Grayson Evans KJ7UM is the author of Hollow-State Design for the Radio Amateur, a wonderful book about using Thermatrons (aka tubes, or valves) in radio projects. Buy it here:
More info on the book is here: https://kj7um.wordpress.com/2020/12/02/hollow-state-design/ In this video, Grayson talks about construction techniques (including the use of Thermatron Me-Pads), and Manhattan construction for Thermatron projects. FB! Visit Grayson's blog: https://kj7um.wordpress.com/Podcasting since 2005! Listen to Latest SolderSmoke
Monday, February 19, 2024
Jean Shepherd has Trouble with his Heising Modulator (and his date)
This is probably Jean Shepherd's best program about homebrew ham radio. It is about how we can become obsessed with the problems that arise with equipment that we have built ourselves, and how normal people cannot understand our obsessions.
I posted about this back in 2008, but I was listening to it again today, and quickly realized that it is worth re-posting. Realize that Shepherd's Heising modulation problems happened almost 90 years ago. But the same kind of obsession affect the homebrewers of today.
Note too how Shepherd talks about "Heising" in Heising modulation. Heising has an entire circuit named for him, just like Hartley, Colpitts, and Pierce of oscillator fame. Sometimes, when I tell another ham that my rig is homebrew, I get a kind of snide, snarky, loaded question: "Well, did you DESIGN it yourself?" This seems to be a way for appliance operators to deal with the fact that while they never build anything, someone else out there does melt solder. They seem to think that the fact that you did not design the rig yourself makes your accomplishment less impressive, less threatening. This week I responded to this question with Shepherd's observation -- I told the enquiring ham that my rig is in fact homebrewed, but that I had not invented the Colpitts oscillator, nor the common emitter amplifier, not the diode ring mixer, nor the low-pass filter. But yes, the rig is homebrew, as was Shepherd's Heising modulator.
Guys, stop what you are doing. Put down that soldering iron, or that cold Miller High Life ("the champagne of bottled beer") and click on the link below. You will be transported back to 1965 (and 1934!), and will hear master story-teller Jean Shepherd (K2ORS) describing his teenage case of The Knack. He discusses his efforts to build a Heising modulated transmitter for 160 meters. He had trouble getting it working, and became obsessed with the problem, obsessed to the point that a girl he was dating concluded that there was "something wrong with him" and that his mother "should take him to a doctor."
This one is REALLY good. It takes him a few minutes to get to the radio stuff, but it is worth the wait. More to follow. EXCELSIOR! FLICK LIVES!Saturday, February 17, 2024
Nate KA1MUQ's Amazing Thermatron Receiver
Wow, some really wonderful work is taking place in Nate KA1MUQ's basement in California.
-- I really like the pill bottle coil forms. I wonder if Nate faced suspicion (and possible arrest) in the pharmacy when he asked for the pill bottles. (I got some suspicious looks when I went I asked for empty pill bottles while building my thermatron Mate for the Mighty Midget receiver back in 1998.)
-- The variable capacitors are also quite cool, as is the big rotary switch. Is that for band switching?
-- Oh man, all on a plywood board. Frank Jones would approve!
-- Indeed Nate, that beautiful receiver NEEDS an analog VFO. And we need to hear it inhaling phone sigs, not that FT8 stuff.
-- Please keep us posted on your progress. And of course, one hand behind your back OM. Lots of high voltage on those thermatrons.
Thanks Nate!
Saturday, February 3, 2024
Armand's Receiver -- A Beautiful Regen from WA1UQO
Monday, January 29, 2024
The System Source Museum (Computers, Maryland)
Wow, that bank vault in the basement is really intriguing. We need to find more of those.
The Usagi guy's 6AU6A T-shirt is pretty cool. I also liked his reference to Tracy Kidder's book "The Soul of A New Machine." I happen to be re-reading that book now. I'm struck by the complexity of even the computers of the late 1970s. At one point Kidder notes that there is only one guy on the hardware team who has a complete grasp of how the hardware in the new machine actually works. The software was probably even more inscrutable. And of course, things have gotten a LOT more complex. This is the big reason that I have decided to stick with simple, analog, discrete component, HDR rigs that I can understand. To each his own. One look at the wiring on some of those old computers tells me that this is not for me.
