[Elecraft] K3 in a cw pileup - needs work
Dave Hachadorian
times I had a pileup of four or five loud stations calling me.
With AGC turned on, they were all mushed together, and I couldn't
copy any of them.
AGC settings:
dcy soft
hld 0.2
pls nor
slp 000
thr 008
f 200
s 020
I tried both fast and slow agc. No joy.
So I turned the AGC OFF. Now this introduces another problem -
the very low threshold of the AF Limiter. The AF limiter, even at
its highest setting of 030 introduces gross distortion on loud
signals. This is even worse than the mushy AGC.
So I transfer the headphones to the speaker output, so I can
reduce the AF gain setting in an attempt to get away from the
raucous AF limiter. This works for a while, until finally one
loud signal blows out the K3's audio amplifier. This is the
second time that has happened to me. I guess I'm a slow learner
on that issue.
Something really needs to be done here. My suggestions would to
raise the agc threshold further, and increase the slope of the
agc line (that would mean a slp setting of less than zero). The
AF limiter threshold also needs to be raised, and the AF speaker
output needs better protection.
Dave Hachadorian, K6LL
Yuma, AZ
.
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Ken Kopp
I also lost an audio output chip last year when an
unexpectedly LOUD SSB signal appeared during
a roundtable QSO.appeared. Heard a part of a
syllable, a pop and then silence.
Was sent a replacement chip immediately.
Your phones ... and their plug ... -are- stereo, aren't
they?
73! Ken - K0PP
k0...@ElecraftCovers.net
Guy Olinger K2AV
Using slope 000 is likely most of your problem. With that setting all
signals regardless of strength are set to the same level regardless of
how loud they are coming in. If they are zero beat or close, it will
mush the dickens out of the copy by making them all the same level in
your ear. I set AGC SLP to 15 for contests. I also use slow AGC the
entire time. If there are key clicks, I use NB with IF off and dsp to
t3-7 or t2-7. It rounds off CW bauds some but does not make them
uncopyable.
Make sure your ATT/PRE/RFGAIN use conforms to something like:
160m ATT plus RF gain at 2 oclock
80m ATT plus RF gain at 3 oclock
40m ATT plus RF gain fully clockwise.
20m " "
15m off plus RF gain fully clockwise.
10m PRE plus RF gain fully clockwise.
6m " "
...if you are listening on your transmit antenna. At least to start.
Make sure the ambient noise on the band is moderately low audio
listening on a clear frequency.
Using the NB with those settings, including the ATT/PRE/RFGAIN
settings. Just today I was listening to an S4 Cuban underneath what
were S9/5 key clicks with the NB off. Offending station up 500 Hz at
30 over 9 (really), and was using 250 filter running at WIDTH 350.
Good luck in Sprint this weekend!
73, Guy.
Dave - AB7E
Wrong ... you have that totally backwards. AGC SLP = 000 gives the LEAST amount of AGC action you can get in the K3. AGC SLP = 015 is the setting that makes all signals above the threshold sound the same, and potentially creates mushy distortion for multiple signals depending on what setting you use for AGC THR. Read the manual, or check out http://www.cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm if you want to see it graphically.
K6LL's AGC settings are exactly the same as those I use for contesting.
73,
Dave AB7E
------Original Mail------
From: "Guy Olinger K2AV" <oli...@bellsouth.net>
To: "Dave Hachadorian" <k6...@arrl.net>,
"Elecraft Reflector" <elec...@mailman.qth.net>
Sent: Sat, 6 Feb 2010 00:17:32 -0500
Subject: Re: [Elecraft] K3 in a cw pileup - needs work
Hi Dave,
Using slope 000 is likely most of your problem. With that setting all
signals regardless of strength are set to the same level regardless of
how loud they are coming in. If they are zero beat or close, it will
mush the dickens out of the copy by making them all the same level in
your ear. I set AGC SLP to 15 for contests. I also use slow AGC the
entire time. If there are key clicks, I use NB with IF off and dsp to
t3-7 or t2-7. It rounds off CW bauds some but does not make them
uncopyable.
______________________________________________________________
The Smiths
Having the Slope set to 000 is like not having the AGC on at all.
If you're going to have a theshold, then why bother to keep the AGC from actually doing anything? At least put that Slope to 04 or something where it actually makes a difference. If your concern is having loud signals be louder than the low signals underneath it, and you want to compress the lower signals to sound as loud as the loud ones (or Vs Versa, have the loud ones squashed to the same level as the low signals), you have to actually set the slope compression to do something, not turn it off by setting it to 00. I agree with Guy completely.
Also, there's a setting in the menu that will allow you to have a "soft" Agc which was designed JUST for this Contest/Pile up situation your describing. If you don't know what or where it is, please let us know and I will dig it up for you.
As for the AGC off level limiter, and creating distortion... Yea, I've noticed that with the loud ones too. I belive that Wayne did something with that setting in the last 2 beta software releases... I don't know if you have access to it yet.
M
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Duncan Carter
Scott Prather
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?
Tnx.
Scott
N7NB
Dave - AB7E
Not true. Read the Clifton labs link that I posted and you'll see that on the K3 AGC SLP = 000 actually gives a slope around 2 ... i.e., it takes 4 times the signal strength to sound twice as loud.
The concern is not about having loud signals sound louder than weaker ones ... the concern is having the least nonlinearity in the signal chain to minimize in-band intermod products. Loud signals override weak signals so intermod isn't an issue there. The problem occurs when multiple signals are approximately the same strength and they lie at or near a nonlinear portion of the gain curve. Take a look at the severe knee in the Clifton Labs AGC plots and you'll see what I mean. The best way to avoid distortion in the presence of multiple signals for the majority of conditions (especially when receiving multiple weak ones) is to set the AGC threshold to maximum (008) and the slope to minimum (000), but that still leaves the opportunity for multiple STRONG signals to find the knee in the curve and generate distortion. It also, of course, leaves you less protected against really strong signals.
