything made at home, it always comes up with a little problem that later is necessary with tinkering, correcting it.

I remember listening to an old radio amateur from Havana (whose callsign I don’t remember) in a pleasant QSO with another colleague, who jokingly said, “… some “Bugs” have now appeared in the band, called Islander, which is worse than the invasion of the Vikings…”, which gives an idea of ​​how many were built at that time, when if you wanted to make radio, you had to manufacture it, something unusual in these times.

As soon as we saw the project we decided to build it, because at that time we had an AM “transmitter” with modulation by “Carrier control” with four tubes, a 12AX7 preamplifier; an ECL82, as a modulator, with cathode output to the final tube Screen grid, a 6DQ6 and a 6BH6 as VFO; and to receive, an old Russian receiver from World War II.

We got involved in the construction and improvements of the project and we managed, with some changes, to improve its performance and quality, because among the modifications to the original, we added:

-A switch, with which you could change the transmission mode to DSB -CW-AM.
-A “Pi” Filter at the input of the RX, which considerably improved its quality.
-An automatic volume control, because since it did not have AGC (Automatic Gain Control), when someone nearby came on, it would break your speaker.
-A filter for the microphone input, which improved the quality of the modulation.
-A final power stage, with a 6146B, with 750 V on the board, for about 70 W of output, taking advantage of the 6P15P as Driver.
-The chassis was built from scratch using aluminum trays that were sold at the hardware store for “four pesos” each and that were special for making cabinets for these purposes.

After the construction was completed in one afternoon, with Reinaldo Martínez Domínguez (CO6UK), from Manicaragua, the balanced modulator was adjusted, since the good transmission of this type of equipment depends on the relationship between the amount of RF and audio that are mixed At that stage, it took us a long time to adjust, until Reinaldo with his expert ear told me, “leave it there, don’t touch it, it’s 99% complete”.

There were many international contacts that I was able to make with this very simple equipment, with very good reports, many of them with Europe, the American continent, that was very normal, since the propagation conditions in those years had nothing to do with the today, you could do half the world in AM, with about 100 W.

Many colleagues at that time asked me what equipment I was using. When I told them it was an Islander, they asked me to send them the plans of the improvements made, they were many modified plans, mimeographed.

Perhaps the youngest do not know what that was and the photos taken by colleague Joel (CO6JC) that helped to illustrate the distribution of the components in the chassis, were sent to radio amateurs from the different provinces, in the interest of contributing modestly to migrate from AM to the Double Side Band, today it is a rarity to listen to someone on AM, there are already few who appear in Double Side Band, which shows that we have developed in these almost 30 years, despite the difficulties, which We went from just under a thousand to about 8,000 throughout the country today.

From time to time, a colleague in the 40 meter Band, from another province, has told me that he still keeps the plans and photos that were sent to him at that time, or as “Kike” (CO6GO) that he still has a Islander as a relic.

Ours passed away a long time ago and part of its components went to other projects, thanks to Joel (CO6JC) there is a graphic record of it, and that at that time I had hair, which I have lost in these bustles.

With this brief comment, we only want the new generations to know what radio amateurs were like in those days and the older ones to remember it.

Nothing, to remember is to live again.

Here he left you some images.






  • (co6ec) Jose de Jesus Enriquez Campos

    The first Image was the prototype presented at the Ganuza meeting, the rest of the photos were the ones we built with the improvements, and the photos and plans were sent to many colleagues, the colleagues who went to that meeting will remember, well, they still have to there are many left, because that was almost 30 years ago,
    greetings CO6EC

  • (co8zz) Raul Verdecie

    Magnificent photographs!!!… They seem to have been taken today with some digital “super camera”!!!
    Really, from what I can see now, the CO6EC Islander was the perfect example… mine (my first radio and built by me) was also made like this, with the plates that the FRC sold and it was good, but very ugly …HI… The AGC worked wonderfully as it came, I don’t know if Jose’s improvements were later! With it I made my first hundred or so entities only in 40 meters / CW (between 7,100 and 7,150) when it was CL8ZZ. I gave it away so that someone would have their license and now I regret not having kept it… I would have liked to show it now to those who regret not having a radio!!!

