#u3s #wspr Resets on 10m when RF adjust above about 50mW #u3s #wspr


Rob Giuliano
 

I have the U3S and relay board with modules fro 10m, 156m, 20m, and 40m with 10m always in the circuit.
I have tried several options to adjust the output to above the 50mW on 10 meters ONLY:
1. Use the 5V supply for both PA and uP.

With this setup I was able to adjuct the power to almost 200mW, but as I adjust the bias to increase output, the LCD dims, and then the module resets.
If I adjusted the output to about 50mW (or just above), before it reset, the module would reset on next 10m TX.
So I thought separate PA and 5V microprocessor (uP) regulators would help.

I set the PA voltage 7.6V/3A supply voltage and used the following for the uP:
   a) LM2596 DC/DC buck converter / regulator (3 Amps)
   b) LM7805 Linear regulator (1.5A)
   c) LM1117-5 Linear regulator (1.0A)

Then I thought RF was getting into the regulator(s), so I changed input and output capacitors.
Still reset.

I read where the windingsa on the LPF can have an impact on the output, so I made some adjustments to winding spacing, but thet had no impact.

I noted the 10m module is the only LPF in the circuit when using it this way.
I ordered a 6m module to use as the 'always in the circuit' module to see if that makes a difference.

I have the LCD module controlled brightness configuration and it is set to 7, so next I will try full brightness and and lower brightness to see if that makes a difference.


KEN G4APB
 

Hi Rob,
try a large value electrolytic cap across the uP 5v input close to the board.

73 Ken g4apb 


Rob Giuliano
 

Tried a large capactor for inrush and a small capcitor for RF, neither helped.

Another piece of infomration:
I was running 2 BC170s, but after reading about the capacitance on higher frequencies, I am now using only one.
I am concerned about the one, so I plan on replacing it this evening.


Rob Giuliano
 

I am now running only 1 BS170
I tried a lower (less bright) setting on the LCD with the same results.
Now I am running the LCD full ON.
With LCD ON and 1 BS170, it is an improvement but only in that the uP no longer resets.

When I dial the 10m output above about 50mW, the LCD is blank, but there is still RF output.
However, it only works once, then there is no RF output any more on any band.
I will check have to check to see if I fried the BS170.


Alan G4ZFQ
 

Rob,

I will check have to check to see if I fried the BS170.
It seems no-one has suggested that you are turning the bias too high.
I think the manual warns against this, yes you can destroy the BS170.
The warning signs were when the display dimmed, too much current taken from the PSU.
The bias control is not a power control unless you want to reduce power from the optimum bias setting, where the monitored current consumption just starts increasing.

73 Alan G4ZFQ


KEN G4APB
 

Hi Rob,
another thought, can you monitor the 5v line to the uP to see if it is dipping? If you have tried running the PA devices from a separate psu, then it should not affect the display. Are you using the unit cased? If so, make sure you have an an actual earth (-ve) wire from the boards back to the psu,i.e don’t rely on chassis connections for the -ve return.
73 ken g4apb 


Rob Giuliano
 

On Mon, May 3, 2021 at 10:05 AM, Alan G4ZFQ wrote:
Rob,
The bias control is not a power control unless you want to reduce power
from the optimum bias setting, where the monitored current consumption
just starts increasing.

73 Alan G4ZFQ
Running off the 5V power, I get ~50mW output. No resets.
Previous posts had other users reporting higher output on 10m than I was getting.  This is why I thought I could do better, so I started looking for ways to get that.
There were suggestions of using 8V for the PA.  I had an adjustable 45W wall wart with output options of: 5, 6, 7.5, 9, 12, 13.5, and 15V at max 3 amps.

I changed to the 7.5V for the PA (different regulators for 5V discussed earlier). 
When the bias control was set at a value I was comfortable with (about 600mW on 40m), all was great until I turned on 10m and the unit reset.
When I adjust the output on 10m such that it doesn't reset (~50mW), there is no benefit in the increased PA voltage. 

My desire would be about 100mW on 10m.  Whatever power is output on 40, 20, and 15m would be acceptable.
If I am limited to 50mW, then I will switch back to 5V for PA and uP and go with it.


Alan G4ZFQ
 

My desire would be about 100mW on 10m.  Whatever power is output on 40, 20, and 15m would be acceptable.
If I am limited to 50mW, then I will switch back to 5V for PA and uP and go with it.
Rob,

That's about what I get, 100mW @ 5V. Measured with a calibrated meter.
Are you sure you are measuring accurately? It is not easy to be certain of such low powers.

What happens at a higher voltage is strange. Does the current rise? Measuring the current taken is a good pointer to what is happening and, as the manual says, is the recommended way to set the bias level. Simply set your multimeter to mA and connect in series with the PSU.


73 Alan G4ZFQ


Rob Giuliano
 

SOLVED!!!
With Alan's comments, I decided to look more closely at the power supply side.
It appears I should be able to run with 5V get what I want.

As I was checking the power connector, it appeared my original jack was not making good contact. 
I could pushed the power connector in a little and the connector seemed to be a bit flacky.
I replaced the connector with a screw on (locking) 2.5x5.5mm connector.
I replaced the BS170 (again - just to be sure) and made the bias adjust measuring the current as described in the manual (anb by Alan).

I am now measuring about 100mW on 10m.  Now to go back through and see the output on each of the bands (10m, 15m, 20m, and 40m).

I am feeling much better now!
Thanks for all the help!
73 Rob KB8RCO