If you can arrange the cold plate to be grounded and use some magnesium or zinc anodes to control the corrosion then water can work, the condensation issue still exists of course.

IIRC There was a version of some of the external anode tubes made with a BeO block and mounting plate precisely so as to enable water cooling, and I seem to remember something similar for the small UHF power tubes, I still say it is a major pain in the tail however (Especially the UHF variant which ran water directly over the anode structure, DI was a must).

Phase change cooling is efficient and has the nice feature that it maintains constant temperature as the boiling point of the coolant (at any given atmospheric pressure) is constant, but I seem to recall some problem the BBC shortwave services had with a very cold winter and freezing the condensers.

All these methods have their issues, and it is only when power becomes large that the benefits outweigh the pain.

Regards, Dan.

I would suspect an aerial or feedline 'issue'. On HF the major limit on receiving is usually sky noise, and a poor aerial will drop the sky noise just as much as it does the wanted signal, so it doesn't hurt you all that much.

On transmit however, that effect does not help  because it is the other guys aerial that is picking up both the sky noise and the wanted signal, so a poor or incorrectly performing aerial will be a far bigger problem.

Do you have a power meter, and if so what does it have to say about both forward and reflected power?

Daft thought, but you do have the mic gain (and RF power) turned up to a reasonable level, see the manual for how to set this.
What does the power meter show when transmitting?

Regards, Dan.

Not for amplifiers, but I have watercooled high power DC supplies (Think 60A @ 200V) for laser applications.

Actually the biggest pain is condensation when the feed water is below the dew point, the condensate drips off the cold plate and well there is one much despised implementation that put the control electronics board right below the cold plate..... It used to result in blowing a great many 2N3055 on a boringly regular basis. 

Electrolysis can be an issue if running the water in contact with high voltage, best to run two loops for that with DI water in the primary, but note that DI water is somewhat corrosive. An ion exchange cartridge is important if trying this. If you can keep the water conductivity low enough it does however make a truly excellent insulator. 

In terms of the cold plate, getting sufficient turbulence to avoid boundary layer effects is important for best efficiency, a fairly open coil spring pushed into the cooling channel combined with a reasonably high flow rate helps here. 

Overall, I am not sure it is worth the pain at less then low 10KW levels, above that or is size and weight are critical and you have a suitable chilled water loop already in place, then fine.

Regards, Dan.

Personally I say government has FAR more important things to do then worry about either, that is why the radio has a VFO!

I am not sure they are actually mutually exclusive, but with a little thought it is always possible to express any content without profanity, and it is obviously always possible to be profane without content. Ham radio is a communications transmission, it is not broadcast radio, a medium for such things as performances where profanity may be appropriate in a dramatic context.

For me the issue is not even profanity, it is setting out to cause offense, which can be done with no profanity at all (After all, swearing has a place, seldom on the air, but I will admit there are times). Further more once past the blindingly obvious, there is speech which some may find offensive, but which is not profane (And should clearly be protected), after all you can always just spin the dial (Religion and Politics often fall into this category, also consider something like a discussion of which abortion clinic has the best doctor.......).

There is a difference for me between profanity, speech which is deliberately intended to cause offense, and speech which causes offense but is not intended to do so. The distinction between the last two being so blurry and so much in the eye of the beholder that both are worthy of protection.

Profanity in a dramatic context in broadcast radio or telly is a whole can of worms.

Regards, Dan.
 

Transceiver output impedance will make NO difference to the SWR measured on the line.....

If you have drive power to spare, a pad in series with the line will significantly reduce the reported VSWR, 6dB or so may help enough.

Regards, Dan.

Controversial matters could be a legitimate subject of discussion for all that such is likely to produce more heat then light and that such discussion is unlikely to change any minds, but that is not the same thing as being offensive. I can disagree with you without being offended by your views, it is called debate and both our political systems are founded on it.
 
On deliberately offensive language, personally I would tend to the view that the answer is that the law should not really enter into this and that one should refrain.  While there is no right not to be offended, I tend to hold that one should generally seek to avoid giving offense, and that this holds irrespective of the question of the legality of so doing.
 
73, Dan.

