I really like Marc's (AL6JV) videos. It is great fun and very educational to watch him and his team troubleshoot some of the old gear they work on. There is also a lot of humor.
In this video Marc delves into the circuitry of the Phase-Locked Loop. I didn't know that the PLL circuitry has its origins in the space program. NASA needed a circuit that would permit very narrow band reception of a signal that was undergoing the kind of Doppler shift that spacecraft produce. Viola! Enter the PLL. Far beyond Apollo, PLL circuits started to show up in ordinary radio gear. The General Electric (and JC Penny!) CB transceivers that we rescued from 11 meter infamy used PLL as the frequency determining circuit.
Marc gives a really good explanation of how the PLL circuit works. Thanks Marc.
However, Marc gives an incorrect pronuniation of "kludge" (it should sound like fudge). But he is a computer guy and is originally from France, so all is forgiven. He also redeems himself by making fun of the inaccuracies that appear in what he calls "data shites."
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.
It's crazy, but it
worked!!
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...
This is something I
remember...
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
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."
Above you can see what I picked up at the Vienna Wireless Society's 2024 Winterfest Hamfest.
-- On the left in the blue box is an MXM Industries SuperRX/TX 40 transceiver. It is a kit from a Texas company. Superhet receiver with IF at 455 kHz. Crystal controlled CW transmitter on 7040 kHz. The oscillator works, but so far no receive signals. I will have to troubleshoot. Does anyone have a schematic?
-- 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!
Login
