Custom asic in a HF Radio? Ouch!
FPGA I could see, but asic normally requires rather bigger production runs then a base station radio likely sells.
Still, that is what the Verilog or VHDL in that 'fully documented radio' is for (And yes I know what to do with them).
The other thing that would be useful in radio manuals would be the details needed for boundary scan testing as being able to plug a jtag lead in during testing (especially after you modified something) could have its uses.
 
This will become a bigger issue as the ADC gets closer to the aerial and more of the differentiating features end up as code of one form or another, but for the present most of the high end stuff does most of the business in an essentially conventional superhet sort of way and there is little in that architecture that you cannot hack with a good SMT soldering kit.

All that said, I do not (and do not plan to) own a commercial state of the art radio because they are too difficult to modify to do interesting things (but I suspect I am not the target market for the FTdx5000MP or whatever), it is a broad church so buy whatever fits your operating tastes, fixability requirements and budget.

Regards, Dan.

That is probably down to the fact that the foundation and intermediate both cover a SMALL part of the full license with the advanced test being a big step up from the intermediate (for all that if your electronics is up to snuff it looks fairly easy).

Given that the only real difference in basic privileges (providing you don't want to go /mm, run high power remotes or get a NOV for something) is +9dB on the power you are allowed at the feedpoint, I suspect that most don't bother with the advanced test. I want /mm so I will be taking it at the RSGB convention, but if I did not want /mm I might not bother as the QTH does not really lend itself to QRO operation.

In any case the level of understanding is largely something that the licensing exams should be only testing to a basic minimum, it is a start, not the end of the learning (Or at least I would hope not).

Regards, Dan.

If the rig is reasonably modular (and is properly documented (And I am not paying $8K for a radio that is not!)) there should be little where even is something has gone unobtainium it cannot be replaced with a superior modern part of the cost of cooking a new daughter board, but it does critically depend on having a way to update the firmware to work with the new part.

AD9851 gone EOL? Cook a new LO board and stick a 9910 in there instead, job done (as long as you can tweak the firmware or add a shim to make the new part look register compatible with the old one)! Same with mixers and DSP (But you really need the code for that). Power transistors, even if you cannot find the originals can usually be replaced with minor changes to the matching networks and drive levels, worst case just cook a new PA board using something available.

Actually the biggest PITA are switches, concentric pots,  and custom displays, sometimes literally the only way is to find a junker to rip a replacement out of, there is a lot to be said for standard text LCD, VGA or QVGA displays with documented interfaces.

If the rig is modular, uses standard front panel parts and has all the internal interfaces documented for protocol and level there is almost nothing a ham cannot fix (Or improve as better becomes available), even BGAs can be reballed at the cost of some eyestrain.

Regards, Dan.

Interestingly the UK also uses volunteer invigilators at the exam centers (Mostly your local club), but does NOT have a published question pool.

The way this works is that when you apply for an exam the RCF send out a personalized exam paper in a sealed envelope together with (for the first two levels) the answer sheet also in a sealed envelope (Computers make producing customized exam papers really easy).
At the exam center there are two invigilators needed and the envelope carrying the paper is opened in your (and their) presence. You take the exam and (for the first two levels) one of the invigilators then opens the answers and marks the answer sheet. For the advanced exam the answer sheet is returned to the RCF who mark it (And take forever for some reason).

While I suspect it would be possible to do a Bash on it, it is not like these things are really hard enough to make the rote memorization easier then actually understanding the subject, so to the best of my knowledge nobody has bothered..

The issue of published questions is orthogonal to the one of paid Vs volunteer invigilator for the exam. 

Our licenses are lifetime as long as you inform Ofcom every 5 years that you are still around.

Regards, Dan.

I fall squarely into the no code category, having only fairly recently gotten around to getting a ticket.
Taking a code test was not offered as an option, so it is not like the code/no code thing is actually something a new operator has a choice about.

Now I am working on my code (In between designing and building the gear for my station), I fully intend to by up to at least 20WPM by the time I get the boards for my radio fully stuffed (And the driver board rebuilt for the ***third*** time (Design improvements for hopefully better IP3 on transmit)) and everything tested to my satisfaction.

Personally I suspect that the bigger problem in the US is the public question pool, always a bad idea in an exam context as it means that rote memorization is a viable way to get a pass. 
The UK licenses (we call them 'foundation', 'intermediate' and 'advanced') have a secret question pool and for the intermediate, require that some sort of practical radio related kit or circuit be constructed as well as a specified simple DC circuit on which measurements must be made.

Doing away with the multiple guess approach in favor of proper essay questions would also be good, how can anyone take multiple guess seriously as a test of knowledge?

The thing is any of the stuff you need to learn for the exams is at best just the beginning, I have entire bookcases on radio engineering, propagation, aerials, modulation theory, coding theory..... Every thing from Langford Smith & Shannon through the ARRL (EMRFD is great!) & RSGB books to proceedings of the ACM and AES, and yet still I find things when operating that make me go "Thats strange", 6M propagation especially.....

