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Author Topic: Indirectly Heated Valve (Tube) Longevity Question.  (Read 16547 times)
K4RVN
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Posts: 260




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« Reply #15 on: December 14, 2017, 02:55:23 PM »

It appears to me that the indirectly heated  valve or tube was not considered in some of the replies.  Mixing apples and oranges, to coin a phrase, will not answer the posted question. Tubes  indirectly heated normally have a longer warm up in order to get the tube heated for HV. application. Also they cost a lot more. If I'm wrong please correct me. Tubes such as the 3-500, 811A, 572B should not be used to compare is my understanding. Just trying  to get the facts not to be contrary. I have an AL 800H with 3CX800 A7 ceramic tubes that requires a 3 minute warm up and before it can be operated. I do not leave it on except for a few minutes cool down time at the end of use. Wear on the blower and reduced life due to hours of operation is enough to turn the amp off.
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MM0IMC
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« Reply #16 on: December 14, 2017, 03:06:32 PM »

I can't speak about the life expectancy of the American 811A valves, as I've no experience of them. The Chinese ones do seem to be a mixed bag, to be honest.  As for the Russian valves, again, I've no experience with their version of the 811A's.  I do like the Russian ceramic valves though.  I get the feeling that there's somewhat of a bias against their valves (excuse the pun), perhaps based on old cold war ideology. Undecided  I don't think this sentiment exists so much in Europe, though...
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KM1H
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« Reply #17 on: December 14, 2017, 03:40:27 PM »

 
Quote
I do like the Russian ceramic valves though.  I get the feeling that there's somewhat of a bias against their valves (excuse the pun), perhaps based on old cold war ideology. Undecided  I don't think this sentiment exists so much in Europe, though...

Europeans appear to be cheaper in general than the US and take less interest in the quality of their signal. IMD was never an important consideration to the Russian military and most of their tubes are very poor in that regard.
It has nothing to do with any US-Russia snits.

Carl
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K8BYP
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« Reply #18 on: December 14, 2017, 03:59:10 PM »

YES its bad. ITs not about being "on" its about the 2X filament current at startup.

I just talked to a Broadcast Engineer who mentioned having to start up high power tubes S-L-O-W-L-Y to keep heater current down during cold startup.

Its a large mechanical shock to pass 2X rated current through the filament.

The filament (s) current, for example, in a Drake TR-3 is 11A cold and 5.5A hot.
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KM1H
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« Reply #19 on: December 14, 2017, 04:56:22 PM »

Quote
The filament (s) current, for example, in a Drake TR-3 is 11A cold and 5.5A hot.

So what? All those tubes have a controlled warm up filament in case you didnt notice and the radio is not Instant On.

This goes back to the 50's when series strings were showing up in multi tube radios and soon TV sets.

Most small signal tubes with an A suffix were the controlled versions and sweep tubes started close to the beginning such as the 12JB6 or the 6GJ5 for National before switching to the 6JB6A where the A meant something else.
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MM0IMC
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« Reply #20 on: December 15, 2017, 01:33:31 AM »

Quote
I do like the Russian ceramic valves though.  I get the feeling that there's somewhat of a bias against their valves (excuse the pun), perhaps based on old cold war ideology. Undecided  I don't think this sentiment exists so much in Europe, though...

Europeans appear to be cheaper in general than the US and take less interest in the quality of their signal. IMD was never an important consideration to the Russian military and most of their tubes are very poor in that regard.
It has nothing to do with any US-Russia snits.

Carl

I looked at both the manufacturer's claimed IMD figures and those tested in a RadCom review, both are comparable to other amplifiers that I see on the market at the moment...

http://www.alpinamplifier.com/products/alpin-100
http://www.alpinamplifier.com/products/images/RadCom%20Review.pdf
http://www.alpinamplifier.com/products/images/FunkAmateurReview.pdf Unfortunately, my German is very rusty...

I looked at other manufacturer's claimed figures, like Ameritron using Eimac valves, OM Power and Acom using Russian tubes. They all  quote nearly the same IMD figures, give or take a few dB.

I'm not an expert, just a layman trying to make some headway with this stuff. So, if I'm wrong or am looking at the figures wrong, please point me in the right direction.
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MM0IMC
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« Reply #21 on: December 15, 2017, 07:50:28 AM »

I wrote to Veselin LZ1HD, who makes the Alpin range of amplifiers regarding the maximum power ratings of the GU-74B tetrodes and the IMD figures for the amplifier. Here was his response in an email.  I'm sure that he won't mind me posting it here for clarification purposes...

