ken3983

I recently was given a 30" parabolic dish from a friend who worked in a now closed electronics store. I thought what could I ever use this thing for and it hit me. Is it possible to take a baby monitor ( I got a used one), and de-solder the microphone from the transmitter and extend it out to the focal point of the dish and make a nice shotgun microphone? It seems feasable since the monitor has a sensitive circuit already plus the system would be wireless as well. Any ideas or thoughts?

Ken

audioguru

The 30" dish will work for frequencies above about 330Hz.
It focusses the sound and makes a very sensitive microphone system.
A shotgun mic isn't sensitive but has a narrow pickup angle for higher frequencies.

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Uncle $crooge

Torben

But it does increase sensitivity along the narrow pickup angle, doesn't it? At least for the higher frequencies? I'm just thinking that it would work a lot like an antenna, narrowing and extending the major lobe in the direction the dish is pointed. But I don't have my ham manual here--still studying for the test --so please correct me if I'm wrong on this.

At any rate, I'd expect it to work and sound tinny.


Torben

ronsimpson

A baby monitor with a 30” dish? You could hear a baby cry at 1 mile!
Most of the world want to know how to avoid hearing a baby cry at 10 feet.

HiTech

The dish isn't concave enough either for audio purposes. It likely wouldn't work much better than a cardboard box!. Now, large salad bowls have been used with good success as an audio parabolic reflector. I'd take that 30" dish and use it as a bird bath out back or check the I-net for a modified LNC circuit project and make a radio telescope out of it... listen to Jupiter farting, Saturn burping, Venutian whistlers, etc. (I'm serious about the radio telescope thing!)

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audioguru

Yes, the parabolic dish increases the sensitivity of a mic in its focal point for on-axis higher frequency sounds.
The sensitivity of a shotgun mic is the same as a normal mic for on-axis sounds. It blocks and cancels off-axis sounds.

"Spy" mics for kids have a very small dish and sound very tinny. A 30" dish will reduce the bass frequencies like a telephone.

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Uncle $crooge

Hero999

Bass frequencies aren't impoirtant for as babies make most of their sound above 330Hz.

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audioguru

I think he is using the electronics from a baby monitor.
I think he wants to spy on what big people are saying, not babies.

The electronics also might reduce bass frequencies.

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Uncle $crooge

ken3983

Well...I was wanting to take it to some local football games, but that 30" dish would probably stick out to say the least. A large salad bowl would be easier but what size would I need? I thought the baby monitor would be a good thought since the circuit was sensitive enough to do the job.

Ken

