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K3 - PSK31 - AGC/No AGC

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Leroy Buller

K3 - PSK31 - AGC/No AGC

Hi guys....

Old topic from a Old Newbie. I have been fooling around with PSK 31 and I
have it set up and working but I do have a question. Do most ops using
this mode turn off the AGC and then ride the RF gain control because of the
stronger signals in the band pass killing off the weaker signals?

Is that how it is done....or am I missing something

Yes, I have searched Google and could not find a good answer.

Lee - K0WA
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Wes (N7WS)

Re: K3 - PSK31 - AGC/No AGC

I only work PSK on occasion. I do work a lot of RTTY tho...like V73D on 10M
about 5 min ago. I never turn AGC off on any mode. Never understood why anyone
would want to but I've only been licensed for 57 years, so maybe I missed something.

On 10/27/2015 3:32 PM, Leroy Buller wrote:

> Hi guys....
>
> Old topic from a Old Newbie. I have been fooling around with PSK 31 and I
> have it set up and working but I do have a question. Do most ops using
> this mode turn off the AGC and then ride the RF gain control because of the
> stronger signals in the band pass killing off the weaker signals?
>
> Is that how it is done....or am I missing something
>
> Yes, I have searched Google and could not find a good answer.
>
> Lee - K0WA
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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Don Wilhelm-4

Re: K3 - PSK31 - AGC/No AGC

In reply to this post by Leroy Buller

Lee,

I do not turn off the AGC, but instead use the filters to isolate the
signal of interest with the Width and Shift controls in the event that a
strong signal is monopolizing the waterfall.

Yes, you can do it your way, but I believe my way will allow you to copy
weaker signals easily. You will not see the full waterfall bandwidth
with the filters narrowed, but then you are only interested in working
one signal at a time. When you have finished the QSO, it is a simple
matter to broaden the width and once again view the entire "battlefield".

73,
Don W3FPR

On 10/27/2015 6:32 PM, Leroy Buller wrote:

Rick WA6NHC

Re: K3 - PSK31 - AGC/No AGC

What Don says, plus if you're using a sound card interface (any flavor)
to decode the digital, keep the LIN OUT low (mine is set to 1, zero is
off) THEN keep the audio as light as possible (driver software) into the
computer decoder. What you want is to NOT let the sound card AGC get
triggered at all. It only screws things up when that happens.

This is a case of least is best. BUT if you listen to a wider than
needed audio bandwidth, the sound card AGC will get tripped which is why
there is blocking from the stronger audio signals. Use tightly placed
filters for QSO, then use a skimmer (wide audio) when hunting.

RTTY seems to need 10 or so dbm above the noise floor for good decoding,
PSK can be run at the noise floor, most times (depends on if atmospheric
or human noises). It requires a lot of experimentation and with
changing conditions, one size doesn't fit all cases. Expect to fiddle
with it, often.

Rick wa6nhc

On 10/27/2015 3:53 PM, Don Wilhelm wrote:

> Lee,
>
> I do not turn off the AGC, but instead use the filters to isolate the
> signal of interest with the Width and Shift controls in the event that
> a strong signal is monopolizing the waterfall.
>
> Yes, you can do it your way, but I believe my way will allow you to
> copy weaker signals easily. You will not see the full waterfall
> bandwidth with the filters narrowed, but then you are only interested
> in working one signal at a time. When you have finished the QSO, it
> is a simple matter to broaden the width and once again view the entire
> "battlefield".
>
> 73,
> Don W3FPR
>
> On 10/27/2015 6:32 PM, Leroy Buller wrote:
>> Hi guys....
>>
>> Old topic from a Old Newbie. I have been fooling around with PSK
>> 31 and I
>> have it set up and working but I do have a question. Do most ops using
>> this mode turn off the AGC and then ride the RF gain control because
>> of the
>> stronger signals in the band pass killing off the weaker signals?
>>
>> Is that how it is done....or am I missing something
>>
>>
>
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Bill Frantz

Re: K3 - PSK31 - AGC/No AGC

In reply to this post by Leroy Buller

When I was using a SignaLink, I used the RF gain control to keep
strong signals from overloading the input to the computer. I
would also use the Shift and Width controls to isolate a signal,
and got a 250 Hz filter to help. Dropping the RF gain control
until the band noise almost disappeared from the waterfall also
seemed to improve decoding.

