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Author Topic: 'Dream Amplifier': Solid State vs Tube  (Read 2584 times)
VR2AX
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« Reply #15 on: August 16, 2018, 05:04:39 AM »

Respectfully think G3RZP has the point: do we wish to claim that our self-training effort is “duly authorized “?
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WB8LBZ
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« Reply #16 on: August 16, 2018, 06:41:55 AM »

Hi Jarrad,
   This one designed and mostly built is one that might be worthy of your consideration https://rf-kit.de/en/Products.php . I have been looking at this one and it is considered a kit but you add a few commonly available components to make it work. They have a one LDMOS device and two LDMOS device kits available.

73, Larry  WB8LBZ
El Paso, TX
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KC4ZGP
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« Reply #17 on: August 16, 2018, 09:15:58 AM »


It works?!

Kraus
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KA4WJA
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« Reply #18 on: August 16, 2018, 07:45:42 PM »

Jarrad,
1)  Although my initial reaction here was that this will be more of a mental exercise, rather than an actual real build, mainly because of cost / complexity, not due to any lack of engineering skill...as you can acquire that skill... Smiley

Then, as I read more of what you wrote, I'm getting the impression that you do really intend tom spend the $$$$ and build this amp??  
So...

So, with that in mind, I have a few thoughts / ideas / recommendations....all based on my USA location and being a US licensed ham since the 70's...

Ok, so one of my 'bucket list' items is to build 'the big one'.  Not because I want to use it on air in a CB Competition, but because of the engineering challenge; after all that is the attraction to some of us in the hobby.
>>>>>>
So the question is, do I build a 5Kw Solid State amp, the bear minimum would be 2x 2 LDMOS pallets with splitters and combiners, but that probably wouldn't achieve the linearity I'm chasing so perhaps 5x 1 LDMOS pallets would be more realistic, or even 5x 2....

If I wanted to hit 10K, we're talking at least a 5x2 and after the associated splitting etc I can't imagine linearity would be much better than -30dBc...

Or, do I bite the bullet and 'go hard or go home' with a proper tube.  Something like a 3CX3000A7 or a 3CPX5000A7 (the 'MRI Pull' tube with handles').

The problem is, transformers for such tubes just don't come about often in VK; I'm almost certain I'd have to have one made up, and that could get expensive very fast.

The plus side would be a much simpler amp, capable of much greater output and/or much better linearity.

What would you use for your 'ultimate amp challenge'... Bear in mind 75% of the goal is to learn/build a 'broadcast quality' product, not something to make a Bird 43 with a '25k' slug 'swing'.  What power level would you go to?  I don't see any point building less than 5Kw when today's market is full of proven 2kW SS designs for all bands, and even proven 4kW tube designs for all bands.

Remember, this is for fun; a project spanning years and a dream.  What would you dream?  As for bands, if I went tube I'd probably only bother building for 80, 40 & 20 with the possibility of 160 also.

The simplicity of single large tube; especially a tetrode if grid driven, really does make a lot of sense for a Ham.

The downside of course is that the skills learnt really only apply to fixing up old broadcast gear, and of course mastering a small section of the past.

On the other side, pursuing the solid state route would likely result in marketable skills.  Its a real catch 22; either way my enclosure (an ex large UPS second battery box) is up to the task.  

The reality is a SS amp would likely top out at 5kw PEP with multiple pallets depending on power supply design (I could acquire some switch modes), where as a single tube amp, despite the weight and pain in transformers, would easily surpass such levels with more than respectable IMD Performance.

The point is simple; producing 2Kw is a commodity item now for Ham Amplifiers.  If I am going to build and maintain something, why not stretch myself to a commercial level?

It is a technical hobby with the specific purpose of self education after all, and if people like myself don't dream big, there will be no one left in VK who has the skills to service or put a SW station on the air in 20 years time.

We've cut national funding to SW like crazy in VK, and the engineers who built and and even maintain the current stations are ageing.

