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KAT2 Hi Cur warning

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KAT2 Hi Cur warning

Just installed the KAT2 in a newly assembled K2. At power levels greater than 8.0 watts, the K2 was displaying the high current warning. The KAT2 power calibration was calibrated by measuring voltage with the K2's RF probe at the feed point to a dummy load.

I removed the KAT2 and remeasured the power across all bands. Again, power was calculated based on DC voltage from RF probe at dummy load feed point. The impedance of the feedline and dummy load were retested. (49 to 51 ohms over the amateur radio bands, measured with a sark-110 calibrated using a set of reference loads)

Here are the results:

Band Power At Load K2 Current
80 9.7 2.2
40 9.2 2.0
30 9.4 2.1
20 9.7 2.1
17 11 2.1
15 9.3 2.0
12 9.4 2.2
10 9.6 2.3

After remeasuring power, the KAT2 was reinstalled, and its power meter verified correct at 5 watts. With the KAT2 reinstalled, rechecked K2 current draw at 10 watts on all bands. For each band it measured 20% to 30% higher than without the KAT2.

With the power level on the K2 set to one watt and the ATU set to CALP, I used the RF probe to measure a few points on the KAT2 control board, and the input from the RF board. At the one watt level, there is approximately 1v drop between K17 pins 2/9 and 4/7.

K17
Pins Volts
2/9 9.9
3/8 9.9
4/7 8.6

K18
Pins Volts
3/8 8.6

Is this expected behavior, or is something amiss with this KAT2?

Thanks,
--mark/ae0mm
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Don Wilhelm

Re: KAT2 Hi Cur warning

Mark,

First, set the CAL CUR in the K2 menu to 3.50 - and also make certain
the power supply voltage as displayed on the K2 display is not dropping
significantly during a TUNE. If it drops more than 1 volt suspect your
power supply or the power cable. A low supply voltage can cause the K2
to report HI Cur - the K2 tries to maintain the power requested, and a
lower voltage requires greater current.

Note that at least 2 watts is required to calibrate the KAT2 wattmeter
and to do a TUNE.

The first step in bringing up the KAT2 is to balance (null) the
wattmeter. Adjust the trimmer capacitor for the lowest reading in ATU
menu CALn.

After that, connect a good 50 ohm dummy load and do the CALP setting.
Use an external wattmeter that you trust, or the measurement of the RF
voltage with the RF Probe will work, but requires some calculation in
between adjustments. The external wattmeter is quicker.

With the ATU menu set for CALP, the relays should be set to open all
paths to the capacitors and to short out the inductors, so I doubt that
those relay measurements are of value - unless one of the relays has an
unsoldered pin 1 or pin 10 which will not allow it to switch.
Check the schematic to see which relay pins should be closed and which
should be open.

73,
Don W3FPR

On 9/25/2018 5:35 PM, AE0MM via Elecraft wrote:

> Just installed the KAT2 in a newly assembled K2. At power levels greater than 8.0 watts, the K2 was displaying the high current warning. The KAT2 power calibration was calibrated by measuring voltage with the K2's RF probe at the feed point to a dummy load.
>
> I removed the KAT2 and remeasured the power across all bands. Again, power was calculated based on DC voltage from RF probe at dummy load feed point. The impedance of the feedline and dummy load were retested. (49 to 51 ohms over the amateur radio bands, measured with a sark-110 calibrated using a set of reference loads)
>
> Here are the results:
>
> Band Power At Load K2 Current
> 80 9.7 2.2
> 40 9.2 2.0
> 30 9.4 2.1
> 20 9.7 2.1
> 17 11 2.1
> 15 9.3 2.0
> 12 9.4 2.2
> 10 9.6 2.3
>
> After remeasuring power, the KAT2 was reinstalled, and its power meter verified correct at 5 watts. With the KAT2 reinstalled, rechecked K2 current draw at 10 watts on all bands. For each band it measured 20% to 30% higher than without the KAT2.
>
> With the power level on the K2 set to one watt and the ATU set to CALP, I used the RF probe to measure a few points on the KAT2 control board, and the input from the RF board. At the one watt level, there is approximately 1v drop between K17 pins 2/9 and 4/7.
>

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Elecraft mailing list

Re: KAT2 Hi Cur warning

Don,

I've done the bridge null adjustment several times. The red c55 trimmer capacitor is very touchy. Using a ceramic screwdriver, I'm able to get the reading in the 7 to 10 range, but after a few moments, or hours, it will read 30 and sometimes up to 90 at 7100KHz into a dummy load on 5w requested power.