Thursday, November 30, 2023
AA9IL's Sputnik Tube, Altoids Tin Transmitter
Tuesday, November 21, 2023
Mr. Carlson's ART-13 Transmitter (with Dynamotor)
Thursday, November 16, 2023
The Grid Leak Detector -- Follow-up from Yesterday's Post on the Whole Earth Catalog's "Hippy" One Tube Receiver
Wednesday, November 15, 2023
Whole Earth Catalog Part II: More on SWL (and a Hippy One-Tube Receiver)
Wednesday, October 11, 2023
Sunburst and Luminary: Apollo "Rope" Memory, and other items of interest
Wow. That is the method that they stored computer memory for the moon missions. When they were satisfied with a program they would say it was time to "put it on the rope."
Here's an article on the women who built the rope memory (and the integrated circuits used in Apollo). This reminded me of the women's collective in Hyderabad that "wove" the ferrite core transformers for Farhan's BITX rigs:
Here is a Wikipedia article on core rope ROM memory with some great illustrations:
https://en.wikipedia.org/wiki/Core_rope_memory
-- Not long before the fatal Apollo 1 fire, an MIT colleague of Don Eyles had a drink with Astronaut Gus Grissom. Grissom unloaded about the poor state of the spacecraft, saying that, "What we have here is a Heathkit." Grissom died in the fire.
-- Eyles mentions the use of 6L6 tubes in analog audio amplifiers.
-- MIT's Doc Draper used a Minox camera.
-- When the Apollo 11 astronauts came back and were living for two weeks in an isolation chamber, NASA had bulldozers on standby to bury the whole thing ("astronauts, staff and all") in case some dangerous moon bug was detected. (Is that true?)
-- At one point soon before an important missile test, engineers realized that they needed an isolation transformer. They did not have enough time to order one. So they took an isolation transformer out of one of their soldering stations and used it in the missile. It worked. Sometimes you just use what you have on hand.
Thursday, September 28, 2023
A Look at Old Radios in Australia (video)
I thought you guys would like Peter Parker's latest video. And in it, Dean KK4DAS might see a clue or two for his Halli restoration/repair project.
Friday, September 15, 2023
HB2HB -- A Contact with Denny VU2DGR (video)
At first I didn't realize it was Denny. On September 11, 2023 at about 2330Z I had walked back into the shack after dinner. I think DX spots showed an Indian station on 20 meter SSB. Without realizing who it was, I tuned him in on my Mythbuster rig, heard the other station sign off, and quickly threw in my call. Denny came back to me right away, and I think both of us then realized that we recognized the call of the other station. Wow, it was Denny, VU2DGR, the Wizard of Kerala! At the time of the QSO, I didn't have my phone with me; after we spoke, I went to get it, so the video above captures part of Denny's subsequent contact. (You can also at one point hear Guapo barking.)
Denny has been running a wonderful station that combines SDR gear with and HDR tube type amplifier and a homebrew Moxon.
Here is Denny's station. The transceiver is a RadioBerry. the amplifier and power supply are on the other table.
Thursday, September 14, 2023
Building Nixie Tubes for a Hiroshima Project
Saturday, August 19, 2023
Valveman -- The Story of Gerald Wells
Tuesday, August 15, 2023
The Wizard of Kerala (India) -- Denny VU2DGR -- SDR and HDR
Tuesday, June 20, 2023
Part 2: CuriousMarc Fixes an All-Discrete Counter -- "Like an IC, but in discrete form."
Marc nicely sums up this project with this line: "It's an IC but in discrete form!" On the same theme, he later says, "Who needs a logic analyzer when you can do a visual debug with neon bulbs?"
Very cool. Lots of troubleshooting and repair lessons in this video:
-- Again we see the benefits of paper manuals. (Todd K7TFC commented astutely on this under yesterday's post.)
-- 2N2222s to the rescue.
-- A surprisingly large number of bad transistors (6?) found. Why did they go bad?
-- Marc repeatedly says, "Let me poke around." Poking around is often important. Mark fixes the reset line after poking around. He is not sure HOW he has fixed it, but he has... by poking around. Sometimes this happens. Thank God for small favors.
-- Marc has some fancy HP board extenders. I am jealous.