So the point is education; for the sake of the art of radio, and for the sake of my country if needed.

2)  Here are some of my thoughts / ideas / recommendations:

a)  I know that your max power limit is 400w PEP (the 1kw trial having < 300 applicants, and failing to get any gov't traction, it looks like it'll be 400w for you all in VK-land for quite some time to come?)
So, with a 400w limit, it is understandable that you're looking at just a few kw's as a "Dream Amp", but over here, especially here in SE USA / "good ole boy" locales, if the tube doesn't have a 4 digit number, the amp just isn't big enough!  Smiley
In my neck-of-the-woods, a pair of 8877's and/or 3x3's (3cx3000's) are everyday amps, not the what the big boys use on Saturday nights... Smiley

So, if all you're looking for is 5kw??
---- a pair of 8877's (or 3cpx1500's w/ 5kv on the plate) w/ a stiff PS....(I know "everyone" says never use two tubes when one will work, but they are very linear, and an amp using them is easy to build, etc...lots of plans/skematics available...) These have such high gain (15db - 17db) that you  can get to your desired output, driving them directly from a good exciter...
---- a 3cx3000 w/ a stiff supply...also very linear and stable...but with a good bit lower gain (12db to 13db), meaning in order to get to 5kw you'll need an IPA to drive it....


b)  Your solid-sate ideas might be a bit pricey??  And, as you say if you desire good linearity and cooling, it'll be complicated project....but...
But, if you could accept copying an existing design, why not just copy the THP HL-5Kfx??



FYI, everyone here knows I am "tube guy", but my two best friends did the EMC compliance / FCC certification testing for some of the THP hf amps and they commented not just on the superb design, but the true professional/commercial construction!!  (as a opposed to some of the "modern" LDMOS amps being sold now, not to mention the actual crap made by Sunair....who would've thought that THP is still regarded as the "Alpha" of SS amps!!)
So, if I had to go SS, I'd choose THP, hands down!

So, if you're looking for 4kw to 5kw solid state??
The "easiest" way would be to copy the THP HL-5Kfx!  (although, it never got FCC certified, as THP was having financial issues and never spent the $$$$ to have it tested, but I suspect it would meet your criteria..)


c)  But, if you're looking for a "Dream Amp" that would meet that goal / criteria based on my locale in the southeast US, then you'd need to look bigger....a LOT bigger...
Yep, that means tubes with 4-digit numbers....

And, this isn't about ego...
It's just that in order to see any significant advantage on-the-air, you've got to go bigger...
While 5db isn't bad, to make the project worth the effort (and $$$$), in my opinion, think 10db higher than what you can readily buy off-the-shelf....(and that's 15kw to 25kw to 30kw+, output!)

Air-cooled: nothing like a grid-driven 4cx15,000....
Clean 25kw to 30kw out, with 3rd order IMD of - at least 39dbc / -45db(PEP), or better, driven from a clean HF exciter...

Many of my fellow US hams will remember the guys using them on 75m back-in-the-day... Smiley

FYI, in full-disclosure, I was given a clean, shinny, full-output 4cx15,000j regular-maintenance pull, a few decades ago by a friend (who had sold a few of them to some hams in SE USA / in Mississippi-valley area....one guy ran 18-20kw out, and one guy ran 26kw out....on 75m)....
{Now, I doubt I will ever attempt an amp using this tube (heck, just the filaments use 158amps @ 7.5v...that's ~ 1200 watts just to heat the tube!)....but it's a nice conversation piece...it's somewhere in my closet, and is NOT for sale!}

If you desire a water-cooled tube, use the 4cw25,000 (the water-cooled version of the 4cx15,000)....

With adequate power supply and cooling, using just one of these (either 4cx15,000 or 4cw25,000) will provide you with a clean, linear output of 25kwPEP to 30kwPEP, with no time limit....and depending on power supply and cooling you could have 25kw FSK, 100% duty-cycle, output....