  • (co8zz) Raul Verdecie

    Ah, I can never forget those headphones!!!… my external hearing aids (read ears) are much smaller today thanks to them, they exerted tons of force on the operators’ skulls!!!

  • (cm6vml) Vidal

    Very good article, I hope that one day, with a good teacher, I can build my own team, congratulations Jose, regards Vidal.

  • (co7wt) Pavel Milanes (CO7WT)

    Sure…

    My first radio and with which I got my CL7WT license back in the 90’s an ISLANDER, like that in capital letters.

    I remember that the CL only had a small 40m segment (like now) and that it was full of broadcasts as soon as the afternoon fell, it was an odyssey to speak on the radio… you had to find a “little hole” between the Broadcastings where it wouldn’t bother you ” a lot” to be able to talk.

    I remember that the old CO7OC (he is no longer a radio amateur) and CL7HU (now AC7HU) helped me build it with a board I bought at the radio club. I took almost all the valves from the deceased KRIM 218, then I found a store in Camagüey that sold idle things from the workshops…

    Turns out they had such a large inventory of “idle” tubes that they couldn’t put it on the counter…they let me through to the warehouse…huge…stack of tubes, if I remember correctly I ended up with Chinese or Japanese tubes that they were more sensitive in the receiver… the driver went from a 6P14P to a more robust 6P9, by the end that was a humble 6P44 it became two 6P7s that were a Russian version of the RCA 607 if I remember correctly… in the end it had like 80W.

    It goes without saying that when I said on the radio that there were valves in that place “they flew”….

    The VFO was the one from the Jagüey, not the original from the Islander, I never knew about the AGC modifications.

    I would like if someone has the plans with the modifications to send them to me, just for nostalgia…

    My email pavelmc@gmail.com

  • (co2jc) Carlos Alberto Santamaría González

    Brother, your article is very good, because of the nostalgia and also because it talks about what we radio amateurs like: tinkering. I didn’t have an Islander because what I started with in 2000 was a Polosa to which two colleagues helped me adapt it with VFO for 40 and 80 m. But I talked a lot with colleagues who did it with an Islander or a Jagüey and participated in the Rueda del Behique that I started in the 80 m. Others in the Hurricane Wheel that started a little later and were heard well. As you well say, the propagation at that time had nothing to do with what it is now, but it was very good to listen to the colleagues who came out with the equipment they had built. Thank you once again for your article. CO2JC

Needed: More Info on the Cuban Islander or Jaguey DSB Transceivers

CO6CBF: “I began operating on the HF bands using homebrewed radios. Mainly on CW running just 10 Watts. My very first phone transmitter was a controlled carrier AM modulator for the 160m band using tubes and components salvaged from an old TV set.”

My good friend Dean KK4DAS has built a DSB rig for 10 meters and is working a lot of DX with it. Peter Marks in Australia has also jumped into the DSB game. A few of the students we are working with at the local high school may get their General Class licenses and convert their Direct Conversion receivers to Double Sideband transceivers.

All of this has caused me to reminisce about the famous Cuban Double Sideband rigs. Homebrew Hero Arnie Coro CO2KK used to talk about these rigs on his “DXers Unlimited” program on Radio Havana Cuba. But Arnie recently passed away, and with him I think a lot of the background info on the Cuban DSB rigs has also disappeared. I find very little about these rigs on the internet — I have not been able find a single picture. The Radio Havana Cuba archive of Arnie’s shows has disappeared.

Back in February I talked to Yulian CO6YI on 20 meters about the Cuban DSB rigs. He said he had a lot of background info on them, and said he would try to send it to me. I hope he is able to do this.

