Trevor Woods also sent us this report from Arnie Coro. It is not clear to me what difference (if any) there is between the Super Islander Mark IV and the Jaguey Five (described yesterday). But the bit about using parts from old CFL bulbs is interesting. This was something championed by Michael Rainey AA1TJ several years ago. See: https://soldersmoke.blogspot.com/2009/01/soldersmoke-98.html
April 2010:
Today, I will be answering a question sent by listener Bruno from Croatia... Bruno picks up our English language programs via Internet, but he is now also listening on short wave too. He sent a nice e-mail message asking me about the latest version of the Super Islander amateur radio transceiver, because he wants to build one.
Well amigo Bruno, the Super Islander Mark IV is now on the air, and results are very encouraging considering that it is a 40 meters band transceiver built using recycled electronic components.
The Mark IV uses a totally different approach to the receiver design, and it adds two solid state audio filters.
Amazing as this may sound, some of the electronic components used to make the Super Islander Mark IV transceiver came from the circuit boards of broken or damaged Compact Fluorescent Light Bulbs... and that means that there is virtually an endless supply of those parts.
Here is now amigo Bruno, and amigos listening to the program at this moment, a brief description of the Super Islander's Mark IV receiver module.
It starts with a simple resistive signal attenuator that feeds a dual tuned bandpass input filter.
The filter has a limited bandwidth , chosen so as to limit response to out of band signals... The filter is followed by a cascode transistor radio frequency amplifier stage, that feeds a broadband four diodes product detector.
Low level audio from the product detector goes to the audio filtering and amplifying module, made with discrete transistors, of which several of them are also recycled from the Compact Fluorescent Light Bulbs circuit boards...
This version of the Super Islander, the Mark IV , is radically different from any previous ones, as we have now switched over to a totally low cost solid state design , that can be easily reproduced because it uses very common electronic components and straightforward , easy to adjust circuits.
In our upcoming mid week edition I will describe the VFO, or variable frequency oscillator and the transmitter module of this unique low cost amateur radio transceiver, the Super Islander Mark IV... about the lowest possible cost transceiver that will make possible regular two way ham radio contacts on the 40 meters band using either voice or radiotelegraphy modes.
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Bill. This is from October 2011, so eighteen months after the above.
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The other work in progress at my workshop are a pair of identical power supplies that are been built for two Super Islander 40 meters amateur band transceiver... One for my own CO2KK ham station , and the other one for a disabled member of our Plaza Municipal Radio Club. The Super Islander is a hybrid transceiver that yours truly designed using as a guideline CO7PR's famous Islander transceiver that was and still is popular among Cuban radio amateurs, because it can be built using easily found locally electronic components that are recycled from old TV , radios and computers...
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Around the 2010 period, Arnie seemed to be taking a strong interest in the Polyakov mixer. He said things like "The amazing Russian Polyakov mixer." He said because the oscillator was operating at half the desired frequency, it was more stable. I've seen the video where you had built a receiver using the Polyakov mixer. Arnie Coro also talked about how he had found the four diode Polyakov mixer was better than the two diode for weaker signals. This sent me off on a search for the four diode one, I'd only seen the two diode. My limited search brought back one example. Whether it was the same as what Arnie Coro was doing, I don't know. When he talks about the Super Islander and the broadband four diode product detector, I do wonder if that could be a Polyakov. Where he says mid week he will describe the VFO, well I can't find that one. So much about Arnie Coro seems to be so close, but so far. The four diode Polyakov circuit I found is interesting. It's a 40 metre DC receiver using the four blocks you said Farhan refered to. Bandpass filter, mixer, VFO and amplifier. Actually preamplifier only in this schematic. Either side of the four diode Polyakov, is a 51ohm resistor to ground and 0.1uf cap to ground the other side. I'm thinking that might be the diplexer, but I don't have enough knowledge to know. The original circuit by someone else is for eighty metres. He used a discrete component VFO. The person that took that for inspiration, for the 40 metre band, made it simpler except for the VFO. He used an Arduino. This can easily be removed. Not that I have anything against going that route, I just don't have the desire to learn what I would need to.
Trevor: I don't know about the "4 diode" harmonic mixer, but I think the standard two diode model works very well and illustrates very well how and why two diodes and a VFO at 1/2 the operating frequency works: When you have the two diodes in the circuit, each one of them turns on on a voltage peak. But they are back-to-back, so the signal is being sampled TWICE each cycle. This is the equivalent of having the VFO at TWICE the frequency. I don't know if using that circuit made much sense here, because getting a VFO stable at 7 MHz is easy. 73 Bill
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