Solar flux is around 1kw/m^2 at noon at the equator, and the panels manage at best around 20% efficiency, so under optimum conditions that is 200W per m^2, probably more like 100W in reality.

If you assume that by the time all the conversion and ohmic losses are out the way you need 1kw per horsepower delivered to the shaft, then even a modest Naval vessel running say a pair of 500HP engines (which really is not all that big) needs 10,000 square metres of panel for full power (Plus whatever it needs to recharge the batteries for night operation).
For limp home or low speed cruise, say 10% of that would get you maybe a few knots, but it is not a sane option for serious main marine propulsion.
For reference, the tiny 150 tonne displacement hull ~ 70 ft long on the waterline that I am sitting in now, makes about 5 knots at 100HP out of the main engine, and tops out at about 7 knots at 150HP.

Of course I have worked plenty of gigs that made a big thing out of their solar 'green credentials', there was usually an amazing amount of diesel burned in some very large rotating machines back where the public could not see them....  
I suspect there is a fair bit of that going around these days.

It is mostly the link from the inverters to the drive that tends to radiate, but ships are an RFI nightmare anyway, you would think that all those steel compartments would make them really benign from an RF perspective, but it aint always so.

Regards, Dan.

Got to be a bit careful feeding the modulator directly.

The issue is that SSB envelope does NOT follow the baseband real signal envelope, so peak control needs to be done in the analytic domain, not the real one.
This is quite different to the transmitter protection limiting requirements for AM, DSB or FM operation, where peak limiting in the real domain will suffice.

Personally I like a good dynamic mic (Sometimes an RE20 from my mic locker), but whatever works for you.

Remember clarity is probably more important then absolute highest possible average power (at least most of the time), and that does NOT necessarily increase the occupied bandwidth much, it does however imply that compression, limiting and clipping should be kept to sane levels.
I would further note that gross changes in group delay through the IF filters can have a really detrimental effect on ineligibility (Can you tell I like the phasing method), and often a transmit filter closer to linear phase at the expense of stopband can sound  better (If of course the RX has suitable filtering, NOT even close to a given).

Be a little careful of the THAT corp mic preamp chips, very high gain bandwidth product, and IME they need some fairly heavy measures to keep top band and 80M out of them.

And finally, please if you are going here, do take the time to check for off frequency splatter, several things about wideband SSB make it more likely, avoidable, but more likely, so it behoves you to check. 

Regards, Dan.

Cold start is MUCH faster for anything that does not involve steam, for all that big marine diesels cans can still take quite some time (You have to heat the engine before starting it otherwise you risk cracking the castings, and may have to build air pressure in the air start accumulators, can take hours, where large steam can take days).

Current state of the fuel economy art is actually really BIG two stroke blown diesels, running directly at shaft speed with hydraulic valve gear which allows the engine to be operated either forward or reverse by changing the valve timing. 
The downside is throttle response and single point of failure (Also single screw ships are often tricky to manoeuvre astern), but the really big container ships seem to be favouring this technology. The things run at less then 100RPM typically.

There have been steam/electric passenger ships built in the past, usually big DC machines at the time, and current naval construction is quite often worked this way, HMS Albion springs immediately to mind as a reasonable modern example. Multiple diesel prime movers driving a really BIG set of inverter drives to the propulsion motors.

Electric rail traction tends to distribute the motors across many driven wheels (at least in UK passenger service) with a low frequency generator making up the bulk of the locomotive proper. The advantage is the removal of the need for a gearbox and clutch capable of handling the very high starting torque.

73, Dan.

If you fed back the load phase angle as well you could get smarter about it, 2:1 can represent an impedance magnitude of either 100 or 25 ohms after all, and on the low side it might be possible to drop the PA supply voltage to remain within the safe operating area while supplying more current to the low Z load.....

But yea, not running into the supply rail is slightly important!

The reason to shy away from rating that 100W PA at 200W and 1/SWR is probably mainly down to heatsink and DC supply limitations.

The modern trend for built in L network auto tuners probably does much to improve IMD simply because it improves the match in most cases.

Regards, Dan.

There are several.

