Rich Peet wrote:
> imho
>
> How quiet the pickup microphone is determines the reach.
>
> How big the dish is better thought of as what the maximum usable low
> frequency more than the gain.
I think this is a poorly understood concept. The low frequency gain is
somewhat a function of the dish size. But there is no low frequency
cutoff. A Telinga, which is a fairly minimal size dish, will pick up
frequencies well below the theoretical minimums. The bottom frequency is
more limited by the mic used. Though the gain will tail off. It will not
drop below the gain of the bare mic.
I tend to agree on ultimate reach. What you hear out at the limits of
reach will come in very faint from a parabolic mic, and if mic noise is
high that will interfere.
> How close the focal point is to the dish determines the gain more
> than size.
>
> Trades offs to consider:
> Quality of the sound on focus.
> Quality of the sound off focus.
> Amount and quality of sound completely off axis.
> Physical size
> Physical weight
> Size of microphone element
> Size of the focus globe
> Ability to cook dinner in the field at noon.
And hopefully not cook the mic when you point it at the sun.
> If you really don't care about quality of sound at all then a
> multiple resonant pipe tube microphone will give you more reach than
> a parabolic but sounds bad.
Sooner or later I've got to build one of these.
> The best and biggest dishes really don't have that much more reach
> than a person with great hearing having his hands behind his ears.
> Human hearing is pretty good and there comes a distance where just
> not all the sound is getting there.
I'm not sure about this. The Telinga I use can certainly pick up
frogcalls I cannot hear. Of course maybe if I was still young my ears
would do better.
Walt
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