[Elecraft] K3 Hum on Audio...

[Guy Olinger K2AV]

Let's call it buzz.  If it was AC power hum the main components would be
60, 120 and 180 Hz.  Cutting 400 Hz and below would have made it
significantly better.  When the K3 is running on batteries without ANY
mikes and other connections, it has NO way to produce 60/120/180 Hz related
to AC house voltage. (I am PRESUMING that your batteries did not have a
charger running on them, or long leads. Anything connected to the charger
is connected to the K3.)  It DOES have misc low level processing artifacts
that are normally so far down as to be covered up by the normal noise
levels of anything coming in on audio inputs at routine levels.

That said, what you have sounds more like gain gone to maximum looking for
input when power level has never been defined, or has had all prior data
wiped.  Especially if compression is set to max, you will now have many
dB's of amplification in force as the rig attempts to provide 100 watts of
output with no power level or mic gain defined.

Once you set yourself to something less than wide open on all bands and
modes and inputs, and your compression to a realistic level that matches
your voice and microphones, it will no longer be running "open gain" and
amplifying internal circuit noise (always present in ANY electronic gear)
to audible levels.

73, Guy.

On Fri, Jan 13, 2012 at 5:11 PM, Jim Brown <jim at audiosystemsgroup.com>wrote:

> On 1/13/2012 10:30 AM, Phil Hystad wrote:
> > I disconnected EVERYTHING.  Nothing on the back panel of the K3 at all
> except for a Li-nano-phosphate battery as my power source.
>
> Was your antenna connected?  If so, where is the coax shield connected
> to ANYTHING -- the earth, other gear, at a tower, etc.?  These are all
> paths for AC leakage current, and your K3 can be in that path.
>
> >    All AC off at the breaker panel for this room.  The only electrical
> equipment on was my K3 via the battery and my Macbook Pro laptop via its
> battery.
> >
> > Given those conditions, the hum was still there.
> >
> > Jim Brown suggested that I consider TXEQ to cut off the low frequencies,
>  I did max cut for all frequencies up to 400 Hz.  The hum did not start
> being attenuated until 400 Hz cut.  But, max cut on 400 Hz did not
> attenuate it completely.  I did not do higher frequencies.
>
> Then what you have is BUZZ, NOT HUM. HUM would be affected ONLY by the
> 60 Hz  frequency band.  The coupling mechanisms are entirely different.
> That's why it was my first question!
>
> BUZZ is leakage current from the AC mains power, OR, as Ron suggested, a
> flaky shield connection of the mic.  BUZZ is almost never due to
> magnetic coupling, so magnetic shielding doesn't matter.  What DOES
> matter is ELECTRIC shielding, which is what the cable shield provides.
> And MAIN thing that matters is BONDING -- CHASSIS TO CHASSIS, and from
> the combination of those chassis to the station ground, AND to the power
> system ground.
>
> Study   http://audiosystemsgroup.com/HamInterfacing.pdf
>
> 73, Jim Brown  K9YC
> ______________________________________________________________
> 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
>