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KX-3 TX current draw?

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Drew Arnett

KX-3 TX current draw?

What do you see for current draw on the KX-3? Manual says 1 to 2 A typical.

I'm seeing 3 A at less than full power on one band. Yikes! Makes me
wonder if the repair shop is open? Elecraft website says hunkered
down and mostly work from home.

Thanks and best regards,

Drew
n7da
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Drew Arnett

Re: KX-3 TX current draw?

Walter,

50 MHz TX constant 4 W carrier measures 13.53 V on DMM (outside the DC
power plug), 13.3 V on KX3 meter, 2.9 A on KX3 meter and 1.6 to 1 VSWR
on KX3 meter. Microwave dummy load with BNC to N adapter.

I didn't measure all of this when the rig was new, so have no baseline
to know what is normal. :-(

Thanks,

Drew
n7da

On Fri, May 8, 2020 at 11:19 PM Drew Arnett <[hidden email]> wrote:

>
> What do you see for current draw on the KX-3? Manual says 1 to 2 A typical.
>
> I'm seeing 3 A at less than full power on one band. Yikes! Makes me
> wonder if the repair shop is open? Elecraft website says hunkered
> down and mostly work from home.
>
> Thanks and best regards,
>
> Drew
> n7da

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Mooneer Salem

Re: KX-3 TX current draw?

Hi Drew,

I got 2.36A current consumption @ 5W using a dummy load and the TX button
on 50.100MHz USB with my KX3 (S/N 3262). The voltage dropped from 13.74V to
13.67V during transmit. (Measured using an in-line Powerpole meter attached
between a 54Ah LiFePO4 battery and the KX3.) Hopefully this helps!

BTW, I had to recently redo TX calibration because I ended up doing a
factory reset while trying to re-run temperature compensation (long story),
so I'm not sure if this is any more or less indicative of "normal" power
consumption.

Thanks,

-Mooneer K6AQ

On Fri, May 8, 2020 at 4:34 PM Drew Arnett <[hidden email]> wrote:

> Walter,
>
> 50 MHz TX constant 4 W carrier measures 13.53 V on DMM (outside the DC
> power plug), 13.3 V on KX3 meter, 2.9 A on KX3 meter and 1.6 to 1 VSWR
> on KX3 meter. Microwave dummy load with BNC to N adapter.
>
> I didn't measure all of this when the rig was new, so have no baseline
> to know what is normal. :-(
>
> Thanks,
>
> Drew
> n7da
>
> On Fri, May 8, 2020 at 11:19 PM Drew Arnett <[hidden email]> wrote:
> >
> > What do you see for current draw on the KX-3? Manual says 1 to 2 A
> typical.
> >
> > I'm seeing 3 A at less than full power on one band. Yikes! Makes me
> > wonder if the repair shop is open? Elecraft website says hunkered
> > down and mostly work from home.
> >
> > Thanks and best regards,
> >
> > Drew
> > n7da
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

Vic Rosenthal

Re: KX-3 TX current draw?

In reply to this post by Drew Arnett

I think 1.6:1 is high for that kind of dummy load, if it's in good shape. Should be close to 1:1.
Anyway, you can't really say there is a problem unless you have a better match. Current draw is sensitive to mismatch.
--
Vic

On May 9, 2020 2:32:15 AM GMT+03:00, Drew Arnett <[hidden email]> wrote:

>Walter,
>
>50 MHz TX constant 4 W carrier measures 13.53 V on DMM (outside the DC
>power plug), 13.3 V on KX3 meter, 2.9 A on KX3 meter and 1.6 to 1 VSWR
>on KX3 meter. Microwave dummy load with BNC to N adapter.
>
>I didn't measure all of this when the rig was new, so have no baseline
>to know what is normal. :-(
>
>Thanks,
>
>Drew
>n7da
>
>On Fri, May 8, 2020 at 11:19 PM Drew Arnett <[hidden email]>
>wrote:
>>
>> What do you see for current draw on the KX-3? Manual says 1 to 2 A
>typical.
>>
>> I'm seeing 3 A at less than full power on one band. Yikes! Makes me
>> wonder if the repair shop is open? Elecraft website says hunkered
>> down and mostly work from home.
>>
>> Thanks and best regards,
>>
>> Drew
>> n7da
>______________________________________________________________
>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
>Message delivered to [hidden email]

Drew Arnett

Re: KX-3 TX current draw?

