Signals appear multiple times

[pe2bz]

Hi Ben,

Brian (bpadalino) has tracked this down to a ferrite bead on the board. Removing it and shorting its pins appears to work around the issue; a number of kind folks on our IRC channel have made this modification and reported that they too see that the spurs no longer occur.

As I don't know FB on the board needs to be removed off the top of my head, I've asked bpadalino to add this to a wiki page, which I will link from here for you.

Best regards,
Jon

Hi Jon,

any link available for me ?

Kind regards,

Ben

[jynik]

Hi Ben,

I sincerely apologize for for the delay. Brian hasn't posted anything up yet regarding board mods, as he's still investigating further.

However, so far it seems that FB12 is one major culprit; there's still some analysis ongoing WRT FB11.

We've found that replacing FB12 with a 0 ohm resistor (i.e., a short) addresses these 200 - 250 kHz spurs. This is shown below:

bladeRF_fb12_shorted_mod.jpg

Here's a couple captures with and without the modification (with no calibrations or corrections applied). Note that these are two different boards, so there may slight deviations between them. (i.e., differences in the noise floor or other attributes are not necessarily related to the change.)

Without the modification:

without_mod.png

With the modification:

with_mod.png

Let me know if you have any questions!

Best regards,
Jon

[pe2bz]

Jon,

I have had email contact with Brian who helped me out of my problems.

I replaced FB12 and Z6 and Z7 with a drop of SN40PB60

Now, I don't see the "spurious" anymore and I can see weaker signals near stronger repeaters instead of 4 times the strong repeater.

It bothered me a long time but now it's gone.


Thanks for the support !

Ben - PE2BZ

[jynik]

Hi Ben,

Sorry for the trouble, but thank you for sticking with us and writing back to confirm your results! The team's working to have these components changed moving forward.

Cheers,
Jon

[kk6rum]

Does this issue affect all boards? And is the remedy the same if so?

[jynik]

All boards shipping from current inventory should have had the FB12 removal modification. If you see an ferrite bead instead of the 0-ohm resistor, then yes, you should remove the ferrite bead and replace it with either a 0-ohm resistor or short (solder blob, jumper with a piece of wire/component lead, etc).