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Wednesday, May 15, 2024
CuriousMarc Looks at Phase-Locked Loops (PLL)
Monday, April 29, 2024
Old Tricks, Lore, and Art -- Freezing and Baking our LC VFOs -- An Example from Cuba
Pavel CO7WT explained why Cuban hams used a process of thermal endurance to improved the frequency stability of their homebrew rigs:
--------------------
I'm CO7WT from Cuba, I started my endeavor in ham radio with a islander board.
They (FRC, like ARRL but in Cuba) made a print of a PCB to build the Islander, with component numbers and values, making construction fool proof, I think it was on the 90 or end of the 80...
Mine was built with scraps from an old KRIM 218 Russian B&W TV as Coro's explain, later on I get the 6bz6 and 6be6 tubes for the receiver (this worked better than the Russian parts) the VFO was transistorized, made with Russian components. A friend CO7CO Amaury, explain me a trick: thermal endurance:
For a week put a crust of ice on the VFO board by placing it in a frosty fridge during the night. Put them in the sun by day. This indeed improved stability, this was an old trick.
By thermal endurance I
mean improving thermal resistance vs tolerance, meaning that tolerance doesn't
vary as much with temperature changes.
I remember that my vfo was on 7 MHz, with Russian kt315 as normal Russian transistors and capacitors, nothing 1-5%, 20% at most, it ran several khz in 5-10 min, mounted on a Russian "Formica" board (no PCB) and wired underneath.
After that treatment to the complete board with components and everything, including the variable capacitor; I managed to get it to "only" noticeably in the ear after 30-40 minutes.
To me it was magic!!
Basically, what I'm describing is just "thermal annealing", but Cuban-style and with more extreme limits.
In a refrigerator you could easily reach -10 c and in the sun for a day in Cuba 60-80 celsius at least.
In Cuba in the 1990s-2010s many designs of DSB radios proliferated, both direct conversion and super heterodine (using an intermediate frequency)
At first tubes and then transistors, mostly using salvaged parts, so it was common to find 465/500 kHz (if common Russian) 455 khz and 10.7 Mhz with or without "wide" filters since narrow filters for SSBs were not scarce: they were almost impossible to get.
Not only that, crystals, ifs, PCBs, transistors, etc.
Then, around the 2000s, Russian 500 khz USB filters began to appear (from Polosa, Karat, etc. equipment from companies that deregistered and switched to amateur radio) and that contributed to improving... Even though at 7 MHz 500kc if is very close.
I made many modifications with the years mostly from 1998 to 2004 ish... better filters in front of the first RX stage (same IF described between stages) improved selectivity and out of band rejection, remember we had on that days broadcast as low as 7100 khz
Tx part was a pair of russian 6P7 (eq. RCA 807) in paralell, etc.
The Jagüey and others is one of those evolutions...
73 CO7WT
----------------
This is not as crazy as it sounds. We can find versions of the same technique in the writings of Roy Lewellan W7EL, Doug DeMaw W1FB, and Wes Hayward W7ZOI. I found this 2007 message from our friend Farhan VU2ESE:
I think the word 'annealing' is a bit of a misnomer. the idea is to thermally expand and contract the wiring a few times to relieve any mechanical stresses in the coil. after an extreme swing of tempuratures, the winding will be more settled.
this techniques owes itself to w7EL. I first read about it in his article on the 'Optimized transceiver' pulished in 1992 or so.
but all said and done, it is part of the lore. it needs a rigorous proof.