With requested power set to 10w, voltage drops from 13.5 to 12.9 when pressing tune. (atu set to calp)

It seems the biggest current change in current (before KAT2 vs after KAT2) is on 30m, 12m, and 10m. Is it normal for current to increase after installing KAT2? Are these numbers in harmony with what you'd expect? I don't have a watt meter, so I'm relying on the RF probe.

Here are the before and after measurements:
Band Power Current
80 9.7 2.2
40 9.2 2.0
30 9.4 2.1
20 9.7 2.1
17 11 2.1
15 9.3 2.0
12 9.4 2.2
10 9.6 2.3

80 11.2 2.7
40 10.8 2.3
30 10.0 2.9
20 10.8 2.5
17 10.5 2.4
15 10.4 2.5
12 8.2 2.5
10 8.5 2.9

What I'm experiencing, is it normal and expected?

Thanks,
--mark/ae0mm

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, September 25, 2018 5:58 PM, Don Wilhelm <[hidden email]> wrote:

> Mark,
>
> First, set the CAL CUR in the K2 menu to 3.50 - and also make certain
> the power supply voltage as displayed on the K2 display is not dropping
> significantly during a TUNE. If it drops more than 1 volt suspect your
> power supply or the power cable. A low supply voltage can cause the K2
> to report HI Cur - the K2 tries to maintain the power requested, and a
> lower voltage requires greater current.
>
> Note that at least 2 watts is required to calibrate the KAT2 wattmeter
> and to do a TUNE.
>
> The first step in bringing up the KAT2 is to balance (null) the
> wattmeter. Adjust the trimmer capacitor for the lowest reading in ATU
> menu CALn.
>
> After that, connect a good 50 ohm dummy load and do the CALP setting.
> Use an external wattmeter that you trust, or the measurement of the RF
> voltage with the RF Probe will work, but requires some calculation in
> between adjustments. The external wattmeter is quicker.
>
> With the ATU menu set for CALP, the relays should be set to open all
> paths to the capacitors and to short out the inductors, so I doubt that
> those relay measurements are of value - unless one of the relays has an
> unsoldered pin 1 or pin 10 which will not allow it to switch.
> Check the schematic to see which relay pins should be closed and which
> should be open.
>
> 73,
> Don W3FPR
>
> On 9/25/2018 5:35 PM, AE0MM via Elecraft wrote:
>
> > Just installed the KAT2 in a newly assembled K2. At power levels greater than 8.0 watts, the K2 was displaying the high current warning. The KAT2 power calibration was calibrated by measuring voltage with the K2's RF probe at the feed point to a dummy load.
> > I removed the KAT2 and remeasured the power across all bands. Again, power was calculated based on DC voltage from RF probe at dummy load feed point. The impedance of the feedline and dummy load were retested. (49 to 51 ohms over the amateur radio bands, measured with a sark-110 calibrated using a set of reference loads)
> > Here are the results:
> > Band Power At Load K2 Current
> > 80 9.7 2.2
> > 40 9.2 2.0
> > 30 9.4 2.1
> > 20 9.7 2.1
> > 17 11 2.1
> > 15 9.3 2.0
> > 12 9.4 2.2
> > 10 9.6 2.3
> > After remeasuring power, the KAT2 was reinstalled, and its power meter verified correct at 5 watts. With the KAT2 reinstalled, rechecked K2 current draw at 10 watts on all bands. For each band it measured 20% to 30% higher than without the KAT2.
> > With the power level on the K2 set to one watt and the ATU set to CALP, I used the RF probe to measure a few points on the KAT2 control board, and the input from the RF board. At the one watt level, there is approximately 1v drop between K17 pins 2/9 and 4/7.