Regards, Dan.

"Excess precision" is the term, but actually for a SSB radio absolute precision is less important then having a small enough tuning step to allow the signal to be tuned close enough to make it ineligible ~1Hz tuning steps are easy these days, and quite sufficient.

That said, I don't really see the upside, it is not like you  are going to be doing weak signal work with a HT after all. 

Regards, Dan.

The bit that offends me is the dubious claims from some of the aerial companies, you know the "No tune all band vertical end feds" that turn out to require mounting on a 50ft mast insulated from ground (Hint the conventional description is a vertical dipole), or the ones that require a minimum of a hundred feet of RG58 before they will match reasonably.
Yea, I can make anything show better then 20db return loss too, it is called a 10db pad!

But people still buy the silly things.

The UK intermediate exam (Roughly US General class) with a 50W power limit now requires you to build at least some kind of a kit, it can be pretty much anything, but at least it introduces people to which end of a soldering iron gets hot.

The advanced exam however is all theory, including some relatively hardcore circuit theory, but no actual construction.

Well firstly frequency modulation, by definition requires something to carry the information about the frequency, this surprisingly is called the carrier!
Actually the subtle thing about FM is that there are certain values for the modulation index at which the carrier completely nulls out, and only the sidebands are radiated, but this only happens when the modulation index (Deviation/Modulating frequency) hits very precise values given by the roots of a bessel function of the first type, and for anything except a sine wave as the modulating signal the math gets hairy, unlike the  case with SSB the two side bands do not contain two identical copies of the information so removing one will cause distortion.

Secondly, SSB requires linear amplifiers where FM can use class C (non linear but efficient) amplifiers which are smaller, simpler, cheaper and result in far less of your battery ending up as heat in any given transmission, also FM receivers are simpler then SSB ones. You do sometimes see SSB offered on vehicle mounted radios that do not have the power and thermal constraints of a HT.
SSB also requires very precise tuning where FM can work even with substantial frequency errors (and can have simple automatic frequency control to pull it  onto frequency, important in a radio that has to work channelized over say -40 to +30 degrees C.

HTH.

Regards, Dan.

Very difficult (possibly impossible) to know, there are lots of people who would pay good money to know the real plug and play reliability figures for non trivial applications and hardware on the broad church that is the "PC Compatible" computer.

In my experience plug and play usually about half works, specifically the plug bit almost always works.....

Actually given a relatively lax set of deadlines and a sufficiently lightly loaded processor (and they mostly are most of the time), and a relatively lax requirement for the reliability in meeting those deadlines a non RTOS is very often acceptable (And very much easier to code for!), it is when those deadlines become closely spaced (even if the chip is lightly loaded over periods much greater then the deadline) that things start to go pearshaped quickly.

SSB and most data modes are MUCH more forgiving in this respect then CW because SSB typically does not do sidetone, so the latency can afford to be very much greater without it becoming a operational problem. 

Yea I know all about getting the thick end of a volt at the aerial socket from 41M, just be thankful the bloody woodpecker is gone.
I have quite a nice BPF box and actually I see the USRP as more of a very cool bit of test gear for the lab then as a day to day radio for ragchewing on 20M.

To an extent even most of us who do build our own radios buy complete subassemblies, I mean sure you can build a DDS core from transistors but who would want to when the AD9910 and friends are out there (There is that guy in France who builds his own valves, then builds radios around them, I commend the utube video to anyone interested). 

Scary, it ***is** possible to have a civil discussion here, I was beginning to doubt it.

The thing is if you are an experimenter, and DSP is your trip then you are probably better off grabbing an eval board from Ti or AD and running the code on a real DSP core rather then a PC (for all their superficial attraction), there is just too much else going on with the PC, and you control far too little of it. This is arguably less of a problem for an individual experimenter, but becomes a killer when you have to try to support a product on hardware you do not control, with arbitrary drivers (which are notorious for being buggy crap on all operating systems), and random other applications. There is a reason technical support is a job that is feared.
   
If windows had a soft RT scheduling class like say the posix FIFO scheduler class then at least some of the pain would go away, but as far as I can see the nearest thing is the "Multimedia" scheduling class, not really the same thing.

Does Flex actually document their wire protocol to allow independent development? I didn't think they did (One of the things that put me off the idea of getting one), sorry but I want the wire protocol, the source to the control program running on the hardware,  and any relevant Verilog or VHDL source code for the FPGAs (Oh and a complete set of schematics).  I like to experiment, and not having these things tends sooner or later to stop you from making the radio do whatever you want. I am ***VERY*** tempted by a USRP from Ettus research however (Up to 25Mhz bandwidth over Gig E, very cool, but not cheap).

I am thinking of  doing something like a pic or avr with a simple keyer and controls to vary the relevant latency values, so some experiments could actually be done with the CW keying question, but I suspect that good data needs more samples then I can easily obtain. 

Regards, Dan.

