"Hot" K3

[Don Rasmussen]

Guys,

My new K3 #2308 shows two to three S-units high as compared to my other HF radios, and lots of hiss in the speaker audio at low AF levels. It acts as if I had maxed out the value for the crystal filter gain in the firmware, or had the PreAmp on. I have made sure the gain is at zero and moved the crystal filters (12.5 and 2.7) into different spots, but still too hot.

I can make it more normal with respect to AF gain and S-meter if I turn the ATTenuator on. I have the 2.7 filter installed and have not added any gain in the FL1 filter definition. I did a master reset and also loaded old versions of the firmware but no improvement was noted.

I have emailed my request to [hidden email], but want to post this to the list - anyone seen their K3 with these symptoms?

Thanks,
Don Rasmussen
Carlsbad, Ca.
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[w0mu]

Have you calibrated it with a known source?  Elecraft makes a nice signal
generator kit that works great for this.  You do need to enter the gain on
the 5 pole filters.  They are negative numbers so that might change things.

Do you happen to have the pre amp on.  It is generally not needed on 20-160.



CC Packet Cluster W0MU-1
W0MU.NET or  67.40.148.194


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don Rasmussen
Sent: Sunday, March 15, 2009 9:05 PM
To: [hidden email]
Subject: [Elecraft] "Hot" K3


Guys,

My new K3 #2308 shows two to three S-units high as compared to my other HF
radios, and lots of hiss in the speaker audio at low AF levels. It acts as
if I had maxed out the value for the crystal filter gain in the firmware, or
had the PreAmp on. I have made sure the gain is at zero and moved the
crystal filters (12.5 and 2.7) into different spots, but still too hot.

I can make it more normal with respect to AF gain and S-meter if I turn the
ATTenuator on. I have the 2.7 filter installed and have not added any gain
in the FL1 filter definition. I did a master reset and also loaded old
versions of the firmware but no improvement was noted.

I have emailed my request to [hidden email], but want to post this
to the list - anyone seen their K3 with these symptoms?

Thanks,
Don Rasmussen
Carlsbad, Ca.
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[Ignacy]

Did you experiment with AGC threshold? It may be very low in your case. Then K3 has high amplification even for very weak signals.
Ignacy

Don Rasmussen wrote

Guys,

My new K3 #2308 shows two to three S-units high as compared to my other HF radios, and lots of hiss in the speaker audio at low AF levels. It acts as if I had maxed out the value for the crystal filter gain in the firmware, or had the PreAmp on. I have made sure the gain is at zero and moved the crystal filters (12.5 and 2.7) into different spots, but still too hot.

I can make it more normal with respect to AF gain and S-meter if I turn the ATTenuator on. I have the 2.7 filter installed and have not added any gain in the FL1 filter definition. I did a master reset and also loaded old versions of the firmware but no improvement was noted.

I have emailed my request to [e-mail], but want to post this to the list - anyone seen their K3 with these symptoms?

Thanks,
Don Rasmussen
Carlsbad, Ca.
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... [show rest of quote]

... [show rest of quote]

[Steven.Zabarnick]

Don:

I had the same reaction upon first using my new K3 last year. The K3 is
significantly more sensitive than my previous rig (IC-756 non-Pro), and as
my noise environment is fairly high (inner suburb with ~110 dBm background
noise), at first it seemed as if the K3 is fairly noisy. Also, while the S
meter of most rigs are calibrated fairly well at S9, their meters are not
linear (in dB units) at lower S unit readings (the K3 meter is very linear
at 6 dB per S unit)-- with the result that the K3 meter readings are higher
by a few S units.

I find that I often use the attenuator and/or the RF gain to decrease the
band noise in the K3 -- I rarely used these in my other rigs. Also, try
playing with the AGC settings, particularly the THR and SLP settings, which
can be customized to suit your operating conditions. Also, turning off the
AGC and riding the RF gain can really help pull out very weak signals.

Steve N9SZ

Don Rasmussen wrote:

"My new K3 #2308 shows two to three S-units high as compared to my other HF
radios, \
and lots of hiss in the speaker audio at low AF levels."

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[Buck - k4ia]

Yes, it is a "hot" receiver.  I usually  have the RF gain turned to about 50%
- just a little above the band noise.   You can be more aggressive on PSK and
weak signal CW as it is possible to copy  signals below (but not much below)
the band noise.

Also, the K3 was  designed to have excellent dynamic range and if you ride
the RF gain too high,  you are wasting some of that headroom.

Buck
k4ia
K3 #101

In  a message dated 3/16/2009 11:57:22 A.M. Eastern Daylight Time,  
[hidden email] writes:
Don:

I had the same  reaction upon first using my new K3 last year. The K3 is
significantly more  sensitive than my previous rig (IC-756 non-Pro), and as
my noise environment  is fairly high (inner suburb with ~110 dBm background
noise), at first it  seemed as if the K3 is fairly noisy. Also, while the S
meter of most rigs are  calibrated fairly well at S9, their meters are not
linear (in dB units) at  lower S unit readings (the K3 meter is very linear
at 6 dB per S unit)-- with  the result that the K3 meter readings are higher
by a few S units.

I  find that I often use the attenuator and/or the RF gain to decrease the
band  noise in the K3 -- I rarely used these in my other rigs. Also, try
playing  with the AGC settings, particularly the THR and SLP settings, which
can be  customized to suit your operating conditions. Also, turning off the
AGC and  riding the RF gain can really help pull out very weak signals.

