Hi Pete,
> >Somewhere almost 5 dB (69%) of the applied power is missing.
>
> Does this necessarily follow? Trap losses surely aren't the only
> mechanism at work here. I suspect I could all too easily build a monoband
> yagi that would work just as well (or badly) as a TA-33. Why couldn't
> element spacing compromises, real-world traps, etc., all lead to a net
> deterioration in both pattern and F/B?
If an antenna had no noticeable F/B, and the same F/S as a dipole,
then we can reasonably expect the system to have very little gain.
I certainly know that isn't the case with a properly functioning TA-
33.
You be amazed at how hot an inductor gets (especially in a closed
cylinder) with even 30-40 watts of heat!
The matching network of my 160 meter 2 element phased array
had a 10 turn coil of number 8 copper two inches in diameter. The
coil (in open air) would get so hot at 1500 watts, it would discolor
the plating. Dissipation in that coil was only 38 watts, or 0.1 dB.
We know how hot a 60 watt light bulb with its large surface area
gets.
What I'd like to know is how antennas that have "lossy traps" get
away with using plastic forms with no air circulation if the traps are
dissipating over 100 watts each.
A Bird meter has .4 dB of power delta when used at full scale with
a perfect load. It might read .2 dB low, or .2 dB high. Take that
same Bird and measure at 1/4 scale and the error is about + or
minus one dB, or nearly 2 dB delta! That does not include reflected
power errors.
Efficiency is probably the single most difficult thing to measure
accurately, because every step in the process has errors. As far as
I know, the most accurate measurement method is measuring heat.
With that in mind, where is the heat in the system that is losing
over 50% of the applied power in a few square inches of metal?
Remember, we have F/B and F/S. So where does the power go?
73, Tom W8JI
w8ji@contesting.com
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