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[K3] RX Gain Calibration

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k2np

[K3] RX Gain Calibration

All,

I put together a K3 kit about 6 weeks ago. Wow, that was an amazing
project. Many thanks to Elecraft for making that option available. The
problem I am having is that on 180/80/75/40 and sometimes 20, the noise
floor is about S7-9. It is about the same on both my antennas (OCF dipole
and 43' vertical) with the OCF being a smidge quieter. My first thought
was that I had some local noise and asked my dad to bring over is KX3 so I
could walk around the house to find the source of the noise. I did find
that the power supply in the iMac is ridiculously noisy, but that wasn't
getting into my signal, especially since my antennas are almost 100' from
the house. What I DID notice was that when I plugged my antennas into the
KX3, the noise floor was at S0 on 20/40 and around S1 or S2 on 75/80/180
with the pre-amp off. That was MUCH better. Of course, if I fiddle with
the RX gain knob, I can make the noise go away, but it does mess with the
S-Meter and it becomes increasingly useless. So, my thought was that since
my dad had his KX3 factory built, they did a proper RX Gain calibration.
Since I didn't have a calibrated signal generator, I just used the factory
defaults which maybe aren't so great? My question is this: would it make
sense to seek out a calibrated RF source and try and run a proper RX Gain
calibration? Would it likely solve my problem?

Thanks,
Travis
K2NP
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Don Wilhelm-4

Re: [K3] RX Gain Calibration

Travis,

I doubt the RX gain calibration will make that much difference, but
rather I suggest that some alteration of the AGC parameters will make
the most difference for you. Take a look at the "Noisy K3" article on
my website www.w3fpr.com for some guidance in adjusting your settings.
That article was written before the AGC parameters were expanded, so you
will have to experiment a bit, but the article should give you some
guidance on which direction to go.

Turning the preamp off and even turning the attenuator on for lower
bands where the band noise is higher will make a great difference too.
If you can hear an increase in band noise when the antenna is connected,
you have ample gain - turn off the preamp and try connecting the antenna
again - if there is still a substantial increase, try turning on the
attenuator. You are not going to be able to copy signals below the
noise level, so you don't need the added gain - it just makes everything
(including the noise) sound louder.

73,
Don W3FPR

On 3/18/2013 8:24 AM, Travis Brown wrote:

> All,
>
> I put together a K3 kit about 6 weeks ago. Wow, that was an amazing
> project. Many thanks to Elecraft for making that option available. The
> problem I am having is that on 180/80/75/40 and sometimes 20, the noise
> floor is about S7-9. It is about the same on both my antennas (OCF dipole
> and 43' vertical) with the OCF being a smidge quieter. My first thought
> was that I had some local noise and asked my dad to bring over is KX3 so I
> could walk around the house to find the source of the noise. I did find
> that the power supply in the iMac is ridiculously noisy, but that wasn't
> getting into my signal, especially since my antennas are almost 100' from
> the house. What I DID notice was that when I plugged my antennas into the
> KX3, the noise floor was at S0 on 20/40 and around S1 or S2 on 75/80/180
> with the pre-amp off. That was MUCH better. Of course, if I fiddle with
> the RX gain knob, I can make the noise go away, but it does mess with the
> S-Meter and it becomes increasingly useless. So, my thought was that since
> my dad had his KX3 factory built, they did a proper RX Gain calibration.
> Since I didn't have a calibrated signal generator, I just used the factory
> defaults which maybe aren't so great? My question is this: would it make
> sense to seek out a calibrated RF source and try and run a proper RX Gain
> calibration? Would it likely solve my problem?
>
> Thanks,
> Travis
> K2NP
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

k2np

Re: [K3] RX Gain Calibration

Thanks Don.

I will definitely tweak the AGC settings. Someone else recommended that
too. However, I thought the KX3 and K3 had basically the same receiver, and
if I hook the KX3 up to the same antenna that to which my K3 was connected,
the S-meter should report the same values regardless of the AGC setting,
correct?

