<div>Peopper AGC</div>
<div> </div>
<div>RF Gain and No Preamp is often the difference between hearing the weak ones and not on many radios</div>
<div>not just the K3</div>
<div> </div>
<div>Many Orion owners and even old FT-1000MP owners have found the right balance of Gain and AGC</div>
<div>bring signals out</div>
<div> </div>
<div>Operator Technique is still the key !</div>
<div> </div>
<div>cheers !</div>
<div><br clear="all">steve<br><br></div>
<div class="gmail_quote">On Sat, Jul 17, 2010 at 10:50 AM, Randy Prewitt <span dir="ltr"><<a href="mailto:ranprew@foxsale.com">ranprew@foxsale.com</a>></span> wrote:<br>
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<div><font size="2" face="Arial"><strong>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.</strong></font></div>
<div><strong>Randy K4LJA</strong></div>
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<div><font size="2" face="Arial"><strong>FROM TOM WEBB; W4YOK:</strong></font></div>
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<div><font size="2" face="Arial"><strong>> >Charles Harpole, K4VUD, brought his K3 over to my shack a while <br>>>back. Now maybe we were doing something wrong, but we connected the <br>>>K3 in parallel with a coax tee with my Drake R-4C and tuned in a <br>
>>very weak signal on 40 CW which we could copy on the R-4C, but which <br>>>was inaudible on the K3. No amount of knob twisting could bring the <br>>>signal up out of the noise on the K3.</strong></font></div>
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<div><font size="2" face="Arial"><strong>REPLY FROM RANDY FARMER, W8FN:<br>> <br>> Charlie's (very early) K3 must have had something wrong with it. I <br>> know he had lots of issues with the AGC settings when he first got <br>
> the radio. It may seem counterintuitive, but running up the gain and <br>> turning on the preamp is NOT the way to hear signals near the noise <br>> floor, especially on the low bands. High gain together with an overly <br>
> aggressive AGC just lets the noise control the AGC action and greatly <br>> reduces the signal to noise ratio of weak signals. Low sensitivity is <br>> certainly not a problem with the K3, especially on 40 meters where <br>
> the band noise is usually around 20-30 dB above the receiver noise <br>> floor with any kind of an antenna at all.<br>> <br>> I normally run the RF gain (which is really an IF gain control) down <br>> to where the band noise just barely doesn't cause the signal strength <br>
> indicator to fluctuate. Most of the time this is anywhere from <br>> indicated S3 to S7 on 40 meters here. I've set my AGC Threshold to <br>> 008, which puts the onset of AGC action at around -100 dBm. I've set <br>
> my AGC Slope to 001, which allows an audio output change of around 4 <br>> dB for every 10 dB of signal input increase once the AGC kicks in. <br>> These settings keep the output level nearly proportional to the input <br>
> level up to around -50 dBm, where the hardware AGC kicks in to <br>> protect the A/D in the DSP section. This setup maximizes dynamic <br>> range in the audio and provides the best readability of weak signals <br>
> in the presence of big QRM or noise. In big contests I usually end up <br>> switching in the attenuator (the RF gain control) on 40 to keep the <br>> huge signals under control, and I have yet to have any problem <br>
> pulling very weak signals out of the QRM. Of course once a weak <br>> signal is truly buried in the noise no kind of receiver is ever going <br>> to be able to improve the S/N ratio so you can hear it. Once the S/N <br>
> is 0 dB the signal is by definition covered by noise.<br>> <br>> The K3 has lots of adjustments you can twiddle to make it do what you <br>> want, and taking the time to adjust things like the AGC behavior and <br>
> the overall gain can make the difference between hearing and not <br>> hearing weak signals in difficult conditions. The K3 runs circles <br>> around my modified R-4C, and that's really saying something.<br>
> <br>> 73...<br>> Randy, W8FN <br>></strong></font></div></font></div></div><br>_______________________________________________<br>LCC mailing list<br><a href="mailto:LCC@louisianacontestclub.org">LCC@louisianacontestclub.org</a><br>
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