I sometimes hear hams claim that our efforts to build simple direct conversion receivers are "very relevant" to modern technology and are "directly applicable" to today's communications techniques. These hams will say that direct conversion receivers are at the heart of modern rigs.
That's a nice thought, and it might have been true in the past, but I don't think it is true anymore.
I think the future is what you see written on the black box (!) that encloses the receiver in the above video: "DIRECT SAMPLING RECEIVER." In the recent past we did have two direct conversion receivers in the front end of SDR receiving systems. These receivers produced I and Q signals that were fed into the computer (often via the sound card). That was nice.
But the writing has been on the wall for a long time. There is no longer a need for all that direct conversion and I and Q. Just put a fast Analog-to-Digital converter chip at the front end, convert the entire HF spectrum to a digital stream, and send that stream to your computer. Or to another part of your "rig." As in the ubiquitous 7300.
I don't mean to be a Luddite here. That big waterfall is very nice. The receiver sounds great. But I am a homebrewer and I prefer to build my own gear. Ordering this black box on my phone, having it delivered by Bezos to my front step, and then updating the driver, is not what I consider homebrew radio.
A couple of things I spotted: The Si5351 chip in the box -- at least one part was recognizable. And the completely vertical skirts on all the SSB signals -- lots of 7300s out there.
Hey, to each his own, YMMV, whatever floats your boat. Just don't kid yourself into thinking that our beloved DC receivers are still somehow being used in these modern black boxes.
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Sorry Bill but I am 1 of those Hams. I do not even kid myself that amateur radio is relevant anymore! HF is but a drop in the ocean of the huge amateur radio frequency spectrum and it is very unfortunate many homebrewers do not even operate on the frequencies above or below HF. That black box will not work on my favourite 23 cm band watering holes. I could construct a converter with analog parts I suppose. Quadrature yielding DC receivers bridge the gap between modern full digital front end and ye old timers classic analog radios and they do both well. They are sill used in multiple radio devices around the world most of which ostensibly operate above 2 gigahertz. These will note doubt be 1 day replaced by wide band DAC input based front end receiver technologies in the future. When TV sets went digital in 1996, the die was cast. Future digital radio technology would extinct whatever analog dinosaurs that were still standing but some tough old dinosaurs will hang around for a bit longer than others. It boils down to what he/she/them/they prefers. If someone wants to construct and operate radios using 1972 circuits with out of production transistors then that is okay with me. Digital versus analog for communications is a battle already long lost. This applies to all bits of amateur radio. When I got my DXCC is 1976, I spent many late hours in the old shack and earned it the hard way. My grandson used the internet based technology that reports DX stations so it took far less effort and time for him to get the coveted plaque from the ARRL. Regis
ReplyDeleteEven if DC receivers are frowned upon, they are easy to build and work well. If we only had regens, life would be so difficult
ReplyDeleteThe black box has no soul.
ReplyDeleteIn most of the central "flyover" part of the country there is essentially NO activity on any microwave band. So, if you build one station...better build two and give one away. Not the worst idea, but a harsh reality nonetheless
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