Firstly Cruise ships have an interesting usage pattern for power and propulsion. On board power demand peaks in the early evening (All the entertainments, lighting and such) and can use many Megawatts of total power, but propulsion demand peaks in the very early morning when the ship is sprinting to get to its next port of call....
Thus one (redundant) set of generator plant can be put to both uses, at a considerable improvement in overall efficiency.

Second, the electric propulsion does away with a very complex and expensive gearbox (Big ships usually run very low shaft speeds, turbines not so much), and electric propulsion allows (almost requires) that the prime movers run at constant speed which is enough of an efficiency win that it covers the extra conversions required.  Electric also allows relatively simple switching of power between prime movers and shafts so loosing a generator does not take a shaft out of action where in a directly coupled system loss of a engine has a far bigger effect.

Third, it allows for much more flexibility in the layout of the machinery spaces as the motors can be placed almost right next to the stern glands, without needing much in the way of shaft tunnels and such. Very large multi pole induction machines have speed ranges that are a good match for marine propulsion.   

The downsides are that heavy current electrics in a salt water environment are ah 'Fun', marine engineers do not historically have much heavy electrical power experience (This is slowly changing), and that relatively minor flooding can cause much chaos (See also computer controls for more on this).

The MAIB has a few writeups of incidents that are worth pursuing for some of the issues.

Regards, Dan.

Yea, I know all about bloody copper on the mill, do my own machining.

High power is always mainly about thermal and mechanical.

Is copper needed? Valid question actually, I suspect yes if running full transistor ratings into the smallest possible heatsink, but possibly not if running into a somewhat over sized heatsink. This really needs some FEM modelling to see for sure (Or an actual experiment).
Certainly I have an old Redifon Mel PA that does not use copper, but the heatsinks are **Massive** and it makes 250W from a pair of BLW96 (Nominal device rating 200W each). It might be that the copper thing is mainly about allowing the use of physically smaller heatsinks by allowing them to run hotter. 

Some of the 'phase change' heat transfer materials are possibly interesting, or maybe even something like a very thin indium foil (a VERY soft metal).

73 Dan.

Very true, you got to make a clean signal to start with or all the work on the PA is in vain.

Difficult to avoid needing at least 50dB post mixer gain, which is boring, but even level 23 mixers tend not be be particularly clean above 0dBm or so. I suspect the other biggie is getting the matching right (particularly the match out of the mixer), but I have seen some very strange looking matching networks out there.

There is only so much you can do about the screwdriver experts fiddling with the drive power trimmer or modulation bandwidth, try to design "attractive nuisance" trimmers like "Drive power" and "Deviation" out of your design (Digipots are sometimes handy here, or do it as a calibration directly in the DSP). In fact try to keep trim pots out generally, trim caps are not always avoidable, but pots can usually be designed out.

And yea, if you are prepared to pay for it (in capital cost, size and heat) superior IMD is **EASY**, getting nice numbers without using twice the amplifier sand needed and without masses of excess heat is the trick.

Also I hate the 160 - 6M expectation these days, makes magnetics selection more then a little tricky.

Incidentally a good source for small quantities of copper sheet in the UK would be appreciated if anyone has a suggestion, I have been thinking about those copper 'bullion' sellers on ebay and face milling top and bottom, thick copper sheet seems to be a hard problem unless you want square metres of the stuff.

73, Dan.

I am deep in the throws or a 350 mile relocation and starting a new job, but once that is out of the way I might be willing to give it a shot (More so if I can enter a complete transmitter rather then just an amp strip, in which case that 10Khz spacing is too wide, 14.2 & 14.201 would mean audio input could be used). Likely to be summer before the workshop is properly re-established however.

Oh, add a requirement that a schematic, parts list and possibly board layout be published so the work is reproducible.

The real problem with this sort of thing is that it ignores things like production cost & efficiency (Anyone can build a clean 100W by burning 500W DC input in a class A stage).

73, Dan.

Well I suppose you could, but the second harmonic will be a pain.

