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Author Topic: "Legal Limit" Amplifiers-NOT!  (Read 14088 times)
W8JX
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Posts: 6449




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« Reply #45 on: January 23, 2013, 11:10:30 AM »

 I think you and I are in complete agreement that an AL-80 WILL put out 1000 watts on some bands, but not unless the published specs on the single 3-500 are greatly exceeded.

Dick  AD4U

Yes we are complete agreement on this. Smiley
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KB5UBI
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Posts: 97




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« Reply #46 on: January 23, 2013, 03:06:27 PM »

The published maximum Ip of 400 ma is not an instantaneous peak limit. Without power line sag, the AL-80B will output 1KW SSB without exceeding anode dissipation and will do so for many years or harming the tube. What harms a 3-500 is an excess of time-averaged anode dissipation and not Low duty cycle excursions over 400ma of plate current.

http://www.w8ji.com/vacuum_tubes_and_vaccum_tube_failures.htm

KB5UBI
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W8JX
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« Reply #47 on: January 23, 2013, 04:28:03 PM »

The published maximum Ip of 400 ma is not an instantaneous peak limit. Without power line sag, the AL-80B will output 1KW SSB without exceeding anode dissipation and will do so for many years or harming the tube. What harms a 3-500 is an excess of time-averaged anode dissipation and not Low duty cycle excursions over 400ma of plate current.

http://www.w8ji.com/vacuum_tubes_and_vaccum_tube_failures.htm

KB5UBI


Strange how the maker of tube states exceeding design rating will shorten tube life. And as for as how "instantaneous" that peak is and at what point it is damaging is highly debatable as with compression and that "peak" can last a lot longer. 
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KD4LYH
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« Reply #48 on: January 24, 2013, 02:40:18 PM »

 Well came across this post and find it interesting. Since I know enough to get in a pissing contest with someone I wont say anything.
Have a nice day.

Jeff KD4LYH
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WD4ELG
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Posts: 877




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« Reply #49 on: January 24, 2013, 04:16:54 PM »

Jeff, don't hold back if it can foster a healthy debate.  Better to throw in your 2 cents on the dicussion, please.
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K4FX
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Posts: 166


WWW

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« Reply #50 on: January 24, 2013, 07:16:03 PM »

Hi Dick,

I have heard that same thing from AL-80 users for years. It makes no sense to over drive a tube, ruin it's IMD and shorten it's life. One can argue that it does not shorten it, but it does, I have seen way too many AL-80 owners looking for tubes. This is far from normal with a 3-500Z. The last time I changed my SB-220's tubes was 6 years ago. The tubes I pulled out were the original Eimac's shipped with the kit from Heathkit. About 34 years of regular use and they still make full power (ie normal output 1KW to 1.2KW) . I would love to see that done with 1KW out and one 3-500Z.

I owned an AL-80A for a number of years while living in El Salvador. While it was a nice little amp, the manual on mine recommended 550 ma of plate current, which is way over the Eimac's recommended 400ma any way you cut it.  With 3300 volts on the plate and running the tube within specs on the plate current, 1KW ain't gonna happen. And the funny part of all of this is there is no ear on this planet which can tell the difference between 1KW and 800w, unless it's the guy just down the band from you noticing the increased splatter.

Bill K4FX

PS Unless you are running a quality watt meter, like a Powermaster, Telepost or a Bird, who knows how much you are running anyway? Contrary to popular belief, a reasonably accurate watt meter will cost you considerably more than 100 bucks.
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W6UV
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Posts: 540




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« Reply #51 on: January 24, 2013, 09:36:47 PM »

And the funny part of all of this is there is no ear on this planet which can tell the difference between 1KW and 800w,

I keep hearing things like this, but have a hard time believing it. If no one can hear the difference between 800W and 1KW, then one could surmise that no one could hear the difference between 800W and 700W. And since if no one can hear the difference between 700W and 800W and between 1KW and 800W, then no one should be able to hear the difference between 1KW and 700W. You could extend this argument all the way down to no one being able to hear the difference between 100W and 1KW, and this whole thing starts to sound like homeopathy.
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N4RSS
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« Reply #52 on: January 25, 2013, 07:15:54 AM »

[You could extend this argument all the way down to no one being able to hear the difference between 100W and 1KW, and this whole thing starts to sound like homeopathy.

Pointing out the absurdity of this doesn't discredit the original argument because you're not making a logical extension of his argument. 
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W6UV
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Posts: 540




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« Reply #53 on: January 25, 2013, 10:18:19 AM »

Pointing out the absurdity of this doesn't discredit the original argument because you're not making a logical extension of his argument.

My argument was intentionally absurd to draw attention to the original statement.

With high signal levels, sure, no one is likely to hear the difference between 1KW and 800W. But once you start to get right down near the noise level, then even a 1 dB increase in signal level might be enough to boost the signal above the noise and turn a non-contact into a contact.
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W7APM
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Posts: 25




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« Reply #54 on: January 26, 2013, 09:22:24 AM »

My intent when I started this thread was not to debate what the reasonable operating parameters of a 3-500 might be but to warn and inform newbies that to beware of sellers claims of legal limit amps.
I don't mind where the thread went but the original intent was lost... 
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W8JX
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Posts: 6449




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« Reply #55 on: January 26, 2013, 09:56:23 AM »

My intent when I started this thread was not to debate what the reasonable operating parameters of a 3-500 might be but to warn and inform newbies that to beware of sellers claims of legal limit amps.
I don't mind where the thread went but the original intent was lost... 

Well L4b's, SB220, and Kenwood 922 were legal limit amps when they were built but limit was lower then. Most modern built legal limit amps will easily meet or exceed legal limits.
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