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K3 in a cw pileup - needs work

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Guy, K2AV

Re: K3 in a cw pileup - needs work

It would be interesting to know what all is used to create the signal
on VIFGAIN1 on the RF board. It is at least some derivative of the
signal from the "RF" gain control.

73, Guy.

On Sun, Feb 7, 2010 at 10:07 AM, Don Wilhelm <[hidden email]> wrote:

> Barry,
>
> I do not believe that is true, and the graphs at
> http://www.cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm#AGC_SLP_and_AGC_THR
> bear the real facts as well.
> Raising the AGC Threshold allows stronger weak signals (less than -100
> dBm for THR=008) NOT to activate the AGC. Stronger signals will still
> activate AGC. The Hardware AGC is not changed by the threshold setting.
> The result is the range over which the AGC operates, and that is
> different than the dynamic range of the receiver.
>
> The Gain Throttling talk has mostly been with reference to the
> amplification of atmospheric noise rather than the detection of weak
> signals. While related, I do not think they are the same.
>
> The preamp and attenuator DO translate the receiver dynamic range to a
> higher or lower level - and the hardware AGC trigger point is translated
> as well. Since the RF Gain is really an IF gain, it does not alter the
> onset of hardware AGC. Lyle would have to comment on whether the DSP
> AGC is developed before or after the IF gain is applied, I do not know.
>
> 73,
> Don W3FPR
>
> Barry N1EU wrote:
>> If you simply raise AGC Threshold, you will have to lower AF Gain or risk
>> overly loud audio from stronger signals. So what you would effectively be
>> doing is translating upwards the K3's dynamic range into higher rf levels.
>> This is NOT good practice - you want to keep the dynamic range operating at
>> lower rf levels (thus all the talk of gain throttling).
>>
>> 73,
>> Barry N1EU
>>
>>
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Barry N1EU

Re: K3 in a cw pileup - needs work

In reply to this post by Don Wilhelm-4

Don Wilhelm-4 wrote

I do not believe that is true, and the graphs at
http://www.cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm#AGC_SLP_and_AGC_THR
bear the real facts as well.
Raising the AGC Threshold allows stronger weak signals (less than -100
dBm for THR=008) NOT to activate the AGC.

The graphs are dependent on gain level that is set in the rx. If there's any hope of alleviating pileup mush by raising Threshold level, I believe it would be true (that stronger signals will raise audio level).

When I throttle the gain, I notice that lowering Threshold lowers audio level of stronger signals.

73,
Barry N1EU

Guy, K2AV

Re: K3 in a cw pileup - needs work

> When I throttle the gain, I notice that lowering Threshold lowers audio
> level of stronger signals.
>
> 73,
> Barry N1EU

As it should, because you lowered the reference signal level at DSP
input which the AGC "bites". It also means that by throttling the
gain, you have created a situation where YOUR choice of threshold
actually has an effect.

73, Guy.
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KK7P

K3 DSP AGC Question

In reply to this post by Don Wilhelm-4

> ...Lyle would have to comment on whether the DSP
> AGC is developed before or after the IF gain is applied...

Assuming ATT and PRE are OFF, hardware AGC voltage begins to have an
effect on IF amplifier gain with a signal at the antenna in the region
of -60 dBm, plus or minus a few dB. The hardware AGC voltage is
developed at the final IF of 15 kHz and applied to the 8.215 MHz IF
stage. Its purpose is to prevent the 15 kHz A to D converter at the DSP
from being driven beyond its input limits (called over-ranging).

The "onset of hardware AGC" level is influenced by PRE (which increases
gain ab out 10 dB, decreasing the signal required at the antenna by the
same 10 dB), ATT (which reduces signals by 10 dB, thus increasing the
required signal at the antenna), and RF Gain when backed off sufficiently.

What is "sufficiently"? The DSP outputs a voltage to control the IF
gain of the radio. This voltage is compared with the hardware AGC
voltage, and the higher voltage is applied to reduce the IF gain. If
the RF Gain is backed off enough so that the resulting gain control
voltage is grater than the hardware AGC voltage derived from the 15 kHz
IF signal, then the criterion for "sufficiently" has been met.

The DSP reads the hardware AGC voltage, regardless of the source, and
uses the value as part of the S Meter calculation.

The DSP AGC algorithm is computed based on the 15 kHz IF signal applied
to the DSP's A to D converter. Thus it is after the IF gain is applied.

Enjoy!