The results of my initial Googling appear below. There has to be more out there. I’m thinking that there must be a lot of background info on the Islander and Jaguey rigs sitting on the hard drives of radio amateurs. It is time to give this info wider circulation. Please send me any info you have on these rigs. Of particular interest would be schematic diagrams and photos of the rigs.

https://www.paara.org/newsletter/2000/graph200007.pdf

The Super Islander Mark VI: https://docplayer.net/24137256-Radio-havana-cuba-dxers-unlimited-s-weekend-edition-for-sunday-sunday-9-august-2015-by-arnie-coro-radio-amateur-co2kk.html

Date: Mon, 22 Mar 2004 17:48:59 -0500 From: "Prof. Arnaldo Coro Antich"   Subject: Re: GB> 6EH7 vs. 6EJ7 as RF Amplifier  
 Dear amigo Chris: You are absolutely right ! EF184 is the best pentode for RF amplifier duty... But, let me ask you something... have you thought about the ECC88 and the even better ECC189 dual triodes that were designed for TV tuner work, and that incidentally were also about the last vacuum tubes ever designed from ""scratch"" until Phillips and other European manufacturers stopped from making receiving type vacuum tubes. The ECC189 is simply wonderful for a front end !!! I am sure that you are aware of our limitations here at my QTH regarding the possibility of obtaining solid state modern devices... so we still make ""new"" ham radio rigs using mostly vacuum tubes... We even still make a version of "" The Islander"" a DSB transceiver with direct conversion vacuum tube receiver... Tube lineup is EF184 RF amp ECH81 product detector ECH81 triode section not used ECL82 triode audio preamp ECL82 pentode audio output 6AH6 VFO ( Russian equivalent 6*5P ) Audio filter provided by good working brain of operator !!! Keep up the good work amigo !!! 73 and DX YOur friend in Havana Arnie Coro
CO2KK

http://ibiblio.org/modena/GLOWBUGSpiobaire/glowbugs.piobaire.weekly.html

Today’s first question came from a long time listener in India. Rajiv tells me that at this moment he is not able to pick up our station on the shortwave bands, and he rightly assumes that this is because of the very low solar activity… but Rajiv who lives in the garden city of India, Bangalore, the home of the nation’s electronic and other high tech industries, is able to read the scripts of the program that are made available to several short wave listeners clubs e-mail distribution lists. Rajiv tells me that he wants to obtain the electronic files of the Super Islander amateur radio transceiver to compare the circuit diagrams and design philosophy with a similar project that is becoming very popular among Indian radio amateurs. Ok amigo Rajiv… I have already sent you all the files including some nice digital photos of the first prototype of the Super Islander, that as you will see, has two final amplifier options , one built using NPN RF power transistors, and the other one using two vacuum tubes that are very easy to find here in Cuba from recycled TV sets. The Super Islander is a single band transceiver that can be built for the 160, 80 or 40 meter bands. Here in Cuba amigo Rajiv, the most popular amateur band nowadays is two meters, using the FM narrowband mode, and the second most popular band among Cuban radio amateurs is 40 meters, that’s why most of the Super Islanders are built for operating between 7.000 and 7.150 kiloHertz. The double sideband signal generated by the Super Islander simple circuit is very stable, and very few if any radio amateurs that contact stations using the Super Islander are able to detect that it is a double side band and not a single side band signal what they are hearing. One of the most outstanding features of the Super Islander single band amateur radio transceiver is that it is modular, so those who want to build it, are able to build and test each module as a single project, and after all the modules are fully tested, then they are easily wired together . The parts count, that is the number of components required to build a Super Islander was kept intentionally as low as possible, both to simplify its construction and to increase the reliability. I hope that amigo Rajiv in Bangolore , India will be able to make good use of the Super Islander’s files, and maybe even go ahead and build one , as the parts required are almost universally available, because that was one of the design requirements that I set when starting the Super Islander project more than fifteen years ago….You can learn more about this simple amateur band transceiver by sending a request for the Super Islander files to arnie@xxxxxx … I will send it as a dot zip file and you will be able to see circuit diagrams, photos and full descriptions of the different modules of this nice little rig, that has proven itself under the most difficult circumstances, like handling emergency communications links during tropical storms.
http://www.hard-core-dx.com/hard-core-dx/2007/msg02587.html

