Hi Lou, If the transformer was of the same size but without a secondary, with all the space devoted to the dual primary, then you could draw twice as much power from the center tap as you can from yo
Hi Dave, Peter, There are many consideration, but saturation is NOT one of them. The tank inductor in a classical tube amplifier sees no DC, and at HF all magnetic materials in existence will melt do
Hi Tom, A pretty easy and good way to dry out a transformer is simply to apply low voltage DC to one of its windings, to warm it up from the inside. A transformer for a linear amp might need somethin
Hi Wayne, It depends on the actual operating conditions. But for typical conditions, yes. I can't help making a somewhat pedantic correction here: A transformer that is unbalanced both at the input a
Hi Frank, Bad idea! No surprise there. And the power that's heating those wires is RF power that doesn't make it to the antenna! A perfect coil has exactly the same current all along it. If there is
Hi Gary, and all, years ago I wrote a little program to calculate air-core coils. The program will both calculate number of turns for a desired inductance and dimensions, and calculate the inductance
Hi Dave, even if I come in a few days late: No. Nowadays the laminations most often come from the factory with an insulating coating. Several types of coatings are available. One of them is what they
Frank, The NCL-2000 indeed works quite hot. The reasons: It is designed for a very high idling current, which results in excellent IMD but lots of heat; and it doesn't have chimneys on the tubes, so
Hi Carl, Ouch! My mistake, sorry... Mine doesn't... And didn't. As I got it, it idled at 200mA in SSB, and no idle current in CW. In CW mode it required a drive above a few watts to START delivering
Hi Peter, Wasn't it 25W, or was that only for ICAS? Interesting. I hadn't done such a comparison, and indeed the idle dissipation is high on all of them! But in checking data sheets, I found some int
Hi Dan, and all, I will try...! The "red" material is powdered iron with a permeability of 10, while the 43 material is ferrite with a permeability of 850. The two behave quite differently, not only
Hi Dan, These loss figures seem very high. And I cannot make much sense of the test setup you describe. It would be interesting to know how you measured the loss, in terms of which configuration you
Hi Bill, Not really. The 3300pF also has metric threads, but larger than those of the 470pF one. These are M5 threads: 5mm nominal diameter, 0.8mm pitch, 60 degrees. It just happens that the 10-32 sc
Hi David, and all, Oh well, I was trying to stay out! So much for that... Making a properly regulated switchmode power supply isn't really hard, but it requires a good understanding of feedback loops
Hi Dan, Such extreme noise would be strongly driving the transistors, fully into saturation! Are you sure you really have that much noise on the bias? That's a big mistake. To bias bipolar transistor
Hi Dan! In that case it's good to use pretty large diodes, so they can take a large current while their voltage drop is still relatively low. I typically use 3 ampere rectifier diodes for biasing 30
Hi Dan, The output impedance is a rather simple matter. If you like simplified formulae, take the output impedance as the square of the supply voltage divided by twice the power. And for the impedanc
Hi Dan, What are you tracing, exactly? Collector current versus base voltage, or what? At what collector voltage, etc? I would think that the first transistor you traced isn't nearly as heavily balla
Hi Dan, I'm not familiar with that curve tracer, so I can make only partial sense of the above. Does it mean that the tracer produces a family of collector current/voltage curves, for base currents s
Hi Dan, So no surprise there. It must be ballasted, like almost all RF power transistors. Yes, do that. You don't really need the curve tracer for that. Just a single point measurement, done with a p