Steve  N9SZ

Don Rasmussen wrote:

"My new K3 #2308 shows two to three  S-units high as compared to my other HF
radios, \
and lots of hiss in the  speaker audio at low AF  levels."

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[Phil LaMarche-2]

This thread was very helpful to me and I learned a lot about the RF gain
control.  Thank you!

Phil


Philip LaMarche
LaMarche Enterprises, Inc.
www.instantgourmetspices.com

www.w9dvm.com
800-395-7795 pin 02
727-944-3226
FAX [phone]
NASFT 30210

K3  #1605
W9DVM



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Monday, March 16, 2009 12:16 PM
To: [hidden email]
Subject: Re: [Elecraft] "Hot" K3

Yes, it is a "hot" receiver.  I usually  have the RF gain turned to about
50%
- just a little above the band noise.   You can be more aggressive on PSK
and
weak signal CW as it is possible to copy  signals below (but not much below)
the band noise.

Also, the K3 was  designed to have excellent dynamic range and if you ride
the RF gain too high,  you are wasting some of that headroom.

Buck
k4ia
K3 #101

In  a message dated 3/16/2009 11:57:22 A.M. Eastern Daylight Time,
[hidden email] writes:
Don:

I had the same  reaction upon first using my new K3 last year. The K3 is
significantly more  sensitive than my previous rig (IC-756 non-Pro), and as
my noise environment  is fairly high (inner suburb with ~110 dBm background
noise), at first it  seemed as if the K3 is fairly noisy. Also, while the S
meter of most rigs are  calibrated fairly well at S9, their meters are not
linear (in dB units) at  lower S unit readings (the K3 meter is very linear
at 6 dB per S unit)-- with  the result that the K3 meter readings are higher
by a few S units.

I  find that I often use the attenuator and/or the RF gain to decrease the
band  noise in the K3 -- I rarely used these in my other rigs. Also, try
playing  with the AGC settings, particularly the THR and SLP settings, which
can be  customized to suit your operating conditions. Also, turning off the
AGC and  riding the RF gain can really help pull out very weak signals.

Steve  N9SZ

Don Rasmussen wrote:

"My new K3 #2308 shows two to three  S-units high as compared to my other HF
radios, \ and lots of hiss in the  speaker audio at low AF  levels."

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[ab2tc]

Hi all,

I, too. think that with the current firmware the AGC threshold even when adjusted to its maximum is too low, making the receiver excessively "hot" on all bands except 10m. Way back, a firmware change was made that lowered the AGC threshold by 10dB. I thought it was more appropriate prior to that change. I wish for Elecraft to increase the range of the AGC threshold adjustment to be able to raise it another 10dB to tame the receiver on the lower bands (<15m). I have learned to live with this by reducing the RF gain as many others have mentioned. This works well but leaves the S-meter relatively useless. The idea of raising the S-meter base reading as the RF gain is backed off is a good one, but in the K3 with the current firmware the base is raised way too much leaving the S-meter readings highly exaggerated when the RF gain is backed off. Fortunately I don't miss it that much as I use the the S-meter in PowerSDR in conjunction with LP-PAN.

Phil LaMarche-2 wrote

This thread was very helpful to me and I learned a lot about the RF gain
control.  Thank you!

Phil


Philip LaMarche
LaMarche Enterprises, Inc.
www.instantgourmetspices.com

<snip>

[wayne burdick]

Just to provide a counter-example....

I almost never back the RF GAIN control down on my K3. It has huge
dynamic range. Unless I'm besieged by multiple S9+30 or greater signals
within the crystal filter passband, I don't find it necessary. (Note:
We're getting close to a new firmware release that provides additional
DSP AGC tools that will make riding the RF GAIN even less necessary.)

The K3 is not substantially different in overall RX gain from other
modern radios, although it may, as some observed, have a more accurate
S-meter at the low end. During the design process we measured the
antenna-to-AF OUT gain of several radios to make sure we were in the
right ballpark.

I do turn the preamp OFF most of the time below 15 m.

I sometimes use the attenuator with monstrous AM broadcast signals (in
the 0.5-1.6 MHz band), but rarely other than that.

I'm using all of the AGC defaults, and have CONFIG:AF GAIN set to HI.

NR is handy in many cases if you have high atmospheric noise. Try a low
setting first.

If you think there's too much gain, you can set AF GAIN to LOW (making
it more like a K2), turn off the preamp, and adjust the AGC controls.

Also, I suggest using only very low values of CONFIG:FLx GN, as well as
small (+) values of MAIN:RX EQ, if you use these at all.

73,
Wayne
N6KR

---

http://www.elecraft.com

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[David Woolley (E.L)]

[hidden email] wrote:

> In  a message dated 3/16/2009 11:57:22 A.M. Eastern Daylight Time,  
> [hidden email] writes:

> I had the same  reaction upon first using my new K3 last year. The K3 is
> significantly more  sensitive than my previous rig (IC-756 non-Pro), and as
>

I presume you mean has more gain than is more sensitive (it may be
sensitive as well, but that is not defined by the loudness of the output).

--
David Woolley
"The Elecraft list is a forum for the discussion of topics related to
Elecraft products and more general topics related ham radio"
List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm>
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