https://studylibfr.com/doc/10070052/nmrevue-012008

Beginners generally build one of two radios; the vacuum tube Islander or the solid state Jaguey. The Islander is a DSB/CW Cuban design using a very clever low parts count circuit and a direct conversion receiver. The Jaguey, named for the Jaguey Grande Radio Club in Matanzas province, is a generic design, with a DC receiver, DSB and CW, using solid-state components. Many of its ideas are from Wes Hayward's W7ZOI's Solid State Design for the Radio Amateur. The lack of mechanical filters or quartz crystals to homebrew SSB filters made Cuban designers CO5GV, CO2JA and CO2KK choose a DSB and CW rig. Fitted with good quality capacitors for the VFO, it works quite well from a 12-volt car battery in hurricane emergencies.
https://web.archive.org/web/20140917014137/http://www.worldradiomagazine.com/old_wro/articles/features/cuba.html

Direct Conversion Receiver Bandscan — 40 Meters early on a Thursday Morning — With W1AW/4

I superglued a San Jian frequency counter to the front panel of my High School Direct Conversion receiver. Then I tuned it through the 40 meter band. You can hear the W1AW/4 station. And several SSB stations.

The 40 Meter Direct Conversion Receiver We Have Been Working On — Comments Welcome

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:

http://soldersmoke.com/DCRXLTSPICE.net

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:

Watching Shortwave Broadcast Stations on the TinySA Spectrum Analyser

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:

DC Receiver: 100db Gain? Diplexer? VFO in a box?

Here is a progress report on Direct Conversion Receiver developments. Dual Tuned Circuit, Diode Ring with Diplexer, PTO VFO from Farhan’s Daylight rig, two stage 49 db BJT AF amp with a transformer. It works very well. I discuss: Shielding of the VFO — necessary or not? Why brass in the PTO? Do we really need 100db in a receiver, especially with ear buds? Sourcing the AF amplifier’s transformer. Using W7EL’s diplexer. (I think it has solved my Radio Marti breakthrough problem). Developing a DC RX circuit that can be built by students. I end with a bandsweep of 40 meters that includes CW, FT-8, SSB, and AM

How the Diode Ring Multiplies by 1 and -1 — “The Secrets of the Diode Ring” — Plus another Bandsweep with the DC RX

A deeper look into how the Diode Ring detector works: “the particular go of it.” Here I rely on a wonderful diagram from the RSGB. This diagram clearly shows how in this circuit, the switching action of the diodes — controlled by the VFO — results in sum and difference frequencies at the output. This is amazingly illuminating. I then tried to build this actual circuit. It works, but I am also getting a lot of AM breakthrough from a local AM station (WFAX) and Radio Marti at 7335 kHz. I will try again. In any case, the diagram shows how the diode ring does its thing! I need to beef up the Band Pass Filter. I tuned around a bit on 40 meters — you can listen. Students at a local high school have been trying to get the DC receiver I loaned to them going — they may be confused by the intricacies of SSB tuning. I will see them next week.

Here is the RSGB diagram that reveals the secrets of the Diode Ring. (Now that could be the title of a book or movie. I claim the rights to that!) Click on the image for a better view.

Bandsweep with the New Homebrew 40 meter Direct Conversion Receiver

It is inhaling nicely but some improvements are still pending. Click on the video above to see and listen to the bandsweep done on 40 this morning.

— The front end consists of capacitive divider input impedance matching circuit, followed by one LC circuit and an FET RF amp.

— The VFO is a super-simple Colpitts design by Farhan. The two feedback capacitors do double duty in the LC tan circuit.

— I am using an old variable capacitor instead of the PTOs that we have been experimenting with.

— The mixer is singly balanced using one trifilar toroid and two diodes. We have found out that even with these three simple devices, there is significant variation in how people connect them to VFO, RF in and audio out. I think we have found the best way to do this: Be sure to put the VFO on the primary of the transformer, and let this signal turn the diodes on and off.

