I suspect that the IC-705 users are using an external tuner that is probably designed for a long wire, like the AH-705 or similar. I suspect that the same thing may be at play with the KX2 tuner.
The problems may disappear if you use an external tuner with a connection for a balanced antenna 
(not helpful I know)
I would try a earth connection to a peg in the ground.
Now on the list to try.
You may still be suffering from altitude sickness following your recent GM visitā¦ you sure the KX2/KX3/TX-500/705/FT-817/8 users were behind you and not ahead of you? 
Iām with you on this one Kevin - Tim, Iād run a wire to a small nail or metal stake in the ground and attach the wire to the case of the X6100 as the next option to try from what you have found. Iām surprised that there does not appear to be an earth screw on the X6100ās case, provided for this. Perhaps you can use one of the screws that the support leg hinges around?
73 Ed.
Worth a try, Tim. For me, 100 nF worked (different rig and mic). And another 100 nF from mic gnd to gnd, if applicable.
Ahoi
Pom
Hi all, I have been reading this thread with interest.
I picked up a second hand X6100 on Friday, it has had very little use and is around 18 months old.
At home I have a 134ft doublet fed with 450ohm ladderline, currently 80ft in length but I am going to increase that to 93ft. The ladderline comes right into the shack and into the back of an MFJ969 tuner on the balanced input. I am aware I have RF in the shack and am planning to fit a 1:1 current balun and then run the last 6ft into the shack on coax.
I spent all of Saturday trying to figure out what was wrong with the tx audio on the x6100 eventually realising it was getting RF in the hand mic, internal mic was fine. I am not too fussed what happens at home as I purchased the radio for portable operation. I plan to use a 88ft doublet when portable fed with 300ohm ladderline. I presume I will need a 1:1 current balun on the radio end and a short length of feeder from there to the X6100?
Are there any other solutions to fix this problem. I seem to be ok at home on the 20m upwards.
Regards,
Paul
Hi Paul, @G4HLF
Welcome !
The X6100 suffers badly from RF in the Mic if there is any reflected energy into the casing of the radio, via antenna ground.
I have a common mode choke on every antenna with enough impedance to stop 40m and up. I use about 12+ turns of RG174 coax on a FT114-43. I use RG174 for all my antennas apart from VHF and a 10m vertical where RG58 makes a difference.
Thatās the only reliable way Iāve found with the x6100 SDR.
I did fit an inductor on the microphone cable and that worked. But I just prefer to choke the antennas hard.
Itās a great little radio.
Thanks
Tim
Hi Tim and thank you for the quick reply. I have recently returned to amateur radio after a 20+ year break so have some catching up to do, please me patient 
Hope the following makes sense. For portable operation I would like to use the 88ft doublet with a 300ohm ladderline feeder. On the radio end of the ladderline I was planning on putting a 1:1 current balun which is 2x12 turns of 18awg wire on a type 43 ferrite as per this linkā¦
This takes me from the balanced feeder to the coax to the radio.
What I am confused about is, is this enough or do I need something else on the coaxial side of the balun towards the x6100.
The other question would be if I use a different antenna such as a G5RV would that be a better if less efficient option for an antenna?
Best Regards,
Paul G4HLF
HI Paul @G4HLF
Apologies didnāt have a chance to reply.
I find that turns of coax around a torrid is more effective to stop common mode. This is what I do for the Xeigu:
If you are using a doublet or dipole, I would suggest you do the same with a section of coax ?
That said a good resonant antenna like a 1/4 vertical I do not need to choke for the Xeigu !!!
A G5RV or doublet you would need to tune so it only helps.
To be honest the main antenna type I have had issues with RF feedback are random wiresā¦. Absolute nightmare for RF in the Mic.
Never had an issue with a dipole even without a choke. Havenāt tried a G5RV with the Xeigu
Hope this helps! And happy to help with any questions !
Tim
As it appears the specification for CAT-7 ethernet cable is that it must be a shielded cable, I wonder if a CAT-7a patch cable between the X6100 and its microphone would stop RF ingress? The X6200 has a metal ring around the RJ45 socket and the microphone cable has an RJ45 with a metal outer on the plug, but I donāt have an X6100, so I donāt know what the situation is there. I believe this screen connection would be needed to connect to the screening within the cable.
73 Ed.
I checked the microphone ground is also grounded to the metal casing of the radio. And the RF ground is also grounded.
The issue is conducted RF via ground, reflected from the antenna. Not RF via an emission, being picked up somewhere. No amount of cable shielding will stop this.
