TopBand: polarisation

[km1h @ juno.com]

On Wed, 8 Oct 1997 16:02:15 +0100 Peter Chadwick
<Peter.Chadwick@gpsemi.com> writes:
>VE7BS says
>> He answered "The only thing you can say for
>>sure is that is will probably be somewhat different from the way it
>went up."
>
>I believe that conventional wisdom says VLF signals are generally
>vertically polarised, as are ground wave signal over conducting 
>ground.
>A signal coming off the ionosphere isn't travelling, I guess, over the
>ground in the same way as either ground wave or VLF - I believe the
>conventional wisdom says that the wavefront is tilted as it travels 
>over
>the ground, as well as being attenuated. That's how the Beverage picks
>up a vertically polarised signal. The tuned loop when vertical also
>picks up a vertically polarised signal.


Does it Peter?  I thought it was polarization and direction insensitive
to ham band signals (sky wave ?) as long as the loop was under .1 wave. 
I have varied a 5' diameter loop thru all planes and note very little
change in ham band signals. The vertical configuration however is far
superior for nulling local noise sources. 

>
>Now given these postulates, can anyone answer the following:
>
>What is the predominant polarisation of static? Is it different 
>between
>close in static and thunderstorm hundreds/thousands of miles away?

The small loops I have tried here appear to offer no S/N benefit to
static from distant storms. They sure knock down power line and PC crud
tho from around the neighborhood. 
A  full wavength loop at 10' above ground has been reported to offer
excellent S/N under some conditions. For RX purposes in a small area I
see no reason why that loop can not use loading coils....in fact the
reduced bandwidth may be a plus.   

>Is man made noise mainly vertically polarised at 160? If so, what is
>'mainly'? 50%? 90%?

Conventional wisdom claims man made noise is predominantly
vertical....dunno myself but I have much better luck locating power line
noise with a CB HT (old 27MHz AM version)  when the antenna (48"
collapsible whip)  is vertical. The same holds true when locating  noisy
pipe-wrap heaters, electric blankets and fences around here.  

>What is the best horizontally polarised receive antenna with good 
>noise
>rejection for local electrical noise?

A 3el yagi on a .3 wave boom...........................


 And the best for a small (<100
>foot) plot?

A  Crying Towel.
I would also like ur comments on a heavily loaded loop Peter. Here is
another wild idea that needs modeling.....How about a heavily loaded quad
array? Make the elements 10 or 20M size and use proper 160M spacing of .1
to .15 wave.  Could you get  a meaningful quad pattern ???  The closed
loop would have less distortion from the ground than a yagi or phased
dipoles I think....You could even switch  polarizations remotely. Make it
bi- directional with a common DE and relay switched R or D elements.

Just a few crazy ideas....I'll shut up now!



>In QST about 2 or 3 years ago, there was a low noise horizontal loop
>antenna, which was, as I remember it, a small Alford loop. I got no 
>joy
>with it, but as Carl, KM1H, said the other day
>
>"IMO we all need more info on antennas in real world situations."

I'll say it again also. I can only be impressed by theory so far.  Most
mere mortals do not have access to the latest government software that
will tell you what happens in real life. Of course W3LPL is not mortal !
The rest of us have to cut and try. 


>And as locations are different, it doesn't always follow that what 
>works
>in one location will work as well in another.

AMEN Peter.

73  Carl  KM1H


>
>73 Peter G3RZP
>
>
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