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maybach52 Profile
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Freebander
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Zetagi B300P amp.


I have one of these. Works OK but I fully understand that I will never see the full, claimed 300 watts out of it, however what can I expect With a 10 watt input?

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OP: Bob.
24/Jan/2010, 10:25 am Link to this post Send PM to maybach52
 
madmark1 Profile
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Re: Zetagi B300P amp.


the original b300p had a pair of MRF455 transistors these are rated at 70 watts approx output each, so around 140 watts roughly. not taking into account losses in the transformers.

mark 163fb20

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24/Jan/2010, 10:48 am Link to this post Send Email to madmark1   Send PM to madmark1 Blog
 
maybach52 Profile
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Freebander
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Re: Zetagi B300P amp.


I'm reckoning about 120-130 out of mine which would seem about right. I assume thats SSB and not AM/FM?

Even by Zetagi standards 120 from a "300" watt amp seems poor.

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OP: Bob.
24/Jan/2010, 10:56 am Link to this post Send PM to maybach52
 
26fb99 Profile
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Re: Zetagi B300P amp.


it takes some reading,but 140 watts transmits as double (280 watts) because your using half the band width on SSB (eg upper or lower side band).am/fm modulation uses up roughly the same band space as upper and lower combined and so takes double the effort to carry as far so although fm is is more representational of our voices,this is why Dx is usually done on SSB,it is also why we can tx 5 kc,s apart eg [sign in to see URL],560 [sign in to see URL] on fm are spaced 10kcs apart.

a good guide for your linears ssb "effective" output is to double its full fm output in your head.
like mark says.a transitor rated at 70 watts can only produce 70 give or take,so in my kl500,4 of these at over 300 watts is either over driven or dirty harmonics in the power [sign in to see URL] is why Hams often call Cb amps dirty,in some circumstances the harmonics of 11m amps are transmited on other frequencies where they souldnt be.
just keep your power leads thick and short to the PSU or battery and many lads stick pc fans on top of the amps to keep the trannys cool and prolong the life of them.i dont bother switching my fans on and non of my amps have broke yet despite being permanantly on when im on [sign in to see URL] personal preference mate.
100 clean watts will get you round the world with the right aireals more often than will 1000 watts with a mobile whip on a buscit tin but that doesnt stop Simon 26fb204 using this set up LOL.

take it easy Bobster

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yaesu FT857d,rmkl500,wilson5,2element pubical quad(the BBq).split charger aux battery.170a truck battery,mfj 941 versatune2
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I got 99 Problems but a whip aint 1
Brent 26 Fox Bravo 99
73s
24/Jan/2010, 2:56 pm Link to this post Send Email to 26fb99   Send PM to 26fb99
 
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Re: Zetagi B300P amp.


Brent is right.

But, in my mind these are happy watts. Just because the band is half, doesnt mean the watts double, does it?

Ok they go twice as far, theoretically, but watts is watts and a 70 watt transistor or a 100 watt valve does just that, and no more.

If I was selling watts I would double it emoticon

Sorry but I cant get my head around this 100w carrier 200w SSB crap emoticon

Prove it in front of my eyes is the only way emoticon

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By all means think yourself big, but never think others small.... R.F.Scott
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maybach52 Profile
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Re: Zetagi B300P amp.


This is exactly my concern. I understand fully the technical bit but on my meter I get a reading of 120 watts, this is on SSB. So just to clear this up does this mean my real power output is in the region off 240 watts then, give or take.

I did have the amp checked over and was told that it was putting out a healthy 243 watts max! Just need to clear this meter thing up.

Confused.
    

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24/Jan/2010, 5:06 pm Link to this post Send PM to maybach52
 
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Re: Zetagi B300P amp.


Your "real" power is what you are reading.

But because SSB is half the bandwidth of a carrier wave band like FM. It is percieved, using mathmatics that half the band = twice the watts.

I'll look up some diagrams on the internet and post them, but a radio wave goes above and below the carrier, and SSB is either above the carrier USB, or below, LSB. Half, so in theory, 20 watts using all the wave band is 40 watts using only half. But I'm not convinced, as this relies on maths and not proper watts from the radio emoticon

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24/Jan/2010, 5:18 pm Link to this post Send Email to yamanx1   Send PM to yamanx1
 
maybach52 Profile
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Re: Zetagi B300P amp.


