That equates to about 750W of dissipated heat at a dead carrier. With the cost of a good HF capable analog scope price in the basement there is no excuse to not have one mine is an 80's 40MHz Leader that cost $20.Ī pair of 3-500Z's with adequate cooling can run just fine at 1500W PEP using the 375W carrier baseline for symetrical modulation. Get a spectrum analyzer and see what results, I use an ancient 141T system for that purpose.Īssuming the PS and RF components are up to the task the only proper way to tune an AM linear is with a scope which is no different then when it is Class C. Tuning up at say 100W and then dropping to 25W without retuning is a dumb procedure as the tubes load line has completely changed so its going to sound like crap on SSB and AM. There is a lot of that sort of mythology running around. I've read that "rule of thumb" before and it just flies in the face of amplifier specs. I'll admit the 813 is a tough tube and you might do a little better. The rule of thumb is not to exceed 1/2 the total plate dissipation of the tubes. Now continue to advance the loading until the watt meter reads no more than 1/4 the original value. Apply drive power to the amplifier and tune it until you reach saturation. Now reduce drive until the watt meter reads no more than 1/4 the original value.Ģ.
#LK 500ZC MANUAL FULL#
Apply full drive to the amplifier, tune it and note the power output. There are basically two ways to do it (or a combination of the two).ġ. You can't simply tune the amplifier as you would for SSB or CW. Check any of the normal reference books (ARRL Handbook, etc.). As audio is applied, the efficiency will rise, reaching about 60% at 100% modulation. This means that in a static condition (carrier only, no audio) the tubes will be dissipating some very serious power. You have got to provide room for the amplifier to rise to this value. Running a linear amplifier in the AM mode requires over coupling it 400% to prevent clipping of the peaks (splatter) - Remember the peak power of an AM signal is 4 times the carrier power. The L-1000A is spec'd at 375 watts in AM, and that spec is primarily driven by its relatively light power supply and its 13 lb plate xfmr which is primarily designed for SSB service. In addition, I have read quite a few complaints of the L-1000A amp, similar to Darrell's, and can find no basis in facts.