— For the AF amplification, I have one FET, followed by two BJTs. I have a small audio transformer between the speaker and the final AF amp. There is plenty of audio.

You may wonder why, after all the SSB superhet transceivers, I am building a simple Direct Conversion receiver. Well, we hope to help a bunch of high school kids build one, so we need to be really familiar with how it works. And I find that as simple as it is, there is still a lot to learn in a project like this.

Daylight Again on the Sunrise Net! Walter KA4KXX Builds a PTO

Dear Bill:


I had never built a PTO, but after reading Farhan’s Daylight Again Transceiver article I cobbled one together with parts and pieces I had on hand. My observations so far are as follows.


1. The frequency-determining capacitors (shown on the schematic as three 470 pf) are very critical, so I feel the usual experimental cut-and-try technique is a must, even using all NP0 and C0G types.

2. After I built the 2 MHz version like the article (see first photo), the stability was terrific, but when I tried building the companion Daylight Again crystal filter, I was only able to get a bandwidth of 1.6 kHz, which is too narrow for my taste in an SSB radio, so I decided to build the same filter design but with 11 MHz crystals, where I could easily achieve a 2.8 KHz BW.

3. Therefore, now I needed a higher frequency VFO, so I merely reduced the capacitance (from about 1200 to 370 pf) without changing the coil and I am very impressed with the performance of my 4 MHz PTO (see second photo). The bandspread easily covers the entire 40M band, CW and Phone.

4. However, whenever I transmit on the 40M Phone band, I like to first set my VFO within 10 Hz of the operating frequency. That way, if I talk for five minutes or so and get up to 15 Hz of drift (which is quite common with many radios when I operate portable outdoors in the sun and wind), it will not be noticable and I avoid receiving any “you are off-frequency” chastising. But the shortcoming I have with this PTO inductor is that the 1/4-20 bolt has a coarse thread, so it is very difficult for an old fellow like me to get within even 20 Hz of a particular frequency just using this common bolt. Therefore I believe a better choice would be the fine thread 1/4-28 two-inch brass threaded bolt which is available from industrial supply houses like McMaster-Carr. However, for CW use or those with a very steady hand, the 1/4-20 works well enough.

5. I solved my fine tuning problem by adding a varactor circuit using a common 1N914 diode in series with a 100 pf capacitor, operating from 0 to 6 volts. Another advantage to adding this feature is that since I have not so far enclosed my PTO, I can mount the varactor potentiometer several inches from the PTO so my hand capacitance does not affect the frequency like when tuning with the bolt.

6. An easy way to “do the math” in my case with the common Sanjian counters is to simply create a small lookup table listing half a dozen common frequencies and stick it on the radio. For example, 90% of the time in the morning I am tuned to my favorite SouthCars Net frequency of 7251, so using a BFO setting of 10,999.900, I simply set the PTO to 3,748.90 on the 6-digit 10 Hz resolution counter I normally use (see third photo).

7. I am currently using my Daylight Again PTO on a daily basis with an NE602 receiver, and I am thinking of adding a locknut to the bolt so it does not wiggle when I jostle or move the radio, essentially giving me a crystal replacement oscillator that I can use for any single 40M frequency. To date I have been able to listen for hours at a time indoors without even any touch-up of the varactor fine tuning.

8. Also, if continuous frequency readout is desired without building a noise filter circuit board, a separate power supply for the counter is a solution. For portable operation I use Lithium Polymer radio control model airplane batteries which are light, small, and cheap, so one 12V 2000 mAH battery for the transceiver (allows a half hour of transmitting at 15 watts) and a much smaller 12V 350 mAH battery with a series resistor to reduce the current and brightness of the counter has worked well for me.

73, Walter KA4KXX
Orlando, FL

SolderSmoke Podcast #239: Hex DX, VFO Temp Comp, DC RX, Polyakov!, DX-100, Wireless Set, Farhan’s “Daylight Again” HDR rig, MAILBAG

N2CQR Hex Beam Aimed at Europe


SolderSmoke #239 is available for download:

http://soldersmoke.com/soldersmoke239.mp3

TRAVELOGUE:

James Webb Space Telescope. Mars returning to opposition in early December.

