[Elecraft] K3--Too much ALC creates energy on opposite sideband?

[Jim Brown]

Numerical readouts for Mic Gain and Comp are pretty meaningless, because 
the output of good mics varies widely from one model to another, how 
close the mic is to the mouth, how loud we talk. The right way to set 
(and understand) these controls is to look at indicated ALC and CMP on 
the bar graph display while transmitting. Both adjustments should be 
made AFTER setting TXEQ. I have long advocated 10 dB of indicated CMP on 
voice peaks.

It is well known that IMD in the K3 and K3S increases when operating 
from low DC supply voltage. It also increases when the output stage is 
operating near its limit, and when the antenna is not well matched to 
the output stage. If the 100W amp is present, it does not engage until 
output power is set above about 15W, so IMD is also higher when running 
12-15W. The increased IMD of the 100W state can be clearly seen in this 
set of data.  DC voltage was in the range of 12.5V for these 
measurements. http://k9yc.com/P3_Spectrum_Measurements.pdf

Pink noise is widely used by audio professionals because its spectral 
distribution more closely corresponds to music and speech than does 
white noise. For that reason, pink noise is the best test signal for the 
evaluation of speech processing systems (like CMP and peak limiting).

73, Jim K9YC

8/28/2019 10:45 AM, Wes wrote:
> Although the manual doesn't say so, according to an ARRL review, the K3S 
> is specified to have undesired sideband suppression of >50 dB.  ARRL 
> claims an optimistic >70 dB.
> 
> So if you are extremely strong at the other guy's place, he might easily 
> hear an opposite sideband, even though your radio is operating 
> correctly.  Ask him what the ratio is.
> 
> Wes  N7WS
> 
> On 8/28/2019 9:40 AM, Nate Bargmann wrote:
>> I received a note this morning advising that I should check my ALC as he
>> is seeing some energy on USB when I check into a 75m voice net on LSB.
>> I am using an MC-50 microphone and am running the mic gain at 35 and the
>> compression at 11.  My thinking was that generating opposite sideband
>> energy would be quite difficult with the K3's DSP.  Am I wrong?
>>
>> I'll try working with him some morning and back down the mic gain a bit
>> and see what that does for him.