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K2 KPA100 tests

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VE3WDM

K2 KPA100 tests

I have just finished the KPA100 build and all went well with the checkouts and alignments. Now that it is all together I just checked the radio on a dummy load. Here is what I am getting while in CW (Do not have SSB on this rig) Once the Key is released there is a chirping sound coming from the speaker of the K2. I have used my headphones and same chirp is there. I have listened to the code being sent from the K2 with my K3 and there is no chirp coming over the air. It seems to be more noticeable on 80 40 and 30 meters and there is a slight trace of it on 20,15 and so on. I did the test at low power (5 watts) and high power (100 watts) with the same results.
The other issue I noticed was on 15 meters if the k2 was turned up to over 100 watts on the readout the message HI Cur came up but as long as I kept the power to 100 watts or less all was well.
Thanks
Mike
VE3WDM
http://ve3wdm.blogspot.com

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Don Wilhelm-4

Re: K2 KPA100 tests

Mike,

On your "chirping sound", check the K2 menu to be certain you have the
menu 8R parameter set to HOLD. If set to NOR, it could be that you are
hearing the K2 receiver unmute too soon. It does no harm to the
transmitted signal, but it does get irritating.

What menu setting do you have for CAL CUR? It should be set to 3.50
with the KPA100.
Another question is "How much can you trust the wattmeter you used to
calibrate the KPA100 forward power?"
If the K2 was developing an actual 110 watts while your external
wattmeter said 100 watts, that alone can be reason for your problem - a
10% of full scale reading error is not uncommon for wattmeters (even the
much respected Bird only guarantees 5% of full scale immediately after
calibration)

The Hi Cur message refers to the current drawn by the base K2 and not to
the KPA100.
Check your power supply voltage during transmit. If the voltage drops
substantially, more current will be drawn. If you have significant
voltage drop during transmit, check the power cable and all its
connectors and make certain that the connections at the power supply are
really tight - it only takes a few milliohms to create a significant
voltage drop.
To be certain the voltage drop is in the cable and not the power supply,
monitor the voltage at the output of the power supply during both
receive and transmit - if the power supply output voltage drops by a
significant amount, the power supply itself may be to blame.

Lastly, increase the power supply voltage to at least 13.8 volts, but
preferrably to 14.5 or so. The K2 is rated at up to 15 volts, and the
transmit IMD will be improved by the higher voltage.

If none of those conditions solve the problem, please ask again.

73,
Don W3FPR

On 11/21/2010 11:48 AM, Mike Weir wrote:

> I have just finished the KPA100 build and all went well with the checkouts and alignments. Now that it is all together I just checked the radio on a dummy load. Here is what I am getting while in CW (Do not have SSB on this rig) Once the Key is released there is a chirping sound coming from the speaker of the K2. I have used my headphones and same chirp is there. I have listened to the code being sent from the K2 with my K3 and there is no chirp coming over the air. It seems to be more noticeable on 80 40 and 30 meters and there is a slight trace of it on 20,15 and so on. I did the test at low power (5 watts) and high power (100 watts) with the same results.
> The other issue I noticed was on 15 meters if the k2 was turned up to over 100 watts on the readout the message HI Cur came up but as long as I kept the power to 100 watts or less all was well.
> Thanks
> Mike
> VE3WDM
> http://ve3wdm.blogspot.com
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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VE3WDM

Re: K2 KPA100 tests

Good morning Don, The R8 was set to hold but I changed it to normal and tried the chirp was still there. I then went back to hold and tried again still a chirp. As you said it is not doing the rig any harm so I will just leave it as is. The watt meter that I am using is the LP-100A that I built and I had sent it down to Larry for calibration. Now having said that I meter does go through 2 LDG antenna switches before the rig. So I am on the weekend going to remove them and just have the rig and dummy load between the watt meter and see how it goes from there.
Mike
VE3WDM

Don Wilhelm-4

Re: K2 KPA100 tests

Mike,

How old is this KPA100(does it have red toroid cores or blue ones), and
do you have the KDSP2 installed? These may seem like unrelated
questions, but actually they are not. A looong time ago (with the older
KPA100 T/R switch design) there was a problem with "click on unmute"
when the KDSP2 also was installed. The new T/R switch design corrected it.

OK on your wattmeter - if you used a "Larry" calibrated LP100 to set the
KPA100 wattmeter, I think it is set right. The LP-100 is one of the few
wattmeters I trust.