Now, that's a nice "Dream Amp"!!

A JST-245 driving a big "15,000" or "20,000", would get you a CLEAN 25kw - 35kw PEP!!


3)  Since Radio Australia has shut down their whole shortwave broadcast system, you might be able to find some serious iron out there!!  (100kw HF transmitters)
Now, I know you want to design and build your own, but if you want to find something off-the-shelf, you just might have a look around VK-land and see what is available....worst case, you're likely to find lots of high-power transmit parts!!  Smiley



I hope my thoughts / ideas are helpful??

73,
John,  KA4WJA
« Last Edit: August 16, 2018, 08:06:14 PM by KA4WJA » Logged
VK4BG
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Posts: 3




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« Reply #19 on: August 16, 2018, 08:02:38 PM »

I still think my YC108 Econco rebuild with zero time on it is exactly what Jarrad needs....C'mon Jarrad...you know you want to do it  Grin

73
Glenn
VK4BG
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VK3BL
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« Reply #20 on: August 17, 2018, 07:42:29 AM »

I still think my YC108 Econco rebuild with zero time on it is exactly what Jarrad needs....C'mon Jarrad...you know you want to do it  Grin

73
Glenn
VK4BG


Dear Glenn,

I haven't discounted the idea; it has been researched and discussed and has some merit Smiley

Send me an offer via my QRZ.com email if you'd like Smiley

73,

Jarrad
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
KM1H
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« Reply #21 on: August 17, 2018, 12:58:54 PM »

For serious QRO tubes with handles are mandatory at a minimum or a quad of 8877's as one well known ham used on 160-20.
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KD8MJR
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« Reply #22 on: August 17, 2018, 02:28:40 PM »


---SNIP----

b)  Your solid-sate ideas might be a bit pricey??  And, as you say if you desire good linearity and cooling, it'll be complicated project....but...
But, if you could accept copying an existing design, why not just copy the THP HL-5Kfx??



FYI, everyone here knows I am "tube guy", but my two best friends did the EMC compliance / FCC certification testing for some of the THP hf amps and they commented not just on the superb design, but the true professional/commercial construction!!  (as a opposed to some of the "modern" LDMOS amps being sold now, not to mention the actual crap made by Sunair....who would've thought that THP is still regarded as the "Alpha" of SS amps!!)
So, if I had to go SS, I'd choose THP, hands down!

So, if you're looking for 4kw to 5kw solid state??
The "easiest" way would be to copy the THP HL-5Kfx!  (although, it never got FCC certified, as THP was having financial issues and never spent the $$$$ to have it tested, but I suspect it would meet your criteria..)


--Snip--

73,
John,  KA4WJA


I have always wondered what happened to that Demo model HL-5Kfx.  I would have spent good money buying it if I could ever find it.  I heard rumors ranging from it was an empty shell to it was a complete fully functional amp.   I guess we may never know who's possession it is in.  I do know that it was supposed to be the Ultimate Ham Radio amplifier ever built, with a price tag to match.

73
Rob
« Last Edit: August 17, 2018, 02:30:42 PM by KD8MJR » Logged

“A lie can travel half way around the world while the truth is putting on its shoes.”  (Mark Twain)
VK3BL
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« Reply #23 on: August 18, 2018, 08:05:19 PM »

I still think my YC108 Econco rebuild with zero time on it is exactly what Jarrad needs....C'mon Jarrad...you know you want to do it  Grin

73
Glenn
VK4BG


I'm actually actively considering your proposal Glenn Smiley. Have been doing the research since it was put forward as the serviceability and control needed for a multi-pallet SS, clean Ham amp would be nothing short of quite the engineering challenge - sensors everywhere!

Let alone the need for BOTH bandpass filtering and suitable tuning network afterwards, and adding 'a band at a time' or a 'pie at a time' to a large tube amp suddenly seems a lot easier.