BILL’S BENCH

Hex Beam K4KIO – on roof – TV Rotor – 20-17-12 Lots of fun. Working Japan regularly, Australia, South Africa on long path 17,000 miles. 52 countries SSB since July 11.

VFOs and Temp stabilization. Dean KK4DAS found my ceramic resonator VFO for DC receiver drifty. He was right. So I built a real LC Colpitts VFO. Got me into temp stabilization. A new hobby! An obsession. HT-37 and Ht-32 parts. Ovens? WU2D’s second VFO video. Understanding thermal drift and how to address it. Split stator caps. Cut and try.

Built a Polyakov DC Receiver. https://soldersmoke.blogspot.com/2010/03/polyakov-plus-dual-band-receiver-with.html Lauser Plus. Lauser = Imp or Young Rascal! DK2RS. He used a ceramic Resonator VXO at 3.58 MHz. Mine works great on 40 with VFO running 3.5 — 3.65 MHz. See schematic below.

On 40 AM with DX-100 and MMMRX. DX-100 died. 12BY7 VFO buffer went bad. How common is failure in this tube type? Nice QSO with Tim WA1HLR about the DX-100.

Got my Dominican license: HI7/N2CQR! SSSS on the way. Thanks to Radio Club Dominicano and INDOTEL.

Getting more active in the Vienna Wireless Society.

BOOK REVIEW:

“The History of the Universe in 21 Stars” by Giles Sparrow. Written during the pandemic. Published by Welbeck, in London. https://www.amazon.com/History-Universe-21-Stars-imposters/dp/1787394654 Also: From “Atoms to Amperes” by F.A. Wilson available for download. See blog.

SHAMELESS COMMERCE DIVISION:

Todd K7TFC getting ready to launch “Mostly DIY RF.” I used his TIA boards in my 1712 rig. He will have boards like this and much more. Stay tuned.

I need more viewers on YouTube. They want 4,000 hours IN A CALENDAR YEAR! Please watch!

FARHAN’S NEW “DAYLIGHT AGAIN” RIG. Analog. VFO. Comments, observations. We need to get him on the podcast. Maybe two shows: SDR and HDR.

PETE’S BENCH

Time very limited. But still sharing lots of tribal wisdom.

Wireless set with tubes!

Tool recommendation – Air compressor

MAILBAG:

Farhan VU2ESE – Speaking of big antennas “Whenever I look at the huge construction cranes in Hyderabad, I always think how one could make 160m, 4 element yagi using it as a boom..”

Todd K7TFC in Spain, spotting Log Periodics in Madrid.

Andreas DL1AJG: Can Biologists fix Radios?

Janis AB2RA Wireless Girl. Expert on Hammarlunds. And was my first contact with the Tuna Tin 2. She too was HB!

Peter Parker VK3YE on Owen Duffy VK1OD

Lex PH2LB on homebrew radio

Would this really be homebrew? Mail from H-A-D article on FM receiver

F4IET a DSB rig from France

Ciprian got his ticket YO6DXE

Josh G3MOT sent us a good video about the Vanguard satellite and IGY.

Dave Wilcox K8WPE bought Chuck Penson’s Heathkit book.

Rogier — So many great articles and links from PA1ZZ

Bill AH6FC Aloha. Retiring. Wants to build. Mahalo!

Grayson KJ7UM Working on an Si5351. Gasp.

Mike KE0TPE viewing YouTube while monitoring 6 meters. He will have a lot of time to watch!

Chris KD4PBJ spotted Don KM4UDX from VWS FB

Mark WB8YMV building a superhet. Having trouble with 455 kc IF can filter.

Walter KA4KXX Great comment on the Daylight Again rig.

Ramakrishnan Now VU2JXN was VU3RDD. Found lost Kindle with SolderSmoke book on it. Building SDR rig from junk box. Trouble with the LM386.

