Re: [Elecraft] Class - A operatiom (was K3 #441 received)
Jim <[EMAIL PROTECTED]> wrote on Thursday, February 21, 2008 at 2:03 AM: > It only takes a little bit of nonlinearity to create distortion products. For example, suppose an amplifier with 100W output has enough nonlinearity to produce a distortion product that is 1 watt. Such an amp's distortion is only 20dB down. To reach 40 dB down, (.01%) the distortion product would have to be only 10 milliwatts. Not to be forgotten are the distortion products generated by the exciter. A perfect distortion free linear amplifier driven by an exciter whose IMD products are only 30db down will produce an output with products down 30db approximately. A case of 'garbage in - garbage out'. 73, Geoff GM4ESD ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Class - A operatiom (was K3 #441 received)
In a message dated 2/20/08 11:29:20 AM Eastern Standard Time, [EMAIL PROTECTED] writes: > isn't Class A not very efficient? That depends on how you define efficiency. First off, an ideal Class A amplifier that is not overdriven and is dealing only with symmetrical waveforms draws the same DC power regardless of signal level. That means its efficiency goes up and down with signal level. Also means that the amp must be capable of dissipating the full DC input with no signal, or at low signal levels. At full power, when amplifying sine waves, an ideal Class A amplifier can deliver 50% efficiency. IOW, on CW or FM/FSK, an ideal Class A amp can deliver 1 watt of RF for every 2 watts of DC. So even at full power and ideal conditions, a Class A amplifier dealing with sine waves has to dissipate half the DC input. Of course in the real world you don't get ideal efficiency. 35-40% overall is very good - I don't know if manufactured rigs are that good. You can get more power out of class AB1 or AB2 but you have to keep to the > linear portion of the curve to avoid distortion. I guess what is happening > is that the rigs are not keeping to the linear portion of the curve because > of over drive by the operator or by the circuitry to compensate for something > or other. A linear amp has to operated in the linear part of the curve. > Right? So, what are these rigs doing? The "linear part of the curve" is pretty limited for real-world devices. Yet to get max power, the whole curve is used. It only takes a little bit of nonlinearity to create distortion products. For example, suppose an amplifier with 100W output has enough nonlinearity to produce a distortion product that is 1 watt. Such an amp's distortion is only 20dB down. To reach 40 dB down, (.01%) the distortion product would have to be only 10 milliwatts. 73 de Jim, N2EY ** Ideas to please picky eaters. Watch video on AOL Living. (http://living.aol.com/video/how-to-please-your-picky-eater/rachel-campos-duffy/ 2050827?NCID=aolcmp0030002598) ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Class - A operatiom (was K3 #441 received)
On Wed, 20 Feb 2008 08:28:13 -0800 (PST), Lee Butler wrote: >Augie's report on on Mr. Sherwood's remarks were quite interesting. The last >remark concerning poor transmit specifications interested me. > >>From my days in Vo-Tech Electronics in High School some 40 years agoisn't >>Class A not very efficient? You can get more power out of class AB1 or AB2 >>but you have to keep to the linear portion of the curve to avoid distortion. >>I guess what is happening is that the rigs are not keeping to the linear >>portion of the curve because of over drive by the operator or by the >>circuitry to compensate for something or other. A linear amp has to operated >>in the linear part of the curve. Right? So, what are these rigs doing? > >If I remember correctly, isn't Yaesu's FT9000 or FT1000XXX has a button that >allows Class-A operation? The FT-1000MP rigs have Class A capability. I always excited my Alpha 87A in that setting in both CW and SSB. I think the newer high end Yaesu rigs have it too. > >What rigs run Class A? > >How does that sound on the RX end and what do you give up on the TX end? >Power out? > >Interesting discussion with Mr. Sherwood's Data and comments. > >Lee - K0WA > > > >In our day and age it seems that Common Sense is in short supply. If you >don't have any Common Sense - get some Common Sense and use it. If you can't >find any Common Sense, ask for help from somebody who has some Common Sense. >Is Common Sense divine? >___ >Elecraft mailing list >Post to: Elecraft@mailman.qth.net >You must be a subscriber to post to the list. >Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > >Help: http://mailman.qth.net/subscribers.htm >Elecraft web page: http://www.elecraft.com Tom, N5GE - SWOT 3537 - Grid EM12jq "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." --Benjamin Franklin 1775 Support the entire Constitution, not just the parts you like. http://www.n5ge.com http://www.eQSL.cc/Member.cfm?N5GE ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Class - A operatiom (was K3 #441 received)
Augie's report on on Mr. Sherwood's remarks were quite interesting. The last remark concerning poor transmit specifications interested me. >From my days in Vo-Tech Electronics in High School some 40 years agoisn't >Class A not very efficient? You can get more power out of class AB1 or AB2 >but you have to keep to the linear portion of the curve to avoid distortion. >I guess what is happening is that the rigs are not keeping to the linear >portion of the curve because of over drive by the operator or by the circuitry >to compensate for something or other. A linear amp has to operated in the >linear part of the curve. Right? So, what are these rigs doing? If I remember correctly, isn't Yaesu's FT9000 or FT1000XXX has a button that allows Class-A operation? What rigs run Class A? How does that sound on the RX end and what do you give up on the TX end? Power out? Interesting discussion with Mr. Sherwood's Data and comments. Lee - K0WA In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine? ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
