A Hams plans are never really completed

 I've noted in the past, that when you're a Ham, you tend to stack projects that never get completed. I must admit this has always been a  character trait of mine, even before I got my ticket a few years ago. But these days, at least I have a reason, being home one day per week, usually. There simply isn't TIME to accomplish all the things I'd like to.

As an example, Antennas.

I've been trying to get to installing antennas in my back yard...(Garden for some of you) for a couple of years now, but something always seems to get in the way. I design a way to cover all the bands I'd like to cover, and the wife will decide she doesn't like guy wires, or that antennas are "ugly" and so new plans get made to satify that.. Or I get asked to work an additional day or two. Or the weather gets in the way. Even plans that sometimes don't work out, on those occasions when you do actually have the time. And each time, I end up starting over from line 1.

I've had a computer waiting for an OS installation for the last several months, now

I need to re-org my shack, the place is a disaster area, always teetering on self destruction.

Frustration seems a key element of this never ending story. 

Increasingly, however, I have begun to notice a different element in all of this; a desire to improve on the projects I've managed to complete, being never fully satisfied with stuff I've already done. Thus, my list of projects tends to grow exponentially. 

'"At last, I'm organized", he said. And then, he died.'

So goes the old saying, and I suppose it's true.  I get the idea that when it comes time for me to leave this world, I'll be disappointed because I didn't mange to get more of my project list done.

 

 

 

The Shortwave Modernization Coalition?

 

There's been an awful lot of talk the last week or two about a proposal for rule making (PRM)  that's currently before the FCC.

The request has been drawn up by a group which labels itself the "Shortwave Modernization Coalition." (SMC).

Apparently, this group is largely made up of Wall Street types, international Wall Street types in fact. 

They propose transferring data from our continent to theirs,  by way of a single transmitter as opposed to going through the internet, since it exhibits far less in the way of latency. The complaint being that that connection, that late latency that's been going through the internet has been costing these folks large amounts of money. Such is the state of our stock market these days the trades are going that quickly and the thing is in the estimation of the shortwave modernization coalition it's worth the money to invest in those systems, which certainly will not be cheap to erect, use or maintain.  They're talking about using 20KW TPO which is used with a directional antenna (why wouldn't they?) means quite a bit higher in ERP.

(Aside: It's been pointed out that this proposal if enacted, would create a serious and likely insurmountable advantage to the users of these systems. I point this out to show you the weight behind this proposal. But let's still with the technical and Ham radio related aspects, shall we?)

The SMC as I will call them, has been doing test operations since 2014 or so, using 10kw transmitters.. They point out in their PRM that nobody's complained about interference from their operations at the 10K level they've been playing with,  from from anybody else in the electrical neighborhood including maritime, aircraft, and for that matter amateurs and shortwave broadcasters and of course, Ham operators. 

(Aside:Further, I question what the added 3dB will give them, but, no matter for the moment on that part. )

I must admit that my initial reaction came from my technical side and was in effect "Well, that's interesting". But then the more practical side spoke up. As in, " Hold the phone!"

Without even looking at the proposal in detail, one question that pops out is bandwidth, another is harmonics, and with that kind of power, the issue becomes quite serious, in my view.

Let's face it ...if it has the proposal suggests their concern is getting messages through as fast as possible then the standard 300 quad rate isn't going to cut it anymore and at a power output of 20 kilowatts you can make a mess out of large portions of the HF spectrum in a real hurry, that go well beyond the primary frequency.

For their part, the FCC seems amenable to these ideas and has been pointing out for as long as I can remember that the HF spectrum is underutilized.  so I'm guessing that without a serious amount of pushback commission is going to be inclined to Grant the request and put forward an NPRM before the echo dies from the comment period.

But again, hold the phone, here. 

Before you get the wrong idea I do not believe that at least initially we're going to have problems with our proposed new neighbors. But I do believe the trend being signaled here is worth watching if we value our Ham radio future on HF

Large as the concern about problems radiating from this proposal, (sorry, couldn't resist) The FCC's attitude about this creates an even larger concern for me, when you look at the proposal and see where the money's coming from for it. Places like Ukraine, and Saudi Arabia to name a couple.Now, as traders begin to recognize the financial advantages of using systems like this, the rush for added transmitters and frequency space will skyrocket. Therein, in my view, lies the bigger issue. We're going to be drowning from these new, high power systems. I don't care how tightly they're filtered, there's bound to be problems for other users of these bands, including alas!, us.