Thanks,
Travis

On Mon, Mar 18, 2013 at 9:11 AM, Don Wilhelm <[hidden email]> wrote:

> Travis,
>
> I doubt the RX gain calibration will make that much difference, but rather
> I suggest that some alteration of the AGC parameters will make the most
> difference for you. Take a look at the "Noisy K3" article on my website
> www.w3fpr.com for some guidance in adjusting your settings. That
> article was written before the AGC parameters were expanded, so you will
> have to experiment a bit, but the article should give you some guidance on
> which direction to go.
>
> Turning the preamp off and even turning the attenuator on for lower bands
> where the band noise is higher will make a great difference too. If you
> can hear an increase in band noise when the antenna is connected, you have
> ample gain - turn off the preamp and try connecting the antenna again - if
> there is still a substantial increase, try turning on the attenuator. You
> are not going to be able to copy signals below the noise level, so you
> don't need the added gain - it just makes everything (including the noise)
> sound louder.
>
> 73,
> Don W3FPR
>
>
> On 3/18/2013 8:24 AM, Travis Brown wrote:
>
>> All,
>>
>> I put together a K3 kit about 6 weeks ago. Wow, that was an amazing
>> project. Many thanks to Elecraft for making that option available. The
>> problem I am having is that on 180/80/75/40 and sometimes 20, the noise
>> floor is about S7-9. It is about the same on both my antennas (OCF dipole
>> and 43' vertical) with the OCF being a smidge quieter. My first thought
>> was that I had some local noise and asked my dad to bring over is KX3 so I
>> could walk around the house to find the source of the noise. I did find
>> that the power supply in the iMac is ridiculously noisy, but that wasn't
>> getting into my signal, especially since my antennas are almost 100' from
>> the house. What I DID notice was that when I plugged my antennas into the
>> KX3, the noise floor was at S0 on 20/40 and around S1 or S2 on 75/80/180
>> with the pre-amp off. That was MUCH better. Of course, if I fiddle with
>> the RX gain knob, I can make the noise go away, but it does mess with the
>> S-Meter and it becomes increasingly useless. So, my thought was that
>> since
>> my dad had his KX3 factory built, they did a proper RX Gain calibration.
>> Since I didn't have a calibrated signal generator, I just used the factory
>> defaults which maybe aren't so great? My question is this: would it make
>> sense to seek out a calibrated RF source and try and run a proper RX Gain
>> calibration? Would it likely solve my problem?
>>
>> Thanks,
>> Travis
>> K2NP
>> ______________________________**______________________________**__
>> Elecraft mailing list
>> Home: http://mailman.qth.net/**mailman/listinfo/elecraft<http://mailman.qth.net/mailman/listinfo/elecraft>
>> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
>> Post: mailto:[hidden email].**net <[hidden email]>
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>

Don Wilhelm-4

Re: [K3] RX Gain Calibration

Travis,

The KX3 is a direct to baseband receiver with the DSP being done at
baseband (or if RX shift is on at 8 kHz.) while the K3 downconverts to
the 8 MHz IF before digitizing and sending the data to the DSP.

So the two receiver architectures are different.

73,
Don W3FPR

On 3/18/2013 9:25 AM, Travis Brown wrote:

> Thanks Don.
>
> I will definitely tweak the AGC settings. Someone else recommended that
> too. However, I thought the KX3 and K3 had basically the same receiver, and
> if I hook the KX3 up to the same antenna that to which my K3 was connected,
> the S-meter should report the same values regardless of the AGC setting,
> correct?
>
> Thanks,
> Travis
>

mikerodgerske5gbc

Re: [K3] RX Gain Calibration

In reply to this post by k2np

Travis, that's interesting that the KX3 was quiet. Sometimes I think the k3 is just too sensitive. I don't know if that's it or not. I've certainly wondered.

Please share if you find the secret sauce.

