[Elecraft] K3 Hum on Audio...

[Phil Hystad]

Jim,

In answer to your first question below, that particular test NOTHING was connected other then the battery to provide power.  That included the antenna.

I will read your paper -- maybe it will describe hum and buzz as to how they sound different.  If you know of a good audio stream available on the web maybe I can listen to that.  But, audio is definitely not a strong suit for me and this is the first time I have heard of a distinction in buzz and hum.  I don't mean that I haven't heard of different kinds of hum or buzz, just that I didn't know that the terms had been so precisely defined.

However, the good news is that the problem no longer occurs (as I had mentioned in a previous post).  Not sure of the cause though but I am heavily leaning towards some kind of loose connection or other electro-mechanical problem with the mic itself (or its connector to the K3).  That seems to be the only source so far that can meet the requirements of all the tests that I did.

73, phil


On Jan 13, 2012, at 2:11 PM, Jim Brown 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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