hundreds of watts per 2879 ???????????????????????

[BOOTY MONSTER]

just because your meters show 300-400 wats pep per 2879 doesnt mean they are really doing that much . yess there is some headroom and using a 14.4 volt power supply helps get a little more out of them , but no where near as much as some suggest/claim .

http://www.firecommunications.com/notreal.txt

heres a small quote that gets to the meat of the matter showing what those meters are actually showing .

"the largest factor contributing to the highly erroneous readings produced by the majority of hf
wattmeters is created when energy begins to appear at frequencies 3, 5, 7 (and higher) times
the fundamental operating frequency. the more the drive and operating voltage is increased the
more pronounced the effect becomes. in addition to the sum addition of the energy present at
these multiples of the operating frequency the problem is compounded by the wattmeter design
itself. the line section is designed to sample a specific amount of energy at the fundamental
operating frequency in a direct relationship to the physical length of the line section as that
length correlates to a given fraction of a wavelength at the intended operating frequency. when
energy begins appearing at the odd harmonics not only is the power added by the line section but
it is also amplified because as frequency is increased the line section becomes longer with
regard to the fractional wavelength represented by the line section initially at 27 mhz.. there
fore the line section is "oversampling" the energy levels occurring at the frequencies previously
mentioned. once these harmonics begin to occur the environment is ripe for a sort of controlled
"oscillation", the harmonic energy present acting as the trigger.

now in addition to the energy present at 27 mhz. you now have substantial levels of vhf and in
some cases even uhf energy directly affecting the accuracy of the measuring device."

id suggest reading the entire article

 

[GLR]

blasphemy!

 

[dxhound]

Ive been telling people this for years...........They will still fight you on it!!

 

[Shockwave]

One might be surprised how much power a 2SC2879 can develop if you're willing to push the heck out of the device. It's interesting to note that the collector dissipation on this transistor is an enormous 250 watts! I've seen them on regulated 18 volts produce every bit of 250 watts PEP output per transistor. At that output the amp would have to be running at a horrendous efficiency below 50% before the transistor dissipation was exceeded. Most that run these voltages run the amps class C at higher efficiency.

Of course when you push the transistor like this you leave yourself no headroom and are always right on the edge of blowing the thing up. Signal quality will also suffer but it's possible to make lots more then 100 watts per transistor. How wise an idea that may be is an entirely different matter.

I'm also not in complete agreement as to how much impact harmonics have on the watt meter. There is no doubt that energy measured by the meter that is several times the frequency of the line section will cause the meter to read higher. I think the writer is expecting much more harmonic content then even the average dirty class C 11 meter amp produces.

If the theory of the meter being thrown of this much by harmonics is true, it would be very easy to confirm if harmonics were the source of the erroneous readings. Just install a decent low pass filter right after the amp and before the meter. If the power drops of by 50%, the man is right. If it just changes a little, that's probably related to the slight change in impedance the filter may cause due to it's coils and caps.

I've done this before and not seen any significant change in measured power with the filter installed. It was no cheap filter either. As I recall it was 7 poles and had a cutoff frequency of 32 MHz with something around 80 db attenuation at 54 MHz. I put it behind everything from a one transistor Rabbit to a Sweet 16 and never noticed big changes in power output.

I think what's happening here is people are confusing harmonic content that doesn't easily show itself on the watt meter with an instable amplifier that's probably oscillating and would show extreme exaggerated power readings. The two conditions are entirely different even though they are often mistaken for each other.

 

[BOOTY MONSTER]

LOL , i guess world wide pirates of DX didnt like the post over there . they heavily edited my post and eliminaded the comments by a few and my replies to them when they moved it to the meter section > AND LOCKED IT so there can be no discussion

WHAT THE HELL ARE THEY AFRAID OF OVER THERE ???

. i did tell smiley in a pm that i didnt have a problem with , moving it from the amp section to the meter section

i got a series of smiley about the post .

..................

first pm from smiley .

"Hey booty. What is this all about?"

my reply .

"its a thread helping to explain how what is shown on watt meters by folks over driving their amps isnt what it appears to be ?
did you read it or go to the link ? im sure some will disagree with it .
i just hope they offer something more than "hes wrong" or "the guy that sells these amps say differently" .

is there a problem with the post ? if the link is an issue ill edit the post and just quote the whole article high lighting those two paragraphs and ask that if someone wants the link that they can PM me and ill PM it to them .


second pm from smiley .