And please don't try to sound so condescending ... I know exactly what the AGC SOFT setting is and I use it exclusively.
Lastly, you should pay attention to whom is posting what. The original poster who complained about the AF LIM situation is Dave, K6LL.
73,
Dave AB7E
------Original Mail------
From: "The Smiths" <notfo...@hotmail.com>
To: "Elecraft Reflector" <elec...@mailman.qth.net>
Sent: Sat, 6 Feb 2010 06:04:58 +0000
Ed Muns
> Using slope 000 is likely most of your problem. With that
> setting all signals regardless of strength are set to the
> same level regardless of how loud they are coming in.
Actually AGC SLP 015 flattens the audio output. AGC SLP 000 is the minimum
AGC action but it still reduces the audio output compared to AGC OFF.
> If
> they are zero beat or close, it will mush the dickens out of
> the copy by making them all the same level in your ear. I set
> AGC SLP to 15 for contests.
This makes a wide range of RF signal levels produce the same audio output
level, probably not ideal for contesting.
> Make sure your ATT/PRE/RFGAIN use conforms to something like:
>
> 160m ATT plus RF gain at 2 oclock
> 80m ATT plus RF gain at 3 oclock
> 40m ATT plus RF gain fully clockwise.
> 20m " "
> 15m off plus RF gain fully clockwise.
> 10m PRE plus RF gain fully clockwise.
> 6m " "
These ATT and PRE settings are generally OK, but band conditions and
antenna/terrain gain can alter them. The RF Gain is seldom optimum at full
scale.
Ed - W0YK
-----------------------------------------------
Ed Muns
Muns Vineyard - www.munsvineyard.com
FaceBook - www.facebook.com/munsvineyard
Ed Muns
> Having the Slope set to 000 is like not having the AGC on at all.
Not really. AGC SLP 000 still produces significant AGC action. See K8ZOA's
paper. There is considerable white space between the Slope=0 curve and the
AGC = OFF line. That's why Dave proposed enhancing the AGC SLP parameter
with negative numbers.
Ed - W0YK
-----------------------------------------------
Ed Muns
Muns Vineyard - www.munsvineyard.com
FaceBook - www.facebook.com/munsvineyard
______________________________________________________________
Arie Kleingeld PA3A
Only mushy experience I had the following situation:
- Being on the DX cluster
- Everybody clicks to you through some bandmap
- Therefore everybody calls on exact the same freq
No wonder it sounds mushy.
(exception: K2's that are mostly more than a few Hz off can be heard :-) )
73
Arie PA3A
K6LE
The only difference is it happens when I go to 2.9.
As I increase the width I see the filter switch at 2.8 (I have the 2.7 SSB filter and 6.0 AM filter) and then at 2.9 it goes dead until I advance it to 3.0 and from then on it continues as it should.
Also when it goes from dead to audio at 3.0 I get a nasty click.
Scott, maybe it's a Prather deal.
Rick Prather
K6LE
Geoffrey Mackenzie-Kennedy
The problem reported has the classic characteristics of in-passband IMD
caused by a small dynamic range (IMDDR3) IF system, rather than being
something caused by the AGC sub-system. Yes changing the AGC's loop
characteristics will alter the effect, but the root cause is still
non-linearity in the signal path. I suspect the second mixer.
Trouble is that large IMDDR3 IF systems can consume a lot of power, and low
power drain by the K3's receiver was a design goal I believe.
73,
Geoff
GM4ESD
Joe Planisky
Just a shot in the dark: Have you checked your filter configuration?
If you happen to have an empty slot enabled for those modes, you'll
get exactly the behavior you described. Use the K3 Utility to look
for a slot that you know to be empty but with the Bandwidth set to 2.8
and the LSB, USB, and AM boxes checked.
73
--
Joe KB8AP
On Feb 5, 2010, at 10:45 PM, 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.
...
> 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.
>
...
W4CCS
LD" error. Now the K3 is basically dumb. In the manual, it says to
unplug the power for 5 seconds, Hold the power button for approximately
10 seconds and then re-load the firmware.
My problem is that I can no longer get the computer to talk to the K3
and therefore cannot attempt a re-load.
I'm using the Microham router software to talk to the K3 and this has
been working great until now.
Question, does the K3 keep the old settings (38400, 8, N, 1) or does it
resort back to the default settings which are ??
I also tried a direct cable (straight and null modem) and cannot get any
communication to occur.
I'm stuck until I get the K3 talking to the computer again..
HELP..!!
de W4CCS
Dick Dievendorff
firmware through the microHAM router. It works sometimes, but this
mechanism is not reliable for firmware load.
Dick, K6KR
Sent from my iPhone
Dick Dievendorff
Utility restores the speed it started with. However if the firmware
load fails, the K3 may stay at 38400.
Dick, K6KR
Sent from my iPhone
On Feb 6, 2010, at 8:14 AM, W4CCS <w4...@w4ccs.com> wrote:
W4CCS
problem.. All firmware uploaded and we are back in business..
Again, Thanks
gdau...@stanford.edu
Sliced? Or unsliced? 8-)
Will you be going to Visalia this year?
73,
George T Daughters, K6GT
CU in the California QSO Party (CQP)
October 2-3, 2010
Scott Prather
however, I'd already checked this. According to the K3 Configuration
Utility, FL3 is enabled for LSB, USB and AM in both receivers. Another point
to keep in mind is that FL3 is only selected at a BW setting of 2.7 kHz or
below, FL2 is still used at 2.8 kHz.
I just received the DSP board upgrade yesterday and intend to install it
this weekend. However, I thought that before I make any hardware changes
there might be some value in trying to determine what happened in case the
swap-out clears this issue.
Scott
N7NB
Dick Green WC1M
or five loud stations. This leads me to wonder if the cause is the K3
hardware AGC threshold being too low, even after the mod introduced two
years ago. That mod was supposed to raise the threshold from S9+5 dB to
S9+25-30 dB.
