K2 S meter

[Howard W. Ashcraft]

I set up my K2 S meter per the manual.  It appeared to work "normally" with S9+ readings on loud signals.  I then borrowed an X-gen and used it to "calibrate" the S-Meter readings.  The "calibrated" settings were much lower than the "per manual" settings, i.e., a signal that was S-9 would read, after calibration, about S-5 or 6.  I don't have a method for measuring the X-gen output.  I do know that the K2 easily picks up the 1 uv low signal used for sensitivity testing.  I will probably just go back to the earlier settings, but I was wondering if anyone else had a similar experience?





HOWARD W. ASHCRAFT, Jr.
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This communication, including any attachments, is confidential and is protected by privilege. If you are not the intended recipient, any use dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender by telephone or e-mail, and permanently delete all copies, electronic or other, you may have. The foregoing applies even if this notice is embedded in a message that is forwarded or attached.


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[n6wg]

Howard
The K2 has a different total system gain on each band, with highest being
on 40m.  So, if you set your S meter to S9 with a certain input on 40m,
then it will read lower on other bands for the same input level.

If I ever want to use the S meter seriously, such as in a single band
contest,
like 160m cw, say, then I calibrate on that band and don't worry about the
reading on other bands.

Conversely, if you set your S meter to S9 on some other band, such as 10m,
then
it will read higher on 40m.

Good luck and 73
Bob N6WG

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[David A. Belsley]

Howard:
   The standard means given in the manual for setting the S meter
produces settings that are generally low, i.e., readings that ought be
S9 tend to register much lower than S9.  Many people have simply goosed
up their settings so that signals they feel should be S9 register as
such.  Elecraft produces a little minkit, the  XG1 Receiver Test
Oscillator / S-Meter Calibrator, that creates a highly accurate .5
microvolt signal (at 7.04 MHz).  Using this will give you a very
accurate S meter setting for 40 meters.  I cannot speak for its
behavior on other bands.

best wishes,

dave belsley, w1euy


On Nov 18, 2004, at 5:46 PM, Howard W. Ashcraft wrote:

> I set up my K2 S meter per the manual.  It appeared to work "normally"
> with S9+ readings on loud signals.  I then borrowed an X-gen and used
> it to "calibrate" the S-Meter readings.  The "calibrated" settings
> were much lower than the "per manual" settings, i.e., a signal that
> was S-9 would read, after calibration, about S-5 or 6.  I don't have a
> method for measuring the X-gen output.  I do know that the K2 easily
> picks up the 1 uv low signal used for sensitivity testing.  I will
> probably just go back to the earlier settings, but I was wondering if
> anyone else had a similar experience?
>
>
>
>
>
> HOWARD W. ASHCRAFT, Jr.
> Direct Dial: [phone]
> [hidden email]
> HANSON 333 Market Street, 23rd Floor
> BRIDGETT San Francisco, CA 94105-2173
> MARCUS   Direct: [phone]
> VLAHOS Main: [phone]
> RUDY, LLP Fax: [phone]
>
> This communication, including any attachments, is confidential and is
> protected by privilege. If you are not the intended recipient, any use
> dissemination, distribution, or copying of this communication is
> strictly prohibited. If you have received this communication in error,
> please immediately notify the sender by telephone or e-mail, and
> permanently delete all copies, electronic or other, you may have. The
> foregoing applies even if this notice is embedded in a message that is
> forwarded or attached.
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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[G3VVT]

Howard,
With regard to S meter readings it does appear at least with my K2  #4168 and
a later K2 #4324 tested a few weeks back that 80, 40, 30, 20 and 17m  bands
come out with similar sensitivity in the level required for S9 when  switched
to the same mode and bandwidth. For 15, 12 and 10m there was a  discrepancy
with the later serial number being slightly less sensitive. The  alignment
appeared to be fairly well correct for both K2.
 
With the Elecraft XG1 signal generator the testing for S9 is done at  7040kHz
with the higher level output at 50 microvolts PD (50uV PD = approx  -73dBm).
With the AGC threshold set at 3.80V, 50uV was insufficient  to make S9 with
both these K2. They both needed about 63uV PD to make S9  with the preamp
switched off and were slightly more sensitive when checked  with CW at 700Hz
bandwidth compared to SSB with the SSB filter in circuit.
 
However during testing it was found that small variations in the AGC  
threshold voltage had a substantial effect on the level required to make  S9. With
AGC threshold at 3.80V, as noted 63uV was required for S9. Drop  this by 0.1V to
3.70 V, only 40uV was required and again by another 0.1V to  3.60V, only 25uV
was now needed for S9. With all of the changes in threshold  voltages the CAL
S HI and CAL S LO needs to be reset at each step.
 
The effect noted was posted on the Elecraft Reflector though only raised  two
replies in confirmation. Again has anybody else seen this effect of  rising S
meter sensitivity when lowering the AGC threshold whilst testing the K2  
receiver?
 
The optimum point for the setting of the AGC threshold with my K2 #4168  came
out at 3.70V, which meant the S meter sensitivity came out at 40uV PD for  
S9. This can be fudged to 50uV for S9 by adjusting CAL S HI if desired. Left  
mine as is for ease of S meter HI/LO setting as per the manual.
 
