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K3 - AF/RF Gain [and S-meters]

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k6dgw

K3 - AF/RF Gain [and S-meters]

Lots of good info comes from this list. I segregated all the recent
"How to set AF and RF Gains" postings to try and see if I'm missing
something since other than the EQ settings [K9YC's for SSB TX and "try
to emulate my hearing aid response" for RX], I run pretty much
out-of-the-box-defaults, AGC on, RF max, AF for volume, and am a really
happy ham.

In olden days, which have been mentioned here a lot, we ran CW [and SSB
unless you had a new receiver with a product detector] with AF gain
firewalled and RF gain for adjustment. The reason for this, although no
longer valid with a K3, was to equalize the signal and the BFO injection
amplitudes. Minimum distortion occurred when they were about equal, the
BFO amplitude was fixed, so you adjusted the signal level through the
receiver to sort of the same amplitude. The right point was fairly
obvious. The S-meter followed the RF gain control ... that's just how
it was.

AGC used to be a somewhat brute force thing ... 1st mixers had to be
protected so the AGC line hit the RF stage(s) as well as the IF's.
SX-28? My K3 seems to have an exquisitely designed AGC system [well,
more than one]. I run with it on, I've tweaked the threshold so it's at
my normal noise floor, and my RF gain is at max.

I cannot tell any difference between my ability to copy very weak CW
signals in my normal configuration, and when trying to ride RF gain. In
light of all the reflector chatter on this subject, I've tried to make
this work [I'm retired, I have time :-)]. The WIDTH knob can help, the
APF function can be a big help under some circumstances [not all], and
very occasionally, the manual NOTCH will make a difference. Other than
that, it seems letting my K3 do its job by itself, AGC on, RF max, AF
for volume, works best.

What am I missing here?

For the record, my K3/100 is pretty vanilla: One Rx, "stock" filters,
KDVR, KAT3. I have several locals within 3km of me, their rigs are very
quiet on CW, they are the only signals that get much above S9+20, and I
can get well within 1 KHz of them in contests and still work the weak
ones. They haven't complained, I hope I'm not getting too close :-) I
don't operate SSB a lot, usually only in contests to support my contest
club. If that's what this is all about, I apologize for the BW. If
it's CW, I'm either missing something or I guess I'm less discriminating
that most.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org
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Guy, K2AV

Re: K3 - AF/RF Gain [and S-meters]

You haven't told us what settings you have on ATT/PRE, per band. That
would make a huge difference in how things worked out. 73, Guy

On Thu, May 19, 2011 at 7:59 PM, Fred Jensen <[hidden email]> wrote:

> Lots of good info comes from this list. I segregated all the recent
> "How to set AF and RF Gains" postings to try and see if I'm missing
> something since other than the EQ settings [K9YC's for SSB TX and "try
> to emulate my hearing aid response" for RX], I run pretty much
> out-of-the-box-defaults, AGC on, RF max, AF for volume, and am a really
> happy ham.
>
> In olden days, which have been mentioned here a lot, we ran CW [and SSB
> unless you had a new receiver with a product detector] with AF gain
> firewalled and RF gain for adjustment. The reason for this, although no
> longer valid with a K3, was to equalize the signal and the BFO injection
> amplitudes. Minimum distortion occurred when they were about equal, the
> BFO amplitude was fixed, so you adjusted the signal level through the
> receiver to sort of the same amplitude. The right point was fairly
> obvious. The S-meter followed the RF gain control ... that's just how
> it was.
>
> AGC used to be a somewhat brute force thing ... 1st mixers had to be
> protected so the AGC line hit the RF stage(s) as well as the IF's.
> SX-28? My K3 seems to have an exquisitely designed AGC system [well,
> more than one]. I run with it on, I've tweaked the threshold so it's at
> my normal noise floor, and my RF gain is at max.
>
> I cannot tell any difference between my ability to copy very weak CW
> signals in my normal configuration, and when trying to ride RF gain. In
> light of all the reflector chatter on this subject, I've tried to make
> this work [I'm retired, I have time :-)]. The WIDTH knob can help, the
> APF function can be a big help under some circumstances [not all], and
> very occasionally, the manual NOTCH will make a difference. Other than
> that, it seems letting my K3 do its job by itself, AGC on, RF max, AF
> for volume, works best.
>
> What am I missing here?
>
> For the record, my K3/100 is pretty vanilla: One Rx, "stock" filters,
> KDVR, KAT3. I have several locals within 3km of me, their rigs are very
> quiet on CW, they are the only signals that get much above S9+20, and I
> can get well within 1 KHz of them in contests and still work the weak
> ones. They haven't complained, I hope I'm not getting too close :-) I
> don't operate SSB a lot, usually only in contests to support my contest
> club. If that's what this is all about, I apologize for the BW. If
> it's CW, I'm either missing something or I guess I'm less discriminating
> that most.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 2011 Cal QSO Party 1-2 Oct 2011
> - www.cqp.org
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

______________________________________________________________
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k6dgw

Re: K3 - AF/RF Gain [and S-meters]

On 5/19/2011 5:30 PM, Guy Olinger K2AV wrote:
> You haven't told us what settings you have on ATT/PRE, per band. That
> would make a huge difference in how things worked out.

Sorry! I run the preamp on 12 and 10m, sometimes but not always on 15m,
nothing on 20 and 30, occasionally Attenuator on 40, always on 80 and
160. I've never tried 60m.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Guy, K2AV

Re: K3 - AF/RF Gain [and S-meters]

You've already done the one thing that does the biggest part of
keeping signals, and especially noise, in appropriate range, making
the RF gain at max roughly right. I sometimes back off RF gain about
an 1/8 turn if it's really bad noisy.

The only RF gain adjustments in a K3 are the PRE/ATT settings. The
variable gain is in the IF, even if the pot says RF gain. Strictly
speaking, your RF gain is +10 on 10 and 12, maybe 15, 0 on 20 and
30, -10 on 80 and 160, maybe 40.

I have had numbers of conversations with K3 owners who turned on PRE,
left it there, all bands, all modes and wondered why the K3 roared at
them on the low bands. I'd also have to say that the reasons why were
more often than not hard to explain and get across. Got no idea why
so hard to explain. And a couple guys that simply did not believe it.

" I run the preamp on 12 and 10m, sometimes but not always on 15m,
nothing on 20 and 30, occasionally Attenuator on 40, always on 80 and
160. I've never tried 60m."

...is the most important part of what you described.

73, Guy

On Thu, May 19, 2011 at 9:41 PM, Fred Jensen <[hidden email]> wrote:

> On 5/19/2011 5:30 PM, Guy Olinger K2AV wrote:
>> You haven't told us what settings you have on ATT/PRE, per band. That
>> would make a huge difference in how things worked out.
>
> Sorry! I run the preamp on 12 and 10m, sometimes but not always on 15m,
> nothing on 20 and 30, occasionally Attenuator on 40, always on 80 and
> 160. I've never tried 60m.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 2011 Cal QSO Party 1-2 Oct 2011
> - www.cqp.org
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>