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

[Guy Olinger K2AV]

Hi Bernie,

If you are running QRO over your roof, your RFI proofing needs to be
perfect. Your situation is only exceeded in nastiness by being next door to
a 50 kW AM station and maybe not then. Your induced common mode RF
voltages on conductors can be double and triple the desired signal voltages
on the cables and ridiculously more than microphone voltages.

One CAN get lucky and get by, but if one does it's only by dumb blind luck
and any change to cable routing or position and count of station equipment
can disable or polute electronic functions.

If you succumb to the temptation to attribute the changes to the last thing
changed or moved, you will be sent down the rabbit hole to join company
with Alice and the Mad Hatter where nothing makes sense any more. This can
include complaints to manufacturers straight from Wonderland requiring
apologies afterward. Been there, done that. Know whereof I speak.

It is quite probable that replacing the box changed cable specifics. Any
connection that is not a tenth of an ohm or less needs to be replaced or
repaired. I have no idea where you got 2 ohms as a satisfactory connection
resistance. Maybe the USB signal itself will tolerate that under
otherwise non-stressed circumstances but it's far away out of bounds for
RFI proofing.

In your case, QRO on the roof, you need to take maximum anti-RF measures on
**ALL** conductors in the shack. Otherwise just changing orientation of
cables may remove or incite RFI, or worse makes RFI intermittent leading to
suspicions of poltergeist.

I have finally gotten to the point where all retail audio cables need to be
replaced with soldered coax or shielded pairs with WOVEN shields.
ESPECIALLY audio cables terminated in RCA plugs which typically have the
cheapest shields known to man. No retail manufacturer is testing them for
RFI susceptibility in rooftop QRO conditions.

There is a good selection of shielded pair and coax cable with Teflon
dielectric/insulation and woven shields easily soldered to *quality* RCA
plugs or other connectors without melting the wire.

I know that QRO on the roof is all that's available for many folks. Just
understand that's the very stiffest possible demand on all RFI proofing
issues. No cheapies, no short cuts, no omissions allowed in the protocol.

73, Guy K2AV

On Monday, February 15, 2016, <Bernhard.Horst at bmw.de
<javascript:_e(%7B%7D,'cvml','Bernhard.Horst at bmw.de');>> wrote:

> Dear all,
>
> just an update..the Microham Microkeyer II has definitely a problem with
> RF!
> I replaced the Microkeyer with a homebrew USB and soundcard interface
> (Built in 2008) and made new cable distribution box..And the problems are
> gone.
>
> I have S-NO 280 on the microkeyer..hope the newer ones are better. But
> definitely not my kind of solution for that cost!
>
> 73s
> Bernie
> DL5RDP
>
> -----Ursprüngliche Nachricht-----
> Von: Joe Subich, W4TV [mailto:lists at subich.com]
> Gesendet: Freitag, 12. Februar 2016 14:15
> An: elecraft at mailman.qth.net
> Betreff: Re: [Elecraft] Microham Microkeyer II, RFI in mike with my K3
>
>
> > 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?
>
> That is correct although with the K3/K3S since the Elecraft mic RFI
> change it should not matter (both pin 7 and pin 8 are connected to
> the "ground" foil on the front panel circuit board).
>
> Early K3 front panels included an RF choke in the mic *and* PTT returns
> which made the "pin 1 problem" much worse.  With the RF choke removed
> (bypassed) the issue is significantly reduced but there may still be a
> problem if the overall station installation has any "RF on the coax."
>
> 73,
>
>    ... Joe, W4TV
>
>
> On 2/12/2016 7:59 AM, john at kk9a.com wrote:
> > 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
> >
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to k2av.guy at gmail.com



-- 
Sent via Gmail Mobile on my iPhone