K3 and JT65

[VE3WDM]

I am considering using my base model k3 (without KPA100) for digi modes and was not sure what the duty cycle was for the rig? One of the modes I was looking at was JT65 and it as I understand has long keydown times. Do I have to keep the rig at 5 watts for all digi modes  and more so with the long key down time of JT65 what power recommendations are there for that?MikeVE3WDM    
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[Kjeld Holm]

Hi Mike,

JT65 is one minute transmitting (or more exactly 50 seconds) and 1 minute
receiving.

For other digital modes your transmission length is of course depending on
how much you want to "say" per transmission.

See Owner's Manual on page 9. I am reading this as if it should be possible
to transmit for up to 10 minutes with full power. But I am not 100% sure.
Listen to the fan or check the PA temperature.

Vy 73 de
OZ1CCM Kjeld

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Mike Weir
Sent: 16. marts 2014 02:33
To: [hidden email]
Subject: [Elecraft] K3 and JT65

I am considering using my base model k3 (without KPA100) for digi modes and
was not sure what the duty cycle was for the rig? One of the modes I was
looking at was JT65 and it as I understand has long keydown times. Do I have
to keep the rig at 5 watts for all digi modes  and more so with the long key
down time of JT65 what power recommendations are there for that?MikeVE3WDM

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[Bill Frantz]

I have run a lot of PSK on a K3/10. I have never had a problem
running full power -- all 10-12 watts of it. Sometimes I type a
lot too. I get good IMD reports. Don't worry. Be happy.

Cheers - Bill, AE6JV

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[Jim Brown-10]

On 3/16/2014 10:00 AM, Bill Frantz wrote:
> I have run a lot of PSK on a K3/10. I have never had a problem running
> full power -- all 10-12 watts of it. Sometimes I type a lot too.

The K3, KX3, and the power amps are quite well protected, and designed
to run full power in keydown modes.

> I get good IMD reports. Don't worry. Be happy.

In a tutorial on clean signals to the NCCC last fall, K6XX noted that
the distortion in solid state amps rises with output power, and that all
Elecraft amps are significantly cleaner at half power.

Distortion also rises as power supply voltage drops. So a K3 running on
13.8 - 14.5 VDC will be cleaner than on 11 VDC.

73, Jim K9YC

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[Bruce Chadbourne]

Hi Mike, great question and I look forward to other answers. The one about
page 9 of the operating manual was a good reminder for me. My answer is
more from experience - for digital modes in general, I've stayed under 50
watts and had good results (and hearing the K3 cooling fans stepping up an
extra notch always reminds me to behave myself).
A few of our brothers use too much power and splatter their signal across
the spectrum. Good operating practice calls for using minimum power
necessary anyway, and it's always fun to see a QSO where someone reports
using 20 watts (i.e. for PSK). The whole point of digital is the ability to
transmit long distance with low power and 100% readability.  On occasion a
QRP station works me and I take the hint - dial power down to 5 watts and
we're doing just fine.
My best story - working JT65, from New Hampshire with a New Zealand station
 - we were doing fine, kept dialing back the power, until we finally lost
each other at 100 milliwatts. Almost perfect copy at 500 milliwatts, and by
the way I had a poor vertical antenna.  It reminded me as a kid having a
toy CB walkie-talkie that operated at 100 mW... never worked NZ with that
thing.

BTW - it would be great to have more of us out there experimenting with the
digital modes; I am still fascinated with all of the digital options (I'm
using fldigi software).  The K3 operates great with fldigi. I also find the
K3UK webpage a great meeting place (there is a dedicated subpage for
digital modes).

--
Bruce / KE1CY
Hernando, FL
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[Bruce Chadbourne]

PS - Mike, my apologies, I missed the part of your note that said you were
operating without the KPA100. I hope my answer was still useful. I have no
problems operating digital modes at a "full" 10w.

--
Bruce / KE1CY
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