73,

Lyle KK7P
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Rick Prather

Re: K3 Loses RX Audio at BW of 2.8 kHz

In reply to this post by Paul - WW2PT

Bingo!

I restored my last config (from 1/20) and problem is gone..

Now I am trying to noodle over what configuration item may have changed during the beta upgrade that caused it.

At any rate, all is good now!

Rick
K6LE

On 2/6/2010, at 11:07 , WW2PT wrote:

> My K3 was working fine last time I used it. Tonight I turned it on and
> noticed a similar problem -- no audio in USB or LSB modes whenever I
> set the width to 3.00 kHz or less. Tried downgrading from 3.76 to 3.63
> but no change. Checked all filter settings in the config menu, nothing
> out of place. All other modes were fine.
>
> On a hunch, I restored my last configuration backup file. It worked!
> Everything seems to be behaving well again.
>
> 73 de WW2PT
>
>
>
>
> On Feb 6, 2010, at 12:45 AM, Scott Prather wrote:
>
>> All: This evening when running FW 3.76 I'm seeing a problem with my
>> K3 that
>> I've never seen before.
>>
>> When the K3 is in the LSB, USB or AM mode, adjusting the bandwidth
>> down to
>> 2.8 kHz will result in total loss of audio, even though the S-meter
>> continues to read incoming signal strength. I've tried an EE-Init and
>> reloaded the configuration, but the problem remains. Thinking this
>> might be
>> related to 3.76, I went back to 3.30 and I have exactly the same
>> problem. If
>> I turn on the sub receiver and change its BW using BSET, it loses
>> LSB, USB
>> and AM audio at 2.8 kHz as well. To get audio to return, all I need
>> to do is
>> change the BW to 2.9 kHz or greater on either the main or the sub.
>>
>> Looking through the reflector postings, it looks like someone saw
>> something
>> similar to this in the DATA mode a few months back, and pressing the
>> A/B key
>> would clear it. However, in my case the only way I can restore audio
>> is to
>> change the BW to 2.9 kHz or greater. In the CW and DATA modes, the
>> audio
>> does not drop out at any bandwidth setting.
>>
>> Does anyone have a suggestion as to what might be going on?

Barry N1EU

Re: K3 in a cw pileup - needs work

In reply to this post by Barry N1EU

Barry N1EU wrote

If you simply raise AGC Threshold, you will have to lower AF Gain or risk overly loud audio from stronger signals.

I just realized that the above wording might have caused confusion. What I meant by raising AGC Threshold was to change the firmware to accommodate the requests of those who posted that the existing "8" wasn't high enough.

73,
Barry N1EU

Barry N1EU

Re: K3 in a cw pileup - needs work

In reply to this post by Barry N1EU

Barry N1EU wrote

If you simply raise AGC Threshold, you will have to lower AF Gain or risk overly loud audio from stronger signals.

Lu Romero - W4LT

Re: Firmware upload problem

In reply to this post by W4CCS

Ruben (et. al.):

De ninguna manera, por favor, no use el MicroHAM Router para cambiar la
software en el K3. Sin ninguna excepcion, microHAM no suporta usar el
Router para hacer esto y es muy posible danar el K3 en esta manera. Si
usted utiliza el sistema microHAM Router en esta manera, lo hace a su propio
riesgo para el radio y el equipo de microHAM.

Just making sure everybody understands the importance of what Joe says in
his message.

Here is what I do:

I have a Dell GX280 PC as my ham radio computer. It has one "real" serial
port and 6 USB onboard ports. My K3 is attached to Router using a
Saelig.com FTDI chipset based USB to serial converter. The output of this
converter goes to a $8.00 2 in one out DB9 Mechanical Data switch on port A.
The output of the "real" serial port goes to that same switch on port B. A
short serial DB9 to DB9 cable goes from port C of the switch to the radio.

When I want to use the rig with the microHAM router and the MicroKEYER 2
interface, I switch to port A. When I want to configure the rig using K3-EZ
or the Elecraft K3 Utility, I switch to port B.

I have never had an issue with software uploads or control glitches with
this wiring scheme. Plus, the data switch makes a nice pedestal to mount my
Autek WM1! When I throw the mechanical switch from port to port, microHAM
router recognizes that communication is lost and flashes the frequency
display in the MicroKEYER 2's screen to let me know the radio is not under
MicroHAM control. Switching back to the Router's serial port re establishes
the communication with the MicroKEYER device almost instantly and the
display then shows my selected radio information (in my case, I display both
of the receiver's frequency information. What information is displayed is
selectable in the MicroKEYER 2's configuration tab in Router).