- farhan
And here is another example of coil boiling:
https://www.qsl.net/kd7rem/vfo.htm
-----------
I can almost hear it, all the way from across the continent: Pete N6QW should, please, stop chuckling. Obviously these stabilization techniques are not necessary with his beloved Si5351. Some will see all this as evidence of the barbarity and backwardness of LC VFOs. But I see it as another example of lore, of art in the science of radio. (Even the FCC regs talk about "Advancing the radio art." ) This is sort of like the rules we follow for LC VFO stability: keep the frequency low, use NP0 or silver mica caps, use air core inductors, keep lead length short, and pay attention to mechanical stability. Sure, you don't have to do any of this with an Si5351. Then again, you don't have to do any of this to achieve stability in an Iphone. But there is NO SOUL in an Iphone, nor in an Si5351. Give me a Harley, a Colpitts, or a Pierce any day. But as I try to remember, this is a hobby. Some people like digital VFOs. "To each, his own."
Thanks Pavel.
Monday, March 11, 2024
Radio Items Picked-up at VWS Winterfest 2024 Hamfest
-- Behind the MXM there is a nice box marked "Diode Detector" I opened it up and there is just a solid state diode and a 50 ohm resistor to ground. Box may be useful.
-- I got a couple of books: "Weekend Projects" 1979 from ARRL, and "A History of QST -- Volume 1 Amateur Radio Technology 1915 - 2013" 2013 from ARRL.
-- On top of the Weekend Projects book you see a "Crystal Holder" from Gross Radio of New York City. W1UJR has some good history on this company: https://w1ujr.com/written-word/gross-radio-company-circa-1931/ This device seem to be intended to hold in place a raw piece of quartz! Cool.
-- To the right of the books there is a serious-looking VFO. One dollar! Deal! It is a CB VFO, but the markings say it puts out 5.44 to 5.99 MHz. So it should be useful. The dual speed dial is very nice.
-- Above the VFO is a nice step attenuator from the "Arrow Antenna" company of Loveland Colorado.
-- Further to the right are some Electric Radio and Antique Wireless Association magazines that Armand WA1UQO gave me. Really nice. The AWA mags have a very thoughtful piece (warts and all) on Jean Shepherd. And the ER pile has an article by Scott WA9WFA that mentions my work on the Mate for the Mighty Midget receiver. Thanks again Armand!
-- I also got some ADE6+ surface mount mixers. The price was right!
Thanks to VWS for putting on this great hamfest!
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 10, 2024
SolderSmoke Podcast #250 Dean KK4DAS joins Pete N6QW and Bill N2CQR
http://soldersmoke.com/soldersmoke250.mp3
VIDEO VERSION: (1707) SolderSmoke Podcast #250 -- With Pete N6QW, Dean KK4DAS, and Bill N2CQR - YouTube
Intro: Welcome to Dean KK4DAS. For 2024 Pete and I hope to jazz things up a bit by bringing in fellow homebrewers to talk about their projects. Dean is our first victim. Welcome Dean.
Some good news: Several new homebrew receivers are inhaling: Armand WA1UQO in Richmond has an amazing looking regen. Scott KQ4AOP in Tennessee got his DC RX working. Mike AG5VG in Texas has been homebrewing BITX 20s and BITX 40s. All are on the blog.
Pete's report:
-- Recent blog entries on filters, SSB rig architecture, and of course digital VFOs.
-- Phasing measurements, quadrature, and the Seeed Xiao RP2040
-- Error in QST article on early SSB transceiver. ANOTHER ERROR!
--LC VFO on blog! FB Pete!
Dean's report:
-- Tales of woe on the homebrew sBITX
-- Help from Farhan.
-- Ground Bounce. FFT Hallucinations. Wisdom files.
SHAMELESS COMMERCE DIVISION:
-- Whenever you are tempted to buy something from AMAZON, just start at the Amazon symbol on the right side of the page. We get a cut from Bezos, and it doesn't cost you anything.
-- You can try to do the same thing with E-bay. We are finding a lot of great parts there.
-- If you see a SolderSmoke post on Facebook, please Like and forward.
-- Become a patron! Go to the Patreon page. We put the money to good SolderSmoke use.
-- Visit Mostly DIY RF and buy a PSSST kit!