Just to add a few to the list:

Horowitz & Hill, "The art of electronics", aimed more  at physics students, but a good introduction to the subject, and not too math heavy.
Langford Smith, "Radiotron designers Handbook", If old radios are your thing this is a must have, the reprint has IMHO a poor quality binding, try to find an old one.
Ian Hickman, "Practical RF handbook", does not get referred to much but has a few useful tables in the back as well as a good introduction to  shielding.
Duncan Smith, " Small signal audio design", good for ideas on VLF and audio stages in general.
 
I have a whole shelf on digital signal processing, and at some point need to add a copy of the "Filter design handbook".
This is by no means exhaustive, but just adds to a reasonable subset of the already mentioned.

I will add a shout for EMRFD, if you experiment with electronics this is a must have, and subscriptions to DUBUS & QEX are worth the money.
 
Regards, Dan.

Foundation is 10W, all bands except some high microwave bands. Commercial equipment only, no /MM.
It is broadly equivalent in level to the US Technician exam, and from what I have seen while it can be abused, few do.

Intermediate is ah different to the US General in that it has a practical element, requiring that some kind of simple circuit be built (a DC RX or VFO is common) and that various experiments be demonstrated, gets you 50W. Again it could be abused, but the difference to a 100W rig is only 3dB, and in my experience few do.

Advanced (That I will be taking at the end of January) is a fairly nasty thing unless you have an EE background as it asks some very subtle questions on aspects of radio engineering and is hard for even a very good radio engineer to get more then about 85% on (Passmark is 60%, all exams have a closed question pool), gets you 400W and /MM along with a few other privileges, fortunately I have been playing with electronics since I was about 6 so not a problem.....

Of course the manufacturers lobbied for easier exams, but actually the difficulty of getting an entry to the hobby was a well recognized problem for a long time over here given the (more or less) demise of CB as an entry route.
Creating something the equivalent of a US Technician license reduced that barrier, for all that the step between intermediate and advanced is still a huge one.

Actual reality is that anyone, licensed or not can pick up a transceiver almost no questions asked, and has been able to for a long time, but it does not appear to be a major issue. 

At any level the license exam is at most a test of minimum required knowhow, IMHO it in no way should be seen as a destination, it is a starting point for further learning and research, as are all such tests.

Regards, Dan.

The UK Foundation license is actually very similar to the US Technician license in content, with the major difference being that we use power limits to differentiate the different classes (10W,50W,400W) for the most part with some privileges reserved for Advanced licensees (Maritime Mobile, High power telecommand links, Getting the 60M variation, some extreme microwave bands, a few things like that).

Foundation is also restricted to commercial transmit equipment, while intermediate and advanced can both build their own (And the intermediate requires you to build some kind of simple kit or circuit to pass the practical (A VFO or DC receiver seems to be common)).

IME most countries tests seem to be broadly similar in content with minor differences in level and privileges at each level, not enough to be any kind of problem in reality.
Any of these tests can only be at most a beginning, the real learning comes afterwards.

The other very obvious government administered hobby test is the Private Pilots License, for substantially the same reason (Ability to cause problems for others).

Regards, Dan.

I had thought I was joking about a class C 'linear'! OUCH!
I take it 'Pill' is CB speak for transistor? 

PLEASE tell me that stuff is purely aimed at the 11M market.

Regards, Dan.

I would like a cite on SSB CB being legal in Europe, as far as I can see everything on 11M over here is FM (And the CB band is basically dead on a quick tune around).

CB enjoyed a brief period of popularity in the early to mid  80's, but has largely died, killed by the mobile phone.
In fact it was noticeable that ham radio actually got a lot of converts from CB at the time (Including G0FUW the guy who put our exam course manuals together!), it really was not a bad thing for amateur radio over here. 

I still say KW class CBs are a mostly US problem, and it is noticeable that while a 11M KW class C 'linear' may be illegal to USE, the US is about the only place that requires amplifiers to add hardware to explicitly lock out the 11M band in order for them to be legal to SELL.
Hell a CB and crap 11M amp probably makes a dandy RF source for a plasma generator or a AO Q switch or something, and as long as it does not radiate, wheres the problem?

I suspect you are projecting US problems and to some extent cultural assumptions onto places where it does not apply.

Regards, Dan.

Not really, key the mic in FM should give you 100% PEP for however long the amps duty cycle limit will allow it, which may not be long enough to give a reasonable talk time if the amp was designed for SSB rather then key down FM service, it may in fact be limited to well under a second if the power supply sag is the short term limiting factor (Which could be fine for SSB).

