Power supplies are never easy.

Correct words if ever spoken.

I have little experience with critical onboard supplies other than getting the pinouts wrong but see it coming.

The newer chips are far more critical as to components and layouts which is evident by the increased number of pins.

Hope to learn from you. I have to become more observant of the spec sheets.

Most of my power supply work is with things that go bang and release much smoke when they go wrong.

I will never become accustom to that sound! I have six here that were donated and a few need work.

As the to board when it arrives, I’ll get the transmitter output under control and will look in the code for ‘other’ places that might set the value.

Then we can talk about testing the PA. Want to take bets on smoke?

Again, take your time.

Jim

I think I see the problem with the 5V regulator which has been bothering me. I just looked at the data sheet and it says the ESR of the output cap must be below 1 ohm. The output cap in this case is about .5 ohms but there is a 3.3uH inductor in series and this has a resistance of 1.2 ohms. So either the inductor has to go or be moved or another 10 uF low ESR cap must be added. The the voltage should come up some. The current rating on the inductor is also too low for this design because we are pulling so much current.

Power supplies are never easy. If it's not a voltage issue its noise or heat.

Bob

On Feb 20, 2024, at 8:46 PM, Jim McCullers via pacsat-dev <pacsat-dev@amsat.org mailto:pacsat-dev@amsat.org > wrote:

Bob,

I’ll look further.

Thanks?

Take all the time you need and don’t want to sort out the board to the max before sending it on!

Jim

Jim, There is another place you may be missing and I will have to find it later and let you know. But the code does this by calling a SPI write routine to the AX device and in this routine the value is truncated down to 0xff. However when I tested other values like 0xe0 the thing just stopped transmitting.

I can copy the signal in my lab with 0x0d. Maybe it is increasing power someplace else but I hope not so we can get some more bang.

I plane to ship you a board tomorrow. I thought I was going to get it out today but I kept finding issues on the board I had to fix. This board still has a bit of week power source. The 5V supply is running about 4.75 and the 3.3 is a little low like 3.25. May need the additional headroom from 5V. There is a resistor string on the back of the board that programs the level.

I noticed today that the board did not come up when I powered it and then I removed power and reconnected and that time it worked fine.

The board needs a bit more voltage feeding the preamp on the RX input to get more gain. It is operating with 30 mA and would like to have 60 mA to have full gain. The 3.3V minder chip I thought was set for enough current to feed everything but may need to move the monitor resistor up to allow a full 600 mA.

I did not see these issues on a board I just sent to Chris.

I am ready to share the fun though and instead of continuing to debug and chase problems I am going to send you a setup tomorrow. I may poke at it a little in the morning but not much.

At this point when the board powers up it does transmit and it will receive or at least it will get the rf to the AX5043 inputs. I can see it there.

Your call is programmed into the flash so play with it until you get a programmer.

I will send you a programmer later. Burns is sending me two and soon as I see them and add a connector I will push one on to you.

Bob

_____

From: Jim McCullers via pacsat-dev <pacsat-dev@amsat.org mailto:pacsat-dev@amsat.org > Sent: Tuesday, February 20, 2024 8:24 PM To: 'Pacsat Dev' <pacsat-dev@amsat.org mailto:pacsat-dev@amsat.org > Subject: [pacsat-dev] PacSatSW - Transmitter Power Level

Bob,

Looking at the lastest code I see two places, which is one to many, where the transmit power level is set.

They are:

ax5043-ax25.c Lines 435-436

TxTask.c Line 63 calls radio_set_power() at line 112

They both set the power level to 0x0020 which is very weak.

I don’t see a place that sets the transmit level to 0x0d.

Let me know where you found that reference.

I would suggest setting both places to 0x0FFF for maximum output (+15 dbm)

Jim McCullers

WA4CWI

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