Don, et al:
I do agree that we typically do not need a precision load nor do we
likely need a "full legal limit CCS" load. Most loads have a power vs.
time de-rating curve. Just following that practice will save on lots of
$$ and space.
Yes the Cantenna loads are generally suitable. I find the Z to be 50
ohms +/- 10% or so. They will handle legal limit power for 2 or3
minutes and 100 to 300 watt power for almost CCS times. As a rule, they
are good for HF and become a bit less so suitable for VHF.
I prefer dry loads as they are less "messy" where one uses an oil filled
load it seems they all want to weep a bit. Oh my gosh should on kick
one over and the lid separate. As a suggestion, solder the lid in place
at 3 or 4 locations around the edge.
It would do well for folks to consider switching and tuning methods so
as not to put a signal on the air. Although this typically can't be
done with automatic type tuners, with manual tuners, using an antenna
bridge will allow one to adjust the tuner for a proper match and not put
a signal on the air. Then with older amps, tuning those into a dummy
load again will not put a signal on the air. When the amp is switched to
the tuner then all is well and no QRM has been generated.
73 Bob, K4TAX
K3S s/n 10,163
On 9/17/2015 8:37 PM, Don Wilhelm wrote:
While a dummy load that has a power rating greater than your maximum
transmit power is a worthwhile addition to any hamshack - at higher
power levels, I do not see them being used as precision measurement
devices, but only as a temporary load for the purposes of "tuning up"
or operating into a dummy load for test purposes.
While the "Tune Up" situation has been largely eliminated for "No
Tune" amplifiers, there is still the question of how to do a TUNE into
an antenna when you have a tuner such as the KAT500 in line - but that
tunes into the antenna at reduced power with the Elecraft K-line, and
the tune cycle is relatively short.
The net that I see of all that is one does not need a precision dummy
load for high power levels.
At the 100 watt level, I do find a need for precision dummy loads
which can be used for lab measurement devices, bu at higher power
levels in the normal hamshack, I do not understand a need for a
precise 50 ohm non-inductive load (as long as you do not stray too far
from that 50 ohm point.
In other words, the gallon size "cantenna" dummy loads should suffice
for most purposes in the ham shack that I can conceive of - primarily
providing a suitable load for a high power transmitter for routine
test purposes.
Those who do precision measurements at high power levels will have to
invest in precision dummy loads, but for typical ham use, I don't
think that level of precision is necessary. Such precision comes at a
cost.
73,
Don W3FPR
On 9/17/2015 8:19 PM, Byron Peebles wrote:
I'd love to find Elecraft offering a 500W dummy load to match the
K-Line.
No one even makes a sturdy paint can anymore.
73, Byron
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