73
Mike R

Play me some fiddle, but no stinkin' violin!

Amateur/Ham Radio KE5GBC
HF & Echolink mobile
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Stan AE7UT

Re: [K3] RX Gain Calibration

In reply to this post by k2np

Travis I was in your same situation and understand what your experiencing.
I got my KX3 first and was blown away by how quiet and sensitive it was.
The KX3 was so impressive I sold my entire Ten-Ten station and built a K3.

I was disappointed that the K3 receiver didn't seem to be as "good" as the KX3.
I finally broke down and bought the XG3 signal generator and did all the
calibrations. That has made the world of difference... but I still like the KX3
receiver more. I also read and implimented Don's "Noisy K3" article. The K3
still doesn't seem as quiet and sensitive as the KX3.

Let me know if you find the secret formula! I'm still working on it myself.
I'm 100% satisfied with my K3 and LOVE it compared to the TT stuff.
I just want to be 110% satisfied. LOL

73
Stan AE7UT

k2np

Re: [K3] RX Gain Calibration

Thanks Stan. I ordered a XG3 yesterday and I hope to have it here this
week. I wasn't expecting such a huge discrepancy between the KX3 and K3,
and it really surprised me. If I figure out the secret sauce, I'll
definitely let you know. I am curious, with did you put the KX3 and K3 on
the XG3 and see a discrepancy in the S-Meter reading? If so, how much?

Thanks,
Travis K2NP

On Tue, Mar 19, 2013 at 7:16 PM, Stan AE7UT <[hidden email]> wrote:

>
> I was disappointed that the K3 receiver didn't seem to be as "good" as the
> KX3.
> I finally broke down and bought the XG3 signal generator and did all the
> calibrations. That has made the world of difference... but I still like
> the
> KX3
> receiver more. I also read and implimented Don's "Noisy K3" article. The
> K3
> still doesn't seem as quiet and sensitive as the KX3.
>
> Let me know if you find the secret formula! I'm still working on it
> myself.
> I'm 100% satisfied with my K3 and LOVE it compared to the TT stuff.
> I just want to be 110% satisfied. LOL
>
> 73
> Stan AE7UT
>
>
>
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/K3-RX-Gain-Calibration-tp7571455p7571525.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Gary Gregory-2

Re: [K3] RX Gain Calibration

Running both a k3 and kx3 during a contest there is only 1 clear winner.
The k3 won easily.
Weak signals not copyable at all on the kx3 with it calibrated with the
xg3.....
Close in strong signal rejection is far superior on the k3.
The proof is in the ears.....not a lab quality meter showing numbers.

"Flame suit on"

73

Gary
Vk1ZZ
K3, KX3, KPA500-FT, KAT500-FT,P3.
On 20/03/2013 9:27 AM, "Travis Brown" <[hidden email]> wrote:

> Thanks Stan. I ordered a XG3 yesterday and I hope to have it here this
> week. I wasn't expecting such a huge discrepancy between the KX3 and K3,
> and it really surprised me. If I figure out the secret sauce, I'll
> definitely let you know. I am curious, with did you put the KX3 and K3 on
> the XG3 and see a discrepancy in the S-Meter reading? If so, how much?
>
> Thanks,
> Travis K2NP
>
> On Tue, Mar 19, 2013 at 7:16 PM, Stan AE7UT <[hidden email]> wrote:
> >
> > I was disappointed that the K3 receiver didn't seem to be as "good" as
> the
> > KX3.
> > I finally broke down and bought the XG3 signal generator and did all the
> > calibrations. That has made the world of difference... but I still like
> > the
> > KX3
> > receiver more. I also read and implimented Don's "Noisy K3" article.
> The
> > K3
> > still doesn't seem as quiet and sensitive as the KX3.
> >
> > Let me know if you find the secret formula! I'm still working on it
> > myself.
> > I'm 100% satisfied with my K3 and LOVE it compared to the TT stuff.
> > I just want to be 110% satisfied. LOL
> >
> > 73
> > Stan AE7UT
> >
> >
> >
> > --
> > View this message in context:
> >
> http://elecraft.365791.n2.nabble.com/K3-RX-Gain-Calibration-tp7571455p7571525.html
> > Sent from the Elecraft mailing list archive at Nabble.com.
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