I got into this issue after repeatedly being botherd by thumping from loud
CW stations above my passband during big contests. When I first noticed it,
I was using the 5-pole 500 Hz filters and the DSP set to about 300 Hz. I'd
hear the thumping from stations more than 150 Hz or even 250 Hz above my
frequency. Testing revealed that I could hear thumping from loud CW signals
as far as 700Hz away. The testing also showed that the filters were
effective against a loud continuous carrier, but CW signals were slipping
under the skirts. This suggested that the problem is caused by the hardware
AGC being tripped by the loud signals. I switched to 8-pole 400 Hz filters,
and that improved the situation considerably.
My testing probably wasn't lab-quality, but it showed that the hardware AGC
really kicks in much lower than S9+25-30dB. I think it's more like S9, or
just above. Perhaps if two or more signals in Dave's pileup were that lour
or louder, the hardware AGC kicked in and mushed them together?
73, Dick WC1M
Wes Stewart
For non-portable use how about a "K3 Pro" or "K3 MK V++" that clips a few circuit traces and has a daughter board that uses two or three filter slots to house a stout IF amp, an H-mode second mixer and a PIN attenuator before the DSP? The one remaining filter would only have to be good enough to get rid of the image.
Just thinking out loud.
--- On Sat, 2/6/10, Geoffrey Mackenzie-Kennedy <gm4...@btinternet.com> wrote:
Hi Guy,
The problem reported has the classic characteristics of in-passband IMD
caused by a small dynamic range (IMDDR3) IF system, rather than being
something caused by the AGC
sub-system. Yes changing the AGC's loop
characteristics will alter the effect, but the root cause is still
non-linearity in the signal path. I suspect the second mixer.
Trouble is that large IMDDR3 IF systems can consume a lot of power, and low
power drain by the K3's receiver was a design goal I believe.
73,
Geoff
GM4ESD
Joe Subich, W4TV
> I'm using the Microham router software to talk to the K3 and this has
> been working great until now.
DO NOT use microHAM Router to upload firmware to the K3.
It IS NOT SUPPORTED. Find a computer with a hardware
serial port or a dumb external USB to serial converter.
73,
... Joe, W4TV
Ruben Navarro Huedo
No radio and dissable router queries in the microHAM software.
--
Rubén Navarro Huedo - EA5BZ
http://www.palotes.com
Don Wilhelm
Since Joe W4TV is an authority on microHAM gear, I would say "use it at
your own peril" if you insist. Yes, there have been reports of success,
but Joe says IT IS NOT SUPPORTED! Please do not complain that you broke
your K3 with a firmware load when you used the microHAM router., just
get a good serial port (preferably hardware), follow the steps in the
K3Utility help file and do a proper reload.
73,
Don W3FPR
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.733 / Virus Database: 271.1.1/2671 - Release Date: 02/06/10 02:35:00
Joe Subich, W4TV
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.
Barry N1EU
Dave Hachadorian wrote:
>
> Tonight I used a pair of K3's in the Sprint practice. Several
> times I had a pileup of four or five loud stations calling me.
> With AGC turned on, they were all mushed together, and I couldn't
> copy any of them.
>
> So I turned the AGC OFF. Now this introduces another problem -
> the very low threshold of the AF Limiter. The AF limiter, even at
> its highest setting of 030 introduces gross distortion on loud
> signals. This is even worse than the mushy AGC.
>
You need to maximize your rf/af dynamic range - that is what is going to
turn that mush into a beautiful symphony of distinct signals of varying
levels. What has worked well for me is AGC off (although AGC on works fine
as well), high isolation headphones, and the gain throttling techniques
(most important) described by K3NA, W4ZV, myself, and others.
73,
Barry N1EU
--
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Barry N1EU
Barry N1EU wrote:
>
> You need to maximize your rf/af dynamic range - that is what is going to
> turn that mush into a beautiful symphony of distinct signals of varying
> levels. What has worked well for me is AGC off (although AGC on works
> fine as well), high isolation headphones, and the gain throttling
> techniques (most important) described by K3NA, W4ZV, myself, and others.
>
Just to continue from previous post - I experienced only mush in pileup
reception until fully adopting this technique. High isolation headphones
are critical because you want to set gain such that weak signals are lightly
heard but clearly copiable. You're maximizing the receive dynamic range
delivered to your ears and the high isolation means you can clearly hear
fainter signals without turning up the gain and squashing the dynamic range
(and too frequently engaging AF Limiter with AGC Off).
73,
Barry N1EU
--
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WW2PT
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
Doug Turnbull
the Heil Pro-Set Plus do?
73 Doug EI2CN
-----Original Message-----
From: elecraft...@mailman.qth.net
[mailto:elecraft...@mailman.qth.net] On Behalf Of Barry N1EU
Sent: 07 February 2010 01:01
To: elec...@mailman.qth.net
Bill W4ZV
"High isolation headphones" below means ~30 dB isolation from ambient noise.
Heil does not make any in this range and most active noise reduction
headphones (e.g. Bose) only have 10-15 dB. Here are some examples of what
Barry meant:
http://www.extremeheadphones.com/ex-29.html
http://www.sennheiserusa.com/private_headphones_dj-headphones_004974
http://www.etymotic.com/ephp/er6.aspx
These are all available in the $75-100 range.
73, Bill
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Barry N1EU
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
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Juan EA5RS
Has anyone measured those IMD products under the mentioned conditions and
concluded from the results that they are the culprit for the mushy (somewhat
vague description) audio that makes impossible to copy the different
callsigns?
Some W6s measured in a lab test setup a similar effect on the FT1000MP years
ago and found that the problem was the AGC recovering too fast (in between
symbols) making all signals sound as loud as others. The solution was to
increase the time constant. The loudest signal would then set the radio gain
level. Then characters in-between from weaker signals sounded weaker making
them distinct (or maybe buried).
