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Re: Cooling RPi4 in Sbitx
Thanks for the detailed information. I know that the solution is always in the details.
I noticed that the heat generating components are well placed on the SbitX v2 pcb. It is still hard for me to realize that the device can be protected with control and clever technical solutions. I've always been interested in the line from 'Minima' to 'SbitX'. I especially like the All-In-One endeavor. -- Gyula HA3HZ |
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Re: Needed: replacement PA transformer for sBitx (T8)
As Ashhar pointed out on another thread regarding a T8 failure, the real question is, why did it fail? So after repairing T8 I did some testing. First, power output on all bands was low¡ªabout 1 watt or less. Then one of the finals shorted. Before replacing it I removed both and tested the drivers. The voltages on the collector of Q15 on CW key down was 19V P-P on 80M, 22.5V on 40, then decreasing by band to 4V on 12 M and 2.4V on 10M. These voltages were with Drive=100 and decreased with decreasing drive, and are of appropriate frequency according to the bands. Then the collector voltage suddenly dropped to zero with no ac. The receiver still works and goes silent on key down, and CW side tone persists, but there is zero voltage on the TX line (gate to Q10) on key down. I still see the appropriate CLK2 sine wave at the input (pin 6) of U5, but zero voltage at the output of U5, and no ac, at the output, pins1or 3, and no signal at C68 either on key down or key up.? Then forcing the gate of Q10 to +3.3V gives a oscillation on the collector of Q15 with a DC peak about +14V (the input voltage from my linear power supply) and an rf signal of about 4-5V P-P at an unstable frequency of about 59-73 MHz. This doesn¡¯t change whether or not I press PTT (key down) on CW mode. I understand that forcing Q10 on without any proper rf to the drivers may be causing self oscillation. Please see the oscilloscope screen shot. What should the output of U5 look like? Shouldn¡¯t there be some signal? Does the lack of signal output from this mixer on CW key down suggest that U5 failed? As it happens I already ordered and have replacement FSA3157 parts because I previously saw one burn out (U3) but that was before upgrade #2 with the T/R board, which makes U3 unnecessary. But it¡¯s an SMD part and I don¡¯t want to replace U5 it if it¡¯s working. |
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Re: Raspberry Pi 4 2GB vs Pi 4 8GB
Here are screenshots of loading using htop with the temp monitor enabled in the taskbar.
With the Chrome controls on: With Chrome off: Memory usage never requires swap space, so there is no memory issue with Chrome and the other apps running.? There is a performance issue.? The sound becomes jittery, and the FT8 decodes become erratic. Sorry for the blurry screen blow-ups of the top windows.? I was trying to show the actual values.? The best you can do from these pictures is to note the CPU bars fill the area when running Chrome, indicating there is not enough CPU to run this setup. The DSI screen on the Sbitx is running in this setup: The temperature stays in the low 50s C while running this test.? I should note that the top is off the Sbitx, and the room is 68degF (20degC). 73 Evan AC9TU |
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Re: Raspberry Pi 4 2GB vs Pi 4 8GB
The 2GB model has enough RAM to run the sBitx software comfortably, and to run some other applications alongside it like WSJT-X. Right now, the main time when having more RAM would be an advantage is if you want to create your own builds of the sBitx software; the development software will run better with more RAM. Aside from that, there is no compelling reason to swap the Pis. My DE has a 4GB Pi because that's what I had on hand when I ordered it. (I bought the basic version and supplied my own Pi and display.) I'm not planning to buy the v2 (I got the opportunity to get an mcHF to use as my field rig instead; the DE will stay in the shack), but if I did I would just leave the 2GB Pi inside. On Sat, Apr 15, 2023 at 4:43?PM HA3HZ <gyula@...> wrote: 2GB is suitable for the purpose. |
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Re: Cooling RPi4 in Sbitx
James, I agree with you.
Unfortunately, the construction makes it difficult for me to solve the cooling for several reasons. The heat dissipation of the heatsink shown in the previous message is also unfortunate, because it would be between two mounted PCBs. Therefore, a fan might be a better solution due to free air flow. If you really need it. I accept that it is good to have cooling, so I am looking for a favorable option. -- Gyula HA3HZ |
HA3HZ
John Terrell, N6LN
Shirley Dulcey KE1L