Thank you Jack... I had not seen that. That answers the question.
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources
On 5/4/20 9:11 AM, Jack Brindle wrote:
From the KPA500 manual, Rev E1, page 41 Specifications:
Duty Cycle at 500 Watts10 minutes key down / 5 minutes standby
Sometimes it is very worth while to read the manual. It gives me
something to do when being stuck at home for so long gets me down.
73!
Jack, W6FB
On May 4, 2020, at 6:39 AM, Dave Cole <[email protected]
<mailto:[email protected]>> wrote:
Hi Rick,
This brings up a point I have been unsure about for years... Duty
Cycle... What constitutes 100%? Over how long a time frame?
If I run JT65, (one minute on one minute off), and I use a timeframe
of say 5 minutes, I buy it is 50% duty cycle.
But if I use a timeframe of one minute it is 100% Duty Cycle...
So when stating duty cycle it is important to spec the timeframe, as
you did... Is there an actual timeframe stated someplace as a standard?
I do like the way you stated it by the way... With time to 'catch the
breath'...
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources
On 5/3/20 8:53 PM, Rick Bates, NK7I wrote:
I didn't add the obvious, FT8 in that manner is a 50% duty cycle but
with enough time to 'catch the breath'.
I remember back when it first came out, Wayne suggested to 'run it
with all the LEDs lit' or something along that line but... it's
capable of MUCH more than 500 watts and wisely better limited by
firmware upgrades (in the early days I watched it put out almost 700,
at which point I was far more cautious). It's nice to know there is
a certain amount of 'overhead'.
Rick NK7I
On 5/3/2020 8:23 PM, Dave Cole wrote:
Hi Rick,
That is how mine behaves as well, almost exactly like that...
However, I will be running SSTV, and that is hard on the amp... I
need to do a bit more testing prior to that.
As someone else said upthread, half power is really tough on the amp...
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources
On 5/3/20 7:52 PM, Rick Bates, NK7I wrote:
I spent 15 minutes active on 20M FT8 this afternoon (some lurking).
At 530 watts output (on the display and utility) into a 1.13:1
antenna load (SteppIR) for a ten minute calling period (Mongolia
then Oman), the temp rose to 66C; a few moments of elevated fan
quickly brought that down to the low 60's between transmissions.
Ambient room temp 77F. (Both calls succeeded.)
Rick NK7I
North Idaho
On 5/3/2020 7:42 PM, Andy Durbin wrote:
"It is interesting to hear how others experience their KPA500s
over various conditions."
I have over a years's worth of KPA500 data recorded but it takes
some effort to run it through the Excel templates to make pretty
plots.
My KPA500 temperatures are strongly influenced by ambient
temperature. Shack temperature is often over 30 deg C in the
summer months and it's not at all unusual for my fan to run at
level 3 in FT8 QSO. I think I have only reached fan speed 5 twice
and that was while running temperature tests not while
operating. I terminated those tests at fan speed 5 and didn't
wish to push it any higher.
So many people seem to think reducing the output power will keep
the temperature down. It does not. Half power is about the
worst heat dissipation condition for the KPA500.
73,
Andy, k3wyc
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