Winterfest Loot: Who Can ID the Homebrew Receiver?

First a big congratulations to the Vienna Wireless Society and its President, Dean KK4DAS.  In spite of low temperatures that made the Winterfest Hamfest live up to its name, this year's 'fest was a big success with excellent turnout both by buyers and sellers.  There were a LOT of older rigs -- on one table I saw three HT-37s.   It was all great. Here is a video of the hamfest.  https://www.youtube.com/watch?v=oheht5jCuKE&t=619s  This was shot early on Sunday morning March 19, 2023, about 30 minutes after it opened.  An hour later there were a lot more customers. 

One of the first things I bought was the item pictured above.  I bought it mostly because we are currently building 40 meter receivers with the local high-school students.  I didn't have a screw driver, so I couldn't open up the box.   Something was rattling around in there.   I worried that the box might be mostly empty.  Or that it would have one PC board with a sad collection of ICs.  But in the hope that I would find something truly homebrew, I bought it.  

Below are pictures of what I found inside.  Can anyone tell us what this is?  ( I recognized it immediately.)  More on this device in due course. 

Other loot from the 'fest: 

The one on the left I've been using since around 1998!  It is getting beat up.  I bought the one on the right at the 'fest.  It is in much better condition.  5 bucks.  TRGHS. 

I always wanted one.  I had nice leather case, but I gave it to Dick Dillman years ago. I now feel like a real boatanchor guy.  I got for 15 bucks.  I see on Amazon they are selling for $466! 

I had one as a kid.  Will be useful in the DR.  In great shape. 

Eamon Skelton's book was a great find.  As were the early editions of SSB for the Radio Amateur.  Eight bucks for the whole lot.

I like homebrew speaker enclosures.  They add soul to the new machine. Perhaps a prize for the high-school project.  Three bucks. 

Finally, this thing.  Plagued by guilt for past cannibalizations of QF-1s,   I was going to pass on this one, but I realized that my friend Dean KK4DAS would be on his way, and if I didn't take it (and extract the variable capacitor) he would.  So I bought it.  But I may leave this one as is, for possible use as the The Radio Gods intended.  It could use some cleaning up.  It seems to have a coat of nicotine. Ten bucks. 

I also picked up a few larger knobs that may be of use with the high-school receivers. 

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. 

From: https://www.frcuba.cu/filiales-grupos/villa-clara/contra-el-olvido.html  with translation by Google.  

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! 

Published: 06 August 2018

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

  Monday, 06 August 2018 19:30

  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

  Monday, August 06, 2018 23:12

  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

  Monday, August 06, 2018 23:43

  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

  Tuesday, August 07, 2018 23:40

  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)

  Wednesday, August 08, 2018 09:52

  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

  Monday, August 13, 2018 00:21

  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

A Very Cool Video with NanoVNA, FFT, LC circuits, W2AEW, CuriousMarc, Back-to-Back 1N4148s, and String-Powered Gyroscopes

Don't let the scary nuclear chemistry title put you off -- there is a LOT of very familiar homebrew stuff in this video.  You will feel right at home.  Many of the resonances take place in the ham bands.   The CBLA may have to get involved here. 

Thanks to Chuck WB9KZY for sending this. 

And check out Ben's video on is best projects from the last 10 years: 

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

Listen to Pete Juliano on His Daughter Gina's Podcast -- Pete Discusses Rock Music and Life

https://podcasters.spotify.com/pod/show/gina-juliano/episodes/Mission-To-Music-This-Is-What-You-Need-To-Do--Episode-2-e20a6bs/a-a9ft547

This is really cool.   Pete Juliano N6QW is interviewed by his daughter Gina.  (You can hear it by clicking on the link above.) Gina has a podcast about the music industry called Mission to Music.  I liked it a lot.  I never realized that Pete was such big fan of rock music.  I was especially touched by Pete's closing comments on his words to live by:  "Always tell the truth and do the right thing."  Words to live by indeed.   Thanks Pete.  And thanks Gina!  

