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

[Shockwave]

Another interesting thing is that 250 watts PEP output sounds like a lot for the 2SC2879 but in reality that's only asking and 8 pill amplifier to hold 500 watts average AM on the Bird 43. The 500 watt carrier will still only show about 500 watts average on the Bird 43 when it's 100% modulated. But those audio peaks should be at 2 KW PEP output when you switch on the peak kit on the meter. Those 2 KW peaks are easy to reach on 18 volts without flat topping either.

 

[Shockwave]

thanks robb . i havnt been there in a week or so looking at their threads . i cant post there because i dont have a ham ticket . but i dont have to be a member to see the post , which i think is nice of them to have it that way .

maybe i should have posted this in the meter section or used a different title . i was mainly interested in how the harmonics of the over driven pills/rf transistors affect the meter to show more watts than it is actually producing because of how the meters are made . I HAVE ABSOLUTELY NO PROBLEM WITH ANY OF MY THREADS GOING OFF TOPIC , so admins please DO NOT edit the thread . many times ive seen the peripheral conversations/comments are just as interesting and helpful as those more focused on what started a thread .

i knowa 2879/pill can produce a little more CLEAN power than the pdf toshiba specs it for . i know increasing the voltage can give a little more too . i believe that ammount of headroom and bump from the voltage isnt enough (keeping it fairly clean ) to allow me to make a contact i couldnt make at 12.5 volts without the headroom . they can obviously produce much more watts when over driven , but my goal is to run a clean station .... clean but quality modulation and without adversely affecting other electronics nearby or splattering on folks on adjacent channels . proximity plays a roll in that , but you get the idea .

i thought it interesting that the article explains how someone claiming 400 watts per device are really only getting about half of that and the rest is meter error due to the primary frequency and the pills over driven harmonics together throwing the meter off . the signal is very dirty though .
tit for tat , yin and yang , you dont get something for nothing ...... theres always a tradeoff .

i really hope this thread doesnt get locked .

Booty, if more people ran their equipment like you intend, there would be much less bleed over on 11 meters. Please don't think I'm telling everyone to overdrive their amp, I'm just pointing out what is possible to achieve from the 2SC2879 and there are ways to do it reliably.

 

[BOOTY MONSTER]

no problem here shockwave . it was obvious to to me you were discussing the peak capability of the pill , not the proper use of it

 

[Captain Kilowatt]

Hey BootMon:

There has been a thread started on QRZ about your thread here. Some interesting answers too. I thought you might like to see it. You can thank a member here for going to QRZ trying to make it an object of ridicule.

Actually, I think it was a fair question - considering that some amp mfr claim such large, unqualified numbers for their amps. it appears that these transistors CAN do that many watts; but not for continuous duty cycle C-class amps. Only for short bursts...

Read:
http://forums.qrz.com/showthread.php?t=248732

BTW, I am not taking sides here but I suggest anyone that follows the thread on QRZ about this to pay attention to what Tom, W8JI has to say. For those of you who do not know, Tom is the chief DESIGNER of amplifiers for Ameritron both solidstate and tube types. I believe he also designed and built very high powered amps for the ISM business. Again, I'm not taking sides but offering a credible outside source to pay attention too.

 

[AudioShockwav]

The Thread will not get locked as long a serious debate is adhered to with no name calling. Let the discussion continue, slow down and look at the possibly.
And there is the same kind of debate going on at the ...uhm ..other forum as well...if you look at the last post over there...OK here

1.) There is more to class AB than just slapping a half-xxxed bias system on the amp and pretending it is linear, or pretending the bias is good.

2.) Continuous relates to heat dissipation, not class of operation. Class C can be continuous and the transistor has 250 watts of dissipation, continuous, available. If someone manages 60% efficiency at the collector that's about 625 watts input power. That's 375 watts RF at the collector. If the transformers and filter network is 90% efficient that's 337 watts out with 250 watts of heat.

The key is what other parameter might be exceeded to the point of failure, like voltage or current. The data sheet does not say enough to determine that because the circuitry greatly affects the limit. You have 25 amps available at datasheet ratings. There are a series of conflicting Vce breakdowns, but it looks like 45 volts which means a Vcc of 20 volts or so if things are right. That would be ~500 watts in.

3.) Just because a CB'er or anyone else runs SSB, that does not mean they use a linear amp. Linear is a transfer function issue, NOT amplifier class. Anyone running a 2SC2879 at more than 80-100 watts PEP per device probably has an unacceptable signal for SSB or AM. Let's not pretend that running a certain mode means the equipment is good.