Good point, Victor. And why I included that SWR reading. Other bands
read fine. I have high confidence in the load and adapter (tried
swapping both just in case). I could measure the load and adapter the
next time I'm in the lab at work if I want to be absolutely thorough,
but it is a microwave load and just adapting from BNC to N (no coax).

SWR looks fine on other bands.

Thanks,

Drew
n7da

On Sat, May 9, 2020 at 4:57 AM Victor Rosenthal <[hidden email]> wrote:

>
> I think 1.6:1 is high for that kind of dummy load, if it's in good shape. Should be close to 1:1.
> Anyway, you can't really say there is a problem unless you have a better match. Current draw is sensitive to mismatch.
> --
> Vic
>
> On May 9, 2020 2:32:15 AM GMT+03:00, Drew Arnett <[hidden email]> wrote:
>>
>> Walter,
>>
>> 50 MHz TX constant 4 W carrier measures 13.53 V on DMM (outside the DC
>> power plug), 13.3 V on KX3 meter, 2.9 A on KX3 meter and 1.6 to 1 VSWR
>> on KX3 meter. Microwave dummy load with BNC to N adapter.
>>
>> I didn't measure all of this when the rig was new, so have no baseline
>> to know what is normal. :-(
>>
>> Thanks,
>>
>> Drew
>> n7da
>>
>> On Fri, May 8, 2020 at 11:19 PM Drew Arnett <[hidden email]> wrote:
>>>
>>>
>>> What do you see for current draw on the KX-3? Manual says 1 to 2 A typical.
>>>
>>> I'm seeing 3 A at less than full power on one band. Yikes! Makes me
>>> wonder if the repair shop is open? Elecraft website says hunkered
>>> down and mostly work from home.
>>>
>>> Thanks and best regards,
>>>
>>> Drew
>>> n7da
>>
>> ________________________________
>> 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
>> Message delivered to [hidden email]

John Oppenheimer

Re: KX-3 TX current draw?

In reply to this post by Mooneer Salem

Hi Drew,

50 MHz TX constant 4 W carrier:

KX3 #1658
KX3 PS 13.2 during XMIT
ATU bypass
Elecraft DL1
KX3 SWR 1.5
Current = 2.3A

John KN5L

On 5/8/20 6:52 PM, Mooneer Salem wrote:
> I got 2.36A current consumption @ 5W using a dummy load and the TX button
> on 50.100MHz USB with my KX3 (S/N 3262). The voltage dropped from 13.74V to
> 13.67V during transmit. (Measured using an in-line Powerpole meter attached
> between a 54Ah LiFePO4 battery and the KX3.) Hopefully this helps!
______________________________________________________________
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John Oppenheimer

Re: KX-3 TX current draw?

Additional comments:

Same test at 7MHz results with about 1A current. Suggesting KX3 power
amplifier efficiency difference between 7 and 50 MHz.

Using same DL1, added Elecraft W1 and MS utility to measure SWR. At 50
MHz KX3 displays SWR = 1.5 whereas W1 indicates SWR = 1.1:1.

May I suggest W1 closer to instrument grade measurement than KX3
internal SWR measurement.

John KN5L

On 5/9/20 8:34 AM, John Oppenheimer wrote:

> Hi Drew,
>
> 50 MHz TX constant 4 W carrier:
>
> KX3 #1658
> KX3 PS 13.2 during XMIT
> ATU bypass
> Elecraft DL1
> KX3 SWR 1.5
> Current = 2.3A

Drew Arnett

Re: KX-3 TX current draw?

In reply to this post by Drew Arnett

To follow up on Victor's point, did some more measurements this morning.

Setup:
KX-3 minimal adapters to 40 dB directional coupler to load
terminated unused port of coupler
measured port through 3 ft patch to Kanga US AD8307 RF power meter

I have good calibration data for the power meter, but for the purpose
at hand, I won't correct the meter readings. 60 on the scale is about
-20 dBm. Every 10 on the scale is actually 10.7 dB. Good enough.

Internal tuner bypassed.

Measurements:

Note: RX current in RX was between about .15 and .19 A for all 3 bands.