Fixing the Tuning Problem in the High-School Direct Conversion Receiver (with video)

Here is the problem: 

For the capacitive element in the LC circuit we have essentially two 660 pF caps in series.  This results in a total capacitance of 330 pf.  I measured 362 pF.  

To get a resonant frequency of 7.0 MHz with 362 pF we need 1.428 uH.

To get 1.428 uH on the PTO coil form we need about 21 turns of wire. 

21 turns on our coil form yields 1.440 uH and resonates with 362 pf at 6.9708 MHz

That’s pretty close to what we need, but the problem arises when we screw in the brass tuning screw.   This reduces the inductance and raises the frequency.  Putting the screw all the way in reduces the inductance to 1.138 uH resulting in a resonant frequency of 7.8414 MHz.  So with a coil this large (that we must use if we want to tune down to 7.0 MHz) we end up with a tuning range that is far too large.  We only need 7.0 to 7.3.   In effect, this means that we end up using only a small portion of the tuning range:  We can turn the screw approximately 34 times, but only 6 turns keep us within the range of 7 to 7.3 MHz (the 40 meter band).  There is about 50 kHz per turn of the dial.  This makes tuning difficult.  It becomes more difficult to separate stations and tune them in.  It would be better if we could tune across the band using more turns of the dial.  At least 15 turns of the dial would be nice:  That would mean about 20 kHz per turn.  But how can we do this? 

Possible solution #1:  Steel screw with tighter pitch on the turns.

Just using a steel screw slows the tuning rate down.  In a normal PTO we increase the inductance (and reduce the frequency) by gradually introducing a ferrous material that increases the inductance of the coil, pushing the frequency of oscillation down.  But our brass screw is non-ferrous.  This means that putting it into the core does not change the permeability of the coil.  The permeability of brass is the same as that of air.

What does happen,  however, is that introducing the brass screw into the coil causes currents to flow in the screw.  These are called eddy currents.  In effect they become shorted secondary coils.  And they have the effect of lowering the inductance of the coil – this is why the frequency of the oscillator increases as we screw in the brass screw.

When you use a steel screw you get both effects: As you screw it in, eddy currents flow in the screw, reducing the inductance and increasing the frequency of oscillation.  But you are also introducing ferrous material – this pushes in the opposite direction, increasing induction and lowering the frequency of oscillation.  I think the eddy current effect dominates, but the increase in permeability pushes in the opposite direction.  This means that with a steel screw you have to use more turns to cover the same frequency range.  And that is what we want. 

For example, using the same coil, with screw of the same thread pitch (the same nuts), with both screws ten turns in, one turn of the brass screw moved the inductance .014 uH.  The same single turn of the steel screw only moved the inductance .005 uH.  So just because of metallurgy, the steel screw will lead to a lower (better) tuning rate.  I used a Hillman 45479 screw that is steel with a Zinc (anti-corrosive) coating. https://www.amazon.com/Hillman-Group-45479-Phillips-Machine/dp/B00JDU0PZI   and be sure to get the correct nuts: https://www.amazon.com/Hard-Find-Fastener-014973241704-Piece-100/dp/B00L1L76E0/ref=sr_1_4?crid=UOPEF2HLAD75&keywords=1%2F4-28+nut&qid=1678881552&s=hi&sprefix=1%2F4-28+hex+nuts%2Ctools%2C71&sr=1-4

But there is more:  steel screws are also available with tighter (#28) thread pitches. The Hillman 45479 uses this tighter thread pitch.   This too means that more turns are needed to move through the same tuning range.  Again, that is what we want. 

I found that using a steel screw with #28 thread pitch allowed for the coverage of the 40 meter band in approximately 11 turns of the dial.  That is much better than what we got with the brass screw:  About 27 kHz per turn instead of the 50 kHz per turn that we got with brass.  But it is not quite good enough.   It would be better if we could use the entire range of that PTO coil form.

Solution Two:  Add a fixed inductor in series with the PTO coil. 

