K3: LPF, bass audio, new DSP board: Stirring the pot?

[DOUGLAS ZWIEBEL]

I have to admit, I just have not experienced any of these "issues"
with either of my K3s.  Yes, I am mostly a CW guy and yes, I use
headphones.

So...lacking any "real" test equipment (I assume that if the test
equipment between my ears can't discern it, then who cares what a
meter or scope shows me).  Crude, I know, but this worked well for me
one summer, in 1974 when I worked for Signal/One.  They had all the
test gear and engineers (this was when they moved to NJ), but nobody
there could figure out/understand what was "wrong" with the radios
returned for repair.  All I needed was a couple minute with the radios
(on the air) to quickly "discover" what was wrong and THEN the
engineers could apply a fix/repair.

http://picasaweb.google.com/dougzzz/KR2Q1966ToPresent#5419152602223700290

Anyhow, someone recently made a great post (IMHO)...sorry I can't
remember who it was, listing the three "problems."  So I decided to
"test" the K3s using what I have here (my ears, acoustic nerves, and
brain).

First, I have my cw pitch set to 400hz.  Using the CWT feature, I
"zeroed" in a cw signal.  Heard it FINE via the inboard speaker and
equally as fine via my communication headphones (the headphones sound
great on CW, but I can tell that they are getting "restrictive" on SSB
on the top end).

Then, using my RIT, I dialed in 200hz offset (making the received
signal "lower" in pitch).  Using my headphones, the signal seemed
fine...perfectly readable, good tone, easy to copy.  Then I pulled the
headphone plug to listen via the internal speaker:  NOTHING.  Just
some "thunks" - I could not copy any signal at all and I certainly
could not read any CW.  So I plugged the headphone back in and
BINGO....perfect, smooth, easy copy with a 200hz note.  A real
difference.

I am thrilled that those who have implemented the new DSP board with
LPF can now "hear better," but I have to wonder how much of this has
to do with trying to do too much with an internal speaker.  I don't
know and I am not conjecturing....I'm just wondering.

At least now, I do know why I have not experienced most (any?) of
these audio issues.

If I find a pair of "quality" HI-FI stereo phones around the house
somewhere, maybe I'll plug those in and see if I can duplicate the
"noisy receiver" problem, suspecting that is due to "hiss" as others
have suggested.  Right now, using communication headphones, I can not.

One last thing that I do not understand...and I am hoping someone can
answer me.   Why would riding the RF gain or adding Attenuation in any
way impact "noise" (assuming it is not due to intermod)?  Today I
tried that again and again.  Adding in attenuation simply reduced the
audio output (again, according to my EAR).  Yes, the "noise" went
down, but did the signal.  When I upped the AF gain to compensate,
well, everything sounded "the same" relatively speaking (signal and
noise) as with no attenuation.  If the "noise" is not due to intermod
(what Elecraft calls "desense") then what can cutting back on the
total signal due in terms of making "less noise?"

I am not a "technical" guy.  I just have lots of ham radio experience.
 My UG degree is in Biology (BS).  I did my first graduate work at U
Penn School of Veterinary Medicine (VMD) and my 2nd grad degree
earlier this decade in Healthcare Administration (MHA).  Like I said,
I'm no "techie."  :-)

Wishing everyone a Happy New Year for 2010.

de Doug KR2Q
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[Jim Brown-10]

On Mon, 28 Dec 2009 21:09:46 -0500, DOUGLAS ZWIEBEL wrote:

Your post is excellent, and I agree with most of it. I do want to
correct an important error. See below.

>If the "noise" is not due to intermod (what Elecraft calls
>"desense")

Intermod and desense are VERY different things. Intermod is the
generation of beat frequencies by a non-linear process (that is,
amplitude distortion). Desense (short for desensitization) is the
reduction in the gain of a system by such severe rectification of
the input signal that the bias point is shifted enough (to either
cutoff or saturation) to reduce the gain of the system.

Yes, both are the result of overloading of a gain stage (usually
the input), intermod simply produces trash and spurious responses,
while desense can literally turn the input stage off. As an
example, I once owned a very nice little Yaesu talkie that could
be biased so strongly into cutoff in downtown Chicago that it
couldn't hear a 100W repeater feeding a 9dB gain antenna on a
1,000 ft building two miles away.