14 MHz @ 1 W setting
13.7 V RX (per KX3)
13.4 V TX (per KX3)
1.15 A TX (per KX3)
VSWR 1.3 (per KX3)
FWD 67 (on power meter display, very close to expected)
REV 30 (on power meter display)
--> return loss approx 37 dB

28 MHz @ 1 W setting
13.7 V RX
13.4 V TX
1.15 A TX
1.3 VSWR
FWD 67
REV 30
--> return loss approx 37 dB

50 MHz @ 1 W setting
13.7 V RX
12.9 V TX
2.9 A TX
1.6 VSWR
FWD 71
REV 35
--> return loss approx 36 dB

Hmm. So, I'm seeing 3% or less efficiency. Only one respondent on my
query about TX current draw, and he was getting 15%+ efficiency. No
wonder my PA temp shoots up.

Thanks,

Drew
n7da

On Sat, May 9, 2020 at 11:25 AM Drew Arnett <[hidden email]> wrote:

>
> Good point, Victor. And why I included that SWR reading. Other bands
> read fine. I have high confidence in the load and adapter (tried
> swapping both just in case). I could measure the load and adapter the
> next time I'm in the lab at work if I want to be absolutely thorough,
> but it is a microwave load and just adapting from BNC to N (no coax).
>
> SWR looks fine on other bands.
>
> Thanks,
>
> Drew
> n7da
>
> On Sat, May 9, 2020 at 4:57 AM Victor Rosenthal <[hidden email]> wrote:
> >
> > I think 1.6:1 is high for that kind of dummy load, if it's in good shape. Should be close to 1:1.
> > Anyway, you can't really say there is a problem unless you have a better match. Current draw is sensitive to mismatch.
> > --
> > Vic
> >
> > On May 9, 2020 2:32:15 AM GMT+03:00, Drew Arnett <[hidden email]> wrote:
> >>
> >> Walter,
> >>
> >> 50 MHz TX constant 4 W carrier measures 13.53 V on DMM (outside the DC
> >> power plug), 13.3 V on KX3 meter, 2.9 A on KX3 meter and 1.6 to 1 VSWR
> >> on KX3 meter. Microwave dummy load with BNC to N adapter.
> >>
> >> I didn't measure all of this when the rig was new, so have no baseline
> >> to know what is normal. :-(
> >>
> >> Thanks,
> >>
> >> Drew
> >> n7da
> >>
> >> On Fri, May 8, 2020 at 11:19 PM Drew Arnett <[hidden email]> wrote:
> >>>
> >>>
> >>> What do you see for current draw on the KX-3? Manual says 1 to 2 A typical.
> >>>
> >>> I'm seeing 3 A at less than full power on one band. Yikes! Makes me
> >>> wonder if the repair shop is open? Elecraft website says hunkered
> >>> down and mostly work from home.
> >>>
> >>> Thanks and best regards,
> >>>
> >>> Drew
> >>> n7da
> >>
> >> ________________________________
> >> 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
> >> Message delivered to [hidden email]

Drew Arnett

Re: KX-3 TX current draw?

Just to follow up. When I talked to support, they recommended sending
in for service.

After getting the rig back, I've only used it for IF at 100 mW on 50
MHz with transverter. And had a weird loud audio buzz problem. See
separate email describing that. Have reported to Elecraft; still
waiting for a response. Assuming the buzz problem is unrelated,
here's a set of new measurements made this morning to show post repair
performance for TX.

ATU bypassed. Bench DC supply. Excellent dummy load. No coax, just
a couple of coax adapters between rig and dummy load.

14 MHz @ 1 W setting
13.6 V RX (per KX3)
13.4 V TX (per KX3)
0.660 A TX (per KX3)
VSWR 1.0 (per KX3)

28 MHz @ 1 W setting
13.6 V RX
13.4 V TX
0.765 A TX
VSWR 1.0

50 MHz @ 1 W setting
13.6 V RX
13.2 V TX
1.040 A TX
VSWR 1.5

50 MHz @ 4 W setting
13.6 V RX
13.0 V TX
1.710 A TX
VSWR 1.6

That looks MUCH better. Efficiency on 50 MHz @ 4 W is > 18% and on
par with the one other reported measurement.

Huge thanks to Elecraft for getting the repair done before my next
major contesting event, the first weekend of the 10 GHz and Up. (Hmm.
Some HF contesting coming up soon. Amazing how many different kinds
of fun you can have with a KX3!)

I am a bit disappointed with the SWR meter on 50 MHz. Makes me wonder
how to operate safely on 50 MHz without an external meter or when
using the internal ATU.