This has always worked reliably here.

Regards

Lu Romero - W4LT

Date: Sat, 6 Feb 2010 16:12:47 -0500
From: "Joe Subich, W4TV" <[hidden email]>
Subject: Re: [Elecraft] Firmware upload problem
To: "'Ruben Navarro Huedo'" <[hidden email]>,
<[hidden email]>
Message-ID: <F70ADB3B0F3344EAB53DBAD5D1E9EDE4@laptop>
Content-Type: text/plain; charset="iso-8859-1"

Setting "No radio" does not guarantee transparent operation
by microHAM Router. Again:

DO NOT PERFORM A FIRMWARE UPLOAD USING MICROHAM ROUTER
WITH ANY MICROHAM INTERFACE. NO EXCEPTIONS.

Even though I know my way around Router and the microHAM
interfaces well enough to generally make sure Router is
transparent, there is no way to force and lock the data
rate between the microHAM interface and the transceiver.
I keep a serial cable attached to a serial port on one of
my computers specifically for use when updating K3 firmware.

73,

... Joe, W4TV

No virus found in this outgoing message

Checked by PC Tools AntiVirus (6.1.0.25 - 6.14300).
http://www.pctools.com/free-antivirus/

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AD4C2009

About headphones isolation ?

In reply to this post by Barry N1EU

I own now a complete isolation headset that also have the boom mic,the yamaha CM-500,it covers my whole ears, when my wife talks behind me I cn't hear her anymore (cool!) and the best of all,it cost just $42 no other one will beat this price,audio freq response is 20-20K on the headphones and 100 to 18K on the mic,if anyone is interested I can send the picture of it.

AD4C

"For a refined ham it is compulsory to own a k3"

--- On Sun, 2/7/10, Barry N1EU <[hidden email]> wrote:

From: Barry N1EU <[hidden email]>
Subject: Re: [Elecraft] K3 in a cw pileup - needs work
To: [hidden email]
Date: Sunday, February 7, 2010, 12:42 PM

Doug Turnbull wrote:
>
> Barry, Sorry but what do you mean by 'high isolation headphones'. Would
> the Heil Pro-Set Plus do?
>

I'm only familiar with the Pro Set and that really doesn't have the level of
isolation needed, as Bill said. I researched what drummers are using during
live/recording sessions and ended up buying Sennheiser HD-280 phones, which
work well. A bit more isolation could be had with in-ear phones or perhaps
active isolation phones but the HD-280's are a significant step beyond the
Pro Set.

73,
Barry N1EU

--
View this message in context: http://n2.nabble.com/K3-in-a-cw-pileup-needs-work-tp4523884p4528969.html
Sent from the [K3] mailing list archive at Nabble.com.
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Guy, K2AV

Re: K3 DSP AGC Question

In reply to this post by KK7P

Thanks Lyle,

Some follow-on questions:

1) When you say "The DSP outputs a voltage to control the IF gain of
the radio." are you referring to VIFGAIN1 input to U3B on the RF
board?

2) Assuming so, is there anything that influences the voltage on
VIFGAIN1 other than on behalf of the RF gain pot, and is the voltage
appearing at VFGAIN1 on behalf of the RF gain pot "processed" away
from a linear replication of the pot wiper voltage?

3) The hardware AGC appears to have fixed slope, attack and decay
constants. What would be the DSP slope and decay config constants to
mimic the hardware AGC constants?

4) Is there a table that provides a dBm equivalent of each of the
threshold values? Or alternatively are the values on the Clifton Labs
site correct?

( 2 -117 dBm
3 -110.5 dBm
4 -105 dBm
5 -103.5 dBm
6 -102.5 dBm
7 -101 dBm
8 -99 dBm )

73, Guy.

On Sun, Feb 7, 2010 at 11:10 AM, Lyle Johnson <[hidden email]> wrote:

>
>> ...Lyle would have to comment on whether the DSP
>> AGC is developed before or after the IF gain is applied...
>
> Assuming ATT and PRE are OFF, hardware AGC voltage begins to have an
> effect on IF amplifier gain with a signal at the antenna in the region
> of -60 dBm, plus or minus a few dB. The hardware AGC voltage is
> developed at the final IF of 15 kHz and applied to the 8.215 MHz IF
> stage. Its purpose is to prevent the 15 kHz A to D converter at the DSP
> from being driven beyond its input limits (called over-ranging).
>
> The "onset of hardware AGC" level is influenced by PRE (which increases
> gain ab out 10 dB, decreasing the signal required at the antenna by the
> same 10 dB), ATT (which reduces signals by 10 dB, thus increasing the
> required signal at the antenna), and RF Gain when backed off sufficiently.
>
> What is "sufficiently"? The DSP outputs a voltage to control the IF
> gain of the radio. This voltage is compared with the hardware AGC
> voltage, and the higher voltage is applied to reduce the IF gain. If
> the RF Gain is backed off enough so that the resulting gain control
> voltage is grater than the hardware AGC voltage derived from the 15 kHz
> IF signal, then the criterion for "sufficiently" has been met.
>
> The DSP reads the hardware AGC voltage, regardless of the source, and
> uses the value as part of the S Meter calculation.
>
> The DSP AGC algorithm is computed based on the 15 kHz IF signal applied
> to the DSP's A to D converter. Thus it is after the IF gain is applied.
>
> Enjoy!
>
> 73,
>
> Lyle KK7P
> ______________________________________________________________
> 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
>

KK7P

Re: K3 DSP AGC Question

> Some follow-on questions:
>
> 1) When you say "The DSP outputs a voltage to control the IF gain of
> the radio." are you referring to VIFGAIN1 input to U3B on the RF
> board?
>

Yes.
> 2) Assuming so, is there anything that influences the voltage on
> VIFGAIN1 other than on behalf of the RF gain pot, and is the voltage
> appearing at VFGAIN1 on behalf of the RF gain pot "processed" away
> from a linear replication of the pot wiper voltage?
>
Without staring at the DSP code to verify the veracity of my reply, I
recall that the RF Gain control is the only thing that currently drives
the VIFGAIN1 voltage. Subject to change, of course, since it is a DSP
firmware function. And yes, the value read from the pot is processed by
the DSP on its way to becoming VIFGAIN1. Again, the algorithm applied
is subject to change.
> 3) The hardware AGC appears to have fixed slope, attack and decay
> constants. What would be the DSP slope and decay config constants to
> mimic the hardware AGC constants?
>
Correct as to the first, and I think there may be that there are no
settings that exactly mimic the HAGC. Their purposes are quite
different. To the DSP, influences of the HAGC voltage on the received
signal are treated no differently than changes in propagation.

> 4) Is there a table that provides a dBm equivalent of each of the
> threshold values? Or alternatively are the values on the Clifton Labs
> site correct?
>
> ( 2 -117 dBm
> 3 -110.5 dBm
> 4 -105 dBm
> 5 -103.5 dBm
> 6 -102.5 dBm
> 7 -101 dBm
> 8 -99 dBm )
>

There is no available table, and Jack's measurements were accurate at
the time they were made for the then-current firmware release.

73,

Lyle KK7P

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Paul-285

Re: K3 in a cw pileup - needs work

In reply to this post by Doug Turnbull

Doug Turnbull wrote:
>Barry, Sorry but what do you mean by 'high isolation headphones'. Would
>the Heil Pro-Set Plus do?
> 73 Doug EI2CN

This is what I use to isolate my self from XYL, kid, grandkid, and
great grandkid QRM.

http://www.extremeheadphones.com/

Works great.

Paul N4LCD

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Jack Brindle

Re: K3 in a cw pileup - needs work

Paul, you aren't old enough!

On Feb 7, 2010, at 1:07 PM, [hidden email] wrote:

> This is what I use to isolate my self from XYL, kid, grandkid, and
> great grandkid QRM.

- Jack Brindle, W6FB
---------------------------------------------------------------------------------------------

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Scott Prather-2

Re: K3 Loses RX Audio at BW of 2.8 kHz (Problem Resolved but Questions Remain)

In reply to this post by Rick Prather

As a follow-up to the e-mails that were sent to the reflector and those that
I received privately, I wanted to let the group know that last night I
resolved the problem I was having where audio would be lost in LSB, USB and
AM when the K3's bandwidth was set to 2.8 kHz while running FW 3.30.

As I mentioned yesterday, on Friday I received the DSP upgrade, so before
installing it I re-loaded the K3 with FW 3.76. After doing so, the problem
remained but now the audio would cut off at a BW of 3.0 kHz, returning at
3.1 kHz in all three modes. The full range of bandwidths available in the CW
and DATA modes were unaffected. I replaced the DSP board and the problem
remained (as expected). However, when I performed an EE Init, I found that
everything began working properly. As soon as I re-loaded my latest
configuration file, the problem returned. Unfortunately, my next-newest
configuration file was dated August 09 and turned out to be incompatible
with 3.76, so I manually re-configured the radio from scratch. All is well
now.

