[Lowfer] Ultimate LOWFER Transmitter? (LONG)

[Steve Olney]

G'day John,

>
> G'day, Steve.  Sorry to be contrary, but I'd ask you to rethink about half
> of that assessment.  The loss resistance IS real in almost any sense you
> care to define.  Hard to analyze sometimes, certainly, but the
non-radiated
> power being dissipated is not apparent--it's all too real!
>

I think if you looked more closely at my equation for efficiency (leaving
out the 100x boo-boo) you will see that I did not mean the power is not
dissipated.

>
> The ratio of loss between coil and ground system is not that unusual in
the
> LowFER world.  For all but the luckiest experimenters living atop the most
> conductive soils or working from a yacht over seawater (I wish!), the
earth
> losses dominate the equation something awful.
>

OK, so lets leave it at 50%/50%.

>
> This is not comparable to the conditions as Stewart stated them.  If one
> were to do as you say, then certainly only the coil losses would be in
> parallel, not the ground loss.  Furthermore, the two masts would
effectively
> be in parallel (as, therfore, would the coils) so resonance would not be
> achievable without even larger inductors with still more loss each....
>

Why is it not comparable  ?    Are you saying that if we have two masts over
a continuous ground plane and we measured a certain ground loss.    Then we
break the ground plane in two between the two radiators, the measured losses
are divided by two ?    How does this happen ?

BTW, putting two radiators in parallel requires two coils each of only
*slightly* higher inductance (a few %) due to the paralleling.


>
> If you examine the matter just as Stewart stated it, keep foremost in mind
> that the ground losses are REAL and cannot be disregarded in the analysis.
>

I did not say the losses are not real, quite the contrary.   I said you
can't view them as simple real resistances (like the ones you get out of the
component bin) and use the simple battery/resistor analogy.

>
> The antennas are _not_ just a meter or two apart, and do _not_ share the
> same ground system.  They are separated by enough space that the *ground
> systems* are largely independent of each other (meaning, not carrying very
> much of the displacement current of the adjacent antennas; well within the
> bounds of practical reality when antennas are limited to the size of US
> LowFERs).
>
> When such antennas are fed in parallel and do NOT share a common ground
> system, then it is the *multiple ground system losses* that are in
parallel,
> not just the coil losses as in your postulated conditions
>

They are not, but lets try and convince you why.   Going back to Stewart's
stated scenario where he stated that running the two identical systems in
parallel produces the same radiation resistance as the single system (here
we *all* agree).    Let's say we are going to maintain the same far field
strength (therefore same near field).    If we have the same near field
strength, all the objects which contributed to losses (trees, bushes,
ground, outhouse, etc) are going to suck up the same power irrespective of
whether that near field is produced by one radiator or two.    How can you
gain efficiency when the same power is lost for the same far field strength
?

How about these other losses (like trees, bushes etc.).  Do they suddenly
dissipate half the power in the same field strength ???    How does this
work ?    They still have the same induced currents flowing in them and so
dissipate the same power. If not, how do the trees know what they are
supposed to do :-)

I re-iterate,   I believe those part of the losses which are coil losses or
any other wiring losses are reduced by paralleling, but the ground losses
(which you are trying to cover up by the chicken wire nets) or environmental
losses (trees and bushes) are not.

So the way to gain efficiency is to do what is already been done and
well-known - put out the best and biggest ground plane to cover up the
ground losses and provide a low resistance return.    Cut down any trees and
bushes, knock down any constructions (house optional - but leave the shack
:-)

Now, I know you weren't happy with me when I used a system which you felt
was not the same as Stewart's (but you were apparently perfectly happy with
a battery and a couple of resistors :-), but try this scenario.     Take two
radiators whose ground/environmental losses result in an efficiency of say
0.1% each.    Keep them far enough apart so that they are independant (i.e.
one doesn't upset the other in any way as you stipulated).     Feed one with
1W (the other untuned for the moment so as to not suck out any energy), we
get 1mW radiated.    Now reduce the power of the first one by 1/2 to 500mW
(0.5mW radiated).     Fire up the second one and feed it with 500mW (now
back up to 1W total).   It also radiates 0.5mW.   We now have 1W in and
0.5mW + 0.5mW = 1mW radiated.  Efficiency = 0.1% - same as before.    How
can two independent radiators suddenly double their efficiency just by
feeding them in parallel ?  Note that if each radiator was outside the near
field then connecting them in parallel would result in the halving of *both*
the radiation resistance component and the losses as seen at the terminal.
You say that for close spacings the radiation resistance stays the same, but
the ground losses are halved, but not when they are too close, where you
agree they are not.   Unless you are having an each way bet by making the
ground losses independent, but the mechanism for generating radiation
resistance conveniently not.

So, in summary, to put it another way (and test everyones' patience), I
believe that radiators separated far enough to be truly independant (outside
near field) and placed in parallel will have their impedances halved (Rrad +
Rloss), but maintain the same ratio.    Radiators in the near field of each
other and placed in parallel will maintain the same radiation resistance and
losses (and the same ratio).    That is, they maintain the same
efficiencies.    Maybe there would be some second-order effects, but nowhere
near a 3dB gain.

You, if I understand it correctly, are saying that somewhere in between
closely spaced radiators (my 1m spacing where you say Stewart's assertion
doesn't work) and the larger (greater than near field separation where any
antenna textbook will say it doesn't work), there is a magic zone where
efficiency jumps proportionally to the number of radiators (at least for low
values of N).   A kind of "mummy bear" zone.   I must say that is outside my
knowledge and would be intrigued to learn how this works.

73s Steve Olney VK2ZTO

BTW, Stewart states the radiation resistance stays the same, but you say
your rough measurements show there IS a transformation of radiation
resistance.   So even your own experience doesn't agree with his statements.
Folded radiators exhibit transformation (i.e., folded dipole),  parallel
radiators do not.

"Man made mathematics and models, to *convince him/herself that s/he
comprehends* the reality that God made."