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Author Topic: Why doesn't the ART-13 put out 250 watts or more?  (Read 25035 times)
K1YTG
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Posts: 486




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« on: March 20, 2008, 04:15:36 PM »

I was looking at a car in a garage and there was an ART-13 on a shelf.  I offered $75 for it and took it home.  But not the car.
I built a power supply for it and that took a lot of time.  I checked  out the transmitter and made a repair to the CW relay, open coil there.
I now have it on the air.  
I can get about 150 watts output running 1450 volts on the plate, and that is higher than the 1150 it is built for.
It seems that most transmitters that have 811's modulating an 813 run 375 watts in and I guess 275 watts out or more.
Why is the ART-13 designed to run at such a light load on the tubes?  Can it be souped up to give higher power?
Norm
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WB2WIK
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Posts: 21836




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« Reply #1 on: March 21, 2008, 01:25:10 PM »

I remember some OTs (in my youth) who were using these in the sixties and I think the typical output power was 100-150W.  The original dynamotor power supply provided about 1250Vdc and all the circuits were really only designed to support the relatively low output power generated by that conservative supply.

Old Collins ad for the ART-13:

http://www.effectnet.com/mjnpa/photos/ART-13.jpg

WB2WIK/6
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W8ZNX
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« Reply #2 on: March 22, 2008, 01:18:40 AM »

have an ART-13
never got more than 150 watts out of it

for a WWII mil aircraft transmitter
it puts out lots of power

its hell of a lot better than the BC-375

know somebody that has a WWII
Navy surplus transmitter
that weighs over 500 lbs and only
puts out 75 watts

dit dit
mac
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W5HTW
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Posts: 729


WWW

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« Reply #3 on: March 26, 2008, 06:42:38 PM »

I had two of them (one of them I never got on the air.)  Both were brand new, unused, surplus.  As I recall at the time, they were considered "100 watt class" transmitters, which was rated by output.  The 813 final was run at about 160 watts or so DC input, plate modulated, for roughly 100 watts to maybe 110 out.  But the one I had, and one a friend had, were run at 100 watts output on AM.

One of mine was complete with dynamotor, the other had a homemade power supply for it.  The later is the one I used.  

I also had a BC375, but had it on the air only a couple of times.  It was not a fun rig to use at all!  I think I finally junked it.  

Ed
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W4MEC
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Posts: 8




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« Reply #4 on: June 25, 2008, 12:20:57 PM »

My take on this would be that the plate dissapation of a single 813 is 125 watts.  Being that it is military, goes in an airplane to be bounced around, and sent up to 30K feet or more, the idea was reliablility, not to get every possible watt out of it before the anode sucks itself into the cathode.  Also, actual peak power vs rated carrier power on plate modulated AM approaches 3:1, so you have to build in ability to hit those peaks without smoking the thing in the process.

Charlie
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IW5CI
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« Reply #5 on: December 02, 2010, 08:48:21 AM »

My art-13 delivers 80W of power with 900V HV at 1250 the typical power is about 125-130W
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N2EY
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« Reply #6 on: December 02, 2010, 04:07:45 PM »

W4MEC has it exactly right.

The AN/ART-13 is a WW2-era transmitter meant for use in military aircraft, in a very hostile environment. A plane could take off in sea-level tropical heat and humidity, then climb to 35,000 feet or more with Arctic temperatures. Shock and vibration could be extreme. There could be wide fluctuations in supply voltage, antenna load, etc. There could be all sorts of abuses (such as transmitting into an open or short circuit). Yet the set had to keep on working as intended - without operator attention and without damage.

So everything was run well below typical "amateur" conditions.

The AN/ART-13 isn't the only set built that way. Most others are similarly constructed. For example, the popular "Command sets" run a pair of 1625s in the final, which most hams would consider to be good for 150 watts CW and 120 watts plate-modulated AM 'phone (input, not output). Yet the Command sets run them at about half that level.

73 de Jim, N2EY
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AA4HA
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« Reply #7 on: December 03, 2010, 03:09:16 PM »

Another factor that influences the design of equipment operating at high altitudes is that the distance that a high voltage arc decreases with a decrease in atmospheric density.