Don Wilhelm-4

Re: [K3] RX Gain Calibration

In reply to this post by k2np

Travis,

The real measure of any receiver in the ability to hear weak signals is
not in the S-meter deflection. Within limits both the K3 and KX3
S-meters can be calibrated to read most anything you want to see.
The measurement of actual sensitivity is in the MDS measurement. That
indicates how weak a signal can be heard at 3 dB above the receiver
noise floor.
When you get your XG3, I encourage you to follow the instructions in the
XG3 manual for determining the MDS of a receiver. With the XG3, that is
a number inferred by the response at -107 dBm rather than a measurement
using a well shielded signal generator and switching in attenuation, but
the approximation should be within 1 dB of the actual MDS if you do the
procedure (and math) as instructed.

73,
Don W3FPR

On 3/19/2013 7:26 PM, Travis Brown wrote:
> Thanks Stan. I ordered a XG3 yesterday and I hope to have it here this
> week. I wasn't expecting such a huge discrepancy between the KX3 and K3,
> and it really surprised me. If I figure out the secret sauce, I'll
> definitely let you know. I am curious, with did you put the KX3 and K3 on
> the XG3 and see a discrepancy in the S-Meter reading? If so, how much?
>
>

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k2np

Re: [K3] RX Gain Calibration

Hi Don,

I agree 100%! The S-Meter isn't as big of a concern to me as the fact that the noise floor seems to be so much more prevalent on the K3 than the KX3. I do understand that the more sensitive receiver will dip deeper into the noise floor and you will hear more of it. If I always have to turn down the RF gain though, and the S-Meter shows something even when their is no antenna attached, I think it is worth it to calibrate things. It's not like me to read manual, but so far, I have a pretty good track record of reading everything Elecraft sends me from cover to cover :)

73,
Travis K2NP

On Mar 19, 2013, at 8:12 PM, Don Wilhelm <[hidden email]> wrote:

> Travis,
>
> The real measure of any receiver in the ability to hear weak signals is not in the S-meter deflection. Within limits both the K3 and KX3 S-meters can be calibrated to read most anything you want to see.
> The measurement of actual sensitivity is in the MDS measurement. That indicates how weak a signal can be heard at 3 dB above the receiver noise floor.
> When you get your XG3, I encourage you to follow the instructions in the XG3 manual for determining the MDS of a receiver. With the XG3, that is a number inferred by the response at -107 dBm rather than a measurement using a well shielded signal generator and switching in attenuation, but the approximation should be within 1 dB of the actual MDS if you do the procedure (and math) as instructed.
>
> 73,
> Don W3FPR

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Don Wilhelm-4

Re: [K3] RX Gain Calibration

Travis,

The S-meter should not indicate anything with the antenna disconnected.
You should be searching for the reason the AGC is being activated on
receiver noise - or it could be S-meter calibration. The XG3 can allow
you to properly calibrate the S-meter - the Utility program will guide you.

73,
Don W3FPR
On 3/19/2013 8:34 PM, Travis Brown wrote:

> Hi Don,
>
> I agree 100%! The S-Meter isn't as big of a concern to me as the fact that the noise floor seems to be so much more prevalent on the K3 than the KX3. I do understand that the more sensitive receiver will dip deeper into the noise floor and you will hear more of it. If I always have to turn down the RF gain though, and the S-Meter shows something even when their is no antenna attached, I think it is worth it to calibrate things. It's not like me to read manual, but so far, I have a pretty good track record of reading everything Elecraft sends me from cover to cover :)
>
> 73,
> Travis K2NP
>
> On Mar 19, 2013, at 8:12 PM, Don Wilhelm <[hidden email]> wrote:
>
>> Travis,
>>
>> The real measure of any receiver in the ability to hear weak signals is not in the S-meter deflection. Within limits both the K3 and KX3 S-meters can be calibrated to read most anything you want to see.
>> The measurement of actual sensitivity is in the MDS measurement. That indicates how weak a signal can be heard at 3 dB above the receiver noise floor.
>> When you get your XG3, I encourage you to follow the instructions in the XG3 manual for determining the MDS of a receiver. With the XG3, that is a number inferred by the response at -107 dBm rather than a measurement using a well shielded signal generator and switching in attenuation, but the approximation should be within 1 dB of the actual MDS if you do the procedure (and math) as instructed.
>>
>> 73,
>> Don W3FPR
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Gary Gregory-2

Re: [K3] RX Gain Calibration

In reply to this post by k2np

Exactly

Gary
Vk1ZZ
K3, KX3, KPA500-FT, KAT500-FT,P3.
On 20/03/2013 11:59 AM, "Ron D'Eau Claire" <[hidden email]> wrote:

> Sometimes I truly believe that one of the worst plagues imposed on the Hams
> of the world was the S-Meter.
>
> In short, it means little about whether you can hear a signal or how easily
> it can be copied.
>
> True signal reports are given by what you hear, not what the meter says.
>
> 73 Ron AC7AC
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

N0AZZ

Re: [K3] RX Gain Calibration

Amen! I have worked stations SSB that never move the S-Meter at all.

73,
Fred/N0AZZ
K3 Ser #'s 6730/5299--KX3 # 2573--K2/100--KAT100
P3/SVGA--KPA500--KAT500--W2

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Gary Gregory
Sent: Tuesday, March 19, 2013 9:45 PM
To: Ron D'Eau Claire
Cc: Elecraft List
Subject: Re: [Elecraft] [K3] RX Gain Calibration

Exactly

Gary
Vk1ZZ
K3, KX3, KPA500-FT, KAT500-FT,P3.
On 20/03/2013 11:59 AM, "Ron D'Eau Claire" <[hidden email]> wrote:

> Sometimes I truly believe that one of the worst plagues imposed on the
> Hams of the world was the S-Meter.
>
> In short, it means little about whether you can hear a signal or how
> easily it can be copied.
>
> True signal reports are given by what you hear, not what the meter says.
>
> 73 Ron AC7AC
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net Please help support this email
> list: http://www.qsl.net/donate.html
>

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n7ws

Re: [K3] RX Gain Calibration

If he was DX, I'll bet he was 59.

--- On Wed, 3/20/13, Fred Smith <[hidden email]> wrote:

Amen! I have worked stations SSB that never move the S-Meter at all.

73,
Fred/N0AZZ
K3 Ser #'s 6730/5299--KX3 # 2573--K2/100--KAT100
P3/SVGA--KPA500--KAT500--W2

Exactly

Gary
Vk1ZZ
K3, KX3, KPA500-FT, KAT500-FT,P3.
On 20/03/2013 11:59 AM, "Ron D'Eau Claire" <[hidden email]> wrote:

Edward R Cole

Re: [K3] RX Gain Calibration

In reply to this post by k2np

This discussion prompts me to make the comparisons on my K3 (4340)
and KX3 (475). I have an XG3 which I have installed in a diecast
aluminum box (Hammond Box) so it is able to produce signals down to
-155 dBm using external attenuators and double-shielded coax cables.

I calibrate the XG3 at 0-dBm with my mw power meter (HP432A) and it
is within a dB accurate. Above 200-MHz harmonics are used so one
cannot measure output without using a bw filter, since the
fundamental freq and harmonics add to total power.

One should note measurements with preamp on/off and what bandwidth
they are made. I believe all Elecraft specs are made at 500-KHz bw.

May be a few days until I get the results to post, but I love both
these radios for their differences, as well.

73, Ed - KL7UW

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