I have never understood these linearity issues (which is really what they are) designed into radios at audio frequency after most of the gain has been applied, The hard bit is the IF stages not building a clean audio section!
If you sold a radio with 1% harmonic distortion in the IF amp (or worse the first mixer....) at normal operating level, people would rightly be screaming that it was a steaming pile of merde, but apparently audio frequency problems are acceptable?
However, unlike the others this one can occur in the first mixer, so the strong signals do NOT need to be inside the passband.
Not sure I agree with the conclusion there, for all that I agree that using an SSB radio for a mode that is not 2.4Khz wide is stupid!
Nothing wrong with using an audio frequency first TX IF or last RX IF (for that is really what it is), in fact this can have a few upsides as it removes a tricky DC nulling problem in the IQ modulator in the transmitter.
Also you really do not want to just apply raw digital switching to the phase modulator as you will get switching sidebands for days, much better to go to analogue (either at baseband I/Q or as a low first IF) and shape the transitions with a raised cosine to minimize transmitted bandwidth.

AD have an interesting combined DDS and I/Q mixer that takes its input directly in the digital domain that might be fun to play with for this stuff.

There is nothing much wrong with using analogue radios and even an audio frequency IF, providing the selectivity is there, but there is no point in trying to design a mode much narrower then the selectivity filters in the radio either, so something 500Hz wide makes sense, maybe even 250Hz but only a vanishingly small number of rigs have first IF filters narrower then that.

Regards, Dan.

Indeed, no table of numbers catches things like critical controls buried 5 layers down in a menu (HT makers you know who you are (all of you))!

Any yea, optimizing for a single parameter is almost always a mistake, but I am mainly interested in trying to find out which numbers actually matter as clearly some make far more difference then others.

Buying a radio because it is at the top of that table (which is mainly  concerned with close in IMD) is poor decision making but that table is a very useful benchmark for those parameters for those of us designing and building our own rigs.

The actual point at which any of the numbers become 'good enough' will vary widely between individuals of course, that is a given, so  there is no absolute line in the sand (Hell, I have been using an old FT 101-DZ while I build my dream radio, the thing is pathetic by modern standards, but you can still have fun).

You don't necessarily have to agree with Mr Sherwoods particular set of priorities (I find his Drake obsession a little strange), but the data is undeniably real at least for the samples he tested, and is useful even if it cannot be used as a sole decider of the 'which rig' question.

Regards, Dan.

Apart from the rather "self selected" nature of the reports you get for problems, there is another issue with establishing what is going on here...

People differ, and what may just not be a problem for one can make something completely unusable for another, just the way it is, sensitivity to things like delay and delay jitter can (and do) vary by whole orders of magnitude between individuals (There was work done on this by the musical keyboard crowd), so actually finding values for this stuff is hard (And satisfying everyone needs massive over engineering for the 95% case). 

Now if I had more time, more money and more energy I might consider pulling a "sherwood engineering" on CW keying performance, complete with data tables and calibrated tools, which is really what needs doing here to see what is really going on, as it is my interest is mainly in transmitter performance as the low hanging engineering fruit on the bands these days (30dB below PEP is NOT a respectable 2 tone result, Motorola app notes were managing -35dB below ONE tone 20 years back (Equates to ~41dB below PEP)).

The only folks who really know what the frequency with which technical support is needed for Flex radios are Flex, and even if they were publishing that data it would not tell the whole story, but they are far from the only manufacturer to have major support pain with software systems (You dont want to see what MUSICIANS sometimes manage to perpetrate in terms of ways to break computer based hardware).

Regards, Dan.

Third order intermodulation distortion intercept value.
Basically a measure of how much interference is generated by non linearities in the signal path in the presence of strong signals.

Typically tested by putting tow signals up with a specified spacing and measuring the level at which they result in a 'phantom' signal appearing out of the noise floor spaced one spacing away from either of the signals.

What you typically find is that where one or both signals lies outside the passband of the first IF filtering you get numbers like +30dBm or so for a good radio (Basically measuring the performance of the first mixer) , but when you re run the test with the spacing reduced to say 2Khz in an SSB bandwidth the figure drops right down, which is equivalent to saying that strong signals inside the passband are a much more serious source of interference then equally strong signals outside the IF filter passband.

This is why using as narrow an IF passband as possible is (to a first approximation) a good thing. Like all blanket statements that one has a few holes, but it will do as a general principle unless you are designing a receiver.

HTH.

Regards, Dan.

Of course it is, within the passband of most radios IP3 degrades massively compared to what happens outside the filter passband (especially the roofing filter passband).
No surprise there and no surprise that if you use SSB bandwith for a narrowband mode the radios IF linearity is sometimes going to get stepped on by a nearby signal that is 60 or 70dB stronger at your aerial, this is not the fault of the 60 or 70dB stronger signal....

This has little to do with transmitter power differences which are usually within less then a 30db range (QRP to full US legal limit), propagation is the great equalizer.

Regards, Dan.