High voltage circuits that may work fine at sea level will arc when at altitude. This is called "flashover".

Think of the test engineers who came up with some great idea that worked fine on the test bench or even in an aircraft sitting on the apron. As soon as it gets to altitude then "bad" things happen.

Also, unless you do some sort of forced air cooling system things heat up quickly. Remember that a thermos is actually a dewar flask with a vacuum between the layers of glass. It makes a fantastic insulator. Now think of a tube in a high altitude-low pressure environment, it can just about melt down as heat exchange is no longer conductive through the very thin atmosphere.

It is also one of the reasons that satellites are tested in a vacuum chamber before they send them aloft. Many birds just fail due to overheating. If someone from here is involved with AMSAT they can probably speak to that.

In regards to the ART-13 or the ARC-5's it means you need to be careful about getting the B+ too high and you need to deal with heat buildup.

Tisha Hayes, AA4HA
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
N2EY
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Posts: 5082




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« Reply #8 on: December 03, 2010, 06:54:32 PM »

Good points from AA4HA. However, in WW2 aircraft sets the cooling issue wasn't usually too bad because at high altitudes the thin air is very cold. But the arcing issue could be a big one, particularly when an aircraft took off in tropical humidity and climbed to altitude.

Some later aircraft electronics were actually built into sealed containers to solve some of those problems.

73 de Jim, N2EY



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KA5N
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Posts: 4380




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« Reply #9 on: December 04, 2010, 04:07:16 AM »

Another factor that influences the design of equipment operating at high altitudes is that the distance that a high voltage arc decreases with a decrease in atmospheric density.

High voltage circuits that may work fine at sea level will arc when at altitude. This is called "flashover".

Think of the test engineers who came up with some great idea that worked fine on the test bench or even in an aircraft sitting on the apron. As soon as it gets to altitude then "bad" things happen.

Tisha Hayes, AA4HA
Let's see if I have this right:  high voltage arcs a shorter distance with reduced air pressure, so if you go up in altitude where the air pressure is less things tend to arc more (therefore over longer distances)?  I suppose this is why they make vacuum variable capacitors and relays.  So one would expect that in a humid jungle climate high voltage wouldn't arc or would arc more?  I think someone has their wires crossed.  The explaination of the design of the ART-13 is "that's the way they wanted it!"

Allen
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N2EY
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« Reply #10 on: December 04, 2010, 04:30:27 AM »

Let's see if I have this right:  high voltage arcs a shorter distance with reduced air pressure, so if you go up in altitude where the air pressure is less things tend to arc more (therefore over longer distances)?  

That's right. It's easier to ionize the low-density air - up to a point. (The problem is discharges through ionized air).

I suppose this is why they make vacuum variable capacitors and relays.

When the density gets below a certain level, the process reverses and it gets harder to ionize. When you get to a vacuum, there's nothing left to ionize.
 
So one would expect that in a humid jungle climate high voltage wouldn't arc or would arc more?

Humidity is a whole 'nother factor. Plus condensation.

The explaination of the design of the ART-13 is "that's the way they wanted it!"


But the point is *why* they wanted it that way. And there were good engineering reasons for what they did. It's not just a preference thing.

It seems like a lot of big parts for 100 watts to us hams because we don't design our rigs for the same environment.

There's also the factor of "what are you comparing it to?" The ART-13 was designed to replace and outperform the BC-375. It's smaller, lighter and has the autotune feature, plus no tuning units.

73 de Jim, N2EY
« Last Edit: December 04, 2010, 04:32:32 AM by James Miccolis » Logged
KA5N
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Posts: 4380




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« Reply #11 on: December 04, 2010, 05:45:28 AM »

  Notice that the first quoted sentence doesn't make sense if the following sentences are true.
Maybe :Another factor that influences the design of equipment operating at high altitudes is that the distance that a high voltage "will arc increases" with a decrease in atmospheric density.  Or maybe the breakdown voltage of air decreases with lower density.
Would make more sense.  Of course the altitude limits of WWII aircraft was such that nothing approaching a vacuum would be reached.
One could write a book about the engineering and manufacturing of WWII equipment and the horrible waste involved.  Mostly the stuff was designed to be almost indestructable and passably useful.  
If one wants to refurb and use old military equipment, great!  I had my go at it back in the 1950's
and now just enjoy looking online at what others have done.