Quote
Hello Ian,

In various Russian sources for power dissipation (not output power) two figures are given - 600 and 800W. Although this is not specified, it is likely that long-term military service is considered. However, when defining the power of ham-radio amplifier we are using ICAS (Intermittent Commercial and Amateur Service).  When Alpin 100 producing 1 KW Output , the power dissipation is about 530 W !!! Of course, to achieve maximum power, adequate cooling is needed as well as adequate sources for the Plate and grids.

When I presented this amplifier in Friedrichshafen exhibition, several russians came to the booth and said they did not believe that this tube GU-74B can produce 1KW output. Then I showed them that I use for the demonstration HP wattmeter and Bird Dummy Load, after which I activated the amplifier and it produced more than 1 KW out. The visitors in question said they believed in the measuring equipment but still did not believe that GU-74B can produce 1 KW out !!!
It should be noted that almost all Russian tubes have large differences in parameters. Some brand new pieces GU-74B can produce only 500-600W and other twice more. I use very well selected tubes.

Merry Christmas for you and your family

Veselin lz1hd

Although he didn't specifically address the IMD figures issue, however I would refer you back to my previous post with regards to the reviews of RadCom, etc. where the IMD figures are addressed in their tests...
« Last Edit: December 15, 2017, 07:54:02 AM by MM0IMC » Logged
KX2T
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Posts: 992




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« Reply #22 on: December 15, 2017, 09:30:25 AM »

Well the expert has said it all, his hearsay has totally sunk any Russian tubes from being used, this is just like the BS we get on TV about politics but twice as bad. We should all sell our amps which use Russian tubes or throw them in the trash right now cause KM1H said soo, please give me a frigging break, BTW there at this time are almost as many Acom amp's in many ham shacks world wide Karl as Alpha's amp's. You seem to have a bone to pic cause of the cold war stigma from the 50-60ies but many here look at what you are saying as hearsay cause you dont like any of these Bulgarian built amp's. Acom started after Alpha pulled the contract on the 91B amp but still they produced the 99 for many years but to be honest the 99 was way overpriced and did not sell as well as the Bulgarian 91B did.
In over 40 years I have owned many different amps like SB200,SB220,MLA2500, HB8877,AMP supply LK500Z,Ameritron AL80B, ALS1300,AL1200,AL1500,QRO1000 then Alpha's 78,77DX,91B and this little Acom1000, the least trouble free with zero failures were the QRO1000, the AL1500, Alphas 78&77DX, the Bulgarian Alpha 91B and the Acom 1000.  I had the use of Alpha 87A's and Acom 2000A's when we used to have a contest station back in 1990ies also which btw the Acom 2000 with those Russian tubes cleaned the Alphas 87A clock. As far as raw output the HB8877 was king of the hill, the 77DX was next and the 91B was right behind it then the AL1500 but to be honest I never trusted the Ameritron amps in contest station as much as I trusted the 91b. I think what you have been hearing about the Russian tubes is they had a heavy duty transformer that Acom and Alpha sold to be used with there amp's that some how got into some production samples which was designed for CCS RTTY use but also placed much higher plate voltage on those tubes which is like if you give a kid a hi power new toy he is going to use it, end results those tubes were putting out just over 3Kw and 2.6K was there limit but you should know how hams work by now. You run any amp hard you will find its breaking point but at 1500W out now way and for a single GU74B running 900-1000 out is far better than running an AL80B at 1KW out.
As far as the bull crap as far as your hearsay Karl, the newer GU74B's with the 2017 date code are newer tubes, there base before the cooling anode is higher like what Eimac did in the 3CPX800A7's and they are silver plated like the Eimac's so you BS about changing date codes is far from the truth, there is new stock GU74B tubes to be had and Svetlana tubes are still in production but at a higher cost but in no way are the prices as hi as Eimacs rip off's.
As far as the Chinese knock off tubes they have not learned how to build there tubes with best quality grid structures and this has been documented on the internet, just google it OM.
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KM1H
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Posts: 4722




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« Reply #23 on: December 15, 2017, 02:45:57 PM »

Quote
I just talked to a Broadcast Engineer who mentioned having to start up high power tubes S-L-O-W-L-Y to keep heater current down during cold startup.

Yes, some tubes with handles or needing a hoist to lift fall into that category BUT "typical" ham tubes up to the 3CX10000A7 are instant on. At the 3CX15000/20000A7 level the warmup is 5 seconds Grin Shocked Roll Eyes
Tetrodes are similar being instant on to the 4CX15000 and the 4CX20000 requirement has a requirement to limit instant on current to 2X rated and this can be done with intelligent transformer design.
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KM1H
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« Reply #24 on: December 15, 2017, 03:10:39 PM »

Quote
Well the expert has said it all, his hearsay has totally sunk any Russian tubes from being used, this is just like the BS we get on TV about politics but twice as bad.

