https://www.facebook.com/groups/118053768802799
His e-mail is on his QRZ.com page: https://www.qrz.com/db/LW9DTR
MARTIN LW9DTR has left a new comment on your post " The JF3HZB Digital VFO Dial in the DJ7OO Direct Conversion Receiver (Who is JF3HZB?) ":
Technical support
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 is really looking great. Congratulations to Farhan for bringing yet another amazing rig to the amateur radio community.
Order yours here:
https://www.hfsignals.com/
By Arnie Coro Radio Amateur CO2KK
...
My own personal experience with the original JAGUEY direct conversion transceiver, designed way back in 1982, is that when used with a well
designed front end input circuit, those receivers provide amazing
sensitivity, with signals as low as 1 microvolt easily detected but,
they do have one drawback, their selectivity or ability to separated
between stations is very poor. The direct conversion radio receivers are
used for picking up CW Morse Code Signals , Digital Modes and Single
Side Band, but they are not good for receiving AM signals, and can't pick up FM modulated signals at all...
The original JAGUEY 82 Cuban designed single band amateur transceiver, was tested against a sophisticated and really expensive factory built
transceiver. The tests showed that our design was at least as sensitive
as the very expensive professional equipment, registering a measured
sensitivity of less than one microvolt per meter, producing perfect CW
Morse Code copy of such a signal. Adding well engineered audio filtering
to a direct conversion receiver can turn it into a really wonderful
radio by all standards amigos.
Radio is a fun hobby, and believe me amigos, there is nothing more
magical than listening to a radio receiver you have just finished
building !!!-----
Peter Parker VK3YE Found a nice description of the Jaguey by Cuban radio Amateur Jose Angel Amador from the BITX40 Facebook Group:
A translation. This was apparently in response to someone who thought they'd found a Jaguey schematic:
"That's not an original Jaguey, that was a simple, single band, unswitched, 5 watt, DSB, kit for beginners with no gear and needing something to put on the license.Carbon microphone direct to balanced modulator, two stages with 20 dB gain, W1FB/W1CER style feedback, and final with 2 x 2N2102 class B.
The receiver was more like that of the schematic, with a TAA263, easy to get from the FRC in 1978, and headphones. No need for an RF stage: the mixer was overloaded at night with European broadcasts above 7150.
The VFO is also inspired by Solid State Design for the Amateur Radio, a Colpitts with 2SC372 and a low gain feedback buffer with two 2SC372s.
Binocular ferrites were taken from Soviet TV baluns. The conditions of Cuba 1978.
Today I would make an SSB rig with polyphase networks, mixer with 4066, and VFO Si5351.
The big complication of BitX is the crystal filter, they either get it made, or stick to a recipe, but few have what is needed to measure and tinker with crystal filters.
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.
-------------
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
Continuing our search for information the Cuban "Jaguey" DSB rig, Trevor Woods pointed me to Dick Pascoe's QRP column in the (below) July 1998 issue of Ham Radio Today. I think the first SPRAT article about Eric Sears' ZL2BMI DSB rig was in SPRAT 83 in the summer of 1995. This fits well with the sequence described below by Arnie Coro CO2KK.
I am still looking for a schematic and pictures of the Jaguey rig: If you can help in this, please let me know.
Posts
All Comments
Posts
All Comments
