Humm on hi bands

[ve2rn]

I have a problem with the hi band board, there is a big humm on 10-12-15 Meter bandst he noise is getting louder as i go up on band start at 15 then louder on 12 and more louder on 10 . I have swap the main board with another one and i still have that noise so the problem is on rf board. Also the unit transmit on 15meters on usb without the use of the mic ,it is ok on all other bands. I have check the mod of the display and it is ok on both main boards.All tests are made on battery power and into a dummy load. I need help on this one!

[DL2RMM]

Hello Sylvain,

I`m runnning two hi band (tr)uSDX and had strong hum on both tcvrs, most pronounced on 12 and 10 meters. The noise floor on those bands is lower and the hum becomes audible.
It is not coming from the RF-board but the OLED display. The hum strength changes with the letter count on the display. So, display full of letters = strong hum and display with less letters (i.e. menu 1.8 AGC) almost no hum.

The standard OLED charge pump mod is not taking care of the hum issue on the upper bands.

I changed my tcvrs to the bi-color display (see pic below) and did the 8V regulator upgrade suggested by WA2T.
Running the OLED with 8 volts results in a brighter display with much less hum on the upper bands.

73 de Jens, DL2RMM

[ve2rn]

Hello Sylvain,

I`m runnning two hi band (tr)uSDX and had strong hum on both tcvrs, most pronounced on 12 and 10 meters. The noise floor on those bands is lower and the hum becomes audible.
It is not coming from the RF-board but the OLED display. The hum strength changes with the letter count on the display. So, display full of letters = strong hum and display with less letters (i.e. menu 1.8 AGC) almost no hum.

The standard OLED charge pump mod is not taking care of the hum issue on the upper bands.

I changed my tcvrs to the bi-color display (see pic below) and did the 8V regulator upgrade suggested by WA2T.
Running the OLED with 8 volts results in a brighter display with much less hum on the upper bands.

73 de Jens, DL2RMM

Who is the king here? You are absolutely wright for the letter count on the display ,i have another one hi bands kit and test it and even with my bad earing i can see the difference with less letters, So i can say without testing that i believe you that the 8v mod and two color display will take down the hum level.
Thanks a lot and 73
VE2RN
ps:I will post the final mods results after hunting season when i have time to do the job.

[Luca66]

Is this mod approved by Manuel DL2MAN? I would like to know Manuel's opinion on this mod and its necessity and effectiveness.

[ve2rn]

Is this mod approved by Manuel DL2MAN? I would like to know Manuel's opinion on this mod and its necessity and effectiveness.

Look at the known solutions publish by Manuel
viewtopic.php?t=81

[Luca66]

I had seen the change before when I installed my second Oled, which was burned due to my installation. But I would prefer before applying this mod that it become official in the kits provided by the official sellers.