I now use a Tascam US-122 mkII interface. I don't have to adjust
the RF gain control at all. YMMV.

73 Bill AE6JV

On 10/27/15 at 3:32 PM, [hidden email] (Leroy Buller) wrote:

>Old topic from a Old Newbie. I have been fooling around with PSK 31 and I
>have it set up and working but I do have a question. Do most ops using
>this mode turn off the AGC and then ride the RF gain control because of the
>stronger signals in the band pass killing off the weaker signals?
>
>Is that how it is done....or am I missing something
>
>Yes, I have searched Google and could not find a good answer.
>
>Lee - K0WA

-----------------------------------------------------------------------
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(408)356-8506 |is there are so many to choose| 16345
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CA 95032

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Bob McGraw - K4TAX

Re: K3 - PSK31 - AGC/No AGC

In reply to this post by Leroy Buller

I do run a fair amount of PSK-31 and much enjoy the same. In that
regard I always run AGC-F. For selectivity, in dealing with strong
signals in the midst of weak signals, I shift the passband and tighten
the bandwidth as needed. RF gain is always adjusted based on band
noise such that signals just flicker the S meter. NR and NB can be used
with success. However adjustment of the parameters will be likely
needed, again based on band noise and signals. In other words "there
is no shoe size that fits all". Skill, practice and patience prevails.

73
Bob, K4TAX
K3S s/n 10163

On 10/27/2015 5:32 PM, Leroy Buller wrote:

Frank Precissi

Re: K3 - PSK31 - AGC/No AGC

I run the K3 with AGC-Off in all digital modes and rely on the roofing/DSP
filters to edge out really strong signals. Most of the time the software
will compensate in pulling the weak signals out of the mud a lot better
than your rig making them louder.

I would suggest playing with each setting and see what works the best for
your particular setup. I've read mixed things about AGC pumping, but dont
know if they are relevant to the K3.

Frank
KG6EYC

On Tue, Oct 27, 2015 at 5:04 PM Bob McGraw - K4TAX <[hidden email]>
wrote:

> I do run a fair amount of PSK-31 and much enjoy the same. In that
> regard I always run AGC-F. For selectivity, in dealing with strong
> signals in the midst of weak signals, I shift the passband and tighten
> the bandwidth as needed. RF gain is always adjusted based on band
> noise such that signals just flicker the S meter. NR and NB can be used
> with success. However adjustment of the parameters will be likely
> needed, again based on band noise and signals. In other words "there
> is no shoe size that fits all". Skill, practice and patience prevails.
>
> 73
> Bob, K4TAX
> K3S s/n 10163
>
>
>
> On 10/27/2015 5:32 PM, Leroy Buller wrote:
> > Hi guys....
> >
> > Old topic from a Old Newbie. I have been fooling around with PSK 31
> and I
> > have it set up and working but I do have a question. Do most ops using
> > this mode turn off the AGC and then ride the RF gain control because of
> the
> > stronger signals in the band pass killing off the weaker signals?
> >
> > Is that how it is done....or am I missing something
> >
> > Yes, I have searched Google and could not find a good answer.
> >
> > Lee - K0WA
>
>
> ______________________________________________________________
> 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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> Message delivered to [hidden email]
>

--
CW: NAQCC #6554 | SKCC #10435 | FISTS #16155 | SOC #1038 | FPQRP #3186
Digital: FHC #4224 | 30MDG #6370 | DMC #5698 | FBOM #0
Gear: K3 #7164 | P3 #3134 | KX3 #1787 | KXPA100 #1502
http://vadept.com
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NK7Z

