[Elecraft] K3 #281 Perceived Output Issue

Wed Feb 24 08:25:18 EST 2016

Ian,

Either the LPA or the KPA is compressing above 5/50W.

Set the K3 to 5.5 watts and check power output on each band.  Then set
the K3 to 10 watts and check power output on each band.  Then repeat
the process at 55 and 100 watts.

That should tell you if the LPA or KPA is compressing and will allow
Elecraft Support (when you e-mail or call them) to focus on the source
of your problem.  If you have 5.5 and 10 watts (or close) at the low
power test the LPA is OK and the KPA is going into compression for
some reason (check power supply and the +13V pins on the headers).
If you do not have 5.5/10W on the LPA test, your LPA is going into
compression and it may need to be swapped or connections checked.

73,

   ... Joe, W4TV

On 2/24/2016 7:40 AM, Ian - Ham wrote:
> Jerry,
>
> Thanks for the response. I'm curious, however, why removing the 100W PA and
> running calibration tests at 10W would matter, if I'm already seeing
> expected results at the 10W power level. That is, I set the output power on
> my K3 to 10W, and transmit using a full duty cycle mode. On the external
> power meter, I see 10W, on all bands. This would seem to me to indicate that
> there isn't an issue with the low power amplifier.
>
> Thank you.
>
> --Ian
> Ian Kahn, KM4IK
> Roswell, GA  EM74ua
> km4ik.ian at gmail.com
> 10-10 #74624, North Georgia Chapter #2038
> PODXS 070 #1962
> K3# 281, P3 #688, KAT500 #860, KPA500 #1468
>
> -----Original Message-----
> From: Jerry [mailto:ajermo at carolinaheli.com]
> Sent: Tuesday, February 23, 2016 10:53 PM
> To: Ian Kahn <km4ik.ian at gmail.com>
> Cc: w3fpr at embarqmail.com; elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K3 #281 Perceived Output Issue
>
> Remove hundred watt PA. Install a 10 W jumper. Run through the 10 W
> calibration. Measure record and share the results.
>
> It is logical to expect that this is where the issue is starting.
>
> Sent from my iPad
>
>> On Feb 23, 2016, at 10:25 PM, Ian Kahn <km4ik.ian at gmail.com> wrote:
>>
>> Several people offered some very good suggestions and asked several
>> valid questions about my testing. Here are answers to many of those
> questions:
>>
>> 1. The meter I'm using in the test is a known-good MFJ-815B HF
>> power/SWR meter.
>> 2. I'm using a known-good 300W dummy load for my "antenna", so any
>> reflected power is minimal, as is SWR.
>> 3. I do have the internal ATU installed, but it is in BYPASS, as I
>> have a resonant antenna on 20m-10m and use the KAT500 for 40m/80m, or
>> when I run power.
>> 4. Test results at lower power levels:
>>
>> 10m 10w out - 10w on meter; 25w out - 19-20w on meter; 50w out - ~30w
>> on meter 12m 10w out - 10w on meter; 25w out - 20w on meter; 50w out -
>> 30w on meter 15m 10w out - 10w on meter; 25w out - 20w on meter; 50w
>> out - 35w on meter 17m 10w out - 10w on meter; 25w out - 20w on meter;
>> 50w out - 35w on meter 20m 10w out - 10w on meter; 25w out - 20w on
>> meter; 50w out - 40w on meter 40m 10w out - 10w on meter; 25w out -
>> 20w on meter; 50w out - 40w on meter 80m 10w out - 10w on meter; 25w
>> out - 20w on meter; 50w out - 40w on meter
>>
>> I also ran the TX Gain Calibration from the K3 utility one more time,
>> with a different cable. Here are the results of that calibration (note
>> - I didn't run the milliwatt calibration because I don't use a
>> transverter with the IF Out. It just goes to my P3):
>>
>> K3 Tx Gain Calibration data written on 2016-02-23 at 22:18:30
>> K3 Serial Number 00281
>> K3 MCU revision 05.38. RS-232 speed 38400 bit/s.
>> Elecraft K3 Utility Revision 1.15.8.18
>> 1900 kHz TxGain LP  52
>> 3750 kHz TxGain LP  30
>> 5336 kHz TxGain LP  56
>> 7150 kHz TxGain LP  46
>> 10125 kHz TxGain LP  52
>> 14200 kHz TxGain LP  23
