[Elecraft] K3: transmitted RF feedback with condenser mics?

[O. Johns]

Brian,

I know a guy in Sonoma, CA,  whose porch lights come on (dimly) when he transmits on 160!!  Fortunately, my main problem (on 20 meters) seems not to touch the DSL, WiFi, etc. system.  Fingers crossed.  I think one of the hidden problems we all have is resonance with phone lines, household wiring, or metal weatherstripping, etc.  The RF may be coming directly from the antenna, and no amount of RF proofing in the shack is going to help much then.  Maybe move the antenna?

Maybe try putting 0.01 RF-bypass capacitors ACROSS the phone line at the jack where the DSL modem plugs in.  Probably wouldn't hurt the DSL or POTS signal much, and might bypass the RF.  Maybe it isn't even common mode.

Oliver
W6ODJ


On 25 Jan 2010, at 12:59 PM, Brian Machesney wrote:

> You are so right, Oliver. 
> 
> Now, if I could only figure out why 50W of RF on 160 kills my DSL line. Tried wrapping all of the DSL and wireless router cords through a high-mu ferrite toroid, but no joy. This has been a thorny problem; sensitivity depends on where the modem and router are placed. May have to go back to "wired" and see if that helps.
> 
> No end of "fun" things to do! The XYL will not be happy when I kill the DSL during the CQ WW 160 contest this weekend!
> 
> -- 
> 73 -- Brian -- K1LI
> 
> On Mon, Jan 25, 2010 at 3:24 PM, O. Johns <ojohns at metacosmos.org> wrote:
> Hi Brian,
> 
> Every solution is different, isn't it?  Very glad yours worked for you.
> 
> Oliver
> W6ODJ
> 
> 
> On 25 Jan 2010, at 9:25 AM, Brian Machesney wrote:
> 
>> Thanks for the suggestion, Olvier. In the process of trying to figure things out, they went from bad to worse, so that I even thought I had terrible distortion with just 100W.
>>  
>> Long story short, I think the problem was a bad shield connection in one of the current baluns that uses the small-diameter teflon coax; it's not mechanically robust because the coax doesn't fit snugly inside the PL259 reducer meant for RG58. I re-cabled the RF path from rig to antenna and, voila!, all is well.
>>  
>> Brian
>> 
>> On Mon, Jan 25, 2010 at 12:12 PM, Oliver Johns <ojohns at metacosmos.org> wrote:
>> Try putting a snap-on ferrite bead ON the actual boom of the electret headset microphone.  Put it right at the end, just before the microphone bulb.  Maybe the RF is getting into the electret or its FET and is being rectified there.
>> 
>> Oliver Johns
>> W6ODJ
>> 
>> 
>> On 24 Jan 2010, at 11:53, Brian Machesney wrote:
>> 
>> > I am getting transmitted RF feedback into the K3 when running high power
>> > with a headset that uses a condenser element. With an otherwise identical
>> > setup, I don't have any problems with either of my two headsets that have
>> > dynamic mic elements, using either the front- or the rear-panel mic jacks.
>> >
>> > I hear the distortion in the K3's own monitor, but I have confirmed the
>> > distortion using my K2 as a second receiver (1" wire in the ANT jack, RF
>> > gain near zero, ATT on to prevent front-end overload) and with on-the-air
>> > tests with stations hundreds to thousands of miles away.
>> >
>> > The problem headset is designed for aviation use and, as far as I can tell,
>> > uses a shielded mic cable.
>> >
>> > Has anyone else had and resolved this problem?
>> >
>> > --
>> > 73 -- Brian -- K1LI
>> > ______________________________________________________________
> 
> 
>