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1 3cx1500a7 or 2 3cx800a7's????

D

dxhound

Active Member
Nov 17, 2006
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Basically Im looking at getting either the Ameritron AL-1500 or the Ten Tec Titan 425.

The Ameritron uses the 1500A7 and the Titan uses 2 800a7's

Which would be more suited for sustained rag chewing on AM? Im thinking the Ameritron is more suited for 1500-2kw AM use but just figured I would ask.
 
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I know people who use both for AM. No complaints. I've seen the Ameritron do legal limit AM without melting. Just don't get greedy:D You do mean peak power in your question right?
 
I just want something that will idle along with a 375 watt carrier and 1500 peak AM. I dont want to tax the system for everything it has because I want it to last a long time. Im thinking the Ameritron will be the better solution for this given their claim of a 30 second 2500 watt carrier!!!!

But I love TEN TEC's build quality and products.

Basically I want the amp that will produce the most power! The reason for this is because I know that amp will last longer when ran at legal limit, and possibly a bit more when I get frisky:)
 
The '1500' part of the tube designator is the max plate dissipation of that tube, that's all it's rated for. That means that when it is producing 1500 watts at 100% duty cycle, that's all it's going to do without loosing some serious life span. That's just for the tube, not the rest of the amplifier. The 'rest' of that amplifier is going to get very, very tired, very quickly when the tube is pushed to max output for any length of time.
That 3CX1500 is certainly capable of more than 1500 watts output on a less than 100% duty cycle mode, such as SSB. But not a 100% duty like AM/FM/CW/whatever.
One other little qwerk about those 3CX1500s is that they require very little drive. You 'tickle' them, you don't 'drive' them. But it's your wallet, treat it like you want!
- 'Doc
 
W5LZ said:
The '1500' part of the tube designator is the max plate dissipation of that tube, that's all it's rated for. That means that when it is producing 1500 watts at 100% duty cycle, that's all it's going to do without loosing some serious life span. That's just for the tube, not the rest of the amplifier. The 'rest' of that amplifier is going to get very, very tired, very quickly when the tube is pushed to max output for any length of time.
That 3CX1500 is certainly capable of more than 1500 watts output on a less than 100% duty cycle mode, such as SSB. But not a 100% duty like AM/FM/CW/whatever.
One other little qwerk about those 3CX1500s is that they require very little drive. You 'tickle' them, you don't 'drive' them. But it's your wallet, treat it like you want!
- 'Doc
Click to expand...

Sort of.

1500 watts is the amount of heat the tube can safely dissipate. Heat is produced from efficiency less than 100%

a 2500 watt input ssb amp will output 1500 watts. Dissipation is slightly less than the difference of these 2 figures or about 1000 watts.

Ignoring carrier and looking at P.E.P. the numbers are exactly the same for AM.
 
Basing things on efficiency means that at best you are looking at maybe 60%. Which means that 1500 watts dissipation really is 'pushing' the tube to about what it's going to be capable of and still have a reasonable life span. At that, you are going to be producing LOTS of heat. (Sounds silly, but keeping coffee hot setting over the vents of an AL-1500 is not a joke. And, no, don't do that, it's not a smart idea.)

Mixing input/output power figures is also one of those silly things unless you know how those figures relate to each other. A very rough rule of thumb is that about half of the input power is probably the output power of an amplifier of typical efficiency, maybe.

Ignoring carrier, and even using Pep figures (if a constant tone input is used for testing), the output power levels will be exactly the same for AM mode as if the power were measured in RMS/average units. That's perfectly normal since the peak envelope power is -constant-. The 'trick' is getting a -constant- output, and you can't do that by humanly produced sounds, whistling, etc. So, you end up seeing bigger numbers by using Pep. It also means that the resulting power figures are not very legitimate for any particular use except having 'bigger numbers'. They just don't tell you squat about what's happening. But if that's what you are looking for, then knock yourself out! Unfortunately, that's also what you are doing to that tube, knocking it out. It get's very apparent after you've bought two or three of those 3CX1500's, so why not save your self some trouble to start with? That's also the reason I said 'tickle' that thing instead of 'driving' it. (grid dissipation)

Depending on what you are used to operating, there are some tubes that can be 'abused' and there are some that can't be. The 3CX1500 is one'a them 'non-abusable' tubes. That does not mean that it's unsuitable for amplifiers, it certainly is. It does say that you had better pay attention to what's happening or you will regret it.
- 'Doc
 
W5LZ said:
Basing things on efficiency means that at best you are looking at maybe 60%. Which means that 1500 watts dissipation really is 'pushing' the tube to about what it's going to be capable of and still have a reasonable life span. At that, you are going to be producing LOTS of heat. (Sounds silly, but keeping coffee hot setting over the vents of an AL-1500 is not a joke. And, no, don't do that, it's not a smart idea.)

Mixing input/output power figures is also one of those silly things unless you know how those figures relate to each other. A very rough rule of thumb is that about half of the input power is probably the output power of an amplifier of typical efficiency, maybe.

Ignoring carrier, and even using Pep figures (if a constant tone input is used for testing), the output power levels will be exactly the same for AM mode as if the power were measured in RMS/average units. That's perfectly normal since the peak envelope power is -constant-. The 'trick' is getting a -constant- output, and you can't do that by humanly produced sounds, whistling, etc. So, you end up seeing bigger numbers by using Pep. It also means that the resulting power figures are not very legitimate for any particular use except having 'bigger numbers'. They just don't tell you squat about what's happening. But if that's what you are looking for, then knock yourself out! Unfortunately, that's also what you are doing to that tube, knocking it out. It get's very apparent after you've bought two or three of those 3CX1500's, so why not save your self some trouble to start with? That's also the reason I said 'tickle' that thing instead of 'driving' it. (grid dissipation)

Depending on what you are used to operating, there are some tubes that can be 'abused' and there are some that can't be. The 3CX1500 is one'a them 'non-abusable' tubes. That does not mean that it's unsuitable for amplifiers, it certainly is. It does say that you had better pay attention to what's happening or you will regret it.
- 'Doc
Click to expand...