Re: K3 - PSK31 - AGC/No AGC

I also run with no AGC... It makes a major difference in how the data
is copied...
--
Thanks and 73's,
For equipment, and software setups and reviews see:
www.nk7z.net

For MixW support see;
http://groups.yahoo.com/neo/groups/mixw/info
For Dopplergram information see:
http://groups.yahoo.com/neo/groups/dopplergram/info
For MM-SSTV see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info

On Wed, 2015-10-28 at 00:22 +0000, Frank Precissi wrote:

> I run the K3 with AGC-Off in all digital modes and rely on the roofing/DSP
> filters to edge out really strong signals. Most of the time the software
> will compensate in pulling the weak signals out of the mud a lot better
> than your rig making them louder.
>
> I would suggest playing with each setting and see what works the best for
> your particular setup. I've read mixed things about AGC pumping, but dont
> know if they are relevant to the K3.
>
> Frank
> KG6EYC
>
> On Tue, Oct 27, 2015 at 5:04 PM Bob McGraw - K4TAX <[hidden email]>
> wrote:
>
> > I do run a fair amount of PSK-31 and much enjoy the same. In that
> > regard I always run AGC-F. For selectivity, in dealing with strong
> > signals in the midst of weak signals, I shift the passband and tighten
> > the bandwidth as needed. RF gain is always adjusted based on band
> > noise such that signals just flicker the S meter. NR and NB can be used
> > with success. However adjustment of the parameters will be likely
> > needed, again based on band noise and signals. In other words "there
> > is no shoe size that fits all". Skill, practice and patience prevails.
> >
> > 73
> > Bob, K4TAX
> > K3S s/n 10163
> >
> >
> >
> > On 10/27/2015 5:32 PM, Leroy Buller wrote:
> > > Hi guys....
> > >
> > > Old topic from a Old Newbie. I have been fooling around with PSK 31
> > and I
> > > have it set up and working but I do have a question. Do most ops using
> > > this mode turn off the AGC and then ride the RF gain control because of
> > the
> > > stronger signals in the band pass killing off the weaker signals?
> > >
> > > Is that how it is done....or am I missing something
> > >
> > > Yes, I have searched Google and could not find a good answer.
> > >
> > > Lee - K0WA
> >
> >
> > ______________________________________________________________
> > 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
> > Message delivered to [hidden email]
> >

Jim Brown-10

Re: K3 - PSK31 - AGC/No AGC

In reply to this post by Wes (N7WS)

On Tue,10/27/2015 3:50 PM, Wes (N7WS) wrote:
> I never turn AGC off on any mode. Never understood why anyone would
> want to but I've only been licensed for 57 years, so maybe I missed
> something.

I started three years before you, so maybe I remember more from back
then. :) In those older days, it was quite common for CW ops to turn
down the RF gain and turn up the AF gain. In effect, this more or less
disables AGC. It can also help with listener fatigue with lots of static
QRN.

BUT -- this can be taken to extremes, and doing so is, I think,
responsible for those hams who complain of the K3 being "hissy" and
having "clicks" when switching bandwidth. One of the first important
things we had to learn in the world of pro audio is setting audio gains
properly to minimize both distortion and noise. For every gain stage,
there is a Goldilocks-like "sweet spot" to keep the signal away from
clipping (distortion) and the noise floor (hiss, clicks, etc.).

73, Jim K9YC
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Wes (N7WS)

Re: K3 - PSK31 - AGC/No AGC

Yes but...

Those receivers didn't have product detectors and BFO leakage into the AGC
detector was an issue.

.On 10/27/2015 6:01 PM, Jim Brown wrote:
>
> In those older days, it was quite common for CW ops to turn down the RF gain
> and turn up the AF gain. In effect, this more or less disables AGC.

