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Kattracker
| | Posted on Monday, September 01, 2003 - 12:59 am: | 
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I am a little rusty on this issue.
Can someone give me an explanation of the amp classes? I have seen AB-1, AB, B, and C?
Also, for mobile use for am, ssb and fm, are there any class better than the other?
Thanks,
Kattracker |
bruce
| | Posted on Monday, September 01, 2003 - 9:23 am: |
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Katt
To keep it simple ....here is a quick look at amps when i use power input im talking how much power the AMP used HOW MUCH POWER DOES THE AMP DRAW FRON THE SUPPLY INPUT TO AMP not drive power .... he goes ..
class " A" is on all the time low distorion but high power useage and low output only 30% for what ever power input ( if your amp pulles 100 watts from power supply you will get 30 watts out ) works great with all modes but uses too much power
class "AB" is bias near cutoff more output for a given input draw by the amp good for all modes less overal power used for same output( 40-50% ).
class " B " is bias at cutoff Here we get tuchy a class " B " amp will work well on all modes but harmonics and distorion are now becoming a problem
good output ( 40-60% ) for a given power input to the amp.
class " c " is bias past cutoff HIGH distorion but higher output at a give input as much as 70% output for a given input very good for FM / CW USELESS for am or SSB .... a REAL SPLATTER BOX if your nor carefull.
This was just ment to be a over view of the amps in the ARRL handbook you will find detailed infromation.
Bruce |
Kattracker
| | Posted on Monday, September 01, 2003 - 10:59 am: |
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Bruce,
Excellant explanation!
That must be why my Palomar 250 turns on the touchlamps in my house when I am talking on it in my driveway. I think it is a class c.
Thanks,
Kattracker |
bruce
| | Posted on Monday, September 01, 2003 - 12:49 pm: |
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KATT HE HE HE MY grant LT into the 40-10 meter dipole 4 watts makes out bedroon touch lamps sing! My wife came SCREAMING the other day scared her to death ........ she needed that HE HE HE realy you should have seen them dance cool efect kinda like disco all over again! It has nothing to do with amps the stupid lamps are tuchy to any rf....... now to get that top side up and get my paterin higher and away from them.
bruce |
Bigbob
| | Posted on Monday, September 01, 2003 - 11:17 pm: |
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Touch lamps are rf sensitive any rf whether a,ab,b,or c,I can do it with ssb or am or fm,the more power the better the effect,scares h*** out of the cats. |
Sixkiller505
| | Posted on Saturday, October 18, 2003 - 6:04 pm: |
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for bruce:those x-force amps are class c,so they are not good for am(that's mainly what they have been used for)they also make a ab verison,but there class c is there big seller.so of the two the ab is the best??is most of the watts they generate on the watt meter just distortion on the watt meter????(need to know) sixkiller505 any tech can step in too. |
Bruce
| | Posted on Saturday, October 18, 2003 - 7:56 pm: |
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my big brick i built 3 years back is class c it runs 300 out with less than 10 watts drive on FM on 29.600 it will not do am/ssb at all i tried it on 28.350 and it sounds aufull...... no harm tring at redused drive |
ss8541
| | Posted on Sunday, October 19, 2003 - 3:05 pm: |
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here is something for all you class b comp amp runners. the u.s. military does not use class b amps because of crossover distortion in ssb signals. class b operation is very hard to keep because of heat. there is a very, fine line between class b and class c operation. same goes for class b and class ab. this is why you never see any high dollar ham amps that are biased class b.
what i am trying to say, is that if you are concerned about signal purity, don't fall into the class b hype. if class b was so clean, there would be many other amps besides the comp amps biased class b. |
davey jones
| | Posted on Monday, October 20, 2003 - 6:57 am: |
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Find out what transisters the amp uses and then look at the data sheet you can get it at cb tricks. It will tell you what class it was designed for. Some ameritrons are class b.
For cb the best are texas star's they are class ab-1 they run hot. all you have to do is put a fan on the heat sinks and it will talk all day and night. |
Hawk447
| | Posted on Monday, October 20, 2003 - 7:59 pm: |
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What is the difference between AB and AB-1?
Also what is Side Band delay for? |
ss8541
| | Posted on Tuesday, October 21, 2003 - 5:43 pm: |
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davey jones,
all the ameritrons in production at this time operate in class ab2 with the al-82 having the capability to be switched to class c for fm/cw operation.
hawk447,
the ab classification is broken down into 2 sub-classifications. ab1 and ab2. ab1 is biased so that there is very little to no base current. class ab2 is biased where there is base current flow. ab1 is less efficient than ab2.
ssb delay is so that the amp will not 'unkey' between words. |
Hawk447
| | Posted on Wednesday, October 22, 2003 - 6:08 am: |
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Thanks SS8851... I am assuming that AB-1 is better on sideband than AB. I have another question: Is their any diference between an amplifier and a modulator, or is a modulator just another name for an amp? |
ss8541
| | Posted on Wednesday, October 22, 2003 - 9:19 pm: |
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actually ab2 is a little better distortion wise than ab1. but for all purposes what is -called- ab1 for cb use is just as clean as ab2. the main difference between ab1 and ab2 is that for ab2 the driving ciruit must provide power. that is why the export type cb's have the driver as ab1 and the final as ab2(the driver provides driving 'power').
