Posted by
Bob McGraw - K4TAX on
Apr 26, 2019; 4:49pm
URL: http://elecraft.85.s1.nabble.com/K3S-Audio-buzz-on-transmit-especially-AM-tp7651148p7651162.html
I did listen and look at my K3S on my SDR receiver in AM mode. I do find
there is a small amount of hum on the carrier. Then switching to LSB, I
do not find the hum present.
You may want to check the settings of your TX EQ. If you have any low
frequency boost, that will contribute to the level of the hum. My
operating values are: 50 Hz = -16 dB , 100 Hz = -16 dB , 200 Hz = -16 dB
, 400 Hz = -6 dB, everything above that is set to 0 dB or flat. The
mike is a Shure SM-58.
In AM mode the hum is noted at 120 Hz, 240 Hz, and 360 Hz, all multiples
of the 60 Hz line. At the same time, the hum level of the individual
frequencies, worst case, is some 40 dB below 100% modulation. Some are
50 dB below 100% modulation with the worst case being 120 Hz. In
working several AM stations over the past year or so, I've not had any
comments regarding hum on the carrier. These tests were done with MIC
level set to 0 and COM level set to 0. Everything else normal and
connected to the radio. Different power levels, mike level and comp
level made no difference in the amplitude of the hum components.
73
Bob, K4TAX
On 4/26/2019 10:43 AM, Nicklas Johnson wrote:
> This morning just for yuks, I also temporarily disconnected the ground from
> the rig entirely while also connecting only to a dummy load, so there could
> be no path to ground at all, let alone multiple paths. No change.
>
> I guess the next things I'll probably try are a full factory reset, and
> then perhaps popping it open to make sure nothing has come unseated. But
> first I'll drop a line to Elecraft support too. I've seen a number of
> people post about similar problems that either magically resolved
> themselves or ended up being a fault on the audio board.
>
> Nick
>
>
> On Thu, 25 Apr 2019 at 23:27, Nicklas Johnson <
[hidden email]> wrote:
>
>> Again, the problem persists with all inputs completely disconnected and
>> the mic gain set at 0. And running solely on a battery into a dummy load.
>>
>> Nick
>>
>> On Thu, Apr 25, 2019, 10:10 PM Jim Brown <
[hidden email]>
>> wrote:
>>
>>> On 4/25/2019 8:15 PM, Nicklas Johnson wrote:
>>>> Physically touching the case or grabbing the barrel of the front panel
>>> mic
>>>> connector actually does cause the buzz to get just a little softer.
>>> I suspect either a bonding problem or a problem with the wiring of the
>>> mic.
>>>
>>>> I generally use solar/battery power, though my ground is bonded to my
>>>> utility ground.
>>> I suggest that you carefully study either N0AX's recent ARRL book on
>>> grounding and bonding, or the slides for talks I've given at Visalia and
>>> Pacifion.
>>>
>>> 73, Jim K9YC
>>>
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