Borrowing an FT-847 and getting back into using some HF data modes at home. Quickly put up a HF antenna along the house under the gutter, with about 8 metres of wire fed through 9:1 UnUn and LDG auto ATU.
I changed to a 470nF which I got out of an ADSL filter. The FT-847 manual shows a recommended 2.2K resistor to pull the PTT circuit low. The 470nF and 2.2K would give a cut off frequency of around 150Hz as a high pass filter, just about right.