"Well we know what pills do. opinions are so different. That people are going to argue. So why start a problem.
We will keep a eye out on it. If it becomes a problem. It will get deleted. Just to let you know. Thank you."

my 2nd reply to smiley .

"if people disagree why cant they have a civil conversation stating facts instead of arguing ?

the point of the article is that some folks arnt aware of what ammount of power pills actually do if they are overdriven and how that affects our meters .
...




LOL , you really gotta appreciate the technical prowess and relivancy of this reply from skyhawk

"Lets try this booty monster. How about come to manchester 10. You bring or I can buy you a AB class Texas star...... You choose the final pill amount.

You know what class amp I am going to run. We key into dx..... while you are on those clean watts. I will key my dirty trashy no good damn C clASS amp and watch what happens....

Here is a proposition I have for you. If you win...... I have to use AB class amps though out the cycle. Crush my dirty C class amps..... And say no more about it.

If I win....... YOU have to use C class amps through out the cycle. Crush your clean AB class amps. And say no more about it.
One thing that I have always believed in. Data sheets says this pill does x amount watts. Ok that is for one type condition...... Now lets change the condition and application. What happens.... the sheet are no longer good.

My case in point on data sheets.
Presently we are about to change out one of the machines on a barge. It is a liebherr 994 which I have ran many times. Here is a picture of it to just to give you a idea of what I am talking about changing the application. And to give you a size comparison. If you look under the bucket. There is a spool of cable with a tag line being held by the oiler.


Now here is the "DATA SHEET" made by the manufacture of the new machine. And who else would know the machine better than the company that makes it.... That is what has always been your case in point trying to show every one about these debates.

http://i105.photobucket.com/albums/m216/slowandlowcelicas/Boat20Dock.jpg

When you get to liebherr site. Go to crawler excavator and click on R996 litronic.

Now according to the data sheet I can lift 133,500 pounds......... Well my friend if I tried that on the barge........ I would roll the barge over due to it will lean to the side I have the weight on. Also in consideration we will be changing from short stick to a long stick..... Which this weight is calculated on with that counter weight on back.... And also I have to figure how fast the weight is going to shift when that 750 ton machine swings..... OOOOO the sheet says it only weighs 740.75 tons....... Now how can it be 750 tons????? Which will be the weight when we put the long stick to it......
And this data sheet they give you on the machine is ideal lifting conditions, flat and level on solid ground. But we changed that by putting it on the barge.

So I have to change what I can lift so no one on barge dies due to I read the data sheet that said I can lift that many pounds........ But they make the machine so they should know right?

Call it fake watts, happy watts, harmonic watts... or what ever you want to call it.... but it works."


i hope my reply doesnt cause an argument . .

"my post had nothing to do with bias class or data sheets or how much weight a cable or or crane or barge (or some combination of them) of can handle . it was about how our meters are skewed by harmonics from over driven amps and give inaccurate readings .

if you wish to disagree with the article i have no problem with that . but an on topic reply explaining the technical errors in it would be appreciated . just saying or suggesting its wrong without a reason or evidence why .............. well .............. Rolling Eyes"


LOL , 3rd PM from smiley .

"I can't answer that question Booty. Some people like to see that maybe.

You have made your point SEVERAL times about class AB1 and C. Why push it. It is like Smokers and non Smokers. If you don't like what people do. O-Well.



and my reply .

"if you will read what posted you will see the thread is not about bias class . its about how our meters are skewed by harmonics . bias was mentioned by skyhawk and i gave him the same reply .

its not about bias .
its not about texas star vs. fatboy or x force
its not about messenger or palomar vs stroker or no name or audio illusion .


its about meters and how they can give false readings and the cause of that being overdriven amps . i chose to put 2879 in the title since its the mose popular pill to over drive .

if you would like to move the thread to the meter section that is fine with me or if you prefer i start a new thread there about it that is fine too .


or are you suggesting that only threads/post that make everybody or a chosen majority happy are acceptable or preferred here ?"

...............................

i think my last question was answered with actions rather than words .

it is what it is .................

//////////////////////////////

now WWPDX doesnt recognize my name and pass word . LOL i guess ive been banned for potientally inciting a riot because i couldnt understand a forum not wanting to allow a topic that causes discussion because the mod/owner doesnt trust his forum members to do that without causing problems .