Assuming the alignment is correct on the K2 reported with low S meter  
sensitivity, it may be worth checking that AGC threshold has been set to at  least
the 3.80V initial setting. Well worth checking the K2 Alignment  Instructions
on Don, W3FPR's web site to ensure that you get everything  correct.
 
Bob, G3VVT
K2 #4168
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[Don Wilhelm-3]

Folks,

After playing with the AGC threshold vs. S-9 = 50 uV on several K2s, I can
state that the value of 3.80 volts is only a nominal value, and in my
experience should only be considered as an upper limit.  I have found the
proper AGC threshold to range from 3.65 volts to 3.8 volts.

There is some slight varaition in receiver gain from K2 to K2.  This is
likely due to manufacturing varaiations in the components and could also be
influenced by the loss through the particular IF filter, so the really
correct settings for your K2 may not match another's.

First and most importantly, check with AGC on vs. AGC off to be certain that
there is no AGC activation with receiver noise (no antenna conenected - and
check all bands).  If the background noise increases with the AGC off, the
the AGC threshold is too high.  That means the AGc is being activated on
receiver noise alone, and does not allow hearing the full sensitivity
capabilities of your K2.  The highest voltage point where your reciever
shows no change from AGC on to AGC off is the highest voltage YOUR AGC
threshold should be set.

Now, how does this relate to S-9 indications, you may ask -- well, different
AGC threshold voltage settings will make the S-meter more or less lively
that is for certain, and by 'playing' with the settings of AGC threshold,
S-Lo, and S-hi, one can make the S-meter read almost anything within reason.
If you have a calibrated 50 uV signal (such as the ouptut of the XG-1), you
can set the S-meter on 40 meters for S-9 at 50 uV (I have found that this is
best set  with the pre-amp ON).

I find it helpful to make a chart of the AGC threshold voltage, S-low
setting, S-hi setting, and the resultant s-mater reading.  This chart will
tell you which way to move the AGC setting to achieve a higher or lower
s-meter reading with any given signal input (50 uV is ideal).  I have tried
doing it by 'guess and by gosh', and believe me, creating the chart is the
fastest way to get there - frustration will quickly set in without it - this
is an exercise with 3 variables, and my brain gets confused with only 2
variables.

Bottom line - the K2 S-meter can be made to be 'stingy' or 'lively'
whichever is your choice.  There will be some variation from band to band (a
lot depends on the bandpass filters settings - do that part of the alignment
first), so make your choices and set it to please you.  For my clients and
my own K2s, I set the S-meter to read S-9 with 50 uV input on 7040 Mhz with
the K2 preamp turned on.

Oh yes, for my personal viewpoint -- the S-meter reading is entirely
relative because it only indicates that one particular signal is stronger
than another signal.  The real 'proof of the pudding' is the 'R' in the
RS(T) report which indicates how well you can read the other station - and a
properly aligned K2 can dig them out of the mud, and !!!that!!! is what
really counts.

73,
Don W3FPR

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

> Howard,
> With regard to S meter readings it does appear at least with my K2  #4168
> and
> a later K2 #4324 tested a few weeks back that 80, 40, 30, 20 and 17m
> bands
> come out with similar sensitivity in the level required for S9 when
> switched
> to the same mode and bandwidth. For 15, 12 and 10m there was a
> discrepancy
> with the later serial number being slightly less sensitive. The  alignment
> appeared to be fairly well correct for both K2.
>
> With the Elecraft XG1 signal generator the testing for S9 is done at
> 7040kHz
> with the higher level output at 50 microvolts PD (50uV PD =
> pprox  -73dBm).
> With the AGC threshold set at 3.80V, 50uV was insufficient  to make S9
> with
> both these K2. They both needed about 63uV PD to make S9  with the preamp
> switched off and were slightly more sensitive when checked  with CW at
> 700Hz
> bandwidth compared to SSB with the SSB filter in circuit.
>
> However during testing it was found that small variations in the AGC
> threshold voltage had a substantial effect on the level required to make
> S9. With
> AGC threshold at 3.80V, as noted 63uV was required for S9. Drop  this by
> 0.1V to
> 3.70 V, only 40uV was required and again by another 0.1V to  3.60V, only
> 25uV
> was now needed for S9. With all of the changes in threshold  voltages the
> CAL
> S HI and CAL S LO needs to be reset at each step.
>
> The effect noted was posted on the Elecraft Reflector though only raised
> two
> replies in confirmation. Again has anybody else seen this effect of
> rising S
> meter sensitivity when lowering the AGC threshold whilst testing the K2
> receiver?
>
> The optimum point for the setting of the AGC threshold with my K2 #4168
> came
> out at 3.70V, which meant the S meter sensitivity came out at 40uV PD for
> S9. This can be fudged to 50uV for S9 by adjusting CAL S HI if desired.
> Left
> mine as is for ease of S meter HI/LO setting as per the manual.
>
> Assuming the alignment is correct on the K2 reported with low S meter
> sensitivity, it may be worth checking that AGC threshold has been set to
> at  least
> the 3.80V initial setting. Well worth checking the K2 Alignment
> Instructions
> on Don, W3FPR's web site to ensure that you get everything  correct.
>

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