"Hot" K3

[Don Rasmussen]

Thanks all for entertaining my query.

Actually, in order to get K3 to show the usual 50mv
S9 reading on the S-meter, I need to set the CONFIG
S-Meter Offset and S-Meter range at their reduced stops.

Otherwise S5 signals display S9 bars on the K3 meter.

That's what tells me something is wrong.

If there is a firmware setting or a hardware pot that
adjusts the signal amplification level I'll need to reduce this.

Hopefully, it is not a component out of spec that's
causing this, but this may be the case.



[Elecraft] "Hot" K3

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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[Evert Bakker (PA2KW)]

Hello Don,

I do have a similar effect except that my first and second radio is a K3
(SN-0812 and SN-2185).

- Same power-supply at the same time radio's ON
- both on 50 Ohm dummy load
- same roofing filter (2.7 Kc)
- same filter gain (0 dB)
- same DSP setting (Bw = 3.0 Kc / Fctr = 1.5 Kc)
- same rx equilizers
- same AGC settings (AGC-F, THR=6, SLP=5)
- no S-meter changes (settings are factory default)
- same RF gain setting
- KRX disabled in SN-2185
- Both KANT 3 disabled and ANT 1 selected

Result : 2 to 3 S-units difference (+/- 15 dB) on "internal" noise
difference. This was the first test on 15 meter)

That's a lot. How come?

I can't say anything yet about the sensitivity. I will try to find someone
with a "calibrated" signal source and make conclusions.

It might all be differences in gain, but first of all I have to gain
confidence...

Has one of you a good suggestion a-priori?

73's, Evert PA2KW



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[Evert Bakker (PA2KW)]

Thanks Dave,

 

Easy to forget something, but both are the same, ATT=OFF, PRE=ON

 

I just tested it on all bands: same results on all bands.

 

(May be only S-meter offset if possible ?)

 

73's, Evert PA2KW

 

 

 

  _____  

From: David Gilbert [mailto:[hidden email]]
Sent: Monday, March 16, 2009 20:24
To: [hidden email]
Subject: Re: [Elecraft] "Hot" K3

 


You didn't mention ATT and PRE.  I have found that sometimes when I reset my
K3 it goes back to settings that turned one or the other on without my being
aware of it.

73,
Dave   AB7E




Evert Bakker (PA2KW) wrote:

Hello Don,
 
I do have a similar effect except that my first and second radio is a K3
(SN-0812 and SN-2185).
 
- Same power-supply at the same time radio's ON
- both on 50 Ohm dummy load
- same roofing filter (2.7 Kc)
- same filter gain (0 dB)
- same DSP setting (Bw = 3.0 Kc / Fctr = 1.5 Kc)
- same rx equilizers
- same AGC settings (AGC-F, THR=6, SLP=5)
- no S-meter changes (settings are factory default)
- same RF gain setting
- KRX disabled in SN-2185
- Both KANT 3 disabled and ANT 1 selected
 
Result : 2 to 3 S-units difference (+/- 15 dB) on "internal" noise
difference. This was the first test on 15 meter)
 
That's a lot. How come?
 
I can't say anything yet about the sensitivity. I will try to find someone
with a "calibrated" signal source and make conclusions.
 
It might all be differences in gain, but first of all I have to gain
confidence...
 
Has one of you a good suggestion a-priori?
 
73's, Evert PA2KW
 
 
 
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[Don Rasmussen]

Evert - so I am among fine company. This justfies my mental state, either I am not at all crazy or I have found one soul to share my specific malady.

I am comparing K3 #272 and K3 #2308, and the latter K3 is the "hotter".

The both play so well, at first it was hard to decide which one was "affected". ;-)

My difference can be as much as 20db.

K3 #272 has the HAGC mod.

Either the calibration department at Elecraft is having some bad days, or an unknown variation in parts is causing this.

I hesistate to post issues to the email list without a conversation with Elecraft but in this case maybe we have stumble upon something they don't know.

Cheers,
Don


--- On Mon, 3/16/09, Evert Bakker (PA2KW) <[hidden email]> wrote:

> From: Evert Bakker (PA2KW) <[hidden email]>
> Subject: RE: [Elecraft]  "Hot" K3
> To: "'Don Rasmussen'" <[hidden email]>
> Cc: "'Elecraft Discussion List'" <[hidden email]>
> Date: Monday, March 16, 2009, 11:57 AM
> Hello Don,
>
> I do have a similar effect except that my first and second
> radio is a K3
> (SN-0812 and SN-2185).
>
> - Same power-supply at the same time radio's ON
> - both on 50 Ohm dummy load
> - same roofing filter (2.7 Kc)
> - same filter gain (0 dB)
> - same DSP setting (Bw = 3.0 Kc / Fctr = 1.5 Kc)
> - same rx equilizers
> - same AGC settings (AGC-F, THR=6, SLP=5)
> - no S-meter changes (settings are factory default)
> - same RF gain setting
> - KRX disabled in SN-2185
> - Both KANT 3 disabled and ANT 1 selected
>
> Result : 2 to 3 S-units difference (+/- 15 dB) on
> "internal" noise
> difference. This was the first test on 15 meter)
>
> That's a lot. How come?
>
> I can't say anything yet about the sensitivity. I will
> try to find someone
> with a "calibrated" signal source and make
> conclusions.
>
> It might all be differences in gain, but first of all I
> have to gain
> confidence...
>
> Has one of you a good suggestion a-priori?
>
> 73's, Evert PA2KW
>
>
>
> ______________________________________________________________
> 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

... [show rest of quote]

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