I'm not convinced either.

Mathematics aside though and in simple terms, my B300P is putting out more than 120 watts on SSB. Yes?

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24/Jan/2010, 5:28 pm Link to this post Send PM to maybach52
 
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Re: Zetagi B300P amp.


quote:

maybach52 wrote:

I'm not convinced either.

Mathematics aside though and in simple terms, my B300P is putting out more than 120 watts on SSB. Yes?



ummmm, no, it's putting out whatever your meter says it is, sort of, lol.

A 70W transistor is a 70W transistor, and it will do, yes you guessed it, 70W, lol. This is a manufacture rating, and what the transistor is designed to do at maximum whilst still operating within specified tolerances. Can you make it put out more power? Yeah sure you can, will it be on 27Mhz where you want it to be, umm no it won't. You can overdrive a transistor to give you more power out, but the extra power will be on harmonics and other places you don't want it to be. In short its a big con, no CB amp will even come close to doing the power they claim on the box, unless like Dave said, you take into account the "happy watts". They make your power meter read more, but don't do anything for your signal.

The specs on the amps tell you to overdrive the input, producing harmonics. No filtering in the amps let the harmonics out of the amp and into your power meter, which adds up the real power and the "happy watts" to make your meter read close to what they claim the amp will do.

I've heard what Brent said from countless people, about half the bandwidth meaning you can do twice the power, but I don't buy it either. The other one I have heard is the duty cycle line. FM is constant carrier, so full power 100% of the time, SSB only puts out full power on voice peaks, so you can put out double the power, because you are only using full power for half of the time compared to FM, transistors won't get as hot ect. ect.

Both nonsense really, to get more than the rated power of the transistors you have to overdrive the amp, which is what makes them dirty, that and the lack of filtering.

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Re: Zetagi B300P amp.


from reading your post it seems strange [sign in to see URL] your power meter reads when you whistle is what your amp is [sign in to see URL] it sideband or fm/am,a reading is a reading.
150 watts is the norm for a 300 given that it has 2 70watt trannys.
so maybe the meter on which it was doing 243 watts was in [sign in to see URL], [sign in to see URL] or AVERAGE or some other bull readout which is not really of concern to us in everyday language. its kind of spin used by dealers to seem like the output is more than it is.

example. my brand new kl500 rated at ''''600 watts ssb " "300 fm" driven with 10 watts from my yeasu 857 reads 300 watts fm, 320 watts when i whistle on ssb .on my nearly brand new mfj power meter.
am i gonna send it back? [sign in to see URL] 4 x 70 watt trannys=280 so a little [sign in to see URL] if ive got 2 more of the same trannys in my amp than yours it stands to reason that it do twice the power of yours i.e around 140/150

i used to have a kl 400 rated at 400 ssb which is similar to your b300 and again,it maxed out at 240 watts using all the same conditions as above, which is close to what you had it tested at.
could be that you had a good set of trannys that produced over thier rated power as my 400 had and 1 of them has gone [sign in to see URL] it still work (not quite sure) but if i were you i,d borrow that 243 meter and retest under the same conditions in your shack.
what is your radios output on ssb as opposed to fm and is the ssb audio from your radio/mic sufficient to drive it to its full power?
if you can cook eggs on it,chances are its working perfect,and ignore the power.i would suggest around 140 is bang on with a few losses here and there in patch leads,the tranformer and in the meter if it a cheap un making your 120watts. and to [sign in to see URL] watts fm is still 140 watts ssb when you strip away all the dealer speak.

---
yaesu FT857d,rmkl500,wilson5,2element pubical quad(the BBq).split charger aux battery.170a truck battery,mfj 941 versatune2
100% mobile station
I got 99 Problems but a whip aint 1
Brent 26 Fox Bravo 99
73s
24/Jan/2010, 7:35 pm Link to this post Send Email to 26fb99   Send PM to 26fb99
 


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