>then what can cutting back on the
>total signal due in terms of making "less noise?"

EXACTLY! The vast majority of HF communications circuits are
limited by noise that comes in on the antenna, not circuit noise
in the receiver. This is definitely true on all ham bands below
20M, no matter where you live, and it's usually true above 20M
unless either the bands are dead or you live in a VERY quiet QTH.
W8JI has often observed that if the noise in your headphones
increases when you connect the antenna, noise in the electronics
is NOT a problem.

FWIW, I have ALWAYS used pro quality headphones with my ham gear,
and certainly don't consider the K3 noisy. Of course, I'm 68, have
been a ham for 54 years, and have worked in pro audio for the past
40 years, so my hearing is down a bit on the high end. :)  YMMV.

It should also be noted that while the K3 comes with multiband
graphic RX EQ, there are no bands above 5kHz. That's something
that the crew in Aptos might want to add to the "to do" list.  

73,

Jim K9YC


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[Fred Atchley]

Jim K9YC wrote:

 

>It should also be noted that while the K3 comes with multiband graphic RX
EQ, there are no >bands above 5kHz.

 

This is an interesting point Jim. Human hearing in the 20 kHz range is not
unheard of. I wonder if the K3 design cuts this off above 5 kHz or if it
allows it to pass through the audio stage?

 

Can anyone on the list clarify this?

 

73, Fred, AE6IC

 

 

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[Jim Brown-10]

On Mon, 28 Dec 2009 20:33:03 -0800, Fred Atchley wrote:

> Human hearing in the 20 kHz range is not unheard of.

We start out that way as children, but suffer hearing loss from
multiple sources, mostly due to exposure to excessively loud
sounds.

>I wonder if the K3 design cuts this off above 5 kHz or if
>it allows it to pass through the audio stage?

Good engineering practice would include high pass and low pass
filters at the limits of transmitted bandwidth. For ham
circuits, 300 Hz and 3.5 kHz would be good cutoff frequencies
for 3-pole filters for HF radios. For AM broadcast, 40 Hz and 9
kHz (US) and 8 kHz (EU) are about right. It should also be noted
that roughly two decades ago, AM broadcasting adopted the
practice of HF pre-emphasis like with FM and analog TV. But
PULEEZE don't tell the wideband AM lunatic fringe.

As Riley Hollingsworth said so eloquently when he was running
the FCC's Enforcement Bureau, if you want to be a broadcaster,
buy a broadcast license or get a job at a radio station.

So yes, there ought to be user-definable high pass and low pass
filters in the audio system. There ARE such filters in the IF,
but not in the audio system. The result is that if gains are not
well managed in the K3, some of our younger users could hear
hiss. Since my highs are long gone, I can't comment on that. :)

73,

Jim K9YC



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[K2QI]

Jim,

This is the problem I've experienced, and why I think my receiver is
"noisy."  I can hear a high frequency whine or tone that only gets worse if
I adjust the receive EQ to enhance voice intelligibility.  This can
make working weak signals fatiguing.  I should probably just cough up the
money and swap out DSP boards for a new one with an LPF installed.  However,
I'm not too thrilled about the unannounced price increase from 69 to 89
dollars.  Had I known, I would have ordered one earlier.

73 de James K2QI

On Mon, Dec 28, 2009 at 11:50 PM, Jim Brown <[hidden email]>wrote:

>
> So yes, there ought to be user-definable high pass and low pass
> filters in the audio system. There ARE such filters in the IF,
> but not in the audio system. The result is that if gains are not
> well managed in the K3, some of our younger users could hear
> hiss. Since my highs are long gone, I can't comment on that. :)
>
> 73,
>
> Jim K9YC
>
>
>
> ______________________________________________________________
> Elecraft mailing list
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--
73 de James K2QI
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[Julian, G4ILO]

K2QI wrote

This is the problem I've experienced, and why I think my receiver is
"noisy."  I can hear a high frequency whine or tone that only gets worse if
I adjust the receive EQ to enhance voice intelligibility.  This can
make working weak signals fatiguing.  I should probably just cough up the
money and swap out DSP boards for a new one with an LPF installed.  However,
I'm not too thrilled about the unannounced price increase from 69 to 89
dollars.  Had I known, I would have ordered one earlier.