Food for thought.  Always liked triodes better but then an IPA is required too and if its solid state then all the benefits of that highly linear triode are thrown out the door...
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
G4ZOW
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« Reply #24 on: August 19, 2018, 02:25:16 AM »

Jarrad,

Good luck with the build.

A poster mentioned the HF2K. We have a local here in 5B4 land who runs one and it has been faultless over the past year or so. It sits there at 1500W+ all day long and is not noisy. Reinhards page;

 http://rf-kit.de/en/

Boards come already populated. You just complete the RF wiring and you're on-air in under a day.

An HF 'pallet' that's recently come on the market is this one from Nico at ITALAB in Milan, Italy. First image on the page: https://www.italab.it/prodotti_uk.php?cat=3 This is the only amp in the market which produces proper power on 6m while doing it's job across all the HF bands :-)

John,

I take it that 5kW THP schematic is unobtainium as Google cannot find it.

David  
G4ZOW/5B4

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ZENKI
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« Reply #25 on: August 19, 2018, 02:56:29 AM »

Its nice dreaming, but do you have the antennas to take advantage of such high power. It might seem like a stupid question but 1kw is enough most of the time especially if you have good antennas.

If you dont have at least a 2 element beam on 40 through to 10 meters up at least 70 feet you just wasting your time building  a big amplifier.

My advice would be  to dream about a  100 to 150ft Luso or other tower first with all your antennas 1.5 to 2 wavelengths above the ground.  The first sign of a new  ham is ham who dreams about a 25kw amplifier rather than a 100ft plus tower! Theres lots of big amps for sale from hams who think that they can feed 10kw into G5RV at 30ft and be king of the mountain. I suppose some hams are slow learners!

But getting back to your problems. You can get a single phase Power pole transformer easily in Australia. The Americans call them Pole Pigs. You can get  a dry type  10KVA single phase transformer.  You can order one from China or India fairly cheaply with all the required taps. But if you want to play with big amplifiers get a 3 phase transformer, your technical life will be much easier. Even better is a 12 pulse dual 3 phase transformers, then you can run 25kw out on  your light socket!

A tetrode  like a 4cx10000J is  good way forward. A grounded screen grid driven  will emit a superbly clean signal especially if driven with a class A exciter. Even better is driving the amplifier with a 4cX600J which is driven by something like the Anan radio  with pre-distortion. All the old military 40kw SSB transmitter followed this design. You can  download the TMC manuals for their transmitters. These TMC amplifiers were the cleanest around when military SSB routinely ran 10 to 40kw PEP SSB. They always used Milliwatts from 6550  Tubes driving some others tubes in Class A. Many ways to skin a cat here.

The screen supply will be the big issue. Building a screen supply that sinks and sources 200ma @ 1200 to 1500 volts can be a issue for many. A simple way to go is to build a tube regulator. There was a good design in the GE tube data books in the 60s that was very popular. I have built several of these screen tube supplies over the years. I cant recall every seeing a solid state design. Most of the broadcast transmitters used a  Resonant Choke supply for the screen supply or ran  servo fed  variac to regulate the screen supply. Peter Dahl used to sell matched pairs of  choke and transformer for screen supplies  with the resonating capacitor. I doubt that many transformers places know  how to resonate a  choke these days. Theres a few technical tricks to getting these resonant chokes to work  properly without killing yourself. Other than that these big grid driven tetrodes are as simple as building a pair of 6146B's. Actually its lot easier building a big tube amplifier than building something fiddly like  a pair of 3-500s.

Other excellent tubes are the old TV transmitter tubes from the likes of NEC. I think you should have no trouble finding these TV tubes in Australia. The 7FR71R and 8F71R comes to mind. They have IMD performance thats heads and shoulders above the Eimac tubes. Just watch out for the pink beryllium ceramic and make sure you dont grind and eat the tube!

