I’ve built 99% of this project but to finish it I’d like advice on the "Important Note" that's part of the project download file. Item 2 says:
"IMPORTANT - late testing led us to discover a problem with the BNC input circuitry which affects readings at higher frequencies. Therefore we recommend the following component changes:
a) remove the 100pF SMD capacitor connected to pin 25 of the Explore 100 I/O connector. This is just to the left of CON2 and above IC6.
b) solder a BAV99 SMD diode across the now empty pads provided for that capacitor, with its pin 1 close to IC6 and its pin 3 (middle pin) to the pad closest to the I/O header."
I am confused because:
1. The 100pF capacitor in the feed to pin 25 is from the output of IC5 and the high-frequency (i.e. SMA) input. So is the reference to the "BNC input circuitry" a mistake, only the BNC input circuit feeds through a 100pF capacitor from IC6 to pin 22?
2. The description in the second part of (a) above more closely matches the 100pF capacitor in the feed to pin 22.
The annotated PCB layout shows the components I’ve mentioned.
This “Important Note” does not appear as a correction on the Silicon Chip website. The (E)PE Editor hasn’t been able to provide any advice. Can anyone who has built this help?
"IMPORTANT - late testing led us to discover a problem with the BNC input circuitry which affects readings at higher frequencies. Therefore we recommend the following component changes:
a) remove the 100pF SMD capacitor connected to pin 25 of the Explore 100 I/O connector. This is just to the left of CON2 and above IC6.
b) solder a BAV99 SMD diode across the now empty pads provided for that capacitor, with its pin 1 close to IC6 and its pin 3 (middle pin) to the pad closest to the I/O header."
I am confused because:
1. The 100pF capacitor in the feed to pin 25 is from the output of IC5 and the high-frequency (i.e. SMA) input. So is the reference to the "BNC input circuitry" a mistake, only the BNC input circuit feeds through a 100pF capacitor from IC6 to pin 22?
2. The description in the second part of (a) above more closely matches the 100pF capacitor in the feed to pin 22.
The annotated PCB layout shows the components I’ve mentioned.
This “Important Note” does not appear as a correction on the Silicon Chip website. The (E)PE Editor hasn’t been able to provide any advice. Can anyone who has built this help?
Attachments:
-
forums-6ghz-fm-pcb-layout-markup-1.jpg
(186.1 KB)
You must be logged in to download this attachment.
