[LCC] Texas thoughts on K3# operation

[Steve Lott]

Peopper AGC

RF Gain and No Preamp is often the difference between hearing the weak ones
and not on many radios
not just the K3

Many Orion owners and even old FT-1000MP owners have found the right balance
of Gain and AGC
bring signals out

Operator Technique is still the key !

cheers !

steve

On Sat, Jul 17, 2010 at 10:50 AM, Randy Prewitt <ranprew at foxsale.com> wrote:

>  *I sent a couple of my ham buddies some of the recent LCC email postings
> and thought I'd share their thoughts with you.  They're okay with the idea
> of sharing this.*
> *Randy K4LJA*
> *
> ---------------------------------------------------------------------------------------
> *
> **
> *FROM TOM WEBB; W4YOK:*
>
> **
> *> >Charles Harpole, K4VUD, brought his K3 over to my shack a while
> >>back.  Now maybe we were doing something wrong, but we connected the
> >>K3 in parallel with a coax tee with my Drake R-4C and tuned in a
> >>very weak signal on 40 CW which we could copy on the R-4C, but which
> >>was inaudible on the K3.  No amount of knob twisting could bring the
> >>signal up out of the noise on the K3.*
> **
> *REPLY FROM RANDY FARMER, W8FN:
> >
> > Charlie's (very early) K3 must have had something wrong with it. I
> > know he had lots of issues with the AGC settings when he first got
> > the radio. It may seem counterintuitive, but running up the gain and
> > turning on the preamp is NOT the way to hear signals near the noise
> > floor, especially on the low bands. High gain together with an overly
> > aggressive AGC just lets the noise control the AGC action and greatly
> > reduces the signal to noise ratio of weak signals. Low sensitivity is
> > certainly not a problem with the K3, especially on 40 meters where
> > the band noise is usually around 20-30 dB above the receiver noise
> > floor with any kind of an antenna at all.
> >
> > I normally run the RF gain (which is really an IF gain control) down
> > to where the band noise just barely doesn't cause the signal strength
> > indicator to fluctuate. Most of the time this is anywhere from
> > indicated S3 to S7 on 40 meters here. I've set my AGC Threshold to
> > 008, which puts the onset of AGC action at around -100 dBm. I've set
> > my AGC Slope to 001, which allows an audio output change of around 4
> > dB for every 10 dB of signal input increase once the AGC kicks in.
> > These settings keep the output level nearly proportional to the input
> > level up to around -50 dBm, where the hardware AGC kicks in to
> > protect the A/D in the DSP section. This setup maximizes dynamic
> > range in the audio and provides the best readability of weak signals
> > in the presence of big QRM or noise. In big contests I usually end up
> > switching in the attenuator (the RF gain control) on 40 to keep the
> > huge signals under control, and I have yet to have any problem
> > pulling very weak signals out of the QRM. Of course once a weak
> > signal is truly buried in the noise no kind of receiver is ever going
> > to be able to improve the S/N ratio so you can hear it. Once the S/N
> > is 0 dB the signal is by definition covered by noise.
> >
> > The K3 has lots of adjustments you can twiddle to make it do what you
> > want, and taking the time to adjust things like the AGC behavior and
> > the overall gain can make the difference between hearing and not
> > hearing weak signals in difficult conditions. The K3 runs circles
> > around my modified R-4C, and that's really saying something.
> >
> > 73...
> > Randy, W8FN
> >*
>
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