I wouldn't run the thing at 250 watts out, but it looks like a single device just might do that much.

Seems that Shockwave is not alone in his statements. Now I am sure he will agree that for the Average operator, this would not be a desirable condition to run the stated device at on a daily basis. But can the device do it? I will side with Shockwave...would I build an Amp and expect this kind of output? No... but what he is saying is the 2879 can do the output, NOT at 12 volts ... it would be running on the edge, but based on experience with the 2879 that i have it IS possible ...desirable? No , not in my opinion..

This Topic was started for what ever reason, and has progressed to what Can a 2879 do at its extreme limits, If we want the discussion to continue, just remain civil to each other.

73
Jeff

(on edit, Captain Kilo and me were replying at the same time, and I copied the reply he was talking about)

 

[BOOTY MONSTER]

things that make you go hmmmmmm..................

"3.) Just because a CB'er or anyone else runs SSB, that does not mean they use a linear amp. Linear is a transfer function issue, NOT amplifier class. Anyone running a 2SC2879 at more than 80-100 watts PEP per device probably has an unacceptable signal for SSB or AM. Let's not pretend that running a certain mode means the equipment is good."

so he is the "chief DESIGNER of amplifiers for Ameritron both solidstate and tube types" and made the statement above , but his company sells a amp using four 2879's and advertises it as a 500 watt amp . which is 25-45 watts more per device than his comment above says they can cleanly do .

Ameritron

wassupwitdat ??????

 

[pro151]

Come on out of the closet Richard and show yourself and explain to us all how much more superior you feel now.

FCC Callsign Lookup from QTH.com

Don't be shy, I am sure the 2 gentlemen having this discussion would welcome your views and expertise on the subject in question.

Heck who knows, you might even be able to educate some of us.

 

[Shockwave]

It was refreshing to read what W8JI had to say in the other forum based on his extensive experience. I already knew the most I've ever been able to get out of one 2SC2879 was 291 watts each in class C. I wasn't going to reveal that fact because it seemed so unlikely anyone would believe me. With Tom's calculations showing it's possible to reach 337 watts output deep in class C without exceeding the dissipation rating, can we put the 250 watt output debate to rest now?

 

[BOOTY MONSTER]

i wonder how that 291-337 watts from a single 2879 would sound ?
10-8 ? top shelf ? wall to wall and tree top tall ? walking the dog and kicking the cat ? hehehehe

sorry , couldnt keep from trying to inject a little humor .

so it seems the 2879 can indeed do the 300 watts class c builders claim when highly volted but at the expense of severely compromising the signals fidelity and creating multiple strong harmonics .

 

[Shockwave]

i wonder how that 291-337 watts from a single 2879 would sound ?
10-8 ? top shelf ? wall to wall and tree top tall ? walking the dog and kicking the cat ? hehehehe

sorry , couldnt keep from trying to inject a little humor .

so it seems the 2879 can indeed do the 300 watts class c builders claim when highly volted but at the expense of severely compromising the signals fidelity and creating multiple strong harmonics .

In all honesty Booty, it doesn't sound as bad as one might think on AM. However, slide up or down 10 KHz. and it will become apparent how dirty the signal is as a result of the IMD. If you keep the carrier and modulation level at a sensible point, some even think they sound good. I'm often amazed at how much distortion can actually be on a signal before it seems objectionable to the average listener. I run an HF rig on 11 meters with a spectrum analyzer (pan adaptor) on the receivers wide band IF. Sometimes the IMD contained in the sidebands is absolutely horrendous. Yet the operator asks for a radio check and he's told "sounds great"!

One last thought, while I was able to get 291 watts off a 2SC2879 and W8JI has pointed out that in theory you could reach 337 watts output before exceeding the dissipation, 250 watts PEP is about the practical limit if you don't want to replace transistors all the time.

 

[Captain Kilowatt]

things that make you go hmmmmmm..................

"3.) Just because a CB'er or anyone else runs SSB, that does not mean they use a linear amp. Linear is a transfer function issue, NOT amplifier class. Anyone running a 2SC2879 at more than 80-100 watts PEP per device probably has an unacceptable signal for SSB or AM. Let's not pretend that running a certain mode means the equipment is good."

so he is the "chief DESIGNER of amplifiers for Ameritron both solidstate and tube types" and made the statement above , but his company sells a amp using four 2879's and advertises it as a 500 watt amp . which is 25-45 watts more per device than his comment above says they can cleanly do .