 

[BOOTY MONSTER]

LOL ..
"You said that you were making people aware of this stuff. I kept the link for information. I locked it so people will not argue about it. If you want to complain. Go to another forum. If you do not like the rules here. Go to another forum. Thank you."

im sorry you have so little faith in your forum members that you cant expect them to discuss a difference of opinion or learn some facts without arguing .

.................

i see another hammer comming . LOL

 

[swanny]

are you surprised at all booty monster? i mean, that's one of the first things i noticed here compared to other forums. Here, people can discuss things even if they don't agree. Some of the other ones chastise anyone who doesn't agree and comform lol. I'd rather learn here

 

[dxhound]

One might be surprised how much power a 2SC2879 can develop if you're willing to push the heck out of the device. It's interesting to note that the collector dissipation on this transistor is an enormous 250 watts! I've seen them on regulated 18 volts produce every bit of 250 watts PEP output per transistor. At that output the amp would have to be running at a horrendous efficiency below 50% before the transistor dissipation was exceeded. Most that run these voltages run the amps class C at higher efficiency.

Of course when you push the transistor like this you leave yourself no headroom and are always right on the edge of blowing the thing up. Signal quality will also suffer but it's possible to make lots more then 100 watts per transistor. How wise an idea that may be is an entirely different matter.

I'm also not in complete agreement as to how much impact harmonics have on the watt meter. There is no doubt that energy measured by the meter that is several times the frequency of the line section will cause the meter to read higher. I think the writer is expecting much more harmonic content then even the average dirty class C 11 meter amp produces.

If the theory of the meter being thrown of this much by harmonics is true, it would be very easy to confirm if harmonics were the source of the erroneous readings. Just install a decent low pass filter right after the amp and before the meter. If the power drops of by 50%, the man is right. If it just changes a little, that's probably related to the slight change in impedance the filter may cause due to it's coils and caps.

I've done this before and not seen any significant change in measured power with the filter installed. It was no cheap filter either. As I recall it was 7 poles and had a cutoff frequency of 32 MHz with something around 80 db attenuation at 54 MHz. I put it behind everything from a one transistor Rabbit to a Sweet 16 and never noticed big changes in power output.

I think what's happening here is people are confusing harmonic content that doesn't easily show itself on the watt meter with an instable amplifier that's probably oscillating and would show extreme exaggerated power readings. The two conditions are entirely different even though they are often mistaken for each other.

Hey shock wave, I posted the following on another forum

You know I had to chime in on this one! Lets use a 2SC2879 for reference.

12.5v is 100watt minimum. Up the voltage to 18v(thats an increase of 66.7%)

Now in general, that means the wattage will increase 67% Give or take linear effects

So at 18v the 2sc2879 should produce around 167 watts

Now 167 watts is being VERY generous, because as the voltage goes up, so does heat. When heat goes up, wattage goes down. But we will use 167 Since it will be the MAX the transistor could feasibly do at this voltage

So, 4 2sc2879's at 18V SUSTAINED, will produce 668 watts at the VERY VERY MAX!! This is before taking into consideration the losses in efficeincy and design. So, 12.5 Volts on 4 devices is 400 watts vs 18v at 668. That is a 1.8db gain or a little less than 1/3 of an S unit. Is this worth the lifespan of the transistor or the money? Thats up to you!!!

The one problem with this is, (and I know most dont care) There is alot of IMD now being produced with 18v! Thats why some folks show over 1 kw out of 4 transistors. The zener diode in the meter only reflects the current across it, no matter at what frequency the power is applied to. it reads it all, not just on 27MHZ but all the way into the double digit harmonics.

But yes, volted transistors will produce more power, Just not as much as some think.

This is proven by using a filtered freq. specific power meter or a spectrum analyzer that will show the power on a given frequency.

 

[loosecannon]

i think its high time someone started selling a dosy style wattmeter with a bandpass filter on the input that will only allow 26-28 mhz through it.


i told a local here why his 4 pill wasnt really doing 900 watts, and he said it was one of the dumbest things he'd ever heard. LOL

LC

 

[dxhound]

I know what you mean. We have a real winner here that said his meter is showing him 1200 watts out of his 6 pill. He uses a PDL2. I was running 900 watts on my maco 5/8 wave vertical. and he still couldnt figure out how I was knocking him out to another station 20 miles away!! hahaha And yes I was reading peak output! Then when I tried to tell him about harmonics and meters, his TECHNICAL answer was, My meter is off and I am doing ALOT more... He actually said his dosy was more accurate than my LP100a and that they were garbage meters hahahahahah What an A$$

 

[Shockwave]

Hey shock wave, I posted the following on another forum

You know I had to chime in on this one! Lets use a 2SC2879 for reference.

