K2 Contest

[Julius Fazekas n2wn]

Hi Evert,

First, sorry I missed you in the PACC! I played a
little in it, 160 to 20.

As to your questions:

1)       Is there a noticeable difference in heat-sink
temperature when operating on higher bands?

There is a noticable difference if you're running into
a mismatched load. Also, it gets pretty warm if you're
working at a high rate or sending endless CQs.
(Thant's a good time to go Search and Pounce and give
the finals a break).

2)       Can this amplifier be tuned for 1 hour on a
dummy with full output at any band without any
semi-irreversible side effects?

I don't know, never tried it. I've run mine pretty hot
for hours in the 160M tests. Warm to the touch, but
not painful, I try to place it in the drafty part of
the bench ;o)


3)       I'm used to big tube amplifiers which need
air-flow "throughput". The fan in the K2 is blowing
into the box but there is no way out (kind of short
circuit in terms of air flow). What is the reason for
this cooling fan to blow into the box instead of
making "forced" airflow through/along the heatsink. It
looks to me that some extra holes into the cabinet
might
raise the efficiency of cooling dramatically (inside
the box...

This has been discussed on the reflector a  number of
times in the past. I'm not sure that anyone has added
vents to the cabinets yet. Some have placed added fans
on the top of the rig, I haven't yet. It is my
understanding the power transistors are much better
designed and able to deal with some pretty impressive
heat loads when properly sinked. Glass envelope tubes
are more vunerable to heat.
 

The 2 most important reasons for electronics to stop
functioning is over voltage/current and temperature
stress by cooling - heating - cooling - heating etc.
Even if the heating is within the specs, the overall
product life is degenerating quickly by extremely
temperature changes. It also stresses the solder point
on the PCB.

 

In general: Is the K2 designed to operate at full
specs during contests/expeditions under any normal
environmental condition (0 deg C to 40 deg C) without
cooling down periods?

In the couple years I've been on this reflector and
using a K2/100, I've yet to hear of anyone losing the
final transistors for either contests or DXpeditions.
There are a number of us who are serious contesters
and K2's have been used on several major DX
operations.

Some folks have seperated the KPA100, for various
reasons, this would probably improve the heat
situation as well. Several have added fans, I've
thought about it, but haven't yet.

73,
Julius
n2wn
K2/100 #3311
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