(tr)uSDX Forum

No!
R shunt is the pcb resistor for efficiency calculations!

73 de Chris

Hello OM, there could be a ground loop between gnd of USB and gnd of your power supply originting from capacitive coupling or other coupling. There was also a trick to do in Linux, but as i remember it was only for JS8Call, please search a little bit in the forum therefore. To get rid of a gnd loop,...

Hello OMs, i would not buy a switching power supply for use with (tr)uSDX because they are not really super good in "no ripple on output" olympics :D Meanwell is a well known good supplier for switching PSUs but: I would simply use a battery as Manuel supposes a 3 x 18650 LiIon or a 4 x Li...

Hello OM,

Clicking at QSK can not be avoided 100%.
But i think you know QSK is a very useful thing...
So as described you can switch to semi QSK (about 500ms delay to switch to rx again, not adjustable)
but i prefer QSK to hear what's going on

73 de Chris

Hello OM, if you buy as private importer into EU from a foreign country up to 150 Euro, you only have to pay VAT. VAT is standard added normally already at the chinese shop, so no extra for you. But if your amount is larger than 150 Euro you have to pay full customs fee!!! So you bought things for 2...

It was your fault to buy FDT86256 there: Any semiconductor also an FDT86256 won't be killed by a customs xray scanner never ever! We told everybody not to buy FDT86256 from any chinese supplier.... it is nearly 100% sure that all these "FDT86256" are not FDT86256 :( Only buy these FETs fro...

Hello OM, sounds like bad solder joints at toroids, maybe only at T1 and T2. 99.9% is a bad toroid solder joint, also at SMA connector possibly. Did you switch in Menue to Classic? 0.1 to 0.2W is very very low at start, i can't believe this is really the power. Please check also on extern power mete...

Hello Marco, i have not really an idea. Check all solder joints on Atmega328 and ICs especially, also at OLED I/O. I don't believe it is a bad Atmega328 copy you have in your (tr)uSDX but there are some on the market. At last redo the bootloader and firmware, but seems not the reason if it once work...

Hello Marco, i have not really an idea. Check all solder joints on Atmega328 and ICs especially, also at OLED I/O. I don't believe it is a bad Atmega328 copy you have in your (tr)uSDX but there are some on the market. At last redo the bootloader and firmware, but seems not the reason ift it once wor...

Hello Marco,

we have no 2524 firmware....
are you sure you are right here? this is only for (tr)uSDX no other trx or device here!

73 de Chris

Hello OM, totally wrong programmer choosen! should be .... -c avrisp you used -c arduino Arduino is with the "as ISP SW" now an AVRISP programmer... You now shot maybe everything, maybe not and flashing will correct all. If you have flashed something wrong to the flags your Atmega328 will ...

Hello Marek, R-shunt has nothing to do with SWR reading!!! R-shunt is the shunt value to measure the current on TX and is therefore only responsible for a correct current calculation and gives due to this a correct efficiency value on the display. R-shunt is a line on the PCB and differs as Marek sa...

Hello OM,

i can't understand how that happend with C8? Did you power it up by 5V USB or 12V or higher voltage?

73 de Chris

Hello OM,

it never breaks away on any of my (tr)uSDX!
So i think there is more a problem of how to handle at your side. If properly soldered very solid fixed to the pcb, but you can't pull your car with it

73 de Chris

Hello OM, is the damping value in passband around what DL2MAN measures? Check all your solder points when not! Number of turns.... Wrong band setup choosen Lo, High, Classic? Did you switch to the band before measuring? Are you sure VNA is callibrated before and connected right? I see no other possi...

Hello Sepp,

it's closed source! Everybody who is really interested can read this...
I will close this thread.

73 de Chris

Hello OM, yes there must be a harmonic notch, did you switch to the band before with rf board connected to main? Check all solder joint on T1/T2 and all Lx in lpfs on solder side and on component side if they look good soldered and connected. ...and yes you can extremly easy kill your PA FETs by sen...

Hello OMs,

best to cycle standard LiIon batteries is 85% to 20% (or up to 30%) for a maximum of lifetime in cycles and capacity.

My 2 Cents
73 de Chris

@SP3ML, Check Q1 because 74cbt3253 is only in rx circuit used chip, but it is cut off from antenna/lpf by Q1. So what you explained sounds like a defective Q1, could get damaged by ESD during receive. Your USB / 12V phenomenon is due to not isolated USB and is maybe a ground loop problem.... 73 de C...

Hello OM,

the swr getting higher with frequency looks like an error in the dummy load for me,
for example inductive component from a wound wire resistor in it.....

73 de Chris

Hello OM, maybe the connector you use is not the right one. Mine has no "dip" with smaller diameter at the beginning and now all is okay. I had the connectors with the small diameter "dip" and they did as you describe very bad ... I don't know if your supplier offerded it, but no...

Hello OM, i change the title, because 1:1.5 swr is not a high swr you are joking... it is 4% of power reflected.... I think the reason can be also your dummy load! Many dummyloads have about 55ohm to 60ohm when they are cold so that at high power, when warm, they decrease to around 50ohm. You can ch...

Hello OM,

check your solder joints in the 40m LPF.
If you get normal tx power on other bands than this can be the reason.
Maybe stray rf on 40m because of bad rf ground/common mode problems could also
have an impact.

73 de Chris

Hello OM, all of your solder joints are "cold solder joints" = very bad soldered with no real contact. Additionally i can see wire parts getting out of solder points and touching other pcb structures/lanes, this is an absolute no go on rf circuits! So please first practice soldering with s...

Hello OM,

when you have a usdx than this firmware is not for your hardware!
Maybe you only forgot (tr) ... in the name.

73 de Chris