Bill's bench:
-- Building yet another BITX dual bander. 15-10 again. Tried to use a 25 MHz filter left over from the earlier project, but I had to build another. Built a new VFO using the variable cap and anti-backlash gear recommended by Pete. Was a bit tough to get the receiver sounding good. Had a diode ring as the second mixer, but went back to a singly balanced mixer.
-- 10 meter AM -- Thanks to Jerry Coffman K5JC for mod.
Other topics:
--Counterfeit chips. Why?
MAILBAG:
Wes W7ZOI
Jim Cook W8NSA Transoceanic BFO
Grayson KJ7UM -- Vintage Computer Museum
Chuck Adams --Glad to hear that Chuck is doing well.
Frank Harris K0IYE -- NO CHIPS!!!!
ED DD5LP Antenna software
Eldon KC5U 10 AM We made a contact
Joh DL6ID 10 AM
Phil W1PJE of MIT 10AM Where is L5?
Bob WP4BQV now in UK
Dino Papas KL0S in Wilmington Reverse Polarity protection.
AA7EE Dave Richards Liked Armand's receiver
Rogier PA1ZZ
Jonathan-san W0XO Listened to my ET-2 CW Whoop,whoop
Nick M0NTV Great videos from Nick the Vic
Will KI4POV Working on his own SSB rigs.
John West -- Who is the South American ham who made his capacitors and heat sinks?
Ed KC8SBV Working on DC receiver, experimenting with FETs
Mike WN2A great contributions. Si5351 sole source danger!
Nick N3FJZ -- watch out for dead bands when testing receivers!
Don KM4UDX encouragement from new Prez of VWS
Dave K8WPE Likes QF1 Cap backlash. Says I'm getting soft!
Dave WA1LBP My fellow Hambassador, from Okinawa USMC Sergeant with a workshop.
Wednesday, February 7, 2024
Videos from Mike AG5VG -- His Homebrew BITX Rigs
Tuesday, February 6, 2024
Pine Boards, Analog VFOs, and Homebrew BITX Transceivers -- AG5VG's Magnificent Creations
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,
Friday, January 12, 2024
QF-1 Variable Capacitor Problem -- What Should I do?
Sunday, October 22, 2023
DIAL SCALE LINEARITY -- Spreading out the Frequencies for the 15-10 BITX Rig
Click on the image for a better view
The 15-10 Rig has been performing very well, pulling in a lot of DX contacts on both bands. But there is one thing that has bothered me: The way the transceiver tunes. It can be a bit difficult getting an SSB station tuned in properly. At first I thought this was caused by a lack of lubrication on the variable cap that I've been using (out of an old QF-1), but it turned out that this was not the cause. The problem is something that Pete Juliano has lamented several times: LC style analog VFOs have a tendency to have the frequencies "bunched up" at one end of the tuning range. In other words, the tuning range is far from linear. I was having trouble tuning stations on on the portion of the band where the frequencies were bunched up. I did some quick measurement and found that on this side of the capacitor's tuning range, one turn of the dial would move the frequency about 100 kHz -- that is far too much. On the other end of the capacitor moved only 22 kHz with one turn of the dial (as I recall this is close to the recommended 20 kHz per dial rotation). Clearly I had a lot of the dreaded bunching up. This was what was making tuning difficult.
I had built a pretty standard Colpitts FET VFO. I had a 6.6uH coil, and a 9-135 pF variable cap in series with a 68 pF fixed cap. I was pleased that the VFO worked, and I put it in the circuit. Only later did the bunching up shortcomings become apparent.
I decided to build another VFO, this time paying attention to DIAL SCALE LINEARITY.
I turned to the excellent Bandspread Calculator on Bob Weaver's Electronic Bunker web site: http://electronbunker.ca/eb/BandspreadCalc.html
I plugged in the frequency range that I needed and the values for my variable capacitor. I calculated Cs which was the combined capacitance of the feedback and coupling capacitors. Finally, I had to make a decision about the nature of my variable cap: was it a Midline-Center Cap or was it a Straightline Capacitance cap. I consulted with Bob and he suggested that it might be somewhere between the two. I got out some graph paper and measured it -- it looks to me like a Straight Line Capacitance cap, with the capacitance varying linearly with changes in in the rotation of the shaft.