The YC108 that VK4BG suggests is a good tube if you dont have to have the amp in the shack, otherwise the noisy blower will drive you nuts.A better choice would be the 4cx10000 which you can cool  with a small blower that is quieter than  most ham amps. 0.5inch H2O is enough cooling for ham duty use. The YC108 requires 1 or 2 inches of h2O back pressure for cooling.

These big amps really generate a lot of heat which is not such a bad thing in a cold climate. But trust me you wont be able to stay in your shack for long running a 4cx10000 in your summer. You will have to consider mounting the amp remotely.

And first  thing you should ensure is that you can run a clean signal. Every incompetent ham  that I have known about that tried to run big power with a dirty signal is off the air now. Its never the authorities that put them off the air but other hams talking about their filthy signals.


If all of this is to much to do I am willing to sell my Harris RF-745 if you are willing to pay the shipping. By the time you get it to Australia you could have a nice 150ft tower installed for less money!
.
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ZENKI
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« Reply #26 on: August 19, 2018, 03:00:30 AM »

You can still buy the JRS-900 solid state amplifier/transmitter for JRC. Its the cleanest  10kw solid state amplifier in the world. Many are used as aeronautical HF transmitters around the world. A very fine piece of equipment.

Jarrad,

Good luck with the build.

A poster mentioned the HF2K. We have a local here in 5B4 land who runs one and it has been faultless over the past year or so. It sits there at 1500W+ all day long and is not noisy. Reinhards page;

 http://rf-kit.de/en/

Boards come already populated. You just complete the RF wiring and you're on-air in under a day.

An HF 'pallet' that's recently come on the market is this one from Nico at ITALAB in Milan, Italy. First image on the page: https://www.italab.it/prodotti_uk.php?cat=3 This is the only amp in the market which produces proper power on 6m while doing it's job across all the HF bands :-)

John,

I take it that 5kW THP schematic is unobtainium as Google cannot find it.

David  
G4ZOW/5B4


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VR2AX
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« Reply #27 on: August 19, 2018, 04:43:49 AM »

UK is in that way constrained by location power supply considerations. It is 240v single phase (230 if lucky). Usually max to a domestic property is 80 Amps. And allowance must be made for heating and the most important- cooker.

Three phase although “outside “ usually triggers business tax issues.
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KA4WJA
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« Reply #28 on: August 19, 2018, 04:48:41 PM »

Jarrad, et al,

Can I summarize some of this a bit?

1)  First off, it should go without saying, and I assume that everyone here understands this, antennas first and foremost!  Of course, spend the $$$$ on antennas/towers/etc. first, and only then consider a "Dream Amp".... Smiley

This is why most "big guns" don't have super big "Dream Amps", 'cuz they are NOT needed at all...they've got great antennas!  (I'm not saying that none run over 1500 watts, but most of the big guns are NOT using big/dream amps!)

And, this is also why you'll find most of the guys using these super big amps are on 75m, etc., where getting a "great antenna" isn't easy for everyone, as some have more restrictions than monetary, like size of their land / lot, height restrictions, pleasing the xyl, etc...

FYI, the loudest skywave signals I've ever heard were on 75m:
--- within the past decade here in Florida, one guy ~250 miles away, using a 2-ele 75m yagi at > 75' and a Henry 4k (or 5k?)....and another guy here in Florida, using an Alpha 77Sx and a "lazy-H" / "Jamaica Array"...
--- many years ago (when I was in college in Mass), WB8TNY using his own LK-800TNY (three 3cx800's and a BIG power supply), and some of his friends on 75m...(some using 3cx3000's, etc. and some supposedly using even bigger amps...)
--- and the loudest was a few years later, a W5 from Texas, using a 4cx10,000 or 4cx15,000....don't remember his antenna...