Have a great day
Allen
« Last Edit: December 04, 2010, 07:37:10 AM by Allen C. Ward » Logged
VK2MS
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Posts: 7




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« Reply #12 on: December 26, 2016, 06:13:44 PM »

Many years later....
Perhaps if you understood that increase in input power is not linear to nett-effect you'd be less worried about why in WW11 the ART 13 was not 'hot-rod'd'. People talking of spark over might also ponder airplane antennas. More power=more nuisance and the spoiling of nets for true Hams on low power.

The obsession with input/output RF power in USA and now Australia is a continuing of the drift of 'Hams" away from tradition, to it's ultimate ruination through the foundation course....a glorified, CB radio, pretence at becoming  a Ham.

The difference between the Novice course which many thought was the beginning of the end...and in a way it was....is almost immeasurable as so vast. The lazy minded excuse muttering Z calls and others eventually saw the pride in engineering knowledge and serious testing of it almost vanish as the Ham Licence became a sort of right under the constitution.... with the rites of passage removed. Even immediately after the war mods to services equipment, very often absurdities, showed people thinking they knew more than the brilliant designers...."Ham" nonsense like fitting an S meter to a BC 348....changing bias' and so on and on...Sure if you wanted that tuning cap position operated RF gain control to be totally independent, fine it's your radio, but the designer built-in a solution to the need for gain change as frequency changed. Probably every set suffered some kind of "whatever you can do I can do better" attack some worthwhile in Ham use but not many and some made the sets worse.

KA5N wrote "One could write a book about the engineering and manufacturing of WWII equipment and the horrible waste involved.  Mostly the stuff was designed to be almost indestructable and passably useful". There's the result of Kenwood and Icom...the store bought Ham.

In fact, apart from the 11,19 22 and 62 sets  Australian and English sets were built with the lack of pride and the lack of belief. Both countries were on the brink of bankruptcy, alleviated by equipment provided under Lend-Lease...which some nations are still paying at a comparatively high rate of interest, with Germany's innocent citizens still being sucked-dry by USA and Israel...the later suffering no losses from the Transfer forward. The 3B series was an abomination in looks until the late 3BZ but was a most useful set which AWA leased to customers...not sell. On the other side, USA produced superb workmanship in radio receivers transmitters and transceivers as well as the IFF's and transponders and the like. The BC348 more than the 342N and the post war URR 391 are only two examples. America took great pride as a nation of trades, education and manufacturing. In electronic equipment it had to support (after entering the war militarily) many electronics manufacturers, although I don't think Helena Rubinstein cosmetics was actually geared up to build URR 391's but may have had a deal going to sell their contract.  For a war of uncertain end date...although Cowboy Paton wanting to be head honcho in Europe and Ruthless Montgomery arguing the toss, the war went on for 12 further, unnecessary months killing a million or four more people of axis and allies including horrific numbers of children and women no more 'guilty' than allied equivalents. That an AT-13 was on the Enola Gay would never be a source of pride for me with mine...to the contrary.

Certainly the concept of longevity v cost had to be considered......apart from the human cost, how much cost in materiel can be afforded as loss?. Bean counters had to be involved and thus the BC348 Q P and N models were revision...less cost to build and repair...though who knows not I what the changeover costs from the g.c. series was....it must have been astronomical. Sensible people who have used WW11 gear...(including Command sets) know, generally the excellence of the sets. Most conversions were done with Hams in mind...not SWL or transmission all across the across the frequency range and 18mHz was more a limit to tubes and perhaps even "Q" than inferior design. These sets were not 'passably useful' but just brilliant and considering the commitment to indent there would have been opposition to changing as opposed to mod'ing. Brilliance was exhibited in the acorn tubes, the EF 50, the 713A. My mod'd 830 S and 'full house' with their narrow cw filters perform better than my BC 348 and commande sets but I get more fun from the wartime equipment that I ever has from the commercial sets. I'm not an armchair ham, surrounded by store boughts going out to a commercial antenna system of perhaps $20,000-$100,00 plus, prattling on about gear to which my contribution has been a bank account and connecting-up the gear. Certainly some American and a couple of Australian Ham specialists have been a godsend when after a few years the gear is superseded and some of its poor build qualities arise. For myself someone who has built his own supplies for say an ART 13/BC 348 combo is way ahead of anyone just using a commercial set up...or worse....digital gear.

