Paul,
There are two kinds of loss: dissipative and non-dissipative. A 1 dB
dissipative loss at 1500W is 308W which would clearly blow up the QSK-5
in a second or two. However crummy wiring in an enclosure which raises
the VSWR to 2.66:1 will cause a mismatched loss (into a 50 ohm load) of
1.00dB and dissipate virtually no heat. Likewise a shunt capacitance at
28MHz of 115pF will raise a 50 ohm VSWR to 2.66:1 and again will produce
a mismatched loss of 1.0dB. Also 8" of wiring in a box that looks like
a 300 ohm transmission line will also raise the VSWR and produce a
mismatched loss of 1.0dB on 28MHz.
I suspect you have some of all the above taking place. Mismatched loss
can be mitigated retuning the PI-L output where dissipative loss can not
be eliminated.
73,
Larry, W0QE
Paul Christensen wrote:
>> My rough math indicates that 1500 watts out and 1 dB loss dissipates what,
>> 300 watts in the QSK box?? Can't be? My QSK-1500 runs cold. Also, I don't
>> see any significant loss on the power meter, but I haven't measured
>> closely.
>>
>
> More investigation is needed as I came to the same calculated power
> dissipation for 1.5 dB of loss at 10m. I've validated my measurements on
> three separate devices into a Bird Terma-Line load but the QSK-5 does not
> appear to run unusually hot at 1KW from an SPE Expert amp. I'll report back
> when I find the root cause. Seems like this might be a good use for an
> industrial IR-detecting temperature scanner.
>
> Paul, W9AC
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|