The big problem with a single anything is that the output filter becomes disproportionately more complex, because you need much more second harmonic attenuation, so the ability to use one filter for two bands becomes very much more marginal then it usually is. Granted class A will have lower harmonic output to start with, but still.

I would bet that the extra transistor is more then paid for by the simpler harmonic filtering.

Be a little careful as well, bias voltage temperature compensation is required to avoid the risk of thermal runaway in class A with mosfet stages (contrary to popular belief).

Regards, Dan.

Ok, so for a broadband stage you are going to want to run push pull (Makes the output filters easier), so we are looking for a pair of ~15-20W devices, and we probably want to do this at 24V or just possibly 50V.

Further we need to go from 50mW to ~25W, so in total we need around 27dB of gain, which is probably going to need two stages even with modern parts.

BLW50F springs to mind for the output devices, old school bipolars, can be run in class A (at the cost of much heat), but difficult (and expensive) to source these days, and like all bipolars would need a stiff bias supply.

BLF175 looks like a sane choice to me,  a push pull pair on a 50V rail will get you -35dB[1] or so IMD3 in class AB, and possibly a little more if you up the standing current a bit (heatsink dependent).
However a pair is really good for 50W - 60W with appropriate drain match, so may be overkill.
They are not quite man enough to make 20W push pull in full on class A, but if you have sufficient cooling you could probably run very high bias AB with good results.

Add some negative feedback (bifilar transformer between the drains in the manner of those old moto app notes), and make sure the DC injection ferrite is big enough and you might just hit -40dB[1] or so with as much as 17db of gain.

I would probably design the drain match for maybe 30 - 40W, then by running at 20W you will be well away from saturation (At the cost of rather low efficiency), the drain matching transformer could bear experimentation to optimise for distortion.

Regards, Dan.

[1] Note, I ***THINK*** the datasheet gives this number ref one tone (The wording is a bit weird), if so read as -41dB ref PEP.

Mainline electronics brought Jackson Bros. some years back, then had a major fire!

The fire was in their main business at the time which was all sorts of really cool surplus, but did seriously impact getting things up and running with jacksons.

Regards, Dan.

Pretty sure the washing machine is involved with the socks thing but probably not with the screws.

Mind you, I will see you screws and raise you anything in an SC-70 package, I never buy less then 25 because that way I might not loose all of them before getting the board soldered up, 0201 resistors are also unfunny this way.

What I want to know is what happens to my small screwdrivers, I have bought that many over the years that I should have NO problem locating any number of the things, anywhere in the house.......

There must be some sort of macro scale quantum effect going on.

Regards, Dan.

One thing to remember about those temperature ratings is that electrolytic caps are specified for a rated life at a certain temperature and rated ripple current (Usually just 2,000 Hrs), the service life rises RAPIDLY as the ratio of capacitor temperature to rated temperature falls, so a 105 degree part will have a much longer service life then a 85 degree part, even if both are in a 50 degree C environment.

Nobody (with any sense) designs to run electrolytic caps at anything like rated temperature because the life at that point is so short.

73, Dan.

Part of the problem is that proper protection costs real money, and that it is invisible most of the time.....

Lets see, to do the job right you need:

Airflow and heatsink temperature (Both because that air also cools the output filter and power supply).
Transistor temperature (per device ideally).
Over current.
Over voltage.
Reflectometers at both input and output of the LPF (The input to detect wrong band setting).
Imbalance detection if using multiple PA blocks.
Drive power (and some fast way to fold it back, a relay or ALC will not suffice).

The airflow should be filtered to keep fluff from eventually coating the internals and stuffing up the cooling.
Also careful sequencing so that nothing is ever hot switched.

This is not simple and not particularly cheap, but is basic to most good quality commercial service amps, you seldom see all of it in a commercial ham amp because the cost is just too high.

All this in addition to a well designed PA block with enough margin to start with, and enough heatsink to ensure it works properly in a 40 degree C equipment rack.

Also there is a lot of inertia behind the tube amps, and sometimes a poor understanding of the SS ones (The care and feeding is different).

Regards, Dan.

All too true, I have had capacitors unsolder themselves from the board before now (I dropped a decimal point when calculating the circulating current).

73, Dan.