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David Woolley (E.L)

Re: K3 - PSK31 - AGC/No AGC

In reply to this post by Jim Brown-10

Although I hadn't noticed it before, I would say that design in the K2
is more about stability and DC offsets than anything to do with pick up
of the BFO. The balanced demodulator and last two crystals deal with that.

The old, basically AM sets, used high level, unbalanced detectors. That
required more total gain from aerial to detector, although that might be
split between RF and two IF frequencies.

Balanced detectors can work with much lower level signals, which is
particularly helpful for a single conversion design, like the K2.
However, the AGC detector doesn't want to be balanced, and with a low
level signal, would have a large DC offset, that might exceed the wanted
rectified AGC, therefore additional gain is needed before the AGC
detector. If this were done at the IF frequency, the gain from input to
output at one frequency would be much greater, and proportionately less
stray coupling would be needed to make the whole system oscillate. By
shifting the frequency, which can be done at low signal levels, the
design reduces the gain at any one frequency.

The risk with doing all at one frequency is not pickup of the BFO at the
input of the IF amplifier, but pickup of its own output.

If there were leakage of the BFO it would get amplified just as much as
if additional gain was tapped off at the same point and amplified at the
original frequency. The design seems to rely on the balance of the
detector and the two pole crystal filter, to stop the BFO getting into
the AGC path, and not the difference in frequency.

--
David Woolley
Owner K2 06123
On 28/10/15 03:15, Ron D'Eau Claire wrote:

>
> The most successful solutions (before SDR technology took over) were to
> split the I.F. with a second mixer that was far removed from the main I.F.
> the second I.F. was used to generate the AGC voltage and, since it was on a
> wholly different frequency from the main I.F. the BFO didn't trigger the
> AGC. In fact, the Elecraft K2 uses that technique quite successfully.

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Don Wilhelm-4

Re: K3 - PSK31 - AGC/No AGC

David,

I do not understand your logic.
Let's divorce the AGC from the product detector for a moment. The K2
takes the input to the AGC circuit from the IF and converts it to a
frequency that is removed from the IF signal. The AGC circuit produces
a DC voltage that is used to control the gain of the IF amplifier - period.
That has nothing to do with balanced or unbalanced - the output is a a
DC voltage which is applied to the IF amplifier to control its gain.

That means that the only signals applied to the product detector are the
incoming signal (already controlled by the AGC) and the BFO.

Yes, receivers of old did not use product detectors (mixers) but used a
diode detector, and the BFO signal was injected along with the IF signal
to produce the audio output. The BFO injection level was fixed, and
therefore the gain of the IF input to the detector had to be matched to
the BFO level for proper demodulation to occur. The result is that one
had to ride the RF Gain to make the levels of the IF signal and the BFO
work in harmony with each other. In addition, the AGC was developed
after the detector, so in those old receivers, it was best to turn off
the AGC.

That is not true for receivers using a product detector. BFO pickup is
not a problem with a product detector as long as the output of the mixer
(product detector) is restricted to a bandpass that contains only the
audio frequencies (the input frequencies - BFO and IF - are rejected
leaving only the audio content).

Those old operating habits (ride the RF Gain and set the AF Gain at max)
are still being used by some operators, but it is not necessary for
modern receivers which use product detectors - the K2 is included in
that list.

