K2: Is there an ideal power supply voltage?

[Andrew Moore-3]

While the K2 is capable of operating from a range of input voltages, is
there an ideal power supply voltage it prefers to see for best receiver
performance? If so, what is that voltage (as indicated on the K2 LCD when
"DISPLAY" is pressed twice)?

Would the K2's receiver performance benefit from a realignment (filters/BFO,
IF, 4.0 MHz oscillator, etc.) after the power supply voltage is change? (as
impractical as that may be in real life)

Thanks,
--Andrew, NV1B
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[Don Wilhelm-4]

  Andrew,

For K2 receive, as long as the power supply voltage is between 9.5 volts
and 15 volts, there will be no change in receiver performance.  The
receiver circuits all operate on the output of the 8 volt regulator
(well, except for the AF Amp) which will supply 8 volts until the
voltage drops below the regulator's dropout voltage (it is a low dropout
regulator).

For the same reason, a voltage change will not change the receiver
alignment.

The 4 MHz reference is not critical during operation since it is not
used dynamically.  It is important that it be aligned just before doing
a CAL PLL and/or a CAL FIL operation - it is used at that time to store
DAC values into EEPROM, and those DAC values do depend on the frequency
measured by the internal counter probe - and that frequency is dependent
on the 4 MHz reference oscillator frequency at that time.

73,
Don W3FPR

On 12/31/2010 5:28 PM, Andrew Moore wrote:

> While the K2 is capable of operating from a range of input voltages, is
> there an ideal power supply voltage it prefers to see for best receiver
> performance? If so, what is that voltage (as indicated on the K2 LCD when
> "DISPLAY" is pressed twice)?
>
> Would the K2's receiver performance benefit from a realignment (filters/BFO,
> IF, 4.0 MHz oscillator, etc.) after the power supply voltage is change? (as
> impractical as that may be in real life)
>
> Thanks,
> --Andrew, NV1B
>

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[k6dgw]

On 12/31/2010 2:28 PM, Andrew Moore wrote:
> While the K2 is capable of operating from a range of input voltages, is
> there an ideal power supply voltage it prefers to see for best receiver
> performance? If so, what is that voltage (as indicated on the K2 LCD when
> "DISPLAY" is pressed twice)?

No.  Like many radios these days and especially those designed for
battery power, the radio components operate from a lower voltage than
the supply.  I believe it's an 8V regulator in the K2.  So long as your
supply is above the drop-out voltage for the regulator [10V or maybe a
little less, mine seems to work at around 9.6V or so] and is less than
about 15V, the supply voltage doesn't make any difference.  A really
"dirty" 12VDC might create some problems but something has to be really
wrong with your supply for that to happen
>
> Would the K2's receiver performance benefit from a realignment (filters/BFO,
> IF, 4.0 MHz oscillator, etc.) after the power supply voltage is change? (as
> impractical as that may be in real life)

No.  The power to the radio is regulated at 8V [see above], nothing
changes as the supply voltage goes up or down.  In the field, I run my
K2 from a Li-Ion battery I got from China, it starts at about 12V, and
the voltage declines "sort of kind of steadily" as I drain it.
Everything works fine and stays on frequency until about 10V or a little
less when the K2 shuts down on Lo-volts.

The 4.0 MHz ref oscillator isn't used during normal operation, only when
doing the calibrations, and again, it doesn't matter what the supply
voltage is so long as it is within the published K2 specs.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org
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[Mel]

Since the regulator is a low drop out, the ideal voltage would be about a volt
over the minimum input for the regulator.  That keeps the dissipation at the
lowest level inside the radio.  Of course the Tx is another issue.

Mel, K6KBE




________________________________
From: Fred Jensen <[hidden email]>
To: Elecraft Reflector <[hidden email]>
Sent: Fri, December 31, 2010 4:35:14 PM
Subject: Re: [Elecraft] K2: Is there an ideal power supply voltage?

On 12/31/2010 2:28 PM, Andrew Moore wrote:
> While the K2 is capable of operating from a range of input voltages, is
> there an ideal power supply voltage it prefers to see for best receiver
> performance? If so, what is that voltage (as indicated on the K2 LCD when
> "DISPLAY" is pressed twice)?

No.  Like many radios these days and especially those designed for
battery power, the radio components operate from a lower voltage than
the supply.  I believe it's an 8V regulator in the K2.  So long as your
supply is above the drop-out voltage for the regulator [10V or maybe a
little less, mine seems to work at around 9.6V or so] and is less than
about 15V, the supply voltage doesn't make any difference.  A really
"dirty" 12VDC might create some problems but something has to be really
wrong with your supply for that to happen
>
> Would the K2's receiver performance benefit from a realignment (filters/BFO,
> IF, 4.0 MHz oscillator, etc.) after the power supply voltage is change? (as
> impractical as that may be in real life)

No.  The power to the radio is regulated at 8V [see above], nothing
changes as the supply voltage goes up or down.  In the field, I run my
K2 from a Li-Ion battery I got from China, it starts at about 12V, and
the voltage declines "sort of kind of steadily" as I drain it.
Everything works fine and stays on frequency until about 10V or a little
less when the K2 shuts down on Lo-volts.

The 4.0 MHz ref oscillator isn't used during normal operation, only when
doing the calibrations, and again, it doesn't matter what the supply
voltage is so long as it is within the published K2 specs.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org
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[Bill Coleman-2]

On Dec 31, 2010, at 5:28 PM, Andrew Moore wrote:

> While the K2 is capable of operating from a range of input voltages, is
> there an ideal power supply voltage it prefers to see for best receiver
> performance? If so, what is that voltage (as indicated on the K2 LCD when
> "DISPLAY" is pressed twice)?

Because the receiver works off an internally regulated voltage, it's performance is largely unaffected by the supply voltage, so long as it meets the minimum voltage requirements. (About 11 volts, if my memory serves).

> Would the K2's receiver performance benefit from a realignment (filters/BFO,
> IF, 4.0 MHz oscillator, etc.) after the power supply voltage is change? (as
> impractical as that may be in real life)

Highly unlikely that anything would change.

--

The transmitter, however, especially with the KPA100, is affected by supply voltage, since the finals are directly connected to the power supply.

I run my PS at 14.4 volts, which is well within the supply range (and not untypical for a automobile supply). The higher voltage helps to prevent too much sag under load. I see about 13.5 volts at full output (110 watts).

Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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