>> 18110 kHz TxGain LP  24
>> 21200 kHz TxGain LP  19
>> 24930 kHz TxGain LP  25
>> 29000 kHz TxGain LP  30
>> 52000 kHz TxGain LP  24
>> 1900 kHz TxGain HP  46
>> 3750 kHz TxGain HP  48
>> 5336 kHz TxGain HP  87
>> 7150 kHz TxGain HP  62
>> 10125 kHz TxGain HP  58
>> 14200 kHz TxGain HP  28
>> 18110 kHz TxGain HP  21
>> 21200 kHz TxGain HP  18
>> 24930 kHz TxGain HP  18
>> 29000 kHz TxGain HP  27
>> 52000 kHz TxGain HP  13
>>
>> After running the TX Gain Calibration again, I checked the above
>> output numbers, and they stay the same. It seems as if I am losing
>> about 20% of my output power for any setting above 10w, except on 10m,
>> where at 100w I seem to be losing about 50w. It also seems as if maybe
>> there is an issue with the internal 100w PA, based strictly on my
> observations and a wild guess.
>> If there are any other suggestions/recommendations, I'm all ears. If
>> not, the next step is an email to the good folks in Aptos.
>>
>> Thanks and 73,
>>
>> --Ian
>> Ian Kahn, KM4IK
>> Roswell, GA  EM74ua
>> km4ik.ian at gmail.com
>> 10-10 #74624  North Georgia Chapter #2038 PODXS 070 #1962
>> K3 #281, P3 #688 KAT500 #860, KPA500 #1468
>>
>>> On Mon, Feb 22, 2016 at 5:40 PM, Don Wilhelm <w3fpr at embarqmail.com>
> wrote:
>>>
>>> Ian,
>>>
>>> Try TX Gain Calibration again - use a different coax jumper between
>>> the K3 and dummy load - that could possibly be faulty.  If that does
>>> not correct it, contact Elecraft support.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>>
>>> On 2/22/2016 5:29 PM, Ian Kahn wrote:
>>>
>>> Don,
>>>
>>> I upgraded the MCU and ran the TX Gain Calibration at that time,
>>> successfully. I also ran it again Friday night, while testing, to
>>> make sure that wasn't the issue. It ran successfully both times.
>>>
>>> Thanks.
>>>
>>> Ian, KM4IK
>>>> On Feb 22, 2016 5:24 PM, "Don Wilhelm" <w3fpr at embarqmail.com> wrote:
>>>>
>>>> Ian,
>>>>
>>>> Did you upgrade after MCU version from 5.13 or below to 5.14 or greater?
>>>> That requires you to do the TX Gain Calibration (see 5.14 Release
>>>> Notes).  K3 Utility makes the task easy - just connect a dummy load
>>>> that is good for 1.8 to 54 MHz and capable of 50 watts or greater
>>>> and the process is automatic - follow the prompts in K3 Utility, it
>>>> will take only about 2 minutes to complete after the dummy load is in
> place.
>>>>
>>>> If K3 Utility fails the TX Gain, there is one more chance - do each
>>>> band manually (see the Calibration part of the manual).
>>>>
>>>> If that does not correct it, contact support.
>>>>
>>>> 73,
>>>> Don W3FPR
>>>>
>>>>
>>>>> On 2/22/2016 11:21 AM, Ian Kahn wrote:
>>>>>
>>>>> Reposting, since this didn't seem to get out when I originally sent
>>>>> it last Friday evening. If you get this a second time, please
>>>>> forgive the noise.
>>>>>
>>>>> Thanks and 73,
>>>>>
>>>>> --Ian
>>>>> Ian Kahn, KM4IK
>>>>> Roswell, GA  EM74ua
>>>>> km4ik.ian at gmail.com
>>>>> 10-10 #74624  North Georgia Chapter #2038 PODXS 070 #1962
>>>>> K3 #281, P3 #688 KAT500 #860, KPA500 #1468
>>>>>
>>>>> ---------- Forwarded message ----------
>>>>> From: Ian Kahn <km4ik.ian at gmail.com>
>>>>> Date: Fri, Feb 19, 2016 at 10:37 PM
>>>>> Subject: [Elecraft][K3] K3 #281 Perceived Output Issue
>>>>> To: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
>>>>>
>>>>>
>>>>> All,
>>>>>
>>>>> I have what I think is an output issue with my K3 s/n 281. When set
>>>>> at 100W output, I am getting the following approximate output
>>>>> values:
>>>>>
>>>>> 10m     ~55w
>>>>> 12m     ~40w
>>>>> 15m     ~50w
>>>>> 17m     ~60w
>>>>> 20m     ~60w
>>>>> 40m     ~70w
>>>>> 80m     ~70w
>>>>> 160m    ~70w
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>> jermo at carolinaheli.com
>
>
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