Your reading comprehension is at the grammar school level, I suggest you get professional remedial training.

Quote
As far as the bull crap as far as your hearsay Karl, the newer GU74B's with the 2017 date code are newer tubes, there base before the cooling anode is higher like what Eimac did in the 3CPX800A7's and they are silver plated like the Eimac's so you BS about changing date codes is far from the truth, there is new stock GU74B tubes to be had and Svetlana tubes are still in production but at a higher cost but in no way are the prices as hi as Eimacs rip off's.

Provide a factory link to all that and I may believe you about new production. My #2 sons GF is from St Petersburg and they will be there in early January and have volunteered to contact the factory. He speaks Russian like a native and has a MSEE degree.
As far as the 4CX800A, the tube was washed of the GU-74B labeling and fraudulently relabeled; Ive seen several but cant claim all were that way once Baxter got caught.

The Svetlana engineers report is not hersay as you would love to believe and I never claimed a pair of GU-74B's were bad at 1500W. You really need that remedial course. And you should stick to subjects you actually know.
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KM1H
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« Reply #25 on: December 15, 2017, 03:30:57 PM »




Quote
Although he didn't specifically address the IMD figures issue, however I would refer you back to my previous post with regards to the reviews of RadCom, etc. where the IMD figures are addressed in their tests...

I wonder why? IMD is a touchy subject and is easily nanipulated

Quote
I looked at other manufacturer's claimed figures, like Ameritron using Eimac valves, OM Power and Acom using Russian tubes. They all  quote nearly the same IMD figures, give or take a few dB.

Eimac uses the long accepted IMD measurement method of reference to a single tone and is what the military and other professional users measure against.

The Hammy Hambone ARRL uses the PEP method which is an automatic 6dB improvement and they also cherry pick the two tones which can further improve the IMD3 reading; Radcom apparently does the same as do others trying to inflate the results.
The subject has been discussed in detail on here or/and QRZ.

Carl
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KX2T
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« Reply #26 on: December 15, 2017, 05:33:45 PM »

Karl you are the self proclaimed expert so why should any other ham try and give there opinion on these forum's, everyone else is wrong and you are right plus you want to pick on the ARRL lab and Radcom as well. What is funny is I have never seen any of your reviews in any ham magazine, zero, nada, not even CQ magazine.
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KM1H
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« Reply #27 on: December 15, 2017, 05:55:51 PM »

Quote
Karl you are the self proclaimed expert so why should any other ham try and give there opinion on these forum's, everyone else is wrong and you are right plus you want to pick on the ARRL lab and Radcom as well. What is funny is I have never seen any of your reviews in any ham magazine, zero, nada, not even CQ magazine.

It appears that your reading ability is on a par with comprehension Jimmy. Plus you have such a low technical ability you dont even understand the basics about IMD and how they are manipulated to keep advertisers happy.
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VK3BL
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« Reply #28 on: December 15, 2017, 08:02:16 PM »

Personality aside, Carl's history lesson is correct.

The 3CX800A7 is a better tube than the GU-74B "4CX800" in every single way.  Yes, it costs more, but its still made, and is one of the most linear "small" power tubes ever produced.

The bias requirements alone should be enough to scare people away from the GU-74B; ~500 Watts of heat just to keep it linear, in a tube officially rated at 600 Watts Plate Dissipation.  Those numbers simply don't add up.

Combine that with uncertain future production runs (more unlikely than likely), and its easy to understand why those who have read up on the matter are less enthusiastic about that particular tube.

If you must have a tube amp in this day and age, and the price of the 3CX800A7 or 3CX1500A7/8877 scares you off, your best bet is the FU-728F, although it tends to be pushed pretty hard in Ham amps too, but thats the nature of the game I suppose.  At least most amp vendors allow you to swap in a 4CX1500B (with reduced power output) and you can expect in return a very linear tetrode based amp.



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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
KOP
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« Reply #29 on: December 16, 2017, 12:34:52 AM »


The subject has been discussed in detail on here or/and QRZ.

Carl

Isn't that the truth

http://www.eham.net/ehamforum/smf/index.php/topic,104518.msg861094.html#msg861094

Thought I'd save someone the trouble .

P.S. How ya doin Carl ?
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I considered a microwave oven magnetron and a 4' dish as a drone-killer. The ERP would be on the order of a hundred thousand watts or so. ~anon

November 28, 2018, 09:16:04 AM
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