 I mean, we're talking serious money here and I suspect that if this proposal becomes reality, we're going to start seeing large chunks of HF real estate being sold off with the money going into the FCC's wallet. Money they seem to think is desperately needed, if we observe the process by which large amounts of spectrum were sold off, the sales and the regs surrounding that sale,  rammed through like a bullet from a rail gun, for the cell phone companies.

With that kind of money involved the question becomes whether or not the ARRL (Who is, in all fairness, already reacting to the proposal) will be able to withstand the obvious desire for large growth in HF traffic.

Keep an eye on this thing. If you get some expertise to bring to the table in the way of comments for the commission, do so.

Addendum:

Tom, W9YW responds:

I have two minds on your posit,

. The first one is that we lived with short wave broadcasters around the world in HF for >100years. They were a fact of life. A few were coughing bad signals, but rarely did it cause a problem, even at >100KW of directed signal. Yes, that signal was AM and easy to shape the harmonic slope-- not high speed encrypted digital goo. But we lived with it. Part of the reason for the wide spectrum, I'm guessing, is that the new broadcasters want to prevent jamming, and also optimize their commercial goal-- quickly executed arbitrage that makes them revenue. That's understandable.

The other mind says that it will be random frequency, encrypted data, the kind that hams aren't allowed for both national security reasons, and assurance that other uses of the spectrum aside from the allocation aren't being used.

Their proposal lacks, and this is my other state of mind, a sufficient analysis of a highly sampled, nation-side scatter of what their signal actually looked like so that a FFT reception can be known. Meaning there aren't enough statistics nor boundaries to the signals used to vet that the transmissions won't harm other users of the spectrum to the fifth harmonic of the fundamental. Once it's allowed, the mode used over the bands allowed won't be easy to pull back or halt, and the squabbling will be huge and expensive because of the investments made. We also don't know how many concurrent signals might be used, by whom, and the boundaries of signal mode types. After revealing this, we know much more. Their data as proposed seems insufficient to me, and I have a lot of quality engineering background.

73 Tom W9YW

I can't disagree with your response, Tom.

Having just downloaded a copy of the PRM, I'll be examining it over the next few days. Obviously, (And as I think I indicated)  my comments were of the "first blush" variety.

Your comments bring up a few other thoughts and a clarification or two that perhaps we should explore.

I believe that once one leaves the realm of experimentation, which Ham radio certainly always qualifies as,   as has what the SMC has done so far, it's my belief that the commission should demand the same level of detail, and accept the same levels of public comment as we see in the world of commercial broadcasting. Certainly, this SMC project is a commercial operation, and should be directed to jump through the same hoops... including precise frequencies used, power levels, radiation patterns, testing for harmonic issues, and a standardized operational mode. So far as I'm aware, we've seen none of this.

More succinctly, I agree their data at least so far as I've yet seen, seems vague at least. Must be, nobody's directly commented on it, except to suggest increased bandwidth would be required for the kind of transfer speeds SMC is aiming at, and that seems a no-brainer right at the off.

That's troubling of itself, but further..... and here we get into the non-technical..... I'm made somewhat uneasy by the proposal that the signals be encrypted.

Your historical examples make your point well, and  like you, apparently, I have my doubts that at least in the first wave, we're going to have any serious interference issues.  Thing is, the argument fails to address the idea that they were, shall we say, open source. We knew what they were doing, were able to monitor their transmissions and so understood if harm was intended or not.  As Ham operators we can run any kind of protocol, so long as it is publicly documented. That minimal restriction was imposed for reasons of national security.... a wise precaution.

That's not, however, in what's being proposed here. We're talking about super-fast signals owned by foreign nationals in countries that have no always been friendly to us, and whom we have no guarantee, or even any indication, that they will be in future. (Smiling faces sometimes) 

 Yes, financial data, and I understand that point. Indeed, as I suggested in the OP, this proposal if enacted, would create a serious and likely insurmountable financial advantage to the users of these systems. That of itself may very well impact national security. We're talking about vast money, here, and that kind of money rises to the level of national security in terms of financial impact here in the 'states.

But can we trust that other data, of even more of a national security problem, isn't going to be buried in the data streams? That seems a security red flag at least, but as I suggested in my OP, I was trying to keep my comments (mostly) to the technical issues presented we as Hams by this proposal should it ever be adopted. At the same time, I'm unsure I trust anyone anyone at all, to monitor such things to ensure national security. Taking a chance either way in my view.

The commission appears to be looking at this from a purely technical POV as is their wont. And from a purely technical standpoint, the proposal seems fairly harmless in the short term, as I've suggested. But there seems more at stake here than that, and I wonder if more than just the commission will be involved here.