Ameritron

wassupwitdat ??????

I am guessing the reason is that the specs for the 2879 are at 12 volts. In a mobile environment where the ALS-500 would be, the Vcc would be at least 13.8 volts and since each device would be called upon to provide only 125 watts pep that it is still operating within acceptable FCC IMD limits. Obviously it is because it is certified.Clean operation is relative. there is clean, acceptable, and then down right dirty. op:

 

[dxhound]

By all means, im not hiding, Just cutting grass, I dont live on here like most.
And yes I did start the thread on QRZ to get some outside information from people unaffiliated with this thread. Because shockwave did get me thinking. But Like what was said, it would need an efficiency rating that is astronomical and unfeasible for our purposes. And just like I said, even the engineers agree that pulse is about all your gonna get, NOT sustained work.

And PRO151, my callsign is already on here in a few places.....Im not exactly hiding. As I already said, whoever wants to try this, be my guest. I have no desire to "RELIABLY" get this power because I keep my station and my amplifiers clean.

But I am man enough to stand up and say if I am arguing on the wrong side, and It seems in this case I am. But I still stand behind the fact that the harmonics have an adverse affect on watts meters, and more than 6.6%!!

To the moderators, I will apologize for the name calling.

 

[Captain Kilowatt]

In all honesty Booty, it doesn't sound as bad as one might think on AM. However, slide up or down 10 KHz. and it will become apparent how dirty the signal is as a result of the IMD. If you keep the carrier and modulation level at a sensible point, some even think they sound good. I'm often amazed at how much distortion can actually be on a signal before it seems objectionable to the average listener. I run an HF rig on 11 meters with a spectrum analyzer (pan adaptor) on the receivers wide band IF. Sometimes the IMD contained in the sidebands is absolutely horrendous. Yet the operator asks for a radio check and he's told "sounds great"!

The big problem is that most people have no idea what distortion is or sounds like and think that because it is LOUDER! then it's working just great. I have a back ground in commercial broadcasting and my standards of what sounds good are completely different than most people's. I have sat back and shook my head when I have heard someone tell another that their gear sounds good while I can hear the raspy buzziness of the distortion. Some people think that because they can hear you splatter 5 or 6 channels away then you must have a great station. I have heard stations on the bowl via DX and when listening on ch.7 I could still make out every word they said even tho the signal on ch 6 was only about S-9 so I knew they were not creaming my RX frontend.Whenever I make audio adjustments to my gear and look for signal/quality reports I usually look for one of the regional crowd here that are current/former b'cast engineers like myself to get valued and accurate opinions of what I sound like.A bunch of us get together every Sunday on 80m AM for a round table.

 

[dxhound]

By all means, im not hiding, Just cutting grass, I dont live on here like some.
And yes I did start the thread on QRZ to get some outside information from people unaffiliated with this thread. Because shockwave did get me thinking. But Like what was said, it would need an efficiency rating that is astronomical and unfeasible for our purposes. And just like I said, even the engineers agree that pulse is about all your gonna get, NOT sustained work. BUT he is right, you can get 250 and more.

And PRO151, my callsign is already on here in a few places.....Im not exactly hiding. As I already said, whoever wants to try this, be my guest. I have no desire to "RELIABLY" get this power because I keep my station and my amplifiers clean.

But I am man enough to stand up and say if I am arguing on the wrong side, and It seems in this case I am. But I still stand behind the fact that the harmonics have an adverse affect on watts meters, and more than 6.6%!!

To the moderators, I will apologize for the name calling.

 

[pro151]

By all means, im not hiding, Just cutting grass, I dont live on here like most.
And yes I did start the thread on QRZ to get some outside information from people unaffiliated with this thread. Because shockwave did get me thinking. But Like what was said, it would need an efficiency rating that is astronomical and unfeasible for our purposes. And just like I said, even the engineers agree that pulse is about all your gonna get, NOT sustained work.

And PRO151, my callsign is already on here in a few places.....Im not exactly hiding. As I already said, whoever wants to try this, be my guest. I have no desire to "RELIABLY" get this power because I keep my station and my amplifiers clean.

But I am man enough to stand up and say if I am arguing on the wrong side, and It seems in this case I am. But I still stand behind the fact that the harmonics have an adverse affect on watts meters, and more than 6.6%!!

To the moderators, I will apologize for the name calling.

Good man! My hat is off to you.

This is how we disagree agreeably.