[TowerTalk] Traps and Losses

[Guy Olinger, K2AV]

Good morning, Tom.

Yes, the 200 watt light bulb would get you to a third degree burn if
held long enough. Of course. Good visceral punch in that line Tom. So
why don't we have dozens of hams with permanent burn scars to attest to
the temperature of traps? Easy to explain.

The range test would be satisfied with 4 db of miscellaneous loss or so.

The tribanders I saw had six traps, not one, therefore the loss is now
smaller per trap. On a hundred watt applied signal, ~60 watts of loss is
now ~10 watts per trap.  Further, the heat dissipation will now apply
itself to a combination of surfaces/heat conductors. Depending on the
exact construction of the trap, both the outside shell, and the element
into and out of the trap will dissipate heat. 10 watts outdoors over
that much surface would not even be discernible.

If one got it to operating height, and ran a 1.5 kW signal to it, one
should be able to discern the heat level, if one could get to the trap
to measure it. That's a physical problem in itself. You would have to
run it at some height to make sure it wasn't detuned by proximity to
ground, and then lower it.

Could you lower it quickly enough to measure heat before it radiated
away.

Is there any way to measure heat in situ that would not queer the RF
characteristics of the trap, or not be directly heated by the RF itself?
Some infrared device with a focusing lens? That's a real question,
anyone have an idea here?

Truth be known, for the moment, barring some progress on measuring trap
heat, your assertion regarding the traps is just as precarious on some
points as the published tribander range testing you downplay so
severely, hidden behind a difficult-to-measure-without-extreme-effort
phenomenon. Why should we listen to your objection here if you don't cut
Ward and Steve any slack?

On the Pro 67 for which I have personal knowledge, the *really* rotten
band was forty meters, which was traversing SIX traps per active
element. I think there is a case for ten meters being the least affected
 by the malaise.

Personally, I would have LOVED for the Pro 67 style design to have been
right in there with the rest, validated by the study. At one point I was
going to buy one. The study, however, validates the anecdotal evidence,
and the advice by an owner and others to buy something else, as he
disposed of his.

There's just too much anecdotal smoke, Tom. What's the point of placing
in construction items with acknowledged loss (however one may argue the
magnitude) when alternative design is available that doesn't require
them?

Or at the least, why not avoid them in current-heavy elements like
Cushcraft did in the X7, X9 design. Why did THEY drop the number of
traps. What do THEY know. More smoke.

Really think there's fire.

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

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

----- Original Message -----
From: Tom Rauch <w8ji@contesting.com>
To: <towertalk@contesting.com>; Jim Reid <kh7m@hsa-kauai.net>
Sent: Monday, July 17, 2000 7:51 AM
Subject: Re: [TowerTalk] Traps and Losses


> How silly can we get!
>
> That means loss in a trap is about 20% of applied power for a
> single trap. That means if you had a 40/20 meter vertical handling
> 1000 watts, the trap would be dissipating 200 watts.
>


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