I suspect that the price increase reflected the addition of the LPF board, and the short window of opportunity for purchasing the DSP+LPF at the old price was the time it took for Elecraft to realise they would be losing money on the deal. The $69 was really just for the Rev. C board swap without the LPF. I don't know if anyone actually got one of those, or whether Elecraft delayed fulfilling the orders until the LPF was ready and decided not to ask those who had already paid fro an extra $20.

[Mike K2MK]

Hi James:

I understand from talking to Elecraft service that they will be offering the LPF board as an add-on for those that don't feel the necessity of changing out the DSP board. No technical details yet.

73,
Mike K2MK


<quote author="K2QI">
"I should probably just cough up the
money and swap out DSP boards for a new one with an LPF installed."

[K2QI]

Well, I ended up ordering the DSP upgrade board today, plus a few other
items.  Everything came to a little under 200 dollars including shipping.
Here's what I ordered:

BNC-MM      $6.95       1     Male-Male BNC
K3DSPUPGD   $89.95      1     K3 DSP Upgr. Swap
K3IOBUFFKT  $5.00       1     K3 I/O Output Buffer Kit
XG2         $79.95      1     3 Band 1-uV and 50-uV Rcv. Te

I figured the XG2 would be a good thing to have around as well.  I can
finally get around to properly calibrating my s-meter.
Slightly OT question though; you know the 1 wire mod that's used to protect
the front end?  Where can I buy the type of wire required?  I think it's
Kynar... whatever it is, its insulated, solid-conductor wire that's around
22 guage.  When I performed this mod several months ago, I had a few of
those small, pre-cut and pre-tinned solid conductor wires included in
breadboard electronic kits, and I used one that was the right length.  I
like to buy a spool of this stuff though for a few more breadboard projects
I'm working on.

Mni tnx es vy 73,
James K2QI
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[Geoffrey Downs-2]

Regarding the new DSP board, I was not one of those who had issues with the
old one or considered the K3 to be noisy on rx and I ordered the new one
simply to keep my K3 #266 up to date. I use SSB almost exclusively, these
days seeking dx on 80m with a headset.

Having installed the new board a few days ago my subjective and
non-technical assessment so far is a more pleasing sound in the headphones
with increased bass response and reduced white noise without loss of
sensitivity. On tx slightly fuller audio from my HC4 with more mid range.
(Both rx and tx assessed with equaliser all zeros.) So on the whole I regard
the new board as an improvement. Worth the money? Well that depends on how
you look at it and different people may have different views. I managed to
convince myself that I could afford it and I feel no sense of disappointment
after the event.

73 and Happy 2010 to all

Geoff
G3UCK

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[David Cutter]

What was the delivered price into UK, Geoff ?

David
G3UNA

> Regarding the new DSP board, I was not one of those who had issues with
> the
> old one or considered the K3 to be noisy on rx and I ordered the new one
> simply to keep my K3 #266 up to date. I use SSB almost exclusively, these
> days seeking dx on 80m with a headset.
>
> Having installed the new board a few days ago my subjective and
> non-technical assessment so far is a more pleasing sound in the headphones
> with increased bass response and reduced white noise without loss of
> sensitivity. On tx slightly fuller audio from my HC4 with more mid range.
> (Both rx and tx assessed with equaliser all zeros.) So on the whole I
> regard
> the new board as an improvement. Worth the money? Well that depends on how
> you look at it and different people may have different views. I managed to
> convince myself that I could afford it and I feel no sense of
> disappointment
> after the event.
>
> 73 and Happy 2010 to all
>
> Geoff
> G3UCK
>

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[srife]

        I had already paid for mine before they decided to add the LPF in to
the deal, so I suspect you are correct Julian. Don't know if they initially
were going to offer the LPF as a customer DIY add on, or if they decided it
might be better if they did the work in house to eleviate too many failures.

        It was probably easier for them all around taking the option they
did.


Stan Rife
W5EWA



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Julian, G4ILO
Sent: Tuesday, December 29, 2009 9:50 AM
To: [hidden email]
Subject: Re: [Elecraft] K3: LPF, bass audio, new DSP board: Stirring the
pot?