FYI if anyone else runs into this issue, the repair report:
Repair(s) performed:
Replaced Q6-Q7 (E850047)
Current draw at 2.90 amps or below is acceptable.
-
Updates performed:
Control panel:
Updated firmware.
Updated Q9 (part change)
RF Board:
Replaced C1U and C1P (value change)

Best regards,

Drew
n7da

On Sat, May 16, 2020 at 5:25 PM Drew Arnett <[hidden email]> wrote:

>
> To follow up on Victor's point, did some more measurements this morning.
>
> Setup:
> KX-3 minimal adapters to 40 dB directional coupler to load
> terminated unused port of coupler
> measured port through 3 ft patch to Kanga US AD8307 RF power meter
>
> I have good calibration data for the power meter, but for the purpose
> at hand, I won't correct the meter readings. 60 on the scale is about
> -20 dBm. Every 10 on the scale is actually 10.7 dB. Good enough.
>
> Internal tuner bypassed.
>
> Measurements:
>
> Note: RX current in RX was between about .15 and .19 A for all 3 bands.
>
> 14 MHz @ 1 W setting
> 13.7 V RX (per KX3)
> 13.4 V TX (per KX3)
> 1.15 A TX (per KX3)
> VSWR 1.3 (per KX3)
> FWD 67 (on power meter display, very close to expected)
> REV 30 (on power meter display)
> --> return loss approx 37 dB
>
> 28 MHz @ 1 W setting
> 13.7 V RX
> 13.4 V TX
> 1.15 A TX
> 1.3 VSWR
> FWD 67
> REV 30
> --> return loss approx 37 dB
>
> 50 MHz @ 1 W setting
> 13.7 V RX
> 12.9 V TX
> 2.9 A TX
> 1.6 VSWR
> FWD 71
> REV 35
> --> return loss approx 36 dB
>
> Hmm. So, I'm seeing 3% or less efficiency. Only one respondent on my
> query about TX current draw, and he was getting 15%+ efficiency. No
> wonder my PA temp shoots up.
>
> Thanks,
>
> Drew
> n7da
>
> On Sat, May 9, 2020 at 11:25 AM Drew Arnett <[hidden email]> wrote:
> >
> > Good point, Victor. And why I included that SWR reading. Other bands
> > read fine. I have high confidence in the load and adapter (tried
> > swapping both just in case). I could measure the load and adapter the
> > next time I'm in the lab at work if I want to be absolutely thorough,
> > but it is a microwave load and just adapting from BNC to N (no coax).
> >
> > SWR looks fine on other bands.
> >
> > Thanks,
> >
> > Drew
> > n7da
> >
> > On Sat, May 9, 2020 at 4:57 AM Victor Rosenthal <[hidden email]> wrote:
> > >
> > > I think 1.6:1 is high for that kind of dummy load, if it's in good shape. Should be close to 1:1.
> > > Anyway, you can't really say there is a problem unless you have a better match. Current draw is sensitive to mismatch.
> > > --
> > > Vic
> > >
> > > On May 9, 2020 2:32:15 AM GMT+03:00, Drew Arnett <[hidden email]> wrote:
> > >>
> > >> Walter,
> > >>
> > >> 50 MHz TX constant 4 W carrier measures 13.53 V on DMM (outside the DC
> > >> power plug), 13.3 V on KX3 meter, 2.9 A on KX3 meter and 1.6 to 1 VSWR
> > >> on KX3 meter. Microwave dummy load with BNC to N adapter.
> > >>
> > >> I didn't measure all of this when the rig was new, so have no baseline
> > >> to know what is normal. :-(
> > >>
> > >> Thanks,
> > >>
> > >> Drew
> > >> n7da
> > >>
> > >> On Fri, May 8, 2020 at 11:19 PM Drew Arnett <[hidden email]> wrote:
> > >>>
> > >>>
> > >>> What do you see for current draw on the KX-3? Manual says 1 to 2 A typical.
> > >>>
> > >>> I'm seeing 3 A at less than full power on one band. Yikes! Makes me
> > >>> wonder if the repair shop is open? Elecraft website says hunkered
> > >>> down and mostly work from home.
> > >>>
> > >>> Thanks and best regards,
> > >>>
> > >>> Drew
> > >>> n7da
> > >>
> > >> ________________________________
> > >> 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
> > >> Message delivered to [hidden email]