Receining antennae

Receining antennae

Post by al.. » Tue, 25 Feb 1997 04:00:00

At present my antenna consists of around 50 feet of quite thin copper
wire, salvaged from an old transformer.  This longwire is folded
around (due to constraints of space) but seems to perform fairly well
with my Yaesu FRG-880.
I was wondering if anyone out there could tell me wether there is any
advantage to be gained by using the very much thicker stranded copper
wire which is usually supplied with antenna kits.  Also,  will the
fact that it is bent aroud over its length affect it's performance
over one which is in a straight line..
Any comments would be much appreciated.

Many thanks.

John.

                 [[[[[[[]]]]]]
         [[[[[ A L G O L ]]]]]
                 [[[[[[[]]]]]]

 
 
 

Receining antennae

Post by T. J. » Tue, 25 Feb 1997 04:00:00



> At present my antenna consists of around 50 feet of quite thin copper
> wire, salvaged from an old transformer.  This longwire is folded
> around (due to constraints of space) but seems to perform fairly well
> with my Yaesu FRG-880.
> I was wondering if anyone out there could tell me wether there is any
> advantage to be gained by using the very much thicker stranded copper
> wire which is usually supplied with antenna kits.  Also,  will the
> fact that it is bent aroud over its length affect it's performance
> over one which is in a straight line..
> Any comments would be much appreciated.

> Many thanks.

> John.

>                  [[[[[[[]]]]]]
>          [[[[[ A L G O L ]]]]]
>                  [[[[[[[]]]]]]

Antenna girth has little if any effect other than making for a stronger
antenna structure. The overall length is the most important factor.
Bending the antenna around as you describe is probably not as important
as how resonant the whole thing is on the frequency your listening to. If
your hearing signals and having fun relax and enjoy it for now until
you've got a couple of antenna books under your belt.
--
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++


  Snail Mail: PO Box 644 Waterford Works, NJ 08089              

  Author of: RADIO MONITORING The How-To Guide
            ISBN 1-56866-101-0
    Index Publishing Group, San Diego, CA

     http://www.electriciti.com/~ipgbooks

 
 
 

Receining antennae

Post by David Rickme » Wed, 26 Feb 1997 04:00:00


>I was wondering if anyone out there could tell me wether there is any
>advantage to be gained by using the very much thicker stranded copper
>wire which is usually supplied with antenna kits.  

A long wire's performance is not materially improved by a larger cross
section wire.
Quote:>Also,  will the
>fact that it is bent aroud over its length affect it's performance
>over one which is in a straight line.

Yes.  The directional pattern is altered.  Avoid angles less than 90
degrees and equal length parallel sections;  i.e. a "J" shape works
better than a "U" shape.  Experiment.
dr
 
 
 

Receining antennae

Post by Len Anders » Thu, 27 Feb 1997 04:00:00


AL>Subject: Receining antennae

AL>At present my antenna consists of around 50 feet of quite thin copper
AL>wire, salvaged from an old transformer.  This longwire is folded
AL>around (due to constraints of space) but seems to perform fairly well
AL>with my Yaesu FRG-880.
AL>I was wondering if anyone out there could tell me wether there is any
AL>advantage to be gained by using the very much thicker stranded copper
AL>wire which is usually supplied with antenna kits.

   Probably not.  Impedance of wire antennas is dependent on length to
   diameter ratios and, in the HF spectrum, that ratio is always high.
   The impedance change in replacement with larger wire will be minimal.

AL>  Also,  will the
AL>fact that it is bent aroud over its length affect it's performance
AL>over one which is in a straight line.

   Probably true.  As a general rule, the larger the antenna, the larger
   the signal into the receiver; more wavefront energy is intercepted by
   larger size antennas.  As to bending, that is a much more complex
   question not readily analyzeable.  Bending the antenna changes many
   characteristics:  "Capture area" (equivalence to size of antenna),
   frequency response, impedance.  All parts of bent antennas will react
   with one another in a very complex manner...such can only be analyzed
   by one of the "NEC" antenna computer analysis programs.

   A wire antenna bent once so that its angle is about 90 degrees can be
   considered as two antennas.  One antenna part captures a wavefront
   while the other antenna part acts as a feedline extension.  For
   wavefronts coming in at right angles, the two parts reverse order.
   (that's a very, very approximate simplistic explanation)

   I've used "coil wire" with fair success in a bad location for SWL,
   different lengths of multiple wires for some broadbandedness.  The
   chief difficulty is that coil or transformer wire is "soft drawn" and
   very ductile...it can be strengthened somewhat by manual "hard
   drawing" (literal stretching, have to try it to feel the effect).
   Neither seems to resist bird flight or high winds well; not all birds
   can see small wire although they do manage to perch on the #18
   longwire I do have now.

---
 * OLX 2.1 * I admire atheists...they take a lot of faith...

 
 
 

Receining antennae

Post by David Rickme » Thu, 27 Feb 1997 04:00:00



>   Probably not.  Impedance of wire antennas is dependent on length to
>   diameter ratios and, in the HF spectrum, that ratio is always high.

I thought impedance (Z) has to do with length and frequency;
bandwidth (Q) length and diameter.
dr