Updating older hf amplifier
Having good thermal contact between a plastic FET and diodes is difficult.
So, my brother tasked me with the project to find a place that takes car amps and upgrades their parts to make a say 300 watt amp into a 1000 watt amp. He says it exsists because his friend had two amps sent in and upgraded. So I was curious if anyone on here knew of a site or someone that did this line of work?
Leave the variac at this voltage for at least another 30 minutes.
The older AL811H (prior to drive resistor modification) with good tubes and stable power line, when properly tuned and operating in the linear region, has about 11 d B gain. The largest single problem with significantly greater or less gain (power output) is a poorly calibrated power meter.
Heat is a function of duty cycle and short term average dissipation.
The STW13N60M2 is the lowest gate capacitance available in TO-247, and it's interesting to test a high voltage part against the older generation 100V ones.
I hold also the call sign DK1CG in Germany and in the past I held F5VMW in France.
It is best to monitor the AC current drawn by the unit as it is powered up, which indicates the “health” of the radio or amplifier.
For short periods (IVS service) dissipation can be much higher.811 tubes are designed to be natural convection cooled.
FETs designed for switching power supplies are not ideal but cheap, so I embarked on a project to find a usable part, and make a low-cost amplifier using it.