I cant think why you would ever need a recovery time constant any shorter
than say 150 ms, while shorter time constants are normally used -reading
Clifton I think the FAST setting in the K3 is 73 ms-. At 60 WPM, a dit is
20ms long if I am not mistaken, and an intersymbols spacing (7 time units)
to full gain recovery seems the shortest time that would be necessary for
the receiver to recover full gain.
73 de Juan EA5RS
-----Mensaje original-----
De: elecraft...@mailman.qth.net
[mailto:elecraft...@mailman.qth.net] En nombre de Geoffrey
Mackenzie-Kennedy
Enviado el: sábado, 06 de febrero de 2010 11:56
Para: Guy Olinger K2AV
CC: Elecraft Discussion List
Asunto: Re: [Elecraft] K3 in a cw pileup - needs work
Hi Guy,
73,
Geoff
GM4ESD
__________ Informacisn de NOD32, revisisn 4576 (20091105) __________
Este mensaje ha sido analizado con NOD32 antivirus system
http://www.nod32.com
David Cutter
A low cost solution is to use any in-ear type earphone that suits you plus a
pair of common or garden ear defenders. The earphone lead should be as thin
as possible so that the leakage around the lead as it exits the defender is
as small as possible.
Ear defenders I have come across make the head sweat and therefore
uncomfortable after an hour or so; a cloth cover, such as aircraft
headphones have is a solution, but reduces isolation slightly.
David
G3UNA
>
>
> 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
>
> --
______________________________________________________________
Brendan Minish
have much ambient noise in the shack.
I find my Beyerdynamic DT234PRO headset very good. It's not a very high
isolation headset but it's a fully closed design and my shack is
reasonably quiet
the DT234PRO is a headset that is produced for language lab type
applications and widely used by PC gamers too, it's comfortable to wear
for long periods of time and provides reasonable isolation from the
surroundings.
I get great audio reports from the microphone which is a back electoret
condenser with a cardioid pattern.
It has a presence peak (like most microphones intended for the spoken
word, Heil did not 'invent' this..) and the cardioid pattern helps to
reduce pick-up of any ambient noise
It's completely Plug and play with the K3, plug it in the back and turn
Microphone bias.
I paid about 60 Euro for it on Ebay
73
Brendan EI6IZ
--
73
Brendan EI6IZ
Barry N1EU
Dick Green WC1M-2 wrote:
>
> Dave indicates that the problem occurred when the pileup consisted of four
> or five loud stations. This leads me to wonder if the cause is the K3
> hardware AGC threshold being too low, even after the mod introduced two
> years ago.
>
If gain were throttled (e.g., via ATT on, PRE off, reduced RF Gain),
wouldn't AGC Threshold be effectively raised?
73,
Barry N1EU
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Guy Olinger K2AV
excess gain in RF/IF strip is at the root of some number of
complaints. 73, Guy.
Barry N1EU
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
Guy, K2AV wrote:
>
> This is true, but seems to be a VERY hard point to get across. Running
> excess gain in RF/IF strip is at the root of some number of
> complaints.
>
> On Sun, Feb 7, 2010 at 8:22 AM, Barry N1EU <barry...@gmail.com> wrote:
>> If gain were throttled (e.g., via ATT on, PRE off, reduced RF Gain),
>> wouldn't AGC Threshold be effectively raised?
>
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Don Wilhelm
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
>
>
Guy Olinger K2AV
gain to produce moderately low audio from ambient noise on a clear
frequency. You can set the AGC threshold anywhere you want according
to taste. Some are using NO AGC and the audio limiter to expand
"threshold" to the audio limiter level.
I'm proposing that there is a moderation point between one extreme of
ambient noise shoved up into the AGC reduction range and the other of
no AGC at all. And that changing RF gain during a pile up can
maximize amplitude discrimination.
Particularly for contests, NOT reducing the RF/IF gain per band on the
lower bands just shoves the ambient noise up to a roar where the AGC
winds up REDUCING wanted signals down to the level where noise has
been BROUGHT UP, reducing the apparent signal to noise as perceived by
the ear/brain combination to zero, a researched and documented
phenomenon that has been quite appropriately reported by some here as
"mush". This uncomfortable state is amplified in a pile up where most
of the discrete signals become "noise" for hearing purposes, and the
already used up threshold in the AGC forces them all to the same
level. "Mush" is a very good description.
(One experiment I recall is asking someone to identify individual
conversations out of a monaural recording of a school cafeteria at
lunchtime -- only the very loudest can be discerned.)
AGC under squished circumstances can make "mush" all by itself without
any help from a purported (but never carefully measured and reported)
IMD "problem".
The AGC threshold engages at a fixed voltage out of the RF/IF string
for each step. Only the protective hardware AGC is operative before
this point. If your setting of PRE/ATT/RFGAIN places ambient noise at
what should be reserved for an S3 signal, you have subtracted that
from your selected threshold range, no matter what your threshold
preferences. And at worst case have already engaged AGC for the
ambient noise.
Threshold should allow one to have some range where any level
difference in competing signals come through to allow ear/brain to
tell them apart, AND still have a top where leveling kicks in to
protect the ears.
73, Guy.
On Sun, Feb 7, 2010 at 9:19 AM, Barry N1EU <barry...@gmail.com> 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
>
>
> Guy, K2AV wrote:
>>
>> This is true, but seems to be a VERY hard point to get across. Running
>> excess gain in RF/IF strip is at the root of some number of
>> complaints.
>>
>> On Sun, Feb 7, 2010 at 8:22 AM, Barry N1EU <barry...@gmail.com> wrote:
>>> If gain were throttled (e.g., via ATT on, PRE off, reduced RF Gain),
>>> wouldn't AGC Threshold be effectively raised?
Geoffrey Mackenzie-Kennedy
Thanks for your e-mail. I will reply in full after I return home this
evening, off-list if my answer is long.
