[Elecraft] K3 Hum on Audio...

[Phil Hystad]

Guy,

Thanks for the comments.  Later on I might experiment to see if I can purposely reproduce the buzz by methods you mention.

Yes, my test condition was using ABSOLUTELY no AC and no nearby AC or AC artifacts.  No charger on the battery but then again I had AC switched off at the breaker panel during those tests.  The leads on the batter were about 4 inches long.  The battery by the way was a 4S1P configuration (4 individual cells) producing 1.38 volts of A123 Systems Lithium Nano-Phosphate battery available for lots of money from Buddipole.  I like them so much, I am planning on buying more.

phil


On Jan 13, 2012, at 2:34 PM, Guy Olinger K2AV wrote:

> 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
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