What has any of that to do with opposite sideband rejection?
Wes N7WS
BTW, The HPA kicks in at 12 W.
On 8/28/2019 12:55 PM, Jim Brown wrote:
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.
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