The symptoms, and the cures suggested, strongly suggest that it is a well
known type of IMD problem caused by the IF hardware - which includes the
roofing filter.
I understand the AGC recovery problem that you mention, but do you know if
the in-passband IMD products of the FT1000MP were actually measured? To
measure IMD products with both test signals inside a CW bandwidth passband
usually requires crystal controlled generators for reasons of low phase
noise, especially if the receiver's in-passband odd-order dynamic range is
large. Increasing bandwidth to allow much wider spacings of the test signals
usually paints a false picture, because the signal handling capability of
narrow bandwidth crystal filters is usually worse than that of the wider
filters.
73,
Geoff
GM4ESD
On Sunday, February 07, 2010 at 12:57 PM, Juan EA5RS <ea...@ono.com> wrote:
Are you guys sure this is a frequency domain problem?
Has anyone measured those IMD products under the mentioned conditions and
concluded from the results that they are the culprit for the mushy (somewhat
vague description) audio that makes impossible to copy the different
callsigns?
Some W6s measured in a lab test setup a similar effect on the FT1000MP years
ago and found that the problem was the AGC recovering too fast (in between
symbols) making all signals sound as loud as others. The solution was to
increase the time constant. The loudest signal would then set the radio gain
level. Then characters in-between from weaker signals sounded weaker making
them distinct (or maybe buried).
I cant think why you would ever need a recovery time constant any shorter
than say 150 ms, while shorter time constants are normally used -reading
Clifton I think the FAST setting in the K3 is 73 ms-. At 60 WPM, a dit is
20ms long if I am not mistaken, and an intersymbols spacing (7 time units)
to full gain recovery seems the shortest time that would be necessary for
the receiver to recover full gain.
73 de Juan EA5RS
Guy Olinger K2AV
on VIFGAIN1 on the RF board. It is at least some derivative of the
signal from the "RF" gain control.
73, Guy.
Barry N1EU
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
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Guy Olinger K2AV
> 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.
Lyle Johnson
> ...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
K6LE
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
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
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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
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Luis V. Romero
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" <li...@subich.com>
Subject: Re: [Elecraft] Firmware upload problem
To: "'Ruben Navarro Huedo'" <run...@gmail.com>,
<elec...@mailman.qth.net>
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/
Hector Padron
AD4C
"For a refined ham it is compulsory to own a k3"
--- On Sun, 2/7/10, Barry N1EU <barry...@gmail.com> wrote:
From: Barry N1EU <barry...@gmail.com>
Subject: Re: [Elecraft] K3 in a cw pileup - needs work
Guy Olinger K2AV
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.
Lyle Johnson
> 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.
Pa...@n4lcd.com
>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
Scott Prather
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
Jack Brindle
On Feb 7, 2010, at 1:07 PM, Pa...@N4LCD.com wrote:
> This is what I use to isolate my self from XYL, kid, grandkid, and
> great grandkid QRM.
- Jack Brindle, W6FB
---------------------------------------------------------------------------------------------
Joe Subich, W4TV
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
Lyle Johnson
> 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...
Joe Subich, W4TV
> 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: elecraft...@mailman.qth.net
> [mailto:elecraft...@mailman.qth.net] On Behalf Of Lyle Johnson
> Sent: Monday, February 08, 2010 11:24 AM
> To: elec...@mailman.qth.net
> Subject: Re: [Elecraft] K3 DSP AGC Question
>
>
Guy Olinger K2AV
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.
Lyle Johnson
> 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.
Mike K2MK
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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Guy Olinger K2AV
well-known makers. People are blaming it on everything from the phases
of the moon to the neighbor's dog. It would be good to have that
cleanly targeted.
What's the recommended workaround or is there a workaround? Maybe a
high impedance headphone dongle kit that terminates the stereo speaker
audio in 8 ohms and has both headphone jacks?
73, Guy.
Ken Kopp
Heil HS's that work well with my K3 and can deliver -far-
more audio than my 72 year old ears can handle with the
AF gain parameter set for "LO".
73! Ken Kopp - K0PP
Elecraf...@rfwave.net
Lyle Johnson
with my K3 and they work just fine, as do my Yamaha CM500.
The K3 can easily drive high-impedance headphones.
My point was simply that *if* you have to crank up AF gain to the point
of distortion to get sufficient headphone volume, and *if* you are using
high-impedance headphones, *then* the problem *may* be related to the
headphone impedance.
Mike
So cranking up the AF results is less than optimum operation?
73,
Mike, NF4L
Barry N1EU
Mike K2MK wrote:
>
> 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.
>
I routinely use a 200-ohm Pro Set for ssb plugged into the headphone jack
and it works like a charm.
73,
Barry N1EU
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David Christ
expressed about headsets of 120 to 600 ohms. A close reading of
Lyle's words indicates that higher impedance is only a problem if
there is a need to increase the AF gain too much. As long as you
don't have to crank the AF gain way up there shouldn't be a problem.
I think there is also some confusion about what high impedance means.
The common WW II aircraft headset came in two versions High Z at
4000 ohms and Low Z at 600 ohms. By that standard 120 ohms is very
low and 600 is still low.
If your AF gain is at 3 o'clock maybe your earphones or ears have too
high an impedance.
David K0LUM
-------------------------------------------------------------------
Lew Phelps K6LMP
RadioShack sells one for $2.99. They don't publish the specs in enough detail to tell for sure, but it has a number of taps on the secondary, and would appear to be able to transform the impedance of most headphones into the K3's "sweet spot."
Am I missing something here? a small project box with the transformer enclosed and phone jacks in and out ought to do the trick.
Lew K6LMP
Grant Youngman
>>
>> 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.
There are two factors here. One is impedance. (The impedance actually presented by a headphone is frequency dependent and can vary widely from the "nominal" value). The other is sensitivity.