Thanks to all those who responded.

Scott
N7NB

-----Original Message-----
From: K6LE [mailto:[hidden email]]
Sent: Sunday, February 07, 2010 8:18 AM
To: WW2PT
Cc: Scott Prather; Elecraft Reflector
Subject: Re: [Elecraft] K3 Loses RX Audio at BW of 2.8 kHz

Bingo!

I restored my last config (from 1/20) and problem is gone..

Now I am trying to noodle over what configuration item may have changed
during the beta upgrade that caused it.

At any rate, all is good now!

Rick
K6LE

On 2/6/2010, at 11:07 , WW2PT wrote:

Joe Subich, W4TV-4

Re: K3 DSP AGC Question

In reply to this post by KK7P

Lyle,

> > 4) Is there a table that provides a dBm equivalent of each
> > of the threshold values? Or alternatively are the values
> > on the Clifton Labs site correct?
> >
> > (2 -117 dBm
> > 3 -110.5 dBm
> > 4 -105 dBm
> > 5 -103.5 dBm
> > 6 -102.5 dBm
> > 7 -101 dBm
> > 8 -99 dBm )
> >
>
> There is no available table, and Jack's measurements were
> accurate at the time they were made for the then-current
> firmware release.

Assuming that the threshold values have not changed in a major
way since Jack's measurements, would it be possible to extend
the range of threshold values - say to AGC THR=016 at about
-80dBm (assuming 2 dB per step)?

Such a change would put the K3 more in line with the K2 as
measured by Jack Smith ... as well as numbers reported by
Sherwood for the FT-1000D, FT-1000MP and even the IC-7600.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Lyle Johnson
> Sent: Sunday, February 07, 2010 2:21 PM
> To: Guy Olinger K2AV
> Cc: [hidden email]
> Subject: Re: [Elecraft] K3 DSP AGC Question
>
>
>
> > Some follow-on questions:
> >
> > 1) When you say "The DSP outputs a voltage to control the
> IF gain of
> > the radio." are you referring to VIFGAIN1 input to U3B on the RF
> > board?
> >
>
> Yes.
> > 2) Assuming so, is there anything that influences the voltage on
> > VIFGAIN1 other than on behalf of the RF gain pot, and is
> the voltage
> > appearing at VFGAIN1 on behalf of the RF gain pot "processed" away
> > from a linear replication of the pot wiper voltage?
> >
> Without staring at the DSP code to verify the veracity of my reply, I
> recall that the RF Gain control is the only thing that
> currently drives
> the VIFGAIN1 voltage. Subject to change, of course, since it
> is a DSP
> firmware function. And yes, the value read from the pot is
> processed by
> the DSP on its way to becoming VIFGAIN1. Again, the
> algorithm applied
> is subject to change.
> > 3) The hardware AGC appears to have fixed slope, attack and decay
> > constants. What would be the DSP slope and decay config
> constants to
> > mimic the hardware AGC constants?
> >
> Correct as to the first, and I think there may be that there are no
> settings that exactly mimic the HAGC. Their purposes are quite
> different. To the DSP, influences of the HAGC voltage on the
> received
> signal are treated no differently than changes in propagation.
> > 4) Is there a table that provides a dBm equivalent of each of the
> > threshold values? Or alternatively are the values on the
> Clifton Labs
> > site correct?
> >
> > ( 2 -117 dBm
> > 3 -110.5 dBm
> > 4 -105 dBm
> > 5 -103.5 dBm
> > 6 -102.5 dBm
> > 7 -101 dBm
> > 8 -99 dBm )
> >
>
> There is no available table, and Jack's measurements were accurate at
> the time they were made for the then-current firmware release.
>
> 73,
>
> Lyle KK7P
>
>
> ______________________________________________________________
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KK7P

Re: K3 DSP AGC Question

Hello Joe!
> Assuming that the threshold values have not changed in a major
> way since Jack's measurements, would it be possible to extend
> the range of threshold values - say to AGC THR=016 at about
> -80dBm (assuming 2 dB per step)?
>

Possible? Yes.

Likely? I don't know. There are a lot of side effects that happen when
the threshold is raised...

73,

Lyle KK7P

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Joe Subich, W4TV-4

Re: K3 DSP AGC Question

> Likely? I don't know.

Likely is a better choice since raising the AGC threshold
seems to be the primary goal of much of the "PRE/ATT/RF
Gain dance" we've seen recently.

