fresnel? RE: [Laser] Results form a crude signal to noise versus frequency check on my optical receiver

[Rochte, Robert]

>I purchased a batch of the 4" glass magnifiers from a local 
>99cent store once but haven't seen them again. 

Will a large (~12" square) fresnel work as well or do I really need the
sharper focus that a regular lens provides?  I have a few that I have
salvaged from dead overhead projectors but have not yet tried them...

Thanks.

73,
Robert  KC8UCH