KX3: slow build to full power on 15 meters only

[R Edward]

I have an odd issue that is only happening on 15 meters, and I notice it most in digital modes because they are 100% duty cycle. My first transmissions on the band are at reduced power from my power setting (usually 5 W), but the indicated output slowly builds over 2 or 3 transmission cycles to reach my selected power. The antenna is tuned beforehand with a 1:1 SWR, and my mic gain/ALC settings are all normal.

All other bands behave normally - the meter always immediately indicates full selected power.

Any idea why might be happening only on 15 meters?

Thanks and 73,

Bob KH6BE




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[Don Wilhelm]

Bob,

It sounds like your KX3 is "power hunting".  The KX3 (and other Elecraft
transceivers) control power differently than any other amateur
transceiver, so you must ignore the common internet (and many data mode
instructions) in how to set up the KX3 for data modes.

Do you have sufficient audio into the KX3 on 15 meters?  You should
drive the audio enough to produce 4 bars with the 5th bar flickering on
the ALC meter.  Since the RF Gain can vary from band to band, you really
should check the level on each band.

Check out the document on my website www.w3fpr.com.  Scroll down to the
bottom of the left column for the link to the page.
Ignore the internet advice and set your KX3 properly for audio, and then
control the power with the power knob.

73,
Don W3FPR

Refer to the document on my wesite

On 9/30/2017 7:48 PM, R Edward wrote:
> I have an odd issue that is only happening on 15 meters, and I notice it most in digital modes because they are 100% duty cycle. My first transmissions on the band are at reduced power from my power setting (usually 5 W), but the indicated output slowly builds over 2 or 3 transmission cycles to reach my selected power. The antenna is tuned beforehand with a 1:1 SWR, and my mic gain/ALC settings are all normal.
>
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[Christopher Hoover]

Don's procedure in his doc works great.   But there is a gotcha that I
don't recall being covered.

The ALC meter algorithim "beats" with certain tuning tones and when that
happens, it makes the ALC meter ramp up and down in a fast oscillation.

This has been discussed on this list relatively recently.  I ran into it
last weekend.

The workaround is easy -- move the Tx frequency (shift click in the
waterfall) elsewhere until the ALC reading becomes stable, i.e. only the
last bar is flickering.  Then follow Don's advice.

73 de AI6KG



On Sat, Sep 30, 2017 at 5:30 PM, Don Wilhelm <[hidden email]> wrote:

> Bob,
>
> It sounds like your KX3 is "power hunting".  The KX3 (and other Elecraft
> transceivers) control power differently than any other amateur transceiver,
> so you must ignore the common internet (and many data mode instructions) in
> how to set up the KX3 for data modes.
>
> Do you have sufficient audio into the KX3 on 15 meters?  You should drive
> the audio enough to produce 4 bars with the 5th bar flickering on the ALC
> meter.  Since the RF Gain can vary from band to band, you really should
> check the level on each band.
>
> Check out the document on my website www.w3fpr.com.  Scroll down to the
> bottom of the left column for the link to the page.
> Ignore the internet advice and set your KX3 properly for audio, and then
> control the power with the power knob.
>
> 73,
> Don W3FPR
>
> Refer to the document on my wesite
>
> On 9/30/2017 7:48 PM, R Edward wrote:
>
>> I have an odd issue that is only happening on 15 meters, and I notice it
>> most in digital modes because they are 100% duty cycle. My first
>> transmissions on the band are at reduced power from my power setting
>> (usually 5 W), but the indicated output slowly builds over 2 or 3
>> transmission cycles to reach my selected power. The antenna is tuned
>> beforehand with a 1:1 SWR, and my mic gain/ALC settings are all normal.
>>
>> ______________________________________________________________
> 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]
>

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[R Edward]

Thanks for the replies and suggestions. I have confirmed that my audio levels are fine. This happens both on an antenna and a dummy load on 15 meters. The radio does always wind up transmitting at desired power and with good modulation within less than a minute.

It is apparently just an odd quirk - I was just curious if anyone else had experienced this behavior, and wanted to tell the community about it.

73,
Bob KH6BE


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