[TowerTalk] Traps and Losses

[Guy Olinger, K2AV]

Quite some number of intriguing suggestions on a way to measure heat in
a trap in situ. Much interesting material, quite some bit of it
off-reflector. Many thanks for all the replies. This is an attempt at an
all-in-one reply.

Regarding crayons and paints, to display heat by color change, I wonder
if their compounds are dielectrically sensitive, being heated in some
degree *directly* by the RF in the application we propose, which would
falsely add to the heat indication. Does the manufacturer of these
substances reference this issue?

Regarding these various (infrared?) devices in use by power companies,
anyone know where these can be bought/rented, or is leaning on my power
company acquaintances the only avenue?

Regarding whether or not Mosley traps might prove to be *destroyable*,
e.g. meltdown, by heat at ordinary amateur power levels, I offer this
rather obvious material from Mosley's own web site. See:

     http://www.mosley-electronics.com/amateur.htm

Click on H.F. Multi-Band Beams, then click on "PRO" Series.

For the entire Pro series, they give the following power ratings:

 RTTY  600 watts
 CW      2.5 kW
 SSB      5 kW

It would seem that the maximum power level related to safe margin for
voltage arc-over is at least 5 kW.  Good, stiff , in-your-face voltage
arc-over rating.  CW is derated. Why? The answer is in the RTTY (read
keydown, constant, no breaks for cooling off) rating of 600 watts.
That's 9 dB less than the maximum peak power. It can't possibly be
related to arcing as some have surmised. It will not be related to
pattern degradation, that's just power radiated in less useful
directions. Radiated power doesn't destroy antennas.  All that's left is
heat. The implication is that 1.5 kW is beyond the manufacturer's rated
tolerance for HEAT.

Heat where? In the aluminum elements? Mosley has *trapless* single band
antennas with no reduction for modes. Click H.F. Mono-Beams and then
click Power Master. All aluminum elements, and NO reduction for RTTY.

Arguably because Power Master has NO TRAPS.

If you can't run the trapped antennas safely more than 600 watts (Ah,
the LXC prime directive...) constant power RTTY, and CW is derated 4+ db
from SSB, there is SERIOUS heat loss somewhere. And that concept
certainly would set comfortably beside the gain figures in the tribander
report. Is there a candidate for destructive heat loss on those beams
OTHER than the traps?

Anyone somewhere in driving distance of Raleigh want to risk a trap on
their Mosley trap tribander to a key-down 1.5 kW smoke test while we
take calibrated infrared pictures of the beam on a cool night? We'll
provide the 1.5 kW RTTY-rated amp. Maybe we'll even get the gang to chip
in to replace the antenna in case we smoke it.

- - . . .   . . . - -     .   . . .     - - .   . - . .

73, Guy
k2av@contesting.com
Apex, NC, USA



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