After some noodling, I decided to split up the inductor:  A portion of it would remain fixed, the other portion would continue to be tunable.

I estimated that I was starting out with a coil of about 1.428 uH.  So I just put a 1 uH choke in series with the variable inductor and reduced the variable coil to about .428 uH (about 9 coil turns).  This worked, but it worked a bit too well!  It would not tune the entire 40 meter band.  So I figured I needed less fixed inductance and more variable inductance.  I found an air-cored coil in my junk box and cut it so that it measured about .650 uH.  I added turns to the variable coil, going to a total of 15 turns.  This REALLY worked well and yielded the 26 or 27 turns to tune across 40 meters that you can see in the video.

TWEAKS: 

Later, I tweaked it a bit more:  With 15 turns of #22 wire on the variable inductor, a steel screw tuned from .791 uH (screw out) to .662 uH (screw in).  I put one additional turn on the fixed inductor, making it .749 uH, or about 8 turns of #22 (wound tighter on a cardboard tube from a coat hanger than was the coil on the variable inductor).   With these coils I could tune from 6.9772 to 7.386 MHz.  That's a bit more than we need but this allows us to keep the tuning away from the ends of the coil where tuning is more likely to become non-linear.  I am able to go from 7.0 to 7.3 MHz in 23 turns of the dial.  And the tuning is quite linear:  The first turn from 7.0 MHz moves the frequency 12 kHz.   At the mid-point of 7.150 MHz, one turn of the dial moves the frequency 12 kHz.   At the high end, going down from 7.3 MHz, one turn of the dial moved the frequency 11 kHz.  That, for me, is VERY linear tuning.  You probably will have to adjust the coils a bit (just squeezing the turns together or spreading them apart) to get the tuning range where you want it.    

YMMV – Keep it simple!

Like they used to say in the commercials:  Your Mileage May Vary.  There are many ways of doing this.  The objective is smooth tuning across the 40 meter band.  I think that by varying the pitch of the variable coil turns you could get a more linear tuning response (please let us know if you have any luck).  You might also be able to get similar results by changing the amount of capacitance in the feedback network (which is also the frequency determining element in this simple Colpitts oscillator).   But remember that simplicity and a low parts count were also our objectives in this.  This mod adds only 1 part (the fixed inductor), requires the removal of some turns from the main tuning cap, and perhaps the replacement of the brass screw with a steel #28 screw and nuts.  

We might present to the student this problem and our search for a solution.  This would be a good example of how homebrewers work to make their rigs better and easier to use.  It illustrates well the design dilemmas that can come up, and how amateurs like us can come up with solutions. 

A Great Lecture on Calculus -- With Discussion of Maxwell

Troubleshooting an Intermittent with Mr. Carlson. And Troublesome Tube Re-Branding.

This is a really great video on how Mr. Carlson (VE7ZWZ) did troubleshooting on a tube-type receiver. The problem was an intermittent.  They can drive you nuts, but Mr. Carlson show us how to stay sane. 

-- His use of ordinary observation at the start of the process is very important.  He notices a flickering glow in the voltage regulator tube.  The flickering coincides with the intermittent noise that he is trying to fix.  That is an important clue. 

-- He also can see that the grid of one of the AF amplifier tubes is getting way too hot: grid emission.  That is another important clue.  

-- He checks the grid voltage on the AF amplifier and finds that it is way too low.  It is fine on the other side of the resistor that carries the voltage to the tube.  But it is close to zero at the grid.   This means that the mica capacitors on the grid are suspect. 

-- He uses some fairly esoteric test gear -- a homemade device and an an old Heathkit signal tester -- to check his diagnosis.  They confirm that the mica caps are the problem.  He replaces the caps and the problem is gone.  A very satisfying troubleshoot. 

Mr. Carlson presents us with a lot of good info: 

-- 6K6 tubes were often in fact 6V6 tubes.  And 12AX7s were often 6VJ8s!  Manufacturers were deliberately re-branding tubes. So we shouldn't be surprised if some of our solid state devices turn out to be a bit different from what was promised.  This practice goes way back. 