My point here is, while nobody needs a big super dream amp, most that have 'em still on-the-air only use them on the bands where they provide some significant advantage, and where their antennas are as good as they can get 'em...
(of course there were those guys on 3895 decades ago, who would do "gator shoot-outs"??, "Puke" and "TNY", etc...where there was certainly lots of ego invloved...hi, hi...)

Another part of this, is that this is almost exclusively about SSB operations (or maybe even AM DSB? or just maybe FSK/RTTY), 'cuz nobody needs 20kw+ on CW, nor any of the "zero S/N" modes / JT-modes, etc...


2)  Next, in my opinion when it comes to "dream amps", the ole' "go big, or don't go at all", applies here, so I'm still advocating the 4cx15,000 or 4cx10,000...

But as I wrote above, if all you want to 4kw to 5kw, go with a pair of 8877's or a 3cx3000, or if you really want SS, use a slightly older design SS 5KW amp...

{Rob and David, fyi, one of my best friends has the schematic of the THP HL-5Kfx....a few years back, he was talking with THP about its design and possible testing....but since he was contractually obligated to protect their intellectual property, I doubt he'd release the plans/schematics...but, I'm sure you could find/purchase these plans from some of THP former principles, if you so desired?}


3)  As for the heat...most big transmitters (amps) will have the exhaust air exiting outdoors, not into the transmitter room / ham shack....so, while you would have some conductive and radiant heat from a big amp, you're surely not going to have a 50,000 BTU "blast furnace" pumping hot air into your shack... Smiley


4)  As Zenki pointed out, tube regulators can be used to easily make a regulated screen supply, for a big tetrode...gotta' love Zenki, but still wish you weren't anonymous.
(somewhere in my garage I even have some old equip/sig gen that has tube regulators...no kidding...and the darn things still work!)

Also, if you choose a big triode, there's no reason the IPA would contribute to poor IMD....whether SS or tube, you can make IPA clean....(Actually, if you desire SS, you could make it a nice class A amp, or you could use either a nice 4cx600j, as Zenki suggested, or the ubiquitous 4cx1500b)

And, fyi, here in the US we can buy brand new 50kva "pole pig" transformers for about $1200 USD...but they weigh about 500lbs....not sure what's available down-under??


5)  For your own piece of mind, as well as being a good ham, you really want to have a clean SSB signal!!!  So, you can use a low-level exciter output (transverter-output), in the 0dbm to +10dbm level, and build a clean Class A pre-driver and driver / IPA, as needed for the final tube of your choice...

Or, in the interim, if you just want to use a clean transmitter/transceiver, you can look at the solid-state JRC JST-245, or even an older "tube rig"....or possibly the FT-1000MkV in Class A (with no ALC)...

As I wrote above...this is almost exclusively about SSB operations (or maybe even AM DSB? or just maybe FSK/RTTY), 'cuz nobody needs 20kw+ on CW, nor any of the "zero S/N" modes / JT-modes, etc...so, you have no need for a "100db dynamic range receiver", nor the need for a "waterfall display", etc...so, even if you don't have a rig with a low-level output (although just about any rig can be modified to provide this), you can have a clean SSB signal...


6)  Finally, I'd like to correct an error I wrote earlier....not intentional, just a memory issue... Sad   My own "big tube" is a 4cx15,000a, not the 4cx15,000j....

I'm at home for the weekend, and took a look at it....it was in the padded Eimac box on shelf in my garage....and its tarnished, but clean!
Took it inside and snapped a couple pics of it sitting on the dust cover of my Alpha...have a look... Smiley


That's a Bird wattmeter slug sitting next to the 4cx15,000!!




Hope some of my thoughts are helpful?

73,

John,  KA4WJA


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KC4ZGP
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« Reply #29 on: August 19, 2018, 05:04:05 PM »


Ameritron's AL-82 and AL-800H uses tubes in parallel. Motorola's EB-104 uses MRF-150 MOSFETs in parallel.

You just got to devise enough current for more devices in parallel.

Dr. Frankenstein-it.

There you go.

Kraus

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