-- He also has a cool de-soldering tool. More jealousy. Want one.
-- Marc's understanding of how the HP engineers had to put one of the flip-flops "on the edge of stability," and how his 'scope probe was capable of disturbing this stability.
-- Remember that those Nixies are TUBES with enough voltage on them to really zap you. So be careful in there. This is an especially dangerous mix of transistor tech and tube tech. With transistors you can work on them with the rig fired up. With tubes, well, you have to be careful.
Part III tomorrow.
Sunday, April 23, 2023
Helge LA6NCA's Altoids Tin Receiver
Tuesday, April 18, 2023
CuriousMarc Powers up (and Explains) Old Cathode Ray Tubes
Sunday, April 9, 2023
Arnie Coro CO2KK (SK) Provides More Info on the Islander DSB rig
Peter Parker VK3YE found this message from Arnie CO2KK in the Wayback Machine. We continue to look for more information on the Jaguey solid state DSB rig.
Arnie wrote:
Several years ago an amateur in central Cuba was approached by some of his young friends to help them build their first rig. CO7PR, Pedro, a telecommunications technician for the phone company, had a vast experience both with vacuum tubes and solid state circuits, plus that special gift of designing and building with whatever is available. After a few days, Pedro came out with the "Islander" prototype, a low parts count, easy to build single band transceiver!
Here is the circuit description of that little radio that has provided many cuban young and old, newcomers to our hobby, with their first rig... and the challenge to improve it.
RECEIVER:
It is a direct conversion, YES, a DC receiver made with vacuum tubes. The very thought of having those tube filaments fed from the AC power supply and at the same time having 80 or 90 dB of amplification made me shudder when I first talked to Pedro on the very popular here 40 meter band! You are LOCO Pedro, I told my good friend... CRAZY, those poor kids are going to hear 50 percent 120 hZ hum when they tune across the 7 megahertz band.
Yes Arnie, you are right, it has a little background hum, but by using a small loudspeaker and small coupling capacitors... it's tolerable! The receiver shares, in its original version, the same antenna input as the transmitter output stage, a PI network, but we soon learned to add a separate LC tuned circuit first and latter a bandpass double tuned input filter...PLUS a signal attenuator... a very primitive but effective attenuator... just a 10 k potentiometer!
For an RF amplifier stage the Islander uses a russian pentode, which is the equivalent of the popular TV IF amplifiers of the 50's... looks like a 6CB6, for those of you that fixed TV sets 40 years ago or so.
The 6 "little spider" five, as everyone knows that tube here,has a lot of gain, and it can be kept rather stable by a judicious choice of screen and cathode resistor values.. Noisy pentagrid converter follows!
The 6A2P... a russian 6BE6, was the first tube type used in the Islanders, later some people tried the ECH81 triode-hexode and found it works better.
The circuit of the 6A2P-6BE6 is quite straighforward... a... you guessed right... PRODUCT DETECTOR... fed from the vacuum tube VFO... and providing its audio output to the two stage audio amplifier.
Audio amplifier is made with a triode-pentode tube of which plenty are locally available from defunct TV's... the ECL82 and the 6F4P and 6F5P of east european and russian manufacture respectively provide a lot of gain.
So... that's your receiver.. quite straightforward, works on 160, 80 and 40 meters by just changing the input filter and the VFO injection, it does NOT provide very good selectivity at all, but during the daytime, when the 40 meter band is used for local and regional contacts, it puts those new hams ON THE AIR!
VFO... the big problem amigos!
CO7PR worked very hard to try to make a stable vacuum tube VFO... and he almost made it..
YES, ISLANDERS drift, some not too much, others are not so good, depending on who built the rig, and how close they followed Pedro's advice at first, and Arnie's CO2KK later (as yours truly became quite involved in the project, as soon as I found that it was THE way of getting all those guys ON THE AIR!)
VFO is made with ONE of the 6 "little spider" 5 pentodes... By the way, I am sure you will like to know why the tube is locally known like that... the ZHE letter of the Cyrillic alphabet is something difficult to pronounce to a cuban - or any other non slavic for the matter - and it resembles like a little spider on the tube's carton and... that's why it is not a 6 "ZHE" 5 but a 6 "little spider" five!!!