Pete, Farhan and Tony: Shelves of Shame

Daylight Again by Farhan
The Polyakov receiver I built yesterday (from SPRAT 110, 2002!)

Farhan Takes us Back into the Daylight — An Analog Rig with a Homebrew Crystal Filter and an LC VFO

There is so much radio goodness in this rig and in the blog post that describes it. Farhan’s blog post will keep us busy for a long time. There is much to learn there. But perhaps even more important is his larger view of the role of analog circuitry in ham radio. Here are a couple of excerpts from his introduction:

Here is the memo : The analog never died. The world is analog all the way, until you descend into Quantum madness. The antennas are analog, Maxwell died a content, analog man. Our radios, ultimately, are analog machines and we are all analog beasts too. Amateur Radio technology has evolved into the digital domain. However, it has only made it easier for us to do analog with computers to simulate and print our circuits. So, it’s time to bid good bye to our Arduinos and Raspberry Pis and build an Analog Radio for ourselves. So let’s see what we can achieve in hindsight, a return to our native land and a rethink of our approaches. The radio is called Daylight Again, a nod to being back at the FDIM in 2022 after a gap of two years. It is named after the Crosby, Stills, Nash and Young’s song that had been humming all the time while put this radio together, emerging after 2 years of lockdown. This radio that took two days to come together, no actually two years! That’s: parts of it got built and stowed away, thoughts were struck in the shower, questions popped up during early morning cycle rides and notes and circuits were scribbled in the notebook. I must take the first of many diversion here: I hope you all maintain a notebook. Write down the date and whatever you thought or did on the bench and the result. Nothing is trivial enough to leave out. Wisdom comes to those who write notes. I started to build this on Saturday the 14th May and I checked into the local SSB net on Monday morning, the 16th May 2022.

AND

Having clean VFO is the most important way of increasing the dynamic range of your radio. A free running JEFT VFO that has sufficient power and a good Q components, will be unmatched by any synthesized or direct sampling radios. The math is all on the side of the free running VFO. We are talking -150 db/Hz at 10 KHz spacing, by comparison the Si5351 is -125 db/Hz, it is 300 times worse.

That is just part of the intro. We should all study the rest of Farhan’s blog post very carefully and incorporate the wisdom into our new rigs:

Here is the blog site:


Enough of the darkness. Step into the daylight my friends.

Pete N6QW’s Hybrid Wireless Set — A Thing of Beauty, with Thermatrons

Pete Juliano is amazing. He is admirably carrying a very heavy load of family responsibilities. But he still can build some really unique and innovative rigs. He tells us that getting up at 3 am and only sleeping 5 hours per night allows him to do this.

Pete also blames Grayson Evans KJ7UM for this rig, what with the thrematrons and all. Pete has a 7360 mixer in this rig, something that Grayson had in the 3rd edition of his Hollow-State Design book (get yours here: https://www.ermag.com/product/hollow-state-design-2nd-edition/). Pete reports that he first built the chassis for the tube (I mean thermatron) portion of the rig in the 1970s — it has been in his junkbox ever since. Grayson admires Pete’s compact construction and point-to-point wiring.

I too noticed very poor conditions on Field Day this year.

Three cheers for Pete Juliano!

W8ZAP on 40 AM with a Collins 20V3 Broadcast Transmitter

I was on 40 AM yesterday morning and I talked to Jerry W8ZAP (great callsign) out in Michigan. Jerry was running his Collins 20V3 (above on the right), which was originally an AM broadcast band transmitter. FB.

Here is Jerry’s QRZ.com page: https://www.qrz.com/db/W8ZAP

Farhan’s New Rig: Daylight Again! Analog!

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 printed rock stable, slow tuning PTO with zero backlash.

  • 3D printed toroids

  • You have all the parts in the junk box or you can buy them tonight at the vendor night.

  • Very stable, slow tuning VFO with no backlash

  • Costs less than 20 dollars to build, even in new parts.