In closing on KA5N's comment, the gear was built to give service under severe conditions. In service the equipment had to be built for mechanical and electrical reliability and to not be at such peak performance at one frequency that it collapsed at others....in the main use of frequency they were not 'passably good' nor was it indestructible...it was high-performance for its likely destructible life...often a very short one. The waste was in part owing to not knowing quite when the war would end (the Central bankers, financiers and government criminals kept that secret) and the need to tie manufacturers up on set pricing and long contract periods so the specialist workers (mostly women) could assimilate the grand techniques they developed. Yes it's true ex-war prices were very low but look at it also this way....after suffering years of war or being involved in it a benefit was given to people in buying the materiel at prices from which they could begin again in life and business, and be occupied with their interest, whether 6wd trucks, huge winches or a BC 1206. I think K5AN in that 'tired of living' comment has combined generalisations into absolutes. If you want to think about waste in WW11, read Christopher Creighton's 'opJB' and learn about Peal Harbour, the allied atrocities on its allies to ensure Pearl Harbour went through and the sacrifice at Dieppe....I'd  be more worried about that that 5000 'new in crate' BC 348's coming onto the market at $50 when they cost $500....the only things keeping Ham radio 'alive' today are using sets 50-70 years old, Commemoration AM, MCW,   CW and those wonderful men and women who, always mindful of their task, find, buy and  save old ham stations and restore them to tings of great beauty. To them "I dips me lid".
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VK2MS
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« Reply #13 on: December 26, 2016, 06:24:00 PM »

Hi again I wrote " My mod'd 830 S and 'full house' with their narrow c.w. filters perform better than my BC 348 and commande sets but I get more fun from the wartime equipment that I ever has from the commercial sets...

it should have been " My mod'd 830 S and TS130V  'full house' with their narrow c.w. filters perform better than my BC 348 and command sets but I get more fun from the wartime equipment that I ever has from the commercial sets.

I add that on 7W sideband in the first instance on an immovable beam pointing long-path  from Molendinar Australia I have at a 7:30 pm received a 4/7 on 7W INPUT to Wales after a 4/8 from NZ...and at mid-day 5/9 from Canberra on 7W INPUT using an offset dipole I think S/N facing which drove the other end operator to the verge of insanity as he was no more RTT than I on his 400W and 12dB antenna. The only way of saving Ham Radio is by going back to tube/discrete component sets from about 1956 to 1920.
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VE3LYX
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« Reply #14 on: December 27, 2016, 03:47:43 AM »

not the only WW2 rig so. A No 19 WS as produced on a very good day might make 8 watts out AM. It has an 807 final. Not a lot for a 807. They used an aggressive ADC circuit (6h6) to choke it back and a quick work around will more then double its output on AM without surgery. The ARC5 can stand a lot more HV then normal (I run 770v on mine) A TCS transmitter shuts one PA tube off on AM cutting its AM output back to similar to the No 19s. Works fine though when driving a small linear however one wonders also why cut off the filment of one of the 1625s on AM? And what if you let both run? A pair of 1625s plate/screen  modulated by a pair of 1625s should be able to produce significantly more then under 10 watts. 400v plate I one reason but shutting the tube down on AM I suspect was to limit range when using AM as was the Auto drive level control in the No 19 WS.(Fiend Hort(enemy has ears) as the German radios often say) Of course an 813 is barely awake at 1200 volts too as you already know. I run my No 19 with the wrk around I developed and it became  very practical radio for daily use after I did that. I run my TCS through my twin 811A linear but I know someday I am going to over ride the disable on the outboard PA tube and test to see what happens. You can probably push you 813 final tube a lot harder too without affecting any other part of the circuit as long as you don't apply the same to the mod tubes however do you want to? That is the big Q
donVe3LYX
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