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Hello,

I found this article about the spectral purity of the S5153 Clocks signal
Apparently, there is a SetPower command to set the output current.
The spectral purity of the signals can be improved.
This command does not appear to be used in the KD8CEC sotfware.



cdt

Hi Gerard,

It is used in the ubitx_si5351.ino, see extract below.

It is set at 8mA for ubitx V5 so at the right value.?

I tested this setting on a V3 which defaults to 2mA and it improved the Rx and Tx so I believe it should always be set at 8mA regardless of the model.

73, John

On Wed, May 12, 2021, at 02:56 AM, Gerard wrote:

This command does not appear to be used in the KD8CEC sotfware.

Gerard,
The power level for the Si5351 is set in the ubitx_si5351 tab in lines 63 to 67:
=====================Copied Code======================================

Thank's for your answers

have read the artical?
you can translate in English.

his command is different but do the same???
i (we) have to read operational notice AN619? p 19?

cdt

his command:

Evan,?

you are right
the topic has already been raised by Jerry

Re: Raduino mod to use the SI5351C (groups.io)

cdt

Hi John,

How did it improve the RX and TX?? I am interested to try it, and am wondering what you found?

Thanks!


Mark

Mark and all

I tried the opposite way to lower the values for my sound pbs. That did not change anything.
On the other hand, it would be good to look with a spectrum analyzer at the 3 signals clock 0,1,2. Especially see the harmonics.
I can’t do it, my analyzer’s is at this time out of order.
With Evan, we saw that there was still a modulation signal at the output of the SSB filter. Signal that modulates sound at 16 khz. (Ubitx V2,3,4 with KD8CEC version)
If someone may test this.

cdt

Hello Mark,

I arrived at that comparison when chasing the Rx signal difference between my V5s compared to my V3.

The V3 had a lower receive signal (even when using the audio section of the V5 to eliminate any V3 audio section issues).

I found a significant difference in the received signal?(from memory of 7dB) after the first mixer, as measured by my Antuino.?

After spending several hours chasing this issue I found the difference of drive in the software to and set the drive to 8mA for the V3. And voilà, issue fixed.?

I noticed that the output power was also increased.

Note: my V3 has been heavily modified, so this is a sample of one, on a non-standard unit (Axicom relays, extra inductors at the first IF filter, CW unbalance moved to 2nd IF mixer among other changes).

But the test is so simple, so it may be worth trying on older units.

All the best,

73, John (VK2ETA)