-- I liked Mr. Carlson's final sensitivity test on the receiver -- he just waved his hand near the antenna connection and we could hear the receiver respond.  Excellent. 

-- Mr. Carlson is very negative about the use of polystyrene caps in oscillator circuits.  But we these simple and cheap caps being used to good effect in oscillators in India.  

-- The leaky and bad micas were a bit surprising.  Carlson speculates that their proximity to heat-producing resistors might have caused the trouble. 

Finally, it is interesting to hear the Canadian pronunciation of radio words:  Solder with the L pronounced (as in the UK).  Farad with the second A long and the final D emphasized (I say it just as the first two syllables of Michael Faraday's last name). 

Thanks Mr. Carlson. 

SolderSmoke Podcast #244 PETE IS BACK! TR-7, CK722, BFR106, HP8640B, High-School Receiver, 10 Min TX, MAILBAG

SolderSmoke Podcast #244 Is available:

http://soldersmoke.com/soldersmoke244.mp3

Video version at:

(118) SolderSmoke - YouTube

HE’S BACK! HOORAY! PETE JULIANO N6QW IS BACK! SOLDERSMOKE COMMUNITY WAS SENT INTO A COLLECTIVE FUNK BY PETE’S ABSENCE. ---------------- Pete’s TR-7 (SEE VIDEO ABOVE) CK722 The BFR106

Pete's new blog: https://hamradiogenius.blogspot.com/ ---- Update on the high school project: Mixers made. Harder than they seemed. First QSO with the DC RX. Allan W4AMV Homebrewer TRGHS Ten Minute Transmitter – Better than the MMM! AF4K (SK) crystals. Other supporting projects: Farhan in Hyderabad. Rick N3FJZ, Walter KA4KXX, Andreas DL1AJG Electronics for Biologists. Peter Marks VK3TPM (fighting the siren call of the Si5351) . Steven VK2BLQ built a beautiful one. Daniel VE5DLD will build three of them with his students. Orlando PY2ANE is building one in Brazil. This week: The Bandpass Filter. (Thank you Hans Summers) --- SHAMELESS COMMERCE DIVISION: BECOME A PATRON VIA PATREON. I am posting some fun stuff for the Patrons. AMAZON SHOPPING ADS Now on both the left and right columns. CHECK OUT Mostly DIY RF in the right hand column. ---- My HP8640B Lives to Fight another day. Two new DMMs A low-end Fluke and a AstroAI 6000 Electrolytic Replacement Controversy Continues

Mailbag: -- Dave AA7EE is blogging again! Yea! -- Mike Rainey AA1TJ back in the Hobbit Hole Building a WWVB receiver. -- Farhan is coming to FDIM. -- Tony G4WIF reminds us that 39 bucks for JUST a 60 MHz counter would be great! -- Dave VE3EAC again helped me fix my HP8640B. -- Dean KK4DAS finalizing 10 meter DSB rig. FB. Upgraded my NanoVNA. -- Mike KD4MM giving me a Nano VNA for the SolderSmoke Shack South. -- Ian VK3LA asked what happened to Chuck Adams content. Good question. -- Don ND6T and I have been discussing envelope detection. -- Nick M0NTV working on AM modulators. He has a new video. -- Ciprian YO6DXE built a Ten Minute Transmitter. -- Steve EI5DD Connacht Regional News: https://www.docdroid.net/YJAV800/crnews0223-pdf

Hyderabad DC RX Workshop

Farhan explaining the receiver in Hyderabad

https://soldersmoke.blogspot.com/2023/03/pictures-from-farhans-hyderabad-high.html

Pictures from Farhan's Hyderabad High-School Direct Conversion Workshops

 

Farhan came up with the idea of having high school students build their own receivers. We followed his lead -- there are now several such projects underway around the world. 

The simple but effective Colpitts circuit that Farhan recommended. 

The PTO tuning idea came out of  his "Daylight Again" transceiver. 

Oscillation!