Audio processing at K2ENF

 Well, it took a while, but I've got the external audio processor running correctly.  There's still some tweaking to do, but it's mostly there. I've made some mods to the original design for a bit of simplicity and because of newer hardware now in the shack.

So, here's the path:

Whatever mic I'm using, going to a Gemini GEM-05USB mix console. This brings the level up to common line level, but it also has an EQ in it, which eliminates the need for the EQ I had designed into this stack. 

Then, we have a Behringer Composer Pro-XL (MDX2600) This is a noise gate / compressor/ limiter/ De-esser, This keeps a much hotter input level to the radio, on average, and takes away the heavy lifting from the ALC. The result is a nice dense audio, without the overshoots the ALC is frankly too slow to respond to. (I'll expand on this thought, shortly)

And of course the 991 has an internal EQ as well, so for the moment I'm not running a second EQ on the output of the 2600, though I may tinker with that later on.  The EQ's are set up mostly for bandpass, but also for a little punch.  

Aside: With the two EQ's one on the 2600 input and one on the output, 'm quite sure I'm getting some weird phasing within the band-pass, but not enough to worry about since most of that's being swallowed up in the phase shifting the 2600 is inducing... nobody's going to notice. And, anyway, there's some advantages to phase scramble, in terms of filling the RF envelope. 

 Here's why: The human voice is notoriously asymmetrical. If you look at most folks voices on a scope,you'll notice that the voice tends to swing either more to the positive side or more to the negative. This asymmetry is hugely inefficient when you're talking about maximizing a signal, particularly AM or SSB where the audio IS the power.  With most voices, you leave 25 to 30% of the RF envelope unfilled by audio.A bit of phase scramble over the width of the bandpass tends to counter that. tends to counter that.

Why would an AGC cause phase changes? There are very few phase stable AGC's, in my experience. Ask any broadcast engineer who has dealt with multi-band processing about that.
 

The result of all of this is quite encouraging... I'm seeing higher average power, on the order of a couple dB, and I'm also noting my bandwidth consumption has gone down somewhat, even with the higher amount of audio on air... to the point where I'm now easily within the 2800 hz bandwidth I've been shooting for, whereas before I was seeing ALC overshoots getting out from under the skirt, particularly when I was "getting on it. " Now, no such problems. I've said it before and I'll say it again... the ALC in most transceivers simply isn't up to the drill of maintaining max audio without getting nasty side effects.  I expect the de-esser on the 2600 is helping there, as well.

Next, now that the basic framework is laid out and working well...

I'm considering a DF4ZS RF speech processor. to be placed at the output of the 2600. It's essentially an RF Clipper.. For those who don't know what an RF clipper is, it's basically a transmitter receiver combination.What happens is, line audio is fed to the transmitter side and the audio is run to saturation level of the internal (AM) carrier..  The receiver portion detects the processed audio, and converts it back out to line level, which in my case would be fed directly to the 991a. 

Here's a nice techie explanation of the concepts involved. It explains that AF clipper does work, but has serious limitations.  Tom Kneitel, K2AES, (SK) wrote an article years ago on these topics that alas, now, I can't locate. He called the RF Clipper the "Poor man's linear", and he was right.

. Those beasts are very effective, but rather touchy once you venture outside of their level "sweet spot". Now that the 2600 is in place and working well I should have no trouble with keeping level in the sweet spot of the clipper.  I figure it'll add perhaps 5db worth of talk power.

(Yeah, they advertise up to 9db.... but I figure some of that ground has already been achieved by the stack as I've already described to you, and a bit cleaner, since the clipper only uses clipping as it's gain reduction, the 2600 doesn't. I won't need to drive the clipper nearly as hard for the same result. No danger of over driving the clipper with my current setup. .)

Why go through all of this?

For starters, consider the FCC's RF exposure paperwork, (Which the ARRL linked here) which suggests that conversational SSB has a 20% duty cycle. Supposedly heavy processing brings that up to 50%. In other words, even with the (rather lame) procs in most HF transceivers, the proc adds another 30w of average power in a 100w setup, better than doubling the power and raising the signal on the received end, what, about half an S unit?

Trouble is, as I've already suggested,  pushing most of the procs on even today's HF radios that hard for that rather modest gain, you'll end up taking more bandwidth than most consider wise. The problem is that ALC is used for most of the heavy lifting, and as implemented in even modern day transmitters, it's simply not up to the drill. The ALC lets a fair amount of signal peaks slip by it which results in audio clipping. Drive the ALC hard enough to get a 50% (Or more) duty cycle, and you'll be clipping the bleep out of your audio.... and the filtering following the ALC is, if it exists at all, is simply not up to the drill of keeping your signal "in bounds" under those conditions. That's without even mentioning the other artifacts caused by such a setup.

