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Ted, I am a bit lost too! In previous posts there was an inquiry for heat map of BN43-202 binocular during tx so I had those flir photos of my design which guves similar tesult as QDX. I thiught this

Mine runs cool. Or at least, I haven't noted any heat of significance. Low current draw if it's running right, should mean little heat. Are you running it from USB or an external source? Brock

Hi Barb Assuming that the current consumption is per spec (c.650ma on TX) wouldn't you expect this sort of heatmap after a continuous 5 minute transmit? It looks like the design is working just

Chris, & all here, Here is a fun exercise: Assume that no commutating diode is present at L14 in QDX, and that, for convenience, the PA is drawing 1A through L14. Then at the moment the last BS170

Roger, Fed with USB 5V? Mine takes around 30mA. Shows as a COM port? Mine seems cool but difficult to tell the way it is mounted. 73 Alan

You do realise that the diodes between the source and drain of the BS170s in the QMX schematic (D503 and D504) are place holders for Zener diodes? You need something like 1N4756 47V Zener diodes

Sure thing, Chris. Simulation at 25 ohms (2:1 SWR) shows each BS170 dissipating about half a watt, so there is some margin. JZ <chrisrey1@...> wrote:

I put together my class D PA inspired from QDX PA. It is using the same BN43-202 with 3:2 winding ratio. Here is FLIR images to give an idea of heat distribution over pa mosfets and BN43-202. This is

Jim: I'm trying to increase my CW speed, but I've fallen behind a little because of the T41 project. That said, using the Farnsworth method just proves that the way I learned Morse code for my Novice

“ I was able to obtain a Mirage MP1 which was checked against an?accurate station monitor. “ Dave Morris that looks a good instrument ?I expect you have the manual but just in case (and because

Farnsworth! I'm in a Morse class right now, and we're learning characters at 25 WPM timing, and 5 WPM spacing. That timing is a little bewildering to me, because I learned code 30 years ago at 20

On the subject of heat, the ProgRock2 gets very hot...too hot to touch. Is this usual?

I'll second the use of an absorptive bridge - about no contact with high mismatch that way. Just don't go and leave it in the "tune" position and wonder why the replies are very few and spaced out

Jerry, The diodes in the QMX schematic are Zeners, NOT 1n4148.? Also, the single 1n4148 for the QDX protection is across L14, the RF choke that feeds power to the finals.? My simulations have shown

John Z Thanks for your response. Looks like steady state SWR of 3 will heat the BS170s to their PD limit, so I *assume* SWR <2 is OK. Transients from an auto tuner that can be as high as SWR of 10

Matched antenna sounds good, but I (and a lot of others) use temporary antennas in portable settings. I just activated in a national park yesterday and there was no way to put up a matched antenna.

John, If you decide to test IC5, I would strongly suggest that you remove the BS170s and reduce the supplied voltage to 7 volts.? While trying to do that diagnostic, I destroyed the processor on a

It is very tempting to use RD-16 transistors, but how to create the necessary bias on the gates without complicating the circuit? With a direct replacement as for IRF-510, the RD-16 transistors will

"I have just added 1N4148 diodes as in the QMX schematic." Wut? JZ

*Which Final FET Fails?* My low band QDX has just failed for the fourth time. ?Each time only Q9 has failed (shorted D-S). ?No other parts have been replaced. My high band QDX also failed once,