The hardware AGC (HAGC) would seem to provide an ultimate
limit on level to the ADC - unless the ADC can't handle
the transient peaks - so a higher threshold for the DSP
derived AGC would be helpful in many ways.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Lyle Johnson
> Sent: Monday, February 08, 2010 11:24 AM
> To: [hidden email]
> Subject: Re: [Elecraft] K3 DSP AGC Question
>
>
> Hello Joe!
> > Assuming that the threshold values have not changed in a major
> > way since Jack's measurements, would it be possible to extend
> > the range of threshold values - say to AGC THR=016 at about
> > -80dBm (assuming 2 dB per step)?
> >
>
> Possible? Yes.
>
> Likely? I don't know. There are a lot of side effects that
> happen when the threshold is raised...
>
> 73,
>
> Lyle KK7P
>

Guy, K2AV

Re: K3 DSP AGC Question

It may be a dance, but hopefully careful intelligent musing over the
matter is convincing people that they should get the ambient well down
in the analog-to-digital converter (ADC) operating range. If they do,
a -99 threshold is a -109 threshold, and further backing off RF gain
can make it a -119 or -129 threshold as far as the ADC is concerned,
and headroom is being used for what headroom should be used for.

One thing for sure, there has not been a good-enough presentation of
what is going on, and people really don't seem to get it. For
something that is plain indisputable physics, people are still running
PRE and max RFgain on 80 with fast AGC, and are honestly dismayed and
confused about the inevitable outcome, incorrectly blaming the rig for
being natively noisy, no-work NR and NB, filter "ringing", unable to
pull signals out of noise, and more.

Maybe the variable gain by band in the MP (with a menu override) was
really a better strategy for a default. This same issue dogged Orion
owners, and by the chatter a lot of them never understood either.

There IS something entirely separate with the headphone audio and HI-Z
headsets, high volume levels, maybe a sharp saturation point, and
mush, just haven't nailed it yet.

73, Guy.

On Mon, Feb 8, 2010 at 12:01 PM, Joe Subich, W4TV <[hidden email]> wrote:

>
>
>> Likely? I don't know.
>
> Likely is a better choice since raising the AGC threshold
> seems to be the primary goal of much of the "PRE/ATT/RF
> Gain dance" we've seen recently.
>
> The hardware AGC (HAGC) would seem to provide an ultimate
> limit on level to the ADC - unless the ADC can't handle
> the transient peaks - so a higher threshold for the DSP
> derived AGC would be helpful in many ways.
>
> 73,
>
> ... Joe, W4TV
>
>
>
>
>> -----Original Message-----
>> From: [hidden email]
>> [mailto:[hidden email]] On Behalf Of Lyle Johnson
>> Sent: Monday, February 08, 2010 11:24 AM
>> To: [hidden email]
>> Subject: Re: [Elecraft] K3 DSP AGC Question
>>
>>
>> Hello Joe!
>> > Assuming that the threshold values have not changed in a major
>> > way since Jack's measurements, would it be possible to extend
>> > the range of threshold values - say to AGC THR=016 at about
>> > -80dBm (assuming 2 dB per step)?
>> >
>>
>> Possible? Yes.
>>
>> Likely? I don't know. There are a lot of side effects that
>> happen when the threshold is raised...
>>
>> 73,
>>
>> Lyle KK7P
>>
>
>
> ______________________________________________________________
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

KK7P

Re: K3 DSP AGC Question

> There IS something entirely separate with the headphone audio and HI-Z
> headsets, high volume levels, maybe a sharp saturation point, and
> mush, just haven't nailed it yet.

Note that the headphone audio path of the K3 is designed for 32-ohm and
lower headphone impedances. Higher impedance phones provide less audio
for a given transducer efficiency. Cranking up the AF gain to
compensate can lead to clipping-related distortion.

73,

Lyle KK7P
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Mike K2MK

Re: K3 DSP AGC Question

Hi Lyle:

I was very disappointed to read your post. I purchased a Proset headset directly from Elecraft when I bought my K3. According to Heil this headset has an impedance of 200 ohms. Is that why I have to plug my headphones into the rear speaker jack to get sufficient audio output from them? Why would you folks sell a headset that does not complement the K3? I am really disappointed.

Mike K2MK

>Note that the headphone audio path of the K3 is designed for 32-ohm and
>lower headphone impedances. Higher impedance phones provide less audio
>for a given transducer efficiency. Cranking up the AF gain to
>compensate can lead to clipping-related distortion.
>73,
>Lyle KK7P

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