you have to watch some of the so called ab amps on the market. the palomar/boomer 600 is one such amp. it is actually 2 amps in 1 chassis. the 1st amp/driver is ab, and the main amp(4 'pill' final) is class c. so really the amp is class c. it doesn't matter what starts off the chain but what finishes the chain. yes the distortion here is less than if both amps were class c, but the last part is class c and that is what matters. and the funny part is that it is one of the only amps that stresses 'ab1' on the face of the amp. its almost like they are trying to hide the fact.
their really isn't a difference between an amplifier and a modulator. both take a signal and boosts its level. but what makes the difference is how they do that. a 'linear' amplifier is class ab and the input to output ratio will make a straight line on a graph (hence the name 'LINEar'). so if you put 2w into a linear amp and got 40w out then 3w in would give you 60w out.
a modulator is class c. a low level in will give a low level output since the the input must first bias the rf transistors on( a.k.a., turn the transistors on). there is no dc voltage to do this, so the input signal must do it by itself. the higher the input power is after this 'turn on' the higher the output will be, but not in a linear fashion. so the same amp with 2w in/40w out above that is linear, may only give 20w out with 2w in if is class c. and then at the 3w in level may give 50w out. the amp is not linear in its input to output ratio.
'modulators' are used to push bigger amps because of its non-linear characteristics. it posses a low carrier and high swing. the perfect combination to 'push' a bigger amp. in all honesty the name 'modulator' is a sales gimic for guys to have something that others do not. if one guy has a modulator, then everyone else will want one also.
the texas star mod-v is one such amp. it is class c and designed to push a larger amp(dx1600). the guys there were careful not to call it a modulator, but yet named the amp in a fashion that 'modulator' was implied. it was designed to 'modulate' a bigger amp. |
neil carrick
| | Posted on Friday, November 28, 2003 - 8:59 pm: |
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Hi..Happy Thanksgiving!!!
Can anyone tell what class of amp a Gray mobile bi linear would be? Please let me know so I dont buy something bad.. Thanks Guys |
Ss8541
| | Posted on Friday, November 28, 2003 - 11:35 pm: |
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every gray i have ever seen is class c and very nasty!!!! |
neil carrick
| | Posted on Saturday, November 29, 2003 - 6:46 am: |
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Thanks...I am glad to know that in advance..I guess I will be ordering the Texas Star instead . |
Sparkomatic
| | Posted on Saturday, November 29, 2003 - 2:58 pm: |
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Actually my Palomar 775 splatters worse than any Class C that I own. I think my 775 is a class AB....that blows that theory out of the water.
I thinks it's "Garbage in = Garbage out" |
Bigbob
| | Posted on Saturday, November 29, 2003 - 6:50 pm: |
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From what I've read on here,all the twin driven boxes are splatter/boxes,they produce their own harmonics no matter how clean the input is,you're basically driving a 400 with a 250,would any body in their right mind try to do that,now double up on the finals and you would really have something there,2 driving 8,but thats still a little high,1 driving 8 would be best,basically what you get with a 2995 driving a dx1200 or dx1600 all the watts in the world aint wuth it if you be p e e ing off all your neighbors.Bigbob |
Adshar64
| | Posted on Sunday, November 30, 2003 - 2:10 pm: |
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A extemely detailed explanation is given in the amplificationclasses.rtf file at;
yahoo.com/group/Tube_Amps/
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Ss8541
| | Posted on Sunday, November 30, 2003 - 2:22 pm: |
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sparkomatic,
no 'theory' blowing out of the water here. physics is physics. that is why classes of amplifiers exists. each have their own characteristics.
as for your 775 being nasty, bigbob has the answer. you must consider that your 775 is a 2 driving 4. that is beyond overkill on the driving end. this is the answer to why it is so nasty, excluding any class it may be. |
Sparkomatic
| | Posted on Sunday, November 30, 2003 - 4:00 pm: |
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Actually the 775 bleeds worse but sounds loud and excellent. |
Ss8541
| | Posted on Sunday, November 30, 2003 - 6:16 pm: |
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i don't doubt how the amp sounds at all. i and bigbob, was just letting you know why it is such a splatter box. there could be other possibilties, like the 1st stage is ab and the 2nd stage is c. i know that the palomar/boomer 600 is like this. i haven't seen the 775 yet, so i can't say. but without seeing it, i still know, as does bigbob, that the 2pill driver is a little overkill.
with the 2 driving 4 it should also walk over just about any other 4pill due to the high carrier it will produce. this high carrier will also cause it to heat much faster, so be carefull with how you use that beast.
and for the record, i'm not knocking this amp at all. i am just providing an answer to an observation of a poster. an observation that has roots in the design of the amp itself. does the amp work well???? i think sparkomatic answered this himself. |
neil carrick
| | Posted on Tuesday, December 02, 2003 - 7:04 pm: |
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Hello... What info can anyone give me on a Palomar Magnum? It is supposed to put out 250 watts.
I assume this is on ssb. Is this a decent amp or should I steer clear of it in regards to quality, class of amp....etc. Thanks Neil |
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