Tuesday, September 26, 2023
F6CRP's FB Homebrew Receiver
Friday, May 26, 2023
Coffee with Farhan VU2ESE (video)
Thursday, April 13, 2023
The Franklin Oscillator: A Super-Stable VFO. Why No Attention? Why So Little Use?
Lee KD4RE of the Vienna Wireless Society has been talking about the Franklin oscillator. He has been telling us that it is very stable, and capable of stable operation up through the ten meter band. Lee wants to build an direct conversion receiver for all of the HF bands with one of these circuits.
I was skeptical. First, I'd never heard of this circuit. I'd grown up in ham radio on a steady diet of Hartley and Colpitts and Pierce. Vackar or Clapp were about as exotic as I got. And second, I'd come to accept that it is just not possible to build a good, stable, simple, analog VFO for frequencies above around 10 MHz. For example, in his Design Notebook, Doug DeMaw wrote, "VFOs that operate on fundamental frequencies above, say, 10 MHz are generally impractical for use in communications circuits that have receivers with narrow filters." DeMaw was known for resorting to variable crystal oscillators.
But then this month Mike Murphy WU2D put out two videos about his use of the Franklin oscillator circuit in a direct conversion receiver at 21 MHz. The VFO was shockingly stable. I began to believe Lee. I fired up my soldering iron and built one.
Lee was right, it is in fact remarkably stable, even at higher frequencies. My build (see picture above) was a bit slap-dash and could be improved a bit, but even in these circumstances here is what I got. This was with a stable 6 Volt Supply and with only a cardboard box covering the circuit:
Local time Frequency
0543 19.1114 MHz (cold start)
0636 19.1116
0804 19.1117
1034 19.1118
1144 19.1117
I started digging around for references to the Franklin. There was nothing about it in Solid State Design for the Radio Amateur, nor in Experimental Methods of RF Design. Pat Hawker G3VA (SK) did discuss it in his Technical Topics column in RADCOM, February 1990. Pat gave a great bio on Charles S. Franklin (born in 1879 and a colleague of Guillermo Marconi). But tellingly, Pat writes that, "Despite its many advantages, the Franklin oscillator remains virtually unknown to the bulk of American amateurs."
It wasn't always unknown. In the 1940s, we see articles about the Franklin oscillator circuit. There is a good one in the January 1940 issue of "Radio." The author W6CEM notes that the circuit "is probably familiar to only a few amateurs." It shows up in the "How's DX" column (above). And the 1958/1959 issue of Don Stoner's New Sideband Handbook we see a lengthy description of the Franklin oscillator. Stoner wrote: "The author's favorite oscillator is the 'old time' Franklin, and it is believed to be the most stable of them all! This rock-solid device can put a quartz crystal to shame! Because it represents the ultimate in stability, it is the ideal VFO for sideband applications." And we see a PTO-tuned Franklin oscillator in the July 1964 QST. And it is in the fifth edition of the RSGB Handbook (1976).
Saturday, November 19, 2022
A 1966 73 Magazine Article on a Homebrew Permeability Tuned Oscillator (PTO)
Lewis opened his article with this:
https://worldradiohistory.com/Archive-DX/73-magazine/73-magazine-1966/73-magazine-04-april-1966.pdf
Page 30.
Thanks to Michael (VE2BVW ?) for suggesting that I dig up some old 73 Magazine articles on PTOs. A quick search revealed that there weren't many. If anyone out there knows of good PTO articles in the ham or EE literature, please let me know.
