On 12/27/2011 3:35 PM, Eddy Swynar wrote:
> On 2011-12-27, at 11:55 AM, N6FD wrote:
>
>> Trees are absorbtive, metal is reflective. At least with the metal,
>> your signal goes somewhere.
> Hi Eric,
>
> Now THAT'S what I find to be so contradictory& confusing in all this...
They are different situations.
>
> How can metal possibly be reflective, vis-a-vis a tree, in a similar
> situation...?
Metal can absorb and reradiate as in directors and reflectors
> The metal is grounded,
Grounding may or may not make a huge difference depending on the length
of the metal. I once worked a station in mid pacific using the copper
pipes in our heating system
> and conducts FAR better than wood---if your signal is "absorbed" by the
> tree and consequently dissipated by its ohmic losses, would not, in turn,
> your signal be routed directly to ground by a metal post,
It might although the metal post is likely to detune the antenna, or
just distort the radiated field.
> rather than being "reflected" as you suggest, by virtue of the fact that
> the resistance of metal is miniscule, compared to wood...?
The tree, even in spring when the sap is likely the most conductive is a
poor radiator. Think of taking the elements of a yagi, cutting them
into short pieces and inserting resistors while still maintaining
resonance.
>
> And taking this a step further, why is it NEVER desirable to have an indoor
> receiving antenna,
Never say never...although indoor receiving antennas are a "sometimes
thing" They may or may not be shielded by wiring and duct work, or they
may pick up noise from the electrical wiring, or the wiring may actually
be placed in such a way and be of a proper length to aid in signal pick
up on some frequencies.
> housed in a building with a steel structure...?
"Steel structure" = shielding. That would be like erecting an antenna in
a Faraday Cage. I have one station out in my shop which has an interior
of bonded barn metal. HTs and cell phones do not do well in there. I
doubt you would hear much on HF without connecting to the outside antennas.
> Using the logic of "...wood BAD, steel GOOD," we should be able to receive
> nothing on our portable sets when we're in the woods, right...?
Depending on the bands the signals are attenuated out in the woods. How
much depends on a great many variables, but in general 160 and 75 are
attenuated less than 15 or 10. That's not saying they won't work, only
they will have less signal to work with, *but* how much less is unknown.
> The signal would be absorbed by all those lossy trees around us
To some unknown extent.
> ---but by comparison, reception should be great when we're inside a building
> made of steel beams...the signal(s) we're copying would just "reflect" from
> beam to beam until it reached our antenna.
This does happens on 440 "to some extent". Sometimes it works very
well. Not worth a darn on HF.
>
> I'm not trying to poke fun what you're saying, Eric, but rather, attempting
> to understand how---to ME, at any rate!---the laws of radio (if you will)
> apply in one instance, but not in another...
They don't. It's more a case of how you are looking at them.
>
> Does any of this make sense to anyone else, besides just me...?!
Yes <:-)) I've been there many times.
73, good luck, and I hope what I said/wrote made sense.
> ~73~ de Eddy VE3CUI - VE3XZ
>
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