Thanks to all for the information. The way everyone explained it makes perfect sense. Besides putting up the better antenna, I think the better way is to get a viking 2 or similar radio and get the 125 watts without having to purchase the linear.
73s and thanks again, Paul From: "John Coleman, ARS WA5BXO" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Saturday, December 20, 2003 11:48 AM Subject: RE: [AMRadio] Looking for Linear Amp > The Ranger, Viking, DX100 and the 32V3, etc. rigs are running Class C > finals using plate modulation. They do not have an RF linear amplifier > in them. Being a new comer you may not be familiar with the pros and > cons of linear verses class C. I will try to stir up some interest here > in maybe home brewing a larger rig but first you need to now a little > about what you might build. Rigs such as Yasues, and Kenwoods, and > other more modern SSB type, "Rice Box type" to coin a phrase, including > the ones that have an AM mode, have small linear amplifiers built into > the box. The modulation is done at a very low level (less than a watt) > then the whole envelope (carrier plus sidebands in the case of AM mode) > is amplified by the built in linear amplifiers to a 20 - 150 watt level > depending on the mode and rig. These rigs may use a pair of 6146s for > the linear amp outputs running in class AB1 or AB2. In the case of the > Rangers and others the RF carrier is amplified using non linear class C > circuits. We don't care if the amplifiers have a lot of RF distortion > in the carrier because each stage is tuned with a LC circuit that > removes the distortion and puts the output of each stage back to a pure > sine wave at a single frequency of RF. Prior to tuning, these stages > are rich in harmonic distortion because of the clipping of the current > in the tube's class C biasing. They even tune some of the lower level > stages outputs to the second harmonic so that, for example, the VFO may > run on 1.9 MHZ and the output on 3.8 MHZ. At the last stage of class C > amplification, the signal is tuned and matched to the antenna line. The > carrier that is produce here is modulated by varying the plate supply > voltage to the output stage (6146), with the audio wave form. This > requires a high level audio amplifier (also built in the Ranger box). > This audio amplifier is similar to any PA type amplifier with the > exception that it's output XFMR is not designed to drive speakers but > instead to match the impedance of the Class C final (6146), > Ep/IP=Zmodulated. This is high level modulation. The Class C finals > are good for CW, FM and AM high level modulation because of their high > plate efficiency (70 - 80%). There or efficient because they don't > spend much time between cutoff and saturation. Much like a switch that > doesn't get hot as long as it is all the way on or off. But if you > replace the switch with a normal variable resistor to try to actually > control the level of output power then the resistor will produce a lot > of heat. The power of the heat dissipation in the resistor plus the > delivered output power is equal to the total input power. The linear > amplifiers work similarly as for as efficiency is concerned. This does > not mean that they are not a viable answer to you needs. The class C > rigs of a few hundred watts require a large audio amplifier for the > modulator. For instants, you might use your Ranger in CW mode to drive > a pair of 812s in class C mode at a plate input power of 400 watts. In > class C at this level, these will produce about 300 watts RF output and > dissipate 100 watts in heat. You will need at least 200 watts of audio > to modulate the 400 watt DC to the finals. This could be produce by a > pair of 811As for modulators. You will need a modulation XFMR, filament > XFMRS of finals and modulators. Enough plate voltage supply to power > both modulator and final. You will also need the audio preamp stages > for the modulator unless you plan on extracting the audio for the Ranger > since it is not being used in the Ranger. Remember the Ranger in CW > mode, is their to produce a carrier to drive the 812s and you only need > 10 to 20 watts to do that so the audio circuitry in the Ranger is idle. > I believe it has jumpers on the ACC plug that can be modified for this > purpose. A linear on the other hand uses the AM output of the Ranger > and requires on audio of its own. Simplicity trade off for plate > efficiency. As to which ay is best for you depends, on what's > available, your space, and what you want to learn. > > Good Luck, > John > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Paul Sokoloff > Sent: Friday, December 19, 2003 9:30 PM > To: [email protected] > Subject: Re: [AMRadio] Looking for Linear Amp > > Hello again, > I had no idea I was going to stir up such an interesting discussion. > I > was the person who originally posted this. After reading all of the > replies > and as a newcommer to this, I have one question. If one needs an 800 > watt > amplifier to run 100 watts AM, then how does a Viking with 3 small 6146s > run > 125 watts AM? > I have a Johnson Ranger (45 watts with one 6146) which I wish to > drive > an amplifier for more output (maybe 125 to 150). Should I just get a > viking > 2 or an amplifier? Does anyone have an amp they are interested in > selling? > Thanks, > > Paul WA3GFZ > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio > > > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio >
