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[K3] AGC-OFF

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kevinr@coho.net

[K3] AGC-OFF

I was having a hard time making out characters today during my daily sked
into the Southeast. The QSB was a fast flutter and was chopping up the
letters badly. I was running fast AGC and thought maybe slowing it down
may help. It did - a little. So I took the next logical step and turn
AGC off entirely. The characters popped right out at me. I just rode the
RF gain as the signal went through its slower QSB while the fast flutter
QSB did little to bother me. AF gain was cranked to high as I normally
run it while RF gain was set to where the background QRN was minimized.
Turning off the AGC helped eliminate the fast flutter problems which were
causing me difficulties copying.

This is most likely old news to many of you but I have been running AF
gain at max and controlling volume with the RF (or IF) gain since 1960
when I first started SWLing on my brother's Lafayette receiver.

I hope this helps at least one of you drag out a new one.
73,
Kevin. KD5ONS
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wayne burdick

Re: [K3] AGC-OFF

Administrator

Kevin,

This is a case where you might want to try CONFIG:AGC DCY = SOFT and/
or a nonzero value of AGC HLD. Either could help eliminate the need to
ride the RF gain control, whether you run it at full clockwise or not.

73,
Wayne
N6KR

On Jun 21, 2011, at 10:12 AM, Kevin Rock wrote:

>
> I was having a hard time making out characters today during my daily
> sked
> into the Southeast. The QSB was a fast flutter and was chopping up
> the
> letters badly. I was running fast AGC and thought maybe slowing it
> down
> may help. It did - a little. So I took the next logical step and
> turn
> AGC off entirely. The characters popped right out at me. I just
> rode the
> RF gain as the signal went through its slower QSB while the fast
> flutter
> QSB did little to bother me. AF gain was cranked to high as I
> normally
> run it while RF gain was set to where the background QRN was
> minimized.
> Turning off the AGC helped eliminate the fast flutter problems which
> were
> causing me difficulties copying.
>
> This is most likely old news to many of you but I have been running AF
> gain at max and controlling volume with the RF (or IF) gain since 1960
> when I first started SWLing on my brother's Lafayette receiver.
>
> I hope this helps at least one of you drag out a new one.
> 73,
> Kevin. KD5ONS
> ______________________________________________________________
> 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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Dave Hachadorian

Re: [K3] AGC-OFF

In reply to this post by kevinr@coho.net

There are two major problems with turning off the K3's AGC:

1. There is very little dynamic headroom until the AF Limiter
causes severe distortion on even a moderately loud signal, even
if the AF Limiter setting is max.

2. Never use the speaker amp with AGC turned off. It takes just
one dit from a loud signal to destroy the delicate speaker
amplifier IC. That will require a $110 factory repair, plus
postage.

Dave Hachadorian, K6LL
Big Bear Lake, CA

-----Original Message-----
From: Kevin Rock
Sent: Tuesday, June 21, 2011 10:12 AM
To: Elecraft
Subject: [Elecraft] [K3] AGC-OFF

I was having a hard time making out characters today during my
daily sked
into the Southeast. The QSB was a fast flutter and was chopping
up the
letters badly. I was running fast AGC and thought maybe slowing
it down
may help. It did - a little. So I took the next logical step
and turn
AGC off entirely. The characters popped right out at me. I just
rode the
RF gain as the signal went through its slower QSB while the fast
flutter
QSB did little to bother me. AF gain was cranked to high as I
normally
run it while RF gain was set to where the background QRN was
minimized.
Turning off the AGC helped eliminate the fast flutter problems
which were
causing me difficulties copying.

This is most likely old news to many of you but I have been
running AF
gain at max and controlling volume with the RF (or IF) gain since
1960
when I first started SWLing on my brother's Lafayette receiver.

I hope this helps at least one of you drag out a new one.
73,
Kevin. KD5ONS
______________________________________________________________
Elecraft mailing list
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list:
http://www.qsl.net/donate.html

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kevinr@coho.net

Re: [K3] AGC-OFF

I never use the speaker and I ride the RF gain. When I hear the signal
rising I can catch it in time to avoid limiting. However, I only use this
method when the QSB is a fast flutter which causes me problems. When the
QSB is simply a slow up and down wave I'll use AGC-F which is fine. This
morning I had both rapid and slow QSB. The rapid QSB was the problem
while the slow QSB was easily dealt with by riding the RF gain.
Kevin. KD5ONS

On Tue, 21 Jun 2011 19:24:03 -0700, Dave Hachadorian <[hidden email]> wrote:

> There are two major problems with turning off the K3's AGC:
>
> 1. There is very little dynamic headroom until the AF Limiter causes
> severe distortion on even a moderately loud signal, even if the AF
> Limiter setting is max.
>
> 2. Never use the speaker amp with AGC turned off. It takes just one
> dit from a loud signal to destroy the delicate speaker amplifier IC.
> That will require a $110 factory repair, plus postage.
>
>
> Dave Hachadorian, K6LL
> Big Bear Lake, CA
>
>
>
>
> -----Original Message----- From: Kevin Rock
> Sent: Tuesday, June 21, 2011 10:12 AM
> To: Elecraft
> Subject: [Elecraft] [K3] AGC-OFF
>
>
> I was having a hard time making out characters today during my daily sked
> into the Southeast. The QSB was a fast flutter and was chopping up the
> letters badly. I was running fast AGC and thought maybe slowing it down
> may help. It did - a little. So I took the next logical step and turn
> AGC off entirely. The characters popped right out at me. I just rode
> the
> RF gain as the signal went through its slower QSB while the fast flutter
> QSB did little to bother me. AF gain was cranked to high as I normally
> run it while RF gain was set to where the background QRN was minimized.
> Turning off the AGC helped eliminate the fast flutter problems which were
> causing me difficulties copying.
>
> This is most likely old news to many of you but I have been running AF
> gain at max and controlling volume with the RF (or IF) gain since 1960
> when I first started SWLing on my brother's Lafayette receiver.
>
> I hope this helps at least one of you drag out a new one.
> 73,
> Kevin. KD5ONS
> ______________________________________________________________
> 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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AC7AC

Re: [K3] AGC-OFF

In reply to this post by Dave Hachadorian

CONTENTS DELETED

The author has deleted this message.

kevinr@coho.net

Re: [K3] AGC-OFF

I just realized I picked up my operating traits of always wearing
headphones and riding the RF gain 50 years ago. Shocked me to think I
have been listening to shortwave for so very long! I may be getting old
:) But I did learn them from a WWII radio man while wearing his vintage
phones. All that Marine training sticks after all these years.
Kevin.

On Tue, 21 Jun 2011 20:22:36 -0700, Ron D'Eau Claire <[hidden email]> wrote:

> Saving that $110 plus postage is one advantage of being a "solder
> jockey" -
> but I've never managed to damage one of those IC's with a brief signal no
> matter how loud. They saturate, keeping any voltage spikes inside the
> limits
> they can withstand.
>
> What will kill one, IMX, is a sustained saturated signal (for several
> minutes) that eventually causes the chip to overheat from excessive power
> dissipation.
>
> Big Bear Lake ought to be beautiful this time of the year, Dave. (I was
> raised in Redlands, down below you in the San Bernardino Valley.) But so
> is
> the central Oregon coast this time of the year :-)
>
> 73,
>
> Ron AC7AC
>
> -----Original Message-----
> 2. Never use the speaker amp with AGC turned off. It takes just
> one dit from a loud signal to destroy the delicate speaker
> amplifier IC. That will require a $110 factory repair, plus
> postage.
>
>
> Dave Hachadorian, K6LL
> Big Bear Lake, CA
>

Barry N1EU

Re: [K3] AGC-OFF

In reply to this post by Dave Hachadorian

Dave Hachadorian wrote

There are two major problems with turning off the K3's AGC:

1. There is very little dynamic headroom until the AF Limiter
causes severe distortion on even a moderately loud signal, even
if the AF Limiter setting is max.

That's not necessarily true, although probably true with most headphones on the market. Assuming non-impaired hearing, the effective dynamic range will be highly dependent on your baseline (ambient) noise level and subsequent gain settings. That's why K3NA strongly emphasized the need for high isolation headphone schemes in his original treatise on AGC-less contesting. The higher the isolation, the greater the ability to hear low audio levels, the lower the needed gain setting, and the greater the dynamic range before onset of distortion/clipping/painfully Loud levels. With the highest isolation schemes, distortion/clipping rarely occurs while the weakest signals are still rendered audible. I know that in-ear type phones ("ear buds") can be very successful in this regard, but long term comfort is suspect. Every over-the-ear headphone I've tried so far that was touted as "high" or "extreme" isolation didn't quite deliver the degree of isolation that was hoped for, and weren't any better than my Sennheiser HD-280. I'm still searching for more isolation without compromising comfort.

73, Barry N1EU

Eric Scace K3NA

Re: [K3] AGC-OFF

Another factor at play is the sensitivity/efficiency of the headset. For a
given power level, different headsets will deliver different sound levels to the
ear.

In the case of my in-ear monitors, I found a significant amount of
attenuation of the K3's headphone output was needed to:
1) Suppress the low-level broadband hiss of the K3's audio output amplifier
to a level where I could not hear it.
2) Keep the maximum output level of the K3 (the point where the AF limiter
kicks in) just below the "ouch" level for my ears.

A different set of headphones required much less attenuation (5-10 dB) to
meet (2) above and the hiss couldn't be heard even without the attenuator.

A less efficient set of headphones might cause the operator to think the AF
limiter was kicking in at way too low a level. In this case, that pair of
headphones might need a bit of audio amplification between the K3 and the earpiece.

Regarding Barry's note about long-term comfort: custom-fitted earpieces for
in ear monitors worked for me... but this is a more costly solution (but bought
only once - hi!). I can wear the in ear monitors for 48 hours without even
thinking about it. I could never do that with ordinary headphones. But
everyone is different!

In ear monitors that do not use custom-fitted ear pieces (i.e., use the
rubbery or foam ear plugs) exert some pressure on the sides of the ear canal and
can be annoying after 6-8 hours... at least for me.

— Eric K3NA

p.s.: The contesting wiki has the information to which Barry referred:
<http://wiki.contesting.com/index.php/Setting_receiver_gain_controls>

on 2011 Jun 22 07:03 Barry N1EU said the following:

> Dave Hachadorian wrote:
>> There are two major problems with turning off the K3's AGC:
>>
>> 1. There is very little dynamic headroom until the AF Limiter
>> causes severe distortion on even a moderately loud signal, even
>> if the AF Limiter setting is max.
>>
> That's not necessarily true, although probably true with most headphones on
> the market. Assuming non-impaired hearing, the effective dynamic range will
> be highly dependent on your baseline (ambient) noise level and subsequent
> gain settings. That's why K3NA strongly emphasized the need for high
> isolation headphone schemes in his original treatise on AGC-less contesting.
> The higher the isolation, the greater the ability to hear low audio levels,
> the lower the needed gain setting, and the greater the dynamic range before
> onset of distortion/clipping/painfully Loud levels. With the highest
> isolation schemes, distortion/clipping rarely occurs while the weakest
> signals are still rendered audible. I know that in-ear type phones ("ear
> buds") can be very successful in this regard, but long term comfort is
> suspect. Every over-the-ear headphone I've tried so far that was touted as
> "high" or "extreme" isolation didn't quite deliver the degree of isolation
> that was hoped for, and weren't any better than my Sennheiser HD-280. I'm
> still searching for more isolation without compromising comfort.
>
> 73, Barry N1EU

AC7AC

Re: [K3] AGC-OFF

CONTENTS DELETED

The author has deleted this message.

Rick Dettinger-3

Re: [K3] AGC-OFF

My introduction to Morse code was in 1955. Our Boy Scout Troop used
an Instrograph to teach the code for a merit badge. Its been 55 years
and I still consider the note from that machine to be the gold
standard for code practice oscillators. I don't know if it was a pure
sine wave, but it was music to my ears. I know that real music is
definitely not a sine wave. I suspect that spark was about as far as
its possible to get from a pure sine wave!

73,
Rick Dettinger K7MW

>
> Also, all the concern over a 'sine wave' tone is a modern
> affectation that still gets a chuckle out of me and many other OTs.
> Professional CW operators and Hams alike seldom cared if the tone
> they heard was a sine wave, a square wave or even some odd-ball
> sawtooth or triangular waveform. For many, many years my personal
> favorite sidetone monitor was an RF-activated sawtooth wave
> generator. I operated some gear in professional/military
> installations which the "sidetone" heard while sending was no tone
> at all, just a confused bunch of bloops, squeals and blasts of hum
> from a monitor receiver. No one thought anything of it.
>
> The bottom line is expectations change. Back then we thought nothing
> of taking five or ten minutes to tune up on a different band. Many
> Hams built their stations to operate on only one band.
>
> And some of us are still out there, Hi!
>
> Ron AC7AC
>
>