Generating a JSON file from Excel to be read it in Python

I have a quite big Excel file containing several tables.
I was able to serialize them into JSONs using an ADODB.Stream in VBA code:

This is VBA code:

Dim st As ADODB.Stream
  ' create a stream object
Set st = New ADODB.Stream
' set properties
st.Charset = "utf-8"
st.Type = adTypeText
' open the stream object and write some text
st.Open
st.WriteText myString
st.SaveToFile filepath, adSaveCreateOverWrite
st.Close

Now I want to read it in Python to pass it to a data frame with:

This is Python code:

import JSON
with open(myfilecomplete) as f:
    data = json.load(f)

I get this error:

UnicodeDecodeError: 'charmap' codec can't decode byte 0x9d in position 407330: character maps to

The file is quite big (1MB of text). I dont even know how to find character 407330.

Besides I am supposed to be writting in disc in uft-8 the most common encoding form. Right?

Why is JSON not able to undecode utf-8?

EDIT AFTER ANSWER / WARNING: Don't try to serialise a JSON file from Excel manually. this will end up giving errors almost always. Use a proper library for doing that like in here: