[Elecraft] Microham Microkeyer II, RFI in mike with my K3

[john at kk9a.com]

This week I wired rewired my MicroHAM Micro2R cables for K3S's.  As I
recall, I used pin 7 for the mic ground and pin 8 for the PTT ground. In a
brief test it worked ok into a dummy load. Is this not correct?

John KK9A

Bernhard.Horst at bmw.de Bernhard.Horst at bmw.de
Fri Feb 12 01:43:33 EST 2016

Good morning gents...

I have RFI in the mike since using the Microkeyer II from Mikroham.

Mainly on 20m and the lower bands when transmitting with about 700watts
and above.

My antenna is about 5meters above the shack on the roof of my house (2 el
Ultrabeam), but the effect also can be observed on the lower bands where
the vertical is about 12 meters away from the shack. ==> Direct RFI?

I am using the front mike jack on my K3 and Microkeyer

- I have put a capacitor across USB and connector ground in the Microkeyer
as recommended by Microham.

- All devices are grounded on common ground and same wall plug.

- I have extra grounded my PCs ground with USB ground as the resistance
was not good enough..its now 2 Ohms USB between USB and connector ground.
Also recommendation by Microham.

- Bought an extra shielded USB cable and put ferrite cords on.

- Mic line is shielded and ferrite cords in every cable and line

- Common mode chokes at the antenna feedpoint and also at the end of the
coax going into the shack.

- Pin 8 of the mike jack is not connected. See
http://elecraft.365791.n2.nabble.com/K3-quot-RF-Feedback-quot-and-microHAM-MK2R-or-microKEYER-II-td1080853.html

Microham is stating on their website that it has to do with the wiring of
the K3 mike lines in the frontpanel..

I am really lost and helpful for any ideas. Is there an alternative to
Microham?

Thinking about going back to my old USB interface, but integration of
Radio, Software and Ultrabeam is really nice

We had a similar issue on our clubstation and could cure it with
ferrites...on a YAESU rig.

Any hint is appreciated..and thanks for quick feedback as usual.

Already dropped a line to Elecraft support if they have some hints...

I am glad the effect does not show on CW :-)

Many thanks in advance.

Best 73s
Bernie
DL5RDP