My... what a lot of disconnected issues.. And in a thread about IMD.
But, since you got on the DSP thing..
DSP radios are very noise in noisy atmospheric conditions. My old analog radios kill them in this area alone.
There's no inherent reason why a DSP would be better or worse. more likely, you *prefer* the sound of your analog radio, which is determined by its fillters and audio path. This is much like the vinyl/cd "warmth of analog" argument.
In weak signal detection analog radios are better.
Funny thing. Deep space comm uses digital, and that's about the weakest signals around. I think, again, you're talking about "when you combine the radio with the human detector with years of experience, you prefer that combination".
The new DSP radios also lack a decent audio amplifier they so weak and poor. You turn on a old radio and you can fill the house with audio.
That's a design decision of the manufacturer, not inherent to DSP. I think it's more that they want small compact radios. My IC-7000 has a wretchedly tiny speaker, but then, I don't use it. I use an external speaker, or run it through the car stereo. Are we buying radios to communicate or to fill the house with glorious monophonic sound? When you had to have a half dozen tubes, a whole chain of tuned transformers, and all the power transformers to heat the filaments and provide plate and grid supplies, having a big speaker isn't a big deal.
DSP noise reduction is a waste of space on a radio. I do better with my ears 99% of the time.
Digital noise blankers are poor as well.
DSP NR is a waste *for you*, because you prefer the sound and detection properties of the analog radio you are familiar with; and that meets your other (unstated) requirements. You post under QRPNEW, so I'm going to guess that a full 19" rack of gear isn't something you would consider appropriate, no matter how good it was. And that's fine. I will say that for something like ignition noise suppression when operating mobile, the DSP based version on my IC7000 blows away the analog version on my old FT757.
The AGC's in digital radios need a lot of improving. In CW pileups they are truly lousy they turn the pileup into one big mush. Even DC receiver
does a better job on CW in pileups. DC receiver on receive kills a DSP radio, the CW not is so much better on a good DC receiver.
You are conflating DSP, in general, with specific implementations. The beauty of DSP (and software defined approaches in general) is that one can conceivably duplicate (or better) ANY particular analog implementation. The fact that commercial manufacturers have not done this is more a reflection of their perception of market demand. In days of yore, people would modify their receivers.. swap out filters, change the time constant on the AGC, etc. Today, there's just a start of doing that for DSP.
I have never heard any DSP speech processor that is as effective as a proper RF clipper like the Datong. Someone is kidding someone
when they say a DSP processor is as good as a RF clipper.
You're tarring all DSP with a brush based on specific instances. THere's no reason why one could not build a DSP processor that would provide identical performance to the RF clipper. If one doesn't exist, it's because nobody is willing to pay for it.
Digital radios will have their day of glory at the moment they really giving as lousy radios. Every time I turn on a Collins or old Kenwood tube radio I go WOW how can this new stuff be so poor. The analog and hybrid tube tube radios sound so much better.
Vinyl vs CD, tube vs transistor. There ARE differences in sound. There ARE preferences. But they're not inherently because it's digital. 30 years from now, people will go, "how did anyone tolerate that horrible IMD from those uncompensated tube/transistor rigs". And there will be people restoring AM transmitters from the 40s basking in the glow of the filaments and that rich, warm broadcast sound.
DSP radios cant handle RF field very well. You dont want to bring open wire feeders near a Flexradio! The RF currents flowing over
everything will kill them fast. I can only imagine what would happen if you ran a California Kilowatt on open wire near a digital radio.
That has nothing to do with DSP, and everything to do with general "box design". In the commercial world, they run 50kW broadcast transmitters which use DSP, next to monitor receivers which use DSP, and have no problems. Perhaps you've used a modern (or even not so modern.. old HP 8563s for that matter) spectrum analyzer? Pretty much all DSP after the first mixer, and I don't recall them having any particular problems with RF fields. In a cost constrained market (i.e. ham radio), maybe the manufacturer doesn't spend as much on shielding and case design as they might. Maybe they don't want their radio to weigh 100 lbs. Lots of things drive design decisions, and it's entirely possible that a cheap DSP based rig will be worse than a cheap analog rig. But you don't want to be comparing fit and finish of a Yugo against a Rolls Royce..
Then we need to talk about all the crud on the digital radio signals. The DSP grunge sounds terrible.
Are we talking digital radio in the PSK31 sense, or signals generated by radios which use DSP in the audio path. No question that DSP is like a chainsaw.. it's a tool with the potential for damage and misuse. Some implementations are significantly worse than others. At least in the analog world, the truly bad designs have withered away and died a justly deserved death. Not many people are using carbon granule mics any more.
I wont mention TX IMD since this is a lost cause, the radios are in the toilet and wont be getting out any time soon! 12000 dollars for -16db 3rd order IMD is this a joke, or are you making this up? Thats -10db below one of two tones. I think that figure is wrong and sounds too low. Thats like a buying a radio with no IMD suppression at all, or the radio is faulty. If that figure is right its the perfect radio for clearing the band during contest, just get a sweep tube tetrode amplifier and you will win the worked all the worlds neighbors award.
I will stick with my QRP homebrew radios they are the best and they cost be peanuts. I will give you peanuts for your 12000 dollar -16 db radio though, thats all its worth.
That's your subjective opinion. Others have other opinions. You might want to consider that since you're operating QRP, you have several design advantages:
1) spurious signals are below the noise floor. If you took your transmitter output and ran it through a *perfect* 30dB amplifier, what would people be saying about your signals?
2) you're probably optimizing for power consumption and size. Since you're radiating a watt, you don't need to worry quite as much about good DC power efficiency in the final stage.. Heck, you can run Class A. This probably isn't a viable alternative for someone who wants to run a kilowatt and doesn't want to have a 5kVA power supply.
Other people have different desires. And the manufacturers respond to those desires. Getting back to the original subject of the thread, the real question is how to encourage the manufacturers to realize that there is a *desire* for decent IMD performance. Given the prevalence of modern signal processing in most large volume radios, I think that DSP is going to be the solution, rather than the problem.
But then, I'm biased: I make my living with high performance radios, most of which have a big software component. As much as I appreciate the elegance of a clean all analog design, for the vast majority of applications, a digital approach is going to provide a superior result, on whatever metric you decide to use and optimize the design for. And it will only get better, since Moore's law helps digital get better, particularly in mass production equipment destined for amateur radio.
One of the most attractive aspects of amateur radio is that you can still experiment. You can build your low functionality, high performance, all analog radio and use it. For rock-bottom power, mass, volume, all analog designs tend to be where you go... I'm not sure a SDR is a good fit for a wildlife tracking beacon that has to weigh less than a few grams)