Any amp that does not (at least briefly) make PEP under that test is faulty, BUT that test does not tell you much about what the design duty cycle limits are at PEP, and if the amp was designed for SSB usage then both the duty cycle and the integration time could be very low.

Besides, why use a linear for FM? Class C will do quite nicely and make a great deal less heat. 

I am all for amps which reliably meet whatever service conditions they were designed for, but if that service is ICAS SSB, why should I be buying a CCS RTTY service amp? One hell of a lot of extra weight, fan noise &  size for nothing I am going to use. Just as silly is buying an ICAS SSB amp and using it for RTTY contesting (It may very well let the smoke out).

I used to think that 100% rated amps were cool, then my back had a quiet word.... Now I decide what the design is for then run everything at no more then 70% of data sheet rating under those conditions. The 70%  is for reliability, the duty cycle and PEP/Average ratio is for my back.

Regards, Dan.

I have been experimenting with a sand state transmitter where the bias runs relatively low bias AB up to maybe 5W, gradually tapering to class C as the level comes up.
It is a trick that can only be done with a closed loop transmitter because the power stage gain varies widely, but in combination with drain supply modulation it is starting to post some very good numbers for efficiency with real speech. This scheme tracks the envelope at full modulation bandwidth so is I suspect much faster then what Ameritron use, but then working in sand state I have a bigger cooling problem to contend with....
A linear service RF MOSFET that would accept negative bias would be a win, as it would allow operation further into class C, but most do not specify Vgs over a reasonable negative range.

Running almost class A bias is attractive only because it makes linearity better, but otherwise it is just a waste of power (Both for the rig and the cooling).

An interesting aside on audio frequency amplifiers is that most of the really big stuff for PA use is not in fact continuously rated, something like a Camco V6 (6KW theoretical) will eventually thermal shutdown on you if you try it, so the HIFI Rating would probably somewhere around a KW or so.
What it will do is make 6K for a few tens of seconds or so, which is fine given the duty cycle of the real program audio (even highly compressed dance 'music' has an average power only around 1/8th of the peak power).
There are amps that will do nameplate rating continuously, but the weight, size, and cost make them deeply unattractive as you could never use the capability (because you would be deep into peak clipping).   

Our problem is that firstly there is no standard way to give such a rating for RF kit with any kind of consensus on things like duty cycle and integration time, and secondly that we have modes that do real key down operation.

Regards, Dan.

Ebm-Papst are good kit, the curves are in the datasheets.

Regards, Dan.

Cannot be true surely, with SSB a 1KW amp will spend most of its time well below 400W.
Efficiency does go down at less then 100% power as the drain match degrades, but I cannot see any linear amp being designed to drop off line under those conditions, I could maybe see it in a class C or E design where the heatsinking would not cope with the dissipation caused by inadequate gate drive, but not in a 'linear'.

There is of course no doubt that RM basically make for the 11M market, with some spin off into ham markets, and little doubt that the ah "Value Engineering" is somewhat more extreme then I would be happy to perpetrate, but I will again withhold judgment until some real numbers for that particular implementation become available. There is more to this subject then the data sheet numbers, which in any case are often just given for third order.  

Not all countries have this weird CB/HAM pissing match going on, and most actually do not have a major issue with numpties with KW class CBs.... That is a peculiarly US thing, and while I do not much like the look of RMs stuff, and would probably buy something better if I was in the market, I am not prepared to publicly slate a product I have not even seen a final data sheet for let alone had on the bench. The US has all sorts of regs aimed at their 'CB problem' that do not apply elsewhere, and actually I can see uses for a low drive power PA that are entirely legitimate (Saves a couple of stages when building a rig).

My old Racal TA1816 solid state amp will make full output all the way across the HF spectrum with just 250mW drive, and that is not a pony piece of kit by any means. If you have the space and are satisfied with 500W from a rather old design they are also a bargain (£250 region), and we are limited to (for a full license) no more then 400W at the feed point anyway.

I would note that Italy has for a long time had a somewhat 'relaxed' attitude to such things as the more inconvenient European Directives on things like electromagnetic compatibility, and has also been a long time producer of very cheap (and generally not much loved) radio transmission gear.

Regards, Dan.