The VFO cleverly works at one half the operating frequency... and then it DOUBLES frequency at the plate circuit... output is via a link to the pentagrid or hexode mixer depending on which type you use.
BUT... the VFO also has a second output to the transmitting chain.. Well that's the receiver... OH YES... the VFO is fed from a VR tube, a gaseous discharge voltage regulator similar to a VR-150 or VR-105... CO7PR advises to use the VR105, but when building the Islander, special in the countryside, that's a very hard part to find, as old TV sets don't use VR tubes! So people use whichever VR they can find. ZENERS? They are only available locally for 6 to 24 volts, so they can't be used with this rig.
ISLANDER DSB AND CW transmitter circuit:
From the VFO plate circuit, you pick up 7 mHz energy (usually you must wait at least half an hour for that said 7 mHz energy to be stable enough in frequency) and feed two diodes (ex-video detectors from russian TV type D20) acting as what I like to call BALANCED AND UNBALANCED modulator!
When used for DSB, it is certainly a DSB generator... but when you want to work CW, it must be UNBALANCED.something easy to achieve with just a resistor from the +12 volts line and a switch!
The balanced modulator receives its audio from a carbon microphone capsule salvaged from an old telephone, and conveniently connected to same +12 volts with some additional filtering via biggest possible electrolytic + small ceramic dogbone from TV set IF amplifier as RF bypass... no dogbone capacitor there... strange howls on Islander audio as RF leaks into balanced modulator you know.
So dogbone ceramic capacitor is a must! No, disk ceramics are not locally available, so people must use the next best choice... dogbone ceramics in the 100 pf to 5000 pf range, usually rated at 300 volts or so... (that 300 volt rating we learned the hard way, but more about that later.)
The original version of CO7PR's Islander ran with the carbon microphone, no MIC LEVEL control option, as he really wanted to keep things simple... later versions have audio preamps of various designs, and some even have a sort of primitive compressor.. From the balanced modulator the DSB (plus a little carrier leak that is always there) drives the rig's one or two transistor low level RF amplifier, which is made using whatever NPN silicon transistor is available, usually KT315's salvaged from TV's too. the KT315 is sort of a russian version of the 2N2222, so you understand why we use it here!
RF voltage reaches then the grid of an ex-video output amplifier vacuum tube, and there you are... about 2 to 5 watts of either DSB or CW on 40 meters and a new cuban amateur ON THE AIR!
Before I forget... keying... a little chirpy always because of so many interactions between simple circuits, sometimes not too well shielded, first time builder etc.
BUT... ISLANDER is ON THE AIR providing that young kid from the local junior high school or that doctor that always wanted to be a ham, or maybe the fresh out of school electronic technician, with the fascination of their first ever rig. YES, they drift, and some drift badly, when the frequency determining capacitors in the VFO are not too good... (most of the time), as I said they are a little chirpy. and the receiver's selectivity makes working 40 meters at night almost impossible (although some wizards do make nightime contacts at the low end of 7 mHz) BUT. YES, they are ON THE AIR.
Today there are a few Islanders still on the air, and some are even still built brand new (with many of CO7PR's and CO2KK's mods), but the trend is for all solid state rigs centered around CO5GV's and CO2JA's prototype the "JAGUEY," a design that draws a lot from Wes Hayward's Solid State Design for the Radio Amateur, and as of late, with lots of ideas coming from SPRAT, the G-QRP club magazine and QRPp from NORCAL, the Norther California QRP club!!!
In a future posting I will describe the "Jaguey," too.
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More info on the Cuban DSB and AM rigs can be found here:
https://soldersmoke.blogspot.com/2023/04/more-info-on-cuban-jaguey-solid-state.html
https://soldersmoke.blogspot.com/2023/03/homebrew-am-from-cuba.html
https://soldersmoke.blogspot.com/2023/03/more-cuban-homebrew-from-80s-and-90s.html
https://soldersmoke.blogspot.com/2023/03/schematics-for-cuban-islander-double.html
https://soldersmoke.blogspot.com/2023/03/the-islander-homebrew-dsb-rig-from-cuba.html
https://soldersmoke.blogspot.com/2023/03/needed-more-info-on-cuban-islander-or.html