73,
Don W3FPR

On 10/28/2015 7:33 PM, David Woolley wrote:

> Although I hadn't noticed it before, I would say that design in the K2
> is more about stability and DC offsets than anything to do with pick
> up of the BFO. The balanced demodulator and last two crystals deal
> with that.
>
> The old, basically AM sets, used high level, unbalanced detectors.
> That required more total gain from aerial to detector, although that
> might be split between RF and two IF frequencies.
>
> Balanced detectors can work with much lower level signals, which is
> particularly helpful for a single conversion design, like the K2.
> However, the AGC detector doesn't want to be balanced, and with a low
> level signal, would have a large DC offset, that might exceed the
> wanted rectified AGC, therefore additional gain is needed before the
> AGC detector. If this were done at the IF frequency, the gain from
> input to output at one frequency would be much greater, and
> proportionately less stray coupling would be needed to make the whole
> system oscillate. By shifting the frequency, which can be done at low
> signal levels, the design reduces the gain at any one frequency.
>
> The risk with doing all at one frequency is not pickup of the BFO at
> the input of the IF amplifier, but pickup of its own output.
>
> If there were leakage of the BFO it would get amplified just as much
> as if additional gain was tapped off at the same point and amplified
> at the original frequency. The design seems to rely on the balance of
> the detector and the two pole crystal filter, to stop the BFO getting
> into the AGC path, and not the difference in frequency.
>

Bob McGraw - K4TAX

Re: K3 - PSK31 - AGC/No AGC

Don is absolutely correct.

As many may know, I do assist hams with issues associated with many
different products here and elsewhere. The biggest issue I encounter is
the ham that says " well somebody told me to.... blah blah blah blah
......and it would work best". In many cases, nothing could be further
from the truth. I find today that many hams are more prone to have and
use old school thinking and methods trying to be used with today's
radios. I find this applies to many facets of ham radio equipment as
being used today.

As I've told many, if you expect the radio to operate like a Kenwood,
ICOM or Yaesu, it darn well better say Kenwood, ICOM or Yaesu on the
front panel. Otherwise stated, learn to use the Elecraft radio
correctly in order to attain optimum performance, for indeed they do not
operate like the others.

73
Bob, K4TAX
K3S s/n 10163

On 10/28/2015 7:19 PM, Don Wilhelm wrote:
> Those old operating habits (ride the RF Gain and set the AF Gain at
> max) are still being used by some operators, but it is not necessary
> for modern receivers which use product detectors - the K2 is included
> in that list.
>
> 73,
> Don W3FPR

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k6dgw

Re: K3 - PSK31 - AGC/No AGC

How do I set the AGC on my loose coupler receiver? :-) I'm old, but
I've never used the RF Gain on my K3.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org

On 10/28/2015 6:19 PM, Bob McGraw - K4TAX wrote:

> Don is absolutely correct.
>
> As many may know, I do assist hams with issues associated with many
> different products here and elsewhere. The biggest issue I encounter is
> the ham that says " well somebody told me to.... blah blah blah blah
> .....and it would work best". In many cases, nothing could be further
> from the truth. I find today that many hams are more prone to have and
> use old school thinking and methods trying to be used with today's
> radios. I find this applies to many facets of ham radio equipment as
> being used today.
>
> As I've told many, if you expect the radio to operate like a Kenwood,
> ICOM or Yaesu, it darn well better say Kenwood, ICOM or Yaesu on the
> front panel. Otherwise stated, learn to use the Elecraft radio
> correctly in order to attain optimum performance, for indeed they do not
> operate like the others.
>
> 73
> Bob, K4TAX
> K3S s/n 10163

Bob McGraw - K4TAX

Re: K3 - PSK31 - AGC/No AGC

Back in 1923, in order to receive a signal, the following adjustments
must be made and possibly repeated to get the optimum performance (not a
simple matter and easily upset): The input coil (inside box) is adjusted
to resonate at the desired receiving frequency using the two tap
selectors on the front panel of the box.The inductance of the secondary
coil is set by its tapping switch and tuned by a capacitor to suit the
frequency being received. Moving the secondary coil in and out of the
primary (in the box) allows coupling to adjusted for maximum
performance. With coil pushed in, the sensitivity will be high and the
selectivity will be poor. The reverse occurs with the coil pulled out.

73
Bob, K4TAX

On 10/28/2015 8:47 PM, Fred Jensen wrote:

How do I set the AGC on my loose coupler receiver?

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