12.5v is 100watt minimum. Up the voltage to 18v(thats an increase of 66.7%)

Now in general, that means the wattage will increase 67% Give or take linear effects

So at 18v the 2sc2879 should produce around 167 watts

Now 167 watts is being VERY generous, because as the voltage goes up, so does heat. When heat goes up, wattage goes down. But we will use 167 Since it will be the MAX the transistor could feasibly do at this voltage

So, 4 2sc2879's at 18V SUSTAINED, will produce 668 watts at the VERY VERY MAX!! This is before taking into consideration the losses in efficeincy and design. So, 12.5 Volts on 4 devices is 400 watts vs 18v at 668. That is a 1.8db gain or a little less than 1/3 of an S unit. Is this worth the lifespan of the transistor or the money? Thats up to you!!!

The one problem with this is, (and I know most dont care) There is alot of IMD now being produced with 18v! Thats why some folks show over 1 kw out of 4 transistors. The zener diode in the meter only reflects the current across it, no matter at what frequency the power is applied to. it reads it all, not just on 27MHZ but all the way into the double digit harmonics.

But yes, volted transistors will produce more power, Just not as much as some think.

This is proven by using a filtered freq. specific power meter or a spectrum analyzer that will show the power on a given frequency.

To suggest a transistor with a collector dissipation of 250 watts can't make over 160 watts output running class C indicates a lack of understanding. The fact that Toshiba has published a minimum output of 100 watts has far less to do with what the part can actually make then things like collector dissipation and maximum collector current. The guys that do get hundreds of watts from each 2SC2879 have 18 volt battery banks and charge at 21 volts. These are competition amplifiers that were built to max out the transistors. They don't care if it blows up as long as they get the "five". The amps aren't clean and they aren't running linear either.

Lets apply ohms law here rather then BS. If you raise voltage by 50% power goes up by 100%. Raising voltage causes current to rise proportionally. Since current goes up by 50% when voltages is raised 50%, the power goes up by 100%. Volts times amps give watts. Realizing that the 2SC2879 will blow up at about 23 amps of collector current means that you must reduce drive so as not to exceed this limitation. When you have 18 volts at 20 amps on a 2SC2879 that's 360 watts of input power. I'll be conservative and say it's running 70% efficient in class C. That's 252 watts of output with only 108 watts being dissipated by the transistor.

It becomes clear to see that even at 252 watts of output the transistor hasn't even come close to it's maximum collector dissipation however, it is riding the maximum current close to the limit. Even if you were to bias it up in the linear mode you would still not exceed the maximum collector dissipation at 250 watts output. This is certainly not the best way to run an amplifier but the topic here was "hundred of watts from a 2SC2879" as though it's not possible when it certainly is.

 

[BOOTY MONSTER]

so if a single pill is showing 350-400 watts is it safe to say that probally half of those watts arnt even on frequency ?

 

[W5LZ]

Or perhaps it should have been stated as usable watts? But if that transistor has reached it's maximum current handling ability at less than maximum collector dissipation, it's still reached it's maximum ability, hasn't it? So...
- 'Doc

 

[Shockwave]

so if a single pill is showing 350-400 watts is it safe to say that probally half of those watts arnt even on frequency ?

That could easily be confirmed by simply placing a quality low pass filter after the amp as I've said before. I argue that you will not see a significant drop in output power because the meter is not being thrown off drastically by harmonics. The idea that these amps produce this level of harmonic content that would cause meters to be off by double is ridiculous. If the meter was responding to this much harmonic content you would not be able to achieve a low level of reflected power on the meter into an antenna. I would agree that 350 to 400 watts per transistor is way more then should be expected.

 

[mackmobile43]

so if a single pill is showing 350-400 watts is it safe to say that probally half of those watts arnt even on frequency ?

The junk assed receivers that are used are not anywhere near a set frequency anyhow, they receive 6 to 8 kc's either side of the transmitting station so a lot of the tx'er is picked up that being said if the transmitter is set for wide transmission he most likely will win any and all key downs.