Don Wilhelm

Re: KAT2 Hi Cur warning

Mark,

That is not abnormal.

It is normal for the current required for one band to be a bit different
than for other bands, and yours is not out of line. Yes, the KAT2 draws
a bit more current than without it - that is true for any option.

Move the CAL CUR setting up to 3.50 Amps.

73,
Don W3FPR

On 9/29/2018 12:19 PM, AE0MM wrote:

> Don,
>
> I've done the bridge null adjustment several times. The red c55 trimmer capacitor is very touchy. Using a ceramic screwdriver, I'm able to get the reading in the 7 to 10 range, but after a few moments, or hours, it will read 30 and sometimes up to 90 at 7100KHz into a dummy load on 5w requested power.
>
> With requested power set to 10w, voltage drops from 13.5 to 12.9 when pressing tune. (atu set to calp)
>
> It seems the biggest current change in current (before KAT2 vs after KAT2) is on 30m, 12m, and 10m. Is it normal for current to increase after installing KAT2? Are these numbers in harmony with what you'd expect? I don't have a watt meter, so I'm relying on the RF probe.
>
>
> Here are the before and after measurements:
> Band Power Current
> 80 9.7 2.2
> 40 9.2 2.0
> 30 9.4 2.1
> 20 9.7 2.1
> 17 11 2.1
> 15 9.3 2.0
> 12 9.4 2.2
> 10 9.6 2.3
>
>
> 80 11.2 2.7
> 40 10.8 2.3
> 30 10.0 2.9
> 20 10.8 2.5
> 17 10.5 2.4
> 15 10.4 2.5
> 12 8.2 2.5
> 10 8.5 2.9
>
> What I'm experiencing, is it normal and expected?
>
>

Elecraft mailing list

Re: KAT2 Hi Cur warning

Don,

Thanks for the info.

--mark/ae0mm

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Saturday, September 29, 2018 12:19 PM, Don Wilhelm <[hidden email]> wrote:

> Mark,
>
> That is not abnormal.
>
> It is normal for the current required for one band to be a bit different
> than for other bands, and yours is not out of line. Yes, the KAT2 draws
> a bit more current than without it - that is true for any option.
>
> Move the CAL CUR setting up to 3.50 Amps.
>
> 73,
> Don W3FPR
>
> On 9/29/2018 12:19 PM, AE0MM wrote:
>
> > Don,
> > I've done the bridge null adjustment several times. The red c55 trimmer capacitor is very touchy. Using a ceramic screwdriver, I'm able to get the reading in the 7 to 10 range, but after a few moments, or hours, it will read 30 and sometimes up to 90 at 7100KHz into a dummy load on 5w requested power.
> > With requested power set to 10w, voltage drops from 13.5 to 12.9 when pressing tune. (atu set to calp)
> > It seems the biggest current change in current (before KAT2 vs after KAT2) is on 30m, 12m, and 10m. Is it normal for current to increase after installing KAT2? Are these numbers in harmony with what you'd expect? I don't have a watt meter, so I'm relying on the RF probe.
> > Here are the before and after measurements:
> > Band Power Current
> > 80 9.7 2.2
> > 40 9.2 2.0
> > 30 9.4 2.1
> > 20 9.7 2.1
> > 17 11 2.1
> > 15 9.3 2.0
> > 12 9.4 2.2
> > 10 9.6 2.3
> > 80 11.2 2.7
> > 40 10.8 2.3
> > 30 10.0 2.9
> > 20 10.8 2.5
> > 17 10.5 2.4
> > 15 10.4 2.5
> > 12 8.2 2.5
> > 10 8.5 2.9
> > What I'm experiencing, is it normal and expected?