73,
Don W3FPR

On 11/24/2010 6:17 AM, VE3WDM wrote:

> Good morning Don, The R8 was set to hold but I changed it to normal and tried
> the chirp was still there. I then went back to hold and tried again still a
> chirp. As you said it is not doing the rig any harm so I will just leave it
> as is. The watt meter that I am using is the LP-100A that I built and I had
> sent it down to Larry for calibration. Now having said that I meter does go
> through 2 LDG antenna switches before the rig. So I am on the weekend going
> to remove them and just have the rig and dummy load between the watt meter
> and see how it goes from there.
> Mike
> VE3WDM
>

VE3WDM

Re: K2 KPA100 tests

In reply to this post by Don Wilhelm-4

Good morning again Don,
On my board L16 is blue and the kit was purchased about a year ago maybe less. I'm not at home right now so I can't check the receipt. I also have the KDSP2 unit installed as well. Getting back to the Hi Cur I am going to this weekend setup the K2 so the LP 100A and dummy load are the only pieces of equipment that are connected when I do the power readings. At this time there are some LDG antenna switches and extra coax as well.
Mike
VE3WDM

Don Wilhelm-4

Re: K2 KPA100 tests

Mike,

Remember that the Hi Cur messages are from the base K2. They can be
caused by difficulty in driving the KPA100, or a problem with the KPA100
low pass filter or the wattmeter. Check the wattmeter calibration first.
If the wattmeter is good, then disconnect the power from the KPA100 and
power the base K2 through the coaxial power jack. See if the K2 still
gives a HiCur message at 10 watts - if not, try 12 watts, and then try
15 watts.

If the HiCur messages persist, then remove the KPA100 (physically) and
do the same test with the base K2 only.
If the messages go away in that configuration, look carefully at the
KPA100 low pass filter (an extra turn on the toroids is a common
problem) - but if they persist with only the base K2, you have either a
problem with the Low Pass Filter, or T4, or a problem with the PA
transistors in the base K2.

73,
Don W3FPR

On 11/25/2010 10:28 AM, VE3WDM wrote:
> Good morning again Don,
> On my board L16 is blue and the kit was purchased about a year ago maybe
> less. I'm not at home right now so I can't check the receipt. I also have
> the KDSP2 unit installed as well. Getting back to the Hi Cur I am going to
> this weekend setup the K2 so the LP 100A and dummy load are the only pieces
> of equipment that are connected when I do the power readings. At this time
> there are some LDG antenna switches and extra coax as well.
> Mike
> VE3WDM
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VE3WDM

Re: K2 KPA100 tests

Here is what I did I removed all the coax and coax switches that were in line with the K2 and dummy load. I also used a better dummy load I did have an old one from MFJ replaced it with one I got from Ridge. When all that was done there was no problem on any of the bands with Hi Cur warnings. So thanks very much for your help with this issue Don.
The other thing about the chirp it is still there and I know you asked me about the KPA100 and blue toroids. There are 2 of them in the unit and I checked the date when I purchased the KPA100 from Elecraft and it was 10/16/2009. You had also wanted to know if the KDSP2 was installed and it is. Does any of this help with the chirp noise?
Mike
VE3WDM

Don Wilhelm-4

Re: K2 KPA100 tests

Mike,

The fact that you have no HiCur warnings working onto a known good dummy
load says that the problem is somewhere in your antenna system.

On the "chirp issue", I have no immediate answers. Normally that does
not occur with the new T/R switch design (blue toroids).
If you had the red core toroids, I would have said the you should try
installing KPA100UPKT, but you already have that installed, so I have no
guesses for the cause.

I would suggest a note to [hidden email] to see if anyone else has
an idea about the "chirp".

73,
Don W3FPR

On 11/25/2010 4:11 PM, VE3WDM wrote:

> Here is what I did I removed all the coax and coax switches that were in line
> with the K2 and dummy load. I also used a better dummy load I did have an
> old one from MFJ replaced it with one I got from Ridge. When all that was
> done there was no problem on any of the bands with Hi Cur warnings. So
> thanks very much for your help with this issue Don.
> The other thing about the chirp it is still there and I know you asked me
> about the KPA100 and blue toroids. There are 2 of them in the unit and I
> checked the date when I purchased the KPA100 from Elecraft and it was
> 10/16/2009. You had also wanted to know if the KDSP2 was installed and it
> is. Does any of this help with the chirp noise?
> Mike
> VE3WDM