Consider Collins and the work they did years ago.Example, "Single-Sideband Systems and Circuits by W E Sabin and E O Schoenike", ( ISBN 0-07-054407-7)

(I gather they were working for Collins at the time of publication.)

As dated as that work is, most transceivers, even to this day, do not employ their advice on design and implementation of processing. In short, there's a LOT of room for improvement. And of course with technology improving rather a lot since those days... (including better output filters) the improvements in performance can (and, I think should) be even larger. In short, your signal is not nearly as efficient and clean as it could be.

I suggest reading the work of Leif Asbrink, SM5BSZ for some background. I found this article, particularly interesting.

Asbrink makes mention of that same book in his article, by the way. It, too, is a little dated but since so little has changed in audio proc design on HAM transcivers since then, it's still valid. One of the big points made in this article is that only about 2 or 3 db of ALC action is required for their to be undesirable out of passband products. Again, ALC overshoots. The reason is most ALC's simply are not fast enough to prevent overshoots and thereby clipping which results in splatter given the weak passband filtering is most radios, even today. You simply cannot get the best, most dense audio signal out with that setup. (and by the way, I know of blessedly few HAMs who run only 2-3 db of ALC as a rule.)

Understand me; Part of the object of adding external processing, particularly peak limiting, is to eliminate those overshoots, by removing them before the ALC even gets involved, which in turn allows for "filling the envelope" more fully without the problems ALC overshoots cause, thus allowing for a more effective signal for a given power level.

(I should, I suppose, note that SDR  radios with their digital bandpass filtering (IC7300, FT991, etc) have a tendency to handle such overshoots a bit better than units made even 20 years ago. Still, why allow such overshoots at all?)

And yes, I've heard it before.... SSB has a horrible S/N ratio, you're never going to get broadcast quality audio from that setup, etc. The. thing is that idea ignores that with decent processing at (or in front of) the transmitter, one can attain a much higher S/N ratio. Even doing what Sabin and Schoenike suggested 35 years ago adds 3db to the S/N ratio, or a half an S unit on average.... and that's without any serious compressing, peak limiting and so on, before the audio even gets to the radio. With that combo, with that external processing, I see no reason the average power couldn't be much higher, while still maintaining intelligibility.

That last word... intelligibility.... is critical to understanding what I'm about, here. I'm not in pursuit of broadcast quality audio. For openers, that's flat out impossible in a 3KC bandwidth and it's also counter productive to the goal of maximizing weak signal intelligibility.

What I'm about with my audio experimenting is making the most of available RF power while adding as few undesirable artifacts as possible, which in turn makes the difference between making the contact and being buried in the noise level.

So far, it's working.

73, K2ENF

 

Update:

 As of 8/6/23

I'm pleased with the progress I've been making. I've had a few comments that it tends to sound a bit harsh when in full cry, but it's now made the difference in making the contact or making noise several times. It does add some significant average power, but at this point I'm approaching diminishing returns. 

I must say that this is the first time I've been somewhat disappointed in the documentation surrounding the 991. I would have assumed that the internal audio processor used some kind of audio clipper as well as the internal compressor and ALC. Trouble is, I'm not seeing any clipping on any but the strongest peaks, which for the most part the external processor I'm using eliminates. A little clipping, perhaps up to 3dB or so would be desirable as a wave shaper, and watching the waveform I'm not seeing it on the 991's output.  That wave shaping is the only thing my audio lacks....

The other issue is that once the average audio power being applied to the radio goes up, by means of the external proc, the internal compression reacts too harshly. I'm seeing 15dB or so worth of compression  on the internal compressor, which would be a serious issue were it not for the noise gate I'm running on the input.... all you'd be hearing is background noise.  

I've tried turning the output of the stack down, and even cut the radio's mike gain to near nothing. But, while that lowers the amount of internal compression applied, while still giving a nicely dense audio signal,  it produces an actual loss of audio in the RF envelope less watts to the antenna.  

 Frankly, I wish there was a way to adjust the parameters of the compression in the radio.  Instead it's a sort of black box I can't access. So far, the working solution has been a rather strong setting on the noise gate on the external proc. This cures the issue of the internal compressor riding on the noise level during voice pauses, but the level ends up being a little jumpy as a result, precisely what I've been trying to avoid using this system in the first place.

It's all a learning process, but as I say I'm pleased with the gains I'm making so far. 

Addendum: 9/16/23
Well, I got rid of a lot of the crud I had been chasing. While I had thought it was the 991's clipper, it turned out to be a grounding issue with the mix console. All set now, however. Getting good reports.