K2QI wrote:

>
> This is the problem I've experienced, and why I think my receiver is
> "noisy."  I can hear a high frequency whine or tone that only gets worse
> if
> I adjust the receive EQ to enhance voice intelligibility.  This can
> make working weak signals fatiguing.  I should probably just cough up the
> money and swap out DSP boards for a new one with an LPF installed.
> However,
> I'm not too thrilled about the unannounced price increase from 69 to 89
> dollars.  Had I known, I would have ordered one earlier.
>
>

I suspect that the price increase reflected the addition of the LPF board,
and the short window of opportunity for purchasing the DSP+LPF at the old
price was the time it took for Elecraft to realise they would be losing
money on the deal. The $69 was really just for the Rev. C board swap without
the LPF. I don't know if anyone actually got one of those, or whether
Elecraft delayed fulfilling the orders until the LPF was ready and decided
not to ask those who had already paid fro an extra $20.

-----
Julian, G4ILO. K2 #392  K3 #222.
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

--
View this message in context:
http://n2.nabble.com/K3-LPF-bass-audio-new-DSP-board-Stirring-the-pot-tp4226
184p4228122.html
Sent from the Elecraft mailing list archive at Nabble.com.
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[srife]

        I can't figure out why they are charging 5 bucks for 2 resistors in
the K3 I/O OUTPUT BUFFER KIT, when they are giving away the parts for the
rest of the upgrades for just the price of the postage. Are these two
resistors gold plated or something? I just used a spare 15K 5% leaded
resistor I had in my parts box.

        Shouldn't that be a give away too Eric?
         

Stan Rife
W5EWA



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of James Sarte
Sent: Tuesday, December 29, 2009 10:37 AM
To: [hidden email]
Subject: Re: [Elecraft] K3: LPF, bass audio, new DSP board: Stirring the
pot?

Well, I ended up ordering the DSP upgrade board today, plus a few other
items.  Everything came to a little under 200 dollars including shipping.
Here's what I ordered:

BNC-MM      $6.95       1     Male-Male BNC
K3DSPUPGD   $89.95      1     K3 DSP Upgr. Swap
K3IOBUFFKT  $5.00       1     K3 I/O Output Buffer Kit
XG2         $79.95      1     3 Band 1-uV and 50-uV Rcv. Te

I figured the XG2 would be a good thing to have around as well.  I can
finally get around to properly calibrating my s-meter.
Slightly OT question though; you know the 1 wire mod that's used to protect
the front end?  Where can I buy the type of wire required?  I think it's
Kynar... whatever it is, its insulated, solid-conductor wire that's around
22 guage.  When I performed this mod several months ago, I had a few of
those small, pre-cut and pre-tinned solid conductor wires included in
breadboard electronic kits, and I used one that was the right length.  I
like to buy a spool of this stuff though for a few more breadboard projects
I'm working on.

Mni tnx es vy 73,
James K2QI
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[Geoffrey Downs-2]

Hello David,

$69.95 for the board + $40.50 shipping by USPS International (it came in a
surprisingly large box but very well packed) + VAT on entering UK + (the
worst part) £13.50 Parcelforce handling charge. It all added up to £92.72.
It took about 10 days door to door by USPS International. I could have
chosen USPS Priority Int. for a saving of about $15 but that would have been
of very uncertain duration.

73 and Happy New Year

Geoff
G3UCK

----- Original Message -----
From: "David Cutter" <[hidden email]>


> What was the delivered price into UK, Geoff ?
>
> David
> G3UNA

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[Doug Turnbull]

Geoff and group,
    I also have one on order which has yet to arrive.   This time, I forgot
to ask the good people at Elecraft to ship in as small a box as possible.
Sometimes a small parcel coming by post is just passed through without being
charged VAT by our Post Service.   This never happens with any of the other
carriers.   I may call Elecraft later today to request that when they do
ship that they use a small box.   Good luck with the installation.

            73 Doug EI2CN

-----Original Message-----

Hello David,

$69.95 for the board + $40.50 shipping by USPS International (it came in a
surprisingly large box but very well packed) + VAT on entering UK + (the
worst part) £13.50 Parcelforce handling charge. It all added up to £92.72.
It took about 10 days door to door by USPS International. I could have
chosen USPS Priority Int. for a saving of about $15 but that would have been

of very uncertain duration.

73 and Happy New Year

Geoff
G3UCK



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