On 03/08/14 19:12, Lostgallifreyan wrote:
Looks like I might be getting out the oscilloscope and making some
measurements with the PTT down, try to figure out where the RF is
getting in.

Did my post earlier not help? If your equipment has a frame ground and a
signal ground, or perhaps an analog plus a digital ground, that might help.

I did see your post… basically the frame is purely for the antenna
counterpoise, and nothing else.

Yaesu do connect their negative supply to the antenna ground, which
yields a negative earth, however I do not use this for any kind of DC
path. Not intentionally anyway. (It did happen by accident one day:
+12v came in contact and nearly started a fire. Oopsie!)

Unfortunately, I do not get provided with separate analogue and digital
grounds. I suspect in the set they are one in the same.

Yaesu do supply a separation kit: it basically consists of a mounting
bracket for the head unit, a RJ11-RJ11 round cable for the head unit, a
RJ45-RJ45 flat cable for the microphone and a RJ45-RJ45 adaptor so you
can plug the handmic in.

For the RJ11, I have no idea what the exact pinout is. On that cable
would be serial data (tx/rx), power (probably 5V), speaker output, the
"power/fast tune" button and a signal ground. It'd be nice to know
which one is which but I'm guessing Yaesu probably want to keep that secret.

For the RJ45, it's documented in the handbook. There is +5V, signal
ground, open-collector inputs for PTT, Up, Down and Power/Fast Tune,
then microphone + and -. The microphone input is a nominal 600ohm
impedance, intended for a dynamic microphone.

For convenience, I run 3 lengths of CAT5 with DB25 connectors at each
end. At the ends I then plug in a suitable break-out cable which maps
pins on the RJ11/RJ45 connectors to pins on the DB25.

This is because the cables are frequently connected and disconnected,
particularly on the front basket as I park my bike outside. I found
RJ11 and RJ45 connectors became unreliable when they were used in this
manner. DB25s have been good and reliable however.

I did try wrapping this triple-CAT5 cable in adhesive aluminium tape and
grounding that to the frame, but this did not help. I also have fairly
sizeable ferrite cores clipped on.

I could try running a separate screened cable just for the microphone,
I'd probably have to have a separate connector too. I'll have to
procure parts to do this.