Thank you for all the replies. Thats why I wanted to know the diff. between them. I dont want to run anything to the point of meltdown. I just want to know what I can reasonably expect for 160 meter AM out of the two amplifiers listed. So far everyone has said they will both comfortably run 1500 peak with a 375 watt carrier. My question is, wich will run the MOST power COMFORTABLY???
 
HiDef said:
Sort of.
Click to expand...

That was very "Diplomatic" of you.(y)

dxhound said:
Thank you for all the replies. Thats why I wanted to know the diff. between them. I dont want to run anything to the point of meltdown. I just want to know what I can reasonably expect for 160 meter AM out of the two amplifiers listed. So far everyone has said they will both comfortably run 1500 peak with a 375 watt carrier. My question is, wich will run the MOST power COMFORTABLY???
Click to expand...

<sniff-sniff>I smell Chicken.</sniff-sniff>

IMHO, A station that is qualified to operate 160 meters (Licensed Extra, Advanced, or General) or capable (with a 160 meter dipole or full sized loop) would not be here asking questions that make them sound like Chicken-banders.

A "3cx1500" is an 8877 all day long; it's a bad idea to buy an amp that uses 8877's because of the cost and the fact that the tubes are not "durable". In this case, you are better trying to achieve your 1500 watts out of two tubes instead one that costs 800 bucks to replace.

When you are down on 160 meters, on what specific frequency can I find you and who should I listen out for?

.
 
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Slam Dunk said:
That was very "Diplomatic" of you.(y)



<sniff-sniff>I smell Chicken.</sniff-sniff>

IMHO, A station that is qualified to operate 160 meters (Licensed Extra, Advanced, or General) or capable (with a 160 meter dipole or full sized loop) would not be here asking questions that make them sound like Chicken-banders.

A "3cx1500" is an 8877 all day long; it's a bad idea to buy an amp that uses 8877's because of the cost and the fact that the tubes are not "durable". In this case, you are better trying to achieve your 1500 watts out of two tubes instead one that costs 800 bucks to replace.

When you are down on 160 meters, on what specific frequency can I find you and who should I listen out for?

.
Click to expand...
I think your missing the point here. Im not looking for MAX power out of the tube!! Im looking for the configuration that will allow me to run legal limit with the LEAST stress on the the tube(s). if the two 800a7 are going to be running at 85% and the one 8877 will be runing at 65% I will choose the 8877 because there is a better chance it will last the longest. Or will it be vice versa?? Im not looking to run 3kw and and tax the amp for everything it has!

My call is kb3hlk and you can find me all over the top band, but there are a few guys I seem to talk to the most that are usually within a few k of 1905
 
The short and simple answer to this question is, whichever tube or combination of tubes has the higher plate dissipation. That is where the problem comes from when running AM. Most amps have very similar efficiencies so therefore higher plate dissipation means higher headroom. It just stands to reason. For the same power output, a pair of 4-400's are better than a pair of 833's and a pair of 3-500's are better than the 4-400's and a single 4-1000 is better than any of them when talking about which one will run the lightest.
 
QRN said:
The short and simple answer to this question is, whichever tube or combination of tubes has the higher plate dissipation. That is where the problem comes from when running AM. Most amps have very similar efficiencies so therefore higher plate dissipation means higher headroom. It just stands to reason. For the same power output, a pair of 4-400's are better than a pair of 833's and a pair of 3-500's are better than the 4-400's and a single 4-1000 is better than any of them when talking about which one will run the lightest.
Click to expand...

Commercial amps (which is what he seems to be trying to decide upon) are only designed to do so many watts and that's it; if the OP needs more "Headroom" then he has to move up to an "Export Model" with higher input/oouput rating or go Homebrew.

.
 
Slam Dunk said:
Commercial amps (which is what he seems to be trying to decide upon) are only designed to do so many watts and that's it; if the OP needs more "Headroom" then he has to move up to an "Export Model" with higher input/oouput rating or go Homebrew.

.
Click to expand...

Agreed. That's because the export amps have a higher total plate dissipation rating than those meant for domestic sales. The QRO Technologies HF-2500DX Mk3 has three 4CX800A's whereas the domestic HF-2500 has only two thereby giving the Mk3 half as much plate dissipation again as the regular 2500 model. It still boils down to plate dissipation. If he wants the ultimate amp get this one. :tongue:


RigPix Database - Power amplifiers - Ulvin International Tremendus IV
 
QRN said:
Agreed. That's because the export amps have a higher total plate dissipation rating than those meant for domestic sales. The QRO Technologies HF-2500DX Mk3 has three 4CX800A's whereas the domestic HF-2500 has only two thereby giving the Mk3 half as much plate dissipation again as the regular 2500 model. It still boils down to plate dissipation. If he wants the ultimate amp get this one. :tongue:


RigPix Database - Power amplifiers - Ulvin International Tremendus IV
Click to expand...

Those tremendus amps have horible reviews on eham. As for the QRO amplifiers, they are very nice!!! I looked at them and even in the used market they bring a pretty penny. But it seems to me everyone is hung on the fact I want to run over 1500 watts! I DONT!! I just want to know which setup would run 1500 AM (PEAK) and be stressed the least, THATS IT
 

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