[Tugindia] Space before and after equation in Latex

[Lalu Mansinha]

I am preparing an article with several equations.  The space between 
the text and the equation, both before and after, is excessive, about 
0.75inch.  I have tried reducing the space by inserting \vspace{-0.x 
in} before and after the \begin{equation} and before and after the 
\end{equation}, with bizarre and unpredictable results.
For example, if I use \vspace{-0.5in}, the spacing reduces just 
slightly.  If I use \vspace{-0.6in} the equation overprints the text above.

I will be grateful for any pointers.
Thanks
Lalu Mansinha

%%%%%%Snippet of the article
frequencies below and above the center frequency  $f$ :
\begin{equation}
\sigma = \frac {C} {f}\cdot \frac {2^B +1} {2^B - 1}
\label{e1}
\end{equation}
where constant $C$ is dependent on the form of the Gabor function. Although
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