Tuesday, November 15, 2022
A Treasure Trove of Permeability Tuned Oscillator (PTO) Info and Links (Plus Info on Direct Conversion Receivers)
There is really great info on this page, and even more in the links at the bottom of it. While the page is about PTOs, the links often discuss their use in Direct Conversion Receivers. I really liked the Tin Ear receiver. And it was great to again come across the work of Alan Yates VK2ZAY. Alan very admirably admits that laziness caused him to use an LM386 audio amplifier in place of a more virtuous discrete transistor design.
https://qrpbuilder.com/pto_mechanism
I bought one of the qrpbuilder PTO kits and I will soon put it together. I have been having good results with a Glue Stick PTO and with a brass screw PTO form designed by Farhan and 3D printed for me by Dean KK4DAS.
LET'S GO PTO!
Friday, October 28, 2022
SolderSmoke Podcast #241 Mars, Direct Conversion, PTOs and Glue Sticks, Anniversary of the BITX20, Multus Proficio SDR, Boatanchor Station, MAILBAG
SolderSmoke Podcast #241 is available
Audio (podcast): http://soldersmoke.com/soldersmoke241.mp3
Video (YouTube): (215) SolderSmoke Podcast #241 October 28, 2022 - YouTube
Introduction:
Back on Mars. Opposition
approaching. I have a Mars filter. And (like T.O.M.) a Mars
globe.
N2CQR DXCC done
SolderSmoke in the WayBack
Machine
Sticker news
PARTS CANDY -- Don't Scrimp with a Crimp!
Bill's Bench
School DC RX projects -- in
Hyderabad and Northern Virginia.
Direct Conversion Receivers --
Keeping it Simple, Learning a Lot. A step beyond the Michigan Mighty Mite.
Do we really need 100db? Do we really need to shield VFOs? Farhan's
super-simple and stable Colpitts PTO. Audio amps, 1000-8 transformers and
rolling your own LM386
PTOs and Glue Stick PTOs.
Paul Clark WA1MAC. Brass vs. Steel bolts. #20 thread vs. #28
thread. Backlash Blues. The best Glue Sticks.
2 meters and the VWS.
Bill has a Baofeng.
SHAMELESS COMMERCE:
MOSTLY DIY RF
Pete's Bench
20th Anniversary of the
BITX20 Pete's early BITX rigs.
Computer Woes
The Multus Proficio SDR rig
Simple SSB in China
BA7LNN
Things of beauty: Tempo
One, NCX-3 and a SBE-33
MAILBAG
-- NS7V is listening.
-- Graham G3MFJ
sent SPRAT on a stick.
-- Nick
M0NTV FB Glue Stick and 17 Shelf videos.
-- Dino KL0S
HP8640 Junior
-- Mark AA7TA Read the SolderSmoke Book
-- Steve EI5DD Connaught
(Ireland) Regional News
-- Dave
K8WPE Planting the seeds of ham radio
interest
-- Peter VK3YE
Ruler idea on PTO frequency readout
-- Michael AG5VG Glue
Stick PTO
-- Tobias A polymath with UK and Italy
connections. And cool tattoos.
-- Alain
F4EIT French DC receiver
-- Michael
S. was in USMC, working on PCM/TDM gear
-- Alan Yates
writes up Amazon transformer problem
-- Todd VE7BPO, Dale W4OP, Wes W7ZOI
-- Farhan VU2ESE
sent me an sBITX
-- Todd K7TFC The Revenge of Analog
-- Jim Olds Building QRP HB gear
Saturday, October 15, 2022
DC Receiver: 100db Gain? Diplexer? VFO in a box?
Wednesday, October 12, 2022
World's Most Interesting Man on PTOs and Glue Sticks
Monday, October 10, 2022
Listening on 40 with a Glue Stick PTO in a Direct Conversion Receiver; Some PTO History
And some background on PTOs: https://sites.google.com/site/randomwok/Home/electronic-projects/permeability-tuners-last-stand
Sunday, October 9, 2022
Paul Clark's Dollar Store PTOs made with Glue Sticks or Chap Sticks
Some of Paul's coils:
Friday, September 30, 2022
Bandsweep with the New Homebrew 40 meter Direct Conversion Receiver
-- 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.