I regularly use 250 ohm headphones on the K3 with no issues whatsoever. Why? They require very little drive to reach an acceptable output level. So even given their relatively high Z (compared to 32 ohms) it isn't necessary to drive the output stage of the K3 into clipping or high distortion levels to get plenty of good audio.
I have a set of high end audiophile headphones with 62 ohm Z. I don't use them on the K3 (tried them once). Why? It takes a whole lot of power (relatively) to drive them to reasonable listening levels.
Given the number of people who use Prosets and seem to like them just fine, I don't know why there would be any real concern or any reason to feel disappointment.
Grant/NQ5T
ab2tc
Hi, I use the 200 ohm Heil proset and even with the AF gain set to "LO" I
have no problem getting enough audio or distortion free audio. Either there
is a number of defective prosets or K3s out there because this is making no
sense at all.
Knut - AB2TC
Grant Youngman wrote:
>
>
> <snip>
> There are two factors here. One is impedance. (The impedance actually
> presented by a headphone is frequency dependent and can vary widely from
> the "nominal" value). The other is sensitivity.
>
> I regularly use 250 ohm headphones on the K3 with no issues whatsoever.
> Why? They require very little drive to reach an acceptable output level.
> So even given their relatively high Z (compared to 32 ohms) it isn't
> necessary to drive the output stage of the K3 into clipping or high
> distortion levels to get plenty of good audio.
> <snip>
> Grant/NQ5T
> ______________________________________________________________
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Guy Olinger K2AV
EVERYTHING, including TV. Ask your wives. It's probably not fair or
electronically practical to expect that kind of range in everything.
My Bose QC15's (plugged into headphone jack) would blow my head off if
I turned up the K3 AF past about 9 oclock.
drewko
very light, omfortable and non-fatiguing (but "high isolation" by no
means). They are collapsible and the headband can pivot to behind head
(so you don't muss up your 'do...) Lifetime warranty. They sound
really good to me, but may have too much bass for some. I think
they're great for CW.
73,
Drew
On Mon, 08 Feb 2010 15:47:52 -0600, David K0LUM wrote:
>After Lyle's comment (reproduced below), there has been been concern
>expressed about headsets of 120 to 600 ohms. A close reading of
>Lyle's words indicates that higher impedance is only a problem if
>there is a need to increase the AF gain too much. As long as you
>don't have to crank the AF gain way up there shouldn't be a problem.
>
>I think there is also some confusion about what high impedance means.
>The common WW II aircraft headset came in two versions High Z at
>4000 ohms and Low Z at 600 ohms. By that standard 120 ohms is very
>low and 600 is still low.
>
>If your AF gain is at 3 o'clock maybe your earphones or ears have too
>high an impedance.
>
>David K0LUM
>
______________________________________________________________
O. Johns
DON'T DO IT!!!!
Oliver
W6ODJ
On 7 Feb 2010, at 3:21 AM, Bill W4ZV wrote:
>
> "High isolation headphones" below means ~30 dB isolation from ambient noise.
> Heil does not make any in this range and most active noise reduction
> headphones (e.g. Bose) only have 10-15 dB. Here are some examples of what
> Barry meant:
>
> http://www.extremeheadphones.com/ex-29.html
> http://www.sennheiserusa.com/private_headphones_dj-headphones_004974
> http://www.etymotic.com/ephp/er6.aspx
>
> These are all available in the $75-100 range.
>
> 73, Bill
>
>
> Doug Turnbull wrote:
>>
>> Barry, Sorry but what do you mean by 'high isolation headphones'. Would
>> the Heil Pro-Set Plus do?
>> 73 Doug EI2CN
>>
>> -----Original Message-----
>> From: elecraft...@mailman.qth.net
>> [mailto:elecraft...@mailman.qth.net] On Behalf Of Barry N1EU
>> Sent: 07 February 2010 01:01
>> To: elec...@mailman.qth.net
>> Subject: Re: [Elecraft] K3 in a cw pileup - needs work
>>
>>
>>
>> Barry N1EU wrote:
>>>
>>> You need to maximize your rf/af dynamic range - that is what is going to
>>> turn that mush into a beautiful symphony of distinct signals of varying
>>> levels. What has worked well for me is AGC off (although AGC on works
>>> fine as well), high isolation headphones, and the gain throttling
>>> techniques (most important) described by K3NA, W4ZV, myself, and others.
>>>
>> Just to continue from previous post - I experienced only mush in pileup
>> reception until fully adopting this technique. High isolation headphones
>> are critical because you want to set gain such that weak signals are
>> lightly
>> heard but clearly copiable. You're maximizing the receive dynamic range
>> delivered to your ears and the high isolation means you can clearly hear
>> fainter signals without turning up the gain and squashing the dynamic
>> range
>> (and too frequently engaging AF Limiter with AGC Off).
>>
>> 73,
>> Barry N1EU
>>
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Mike K2MK
Hi Barry:
I was annoyed when I first read Lyle's post. It sounded like the right hand didn't know what the left was doing. Really, why optimize the amplifier for 32 ohms and then only offer a 200 ohm headset for sale. But Lyle's further explanation was reasonable and I probably overreacted.
I know my hearing is not what it used to be. I first used the speaker jack during the ARRL 10 meter contest in Dec 08. The band was noisy so I had the NR on but there just wasn't enough volume available to pull out the barely audible stations. (Having a no gain vertical doesn't help either). There really is no good reason to keep the headphones in the speaker jack on the other bands. I just do and I keep the AF level correspondingly low.
I took note of your recent posting about the HD-280s. I put them away when I got the K3 and the Proset. But after the discussion regarding isolation I pulled them out and they have slightly greater volume then the Proset. I like the Proset because it has very comfortable ear pads. The 280 has a tighter grip on my head and the pads are a bit more rubbery. I think that's why I stayed with the Proset. But the ARRL DX contest is coming up so I think I'll give the 280s a whirl and see which I prefer.
73,
Mike K2MK
From: Barry N1EU [via Elecraft]
Sent: Monday, February 08, 2010 4:44 PM
To: Mike K2MK
Subject: Re: K3 DSP AGC Question
Mike K2MK wrote:
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.
I routinely use a 200-ohm Pro Set for ssb plugged into the headphone jack and it works like a charm.
73,
Barry N1EU
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Jim Brown
> "High isolation headphones" below means ~30 dB isolation from ambient noise.
> Heil does not make any in this range and most active noise reduction
> headphones (e.g. Bose) only have 10-15 dB. Here are some examples of what
> Barry meant:
>
> http://www.extremeheadphones.com/ex-29.html
> http://www.sennheiserusa.com/private_headphones_dj-headphones_004974
> http://www.etymotic.com/ephp/er6.aspx
>
> These are all available in the $75-100 range.
>
headphones for nearly ten years. I first bought them to use in my live
recording work, where I'm mixing a jazz band in the same room with the
musicians, and they're often playing pretty loud. The isolation can be
quite good, in the 30 dB range that Bill talks about, but it depends on
how well they fit your ears. The standard fittings are quite soft, and
they happen to fit my ears very well. Every person's ears are different,
and some need custom "ear molds" from an audiologist for the ultimate
isolation.
As I've gradually slowed down my pro audio work, I've ramped up ham
radio and when I got back on the air in 2003, the Etymotics almost
immediately found their way into my ham shack. They're quite
comfortable, and I can wear them for a long time.
The real question is, ":how much isolation do you need?" When I'm
working a SSB contest, I'm very happy with the sound, comfort, and
isolation of the CM500 headset, but I haven't used it yet in a
multi-multi operation. I suspect it will perform pretty well.
73,
Jim Brown K9YC
Joe Subich, W4TV
> 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.
Perhaps one should get the ambient well down in the ADC operating
range but killing gain (adding loss) before the first mixer and
the roofing filter is not the way to do it. If you want to
better align the dynamic range of the receiver (or specifically
the ADC) to conditions, the attenuation should come in the
IF - preferably divided between the first IF and 2nd IF.
However, there would still be no apparent reason that the K3
should not be capable of sustaining an AGC threshold at least
10 db higher than currently set with AGC THR = 008 whether
that be reached with preamp on, preamp off or attenuator on.
Don Wilhelm
Can you elaborate your reasons for this suggestion. I had come to
believe that the best situation is to place attenuation before the first
mixer to give the greatest amount of dynamic range (headroom).
Yes, I agree that the AGC Threshold could be raised in the K3 and would
be beneficial. I have felt the default of 005 was too low.
73,
Don W3FPR
> ------------------------------------------------------------------------
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Dave - AB7E
I also think that the current max AGC threshold is too low, but I have another question. Why is it necessary for the K3 AGC to have such a sharp elbow at the point where the AGC kicks in? The Clifton Labs plots show such a sharp bend that it seems multi-signal in-band intermod is inevitable, especially with higher SLP settings. Wouldn't it be feasible, and more desirable, to have some more gradual inflection point? I would think that something like a parabolic shape would be better, and the DSP AGC is just the implementation of an algorithm, correct? I suppose that would tend to blur the distinction between different THR settings, but so what?
Maybe somebody can educate me ...
73,
Dave AB7E
------Original Mail------
From: "Don Wilhelm" <w3...@embarqmail.com>
To: "Joe Subich, W4TV" <li...@subich.com>,
<elec...@mailman.qth.net>
Sent: Wed, 10 Feb 2010 01:06:09 -0500
Subject: Re: [Elecraft] K3 DSP AGC Question
Joe,
Can you elaborate your reasons for this suggestion. I had come to
believe that the best situation is to place attenuation before the first
mixer to give the greatest amount of dynamic range (headroom).
Yes, I agree that the AGC Threshold could be raised in the K3 and would
be beneficial. I have felt the default of 005 was too low.
73,
Don W3FPR
Joe Subich, W4TV wrote:
> Perhaps one should get the ambient well down in the ADC operating
> range but killing gain (adding loss) before the first mixer and
> the roofing filter is not the way to do it. If you want to
> better align the dynamic range of the receiver (or specifically
> the ADC) to conditions, the attenuation should come in the
> IF - preferably divided between the first IF and 2nd IF.
>
> However, there would still be no apparent reason that the K3
> should not be capable of sustaining an AGC threshold at least
> 10 db higher than currently set with AGC THR = 008 whether
> that be reached with preamp on, preamp off or attenuator on.
>
> 73,
>
> ... Joe, W4TV
>
>
______________________________________________________________
Don Wilhelm
I believe you are asking for a more "rounded knee" on the AGC attack
curve. I don't know if that is feasible without a lot of work on Lyle's
part - he would have to answer. Right now, (as you noticed) the slope
of the AGC line between the threshold point and the point where the
hardware AGC kicks in is almost linear. I am not certain how much more
computation would be required to produce a more rounded knee, nor how
fast the DSP engine can compute a more complex function - if there is
not adequate engine speed, things could become quite distorted.
Changing that function should not change the threshold levels - the
point where the knee occurs just depends on the threshold, and the shape
of the knee should not influence it. In use, a softer knee may make the
use of a lower threshold more practical.
73,
Don W3FPR
Dave - AB7E wrote:
> I also think that the current max AGC threshold is too low, but I have another question. Why is it necessary for the K3 AGC to have such a sharp elbow at the point where the AGC kicks in? The Clifton Labs plots show such a sharp bend that it seems multi-signal in-band intermod is inevitable, especially with higher SLP settings. Wouldn't it be feasible, and more desirable, to have some more gradual inflection point? I would think that something like a parabolic shape would be better, and the DSP AGC is just the implementation of an algorithm, correct? I suppose that would tend to blur the distinction between different THR settings, but so what?
>
>
Guy Olinger K2AV
transition around the knee is *** HELD *** and only released many,
many cycles later even at the fastest possible FAST AGC, and only
released if the level has subsided.
This is not at all the same thing as having an amplifier device curve
of that shape and subjecting every single audio cycle to such an
amplification curve which would create tons of distortion.
What can happen at a much slower rate (below audio frequencies so
technically not causing distortion), is that the very fastest AGC,
with its quick release, combined with an ambient noise amplified (by
inappropriate PRE/ATT/RFGAIN settings) above the AGC threshold, will
effectively push down every signal to the noise level, presenting to
the ear what sounds like all signals are at the noise level.
In a crowded room our brain neatly interprets stereophonic sound to
separate out a single spatially diverse conversation from dozens of
others at essentially the same level. In research using a monophonic
recording of the multiple conversations from a single microphone in
the same room, very few can discern individual conversations, and most
find any length of listening to the recording irritating and tiring.
The monophonic muddle created by self-defeating PRE/ATT/RFGAIN/AGC
combinations is probably worse than the monophonic room recording, as
we are intending to sit there for a while, like for a whole contest.
At some point the stressed-out brain is emotionally looking for a
scapegoat, and will fasten on the closest object.
Those of us who had Klingon pain-stick training doing traffic nets in
80 meter summer QRN can will ourselves through silly control setting
combinations without learning how to use them. The rest of us will
need to learn how to use them, or go buy a box that decides all our
choices for us.
I decidely prefer to keep the choices. Despite all claims to
contrary, PRE/ATT/RFGAIN/AGC is not rocket science.
73, Guy.
Dave - AB7E
Guy,
That's a terrific explanation ... thanks!
I had thought, however, that AGC DCY = SOFT was added to the menu several months ago because the AGC actually was capable of "bouncing" in response to signals ... even individual elements of CW. If so, that would still imply that a more rounded curve might be beneficial.
73,
Dave AB7E
------Original Mail------
From: "Guy Olinger K2AV" <oli...@bellsouth.net>
To: "Dave - AB7E" <xda...@cis-broadband.com>,
<d...@w3fpr.com>,
<li...@subich.com>,
<elec...@mailman.qth.net>
Sent: Wed, 10 Feb 2010 08:58:00 -0500
Bill W4ZV
Guy, K2AV wrote:
>
> In a crowded room our brain neatly interprets stereophonic sound to
> separate out a single spatially diverse conversation from dozens of
> others at essentially the same level. In research using a monophonic
> recording of the multiple conversations from a single microphone in
> the same room, very few can discern individual conversations, and most
> find any length of listening to the recording irritating and tiring.
>
Interesting comment Guy...I assume that must be based on Bell Labs research.
I use AFX DELAY 5 100% of the time and diversity 99.999% of the time. I
wonder if that could explain why I've never experienced the fatigue some
complain about?
73, Bill
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Guy Olinger K2AV
Lot of people all over the place have done that mono recording
comparison. We did it in college. My labor assignment at Berea
College was the Audio/Visual department. We were incessantly messing
around with stuff when not running a setup.
What was interesting was that two separate mikes and stereo weren't
much better until they were well separated. Stuff I read somewhere
much later (Discover, Scientific American, Science News ??) was
explaining how the shape of the ears contributed to our sense of
direction. Miniature mikes for affordable prices were what got all
that going.
I don't experience the fatigue either. But then again I had the summer
80m Klingon pain-stick training. :>) And I have been known to operate
the entire evening 40m EU opening with AGC off on an MP.
I checked. I do have the AFX on all the time. But can't remember when
I turned it on. I was using the "bin" setting. It seems more
"centered" on speakers. Put on the QC15 headsets and delay 5 has a
better "spread". On the speakers delay 5 seems way left. I wonder
what that is about.
73, Guy.
Joe Subich, W4TV
Don,
> Can you elaborate your reasons for this suggestion.
Adding attenuation before the first active stage (amplifier)
always reduces noise figure because that's where the S/N
ratio is determined provided the first stage has enough
gain to override the noise of the next stage.
> I had come to believe that the best situation is to place
> attenuation before the first mixer to give the greatest
> amount of dynamic range (headroom).
That assumes any IMD is produced only in the first mixer.
In the K3, the limiting factor is almost certainly later in
the chain because of the very good IMD performance of the KR
(first) mixer. Without specific analysis, the weakest link
is probably the ADC followed by the second mixer. If it was
the first mixer, narrowing the roofing filter would not
improve the dynamic range. That's why I would do two stages
of gain reduction - 10 dB in the 30 kHz IF followed by 6 dB
in the 8.125 MHz IF, if needed.
A designer always wants to make sure any amplifier gain is
sufficient for the noise figure of the succeeding stage
but low enough to avoid overload down the line.
Guy Olinger K2AV
There's currently nothing variable after the SA612. Doesn't reducing
the RF (really IF) gain first do fairly much the same thing? Reducing
level at Q1 output by reducing at RF gain knob is just barely in front
of the SA 612 second mixer and lowers input to ADC at the same time.
Seems like a pretty good pragmatic engineering choice.
In terms of what an operator can really do with the controls on a
stock K3 (as opposed to a theoretical modified K3), would you be
recommending leaving PRE set all the time, and only using the RF (IF)
gain to keep ambient noise appropriately to the low end of the
SA612/ADC ranges?
73, Guy.
Joe Subich, W4TV
> In terms of what an operator can really do with the controls
> on a stock K3 (as opposed to a theoretical modified K3),
> would you be recommending leaving PRE set all the time, and
> only using the RF (IF) gain to keep ambient noise
> appropriately to the low end of the SA612/ADC ranges?
I have not considered keeping PRE on all the time though I
seem to need it above 14 MHz due to my poor antennas. I do
not know the range of the ADC but find it extremely odd that
the (relatively sharp) ACG threshold would be less than 50 dB
above the noise floor (-138 dBm MDS).
