Bernhard,
It's NOT common mode, it's the simple fact that the audio interface is a
mess. The antenna on the roof transmitting high power is doing its job,
putting a lot of RF in the shack. If it didn't (based on proxmiity), it
would be a lousy antenna. The problem is that the interface (wiring plus
electronics plus termination) does not reject RF because it fails to
conform to fundamental principles that reject RF. That is, every cable
must be a transmission line, every shield must be terminated at the
shielding enclosure of the equipment at both ends, and every equipment
chassis must have a short, fat, bond to every other equipment chassis.
Yes, the signal is audio, but the interference is RF, and it takes
proper transmission line techniques to reject that RF.
I have VERY limited experience with MicroHam, but the jumble of wires
that I encountered with the MicroHam unit at W6OAT violated all
principles of good engineering practice for operation in a high RF
environment. It was nothing more than a multipin connector with a lot of
wires soldered to that connector. Indeed, it would darn near impossible
to do it right without starting from scratch withunit a properly made
cable from the MicroHam unit to the radio, with each signal path having
its own coaxial cable.
I have no idea if that describes ALL MicroHam units, but it does
describe Rusty's. And don't ask the model number -- I was so disgusted
by what I saw that I just rolled my eyes.
73, Jim K9YC
On Mon,2/15/2016 10:43 PM, bernhard.ho...@bmw.de wrote:
Hi Guy,
Fully agree with your statement, but as stated I have chokes in all Coax, rotor
and control cables.
I am using double shielded USB cables, extra grounding for each device…no idea
what else could be don.
Regarding the 2 Ohm, there is a recommendation by Microham to check that the
USB / Molex connector resistance should not exceed 5 Ohm otherwise your PC has
a USB/Chassis grounding problem.
I had RFI in the Microham already with 300Wtts…now I can run 1200Watts without
any problems with is over the legal limit over here anyway!
Several HAMs observed problems with the Microham and in combination with
K3/other rigs.
The cheap homebrew USB/Soundcard interface works now, that’s all what counts.
73
Bernie
DL5RDP
Von: guyk...@gmail.com [mailto:guyk...@gmail.com] Im Auftrag von Guy Olinger
K2AV
Gesendet: Montag, 15. Februar 2016 18:15
An: Horst Bernhard, MZ-LR; Elecraft Reflector
Betreff: [Elecraft] Microham Microkeyer II, RFI in mike with my K3
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.ho...@bmw.de<javascript:_e(%7B%7D,'cvml','bernhard.ho...@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:li...@subich.com]
Gesendet: Freitag, 12. Februar 2016 14:15
An: elecraft@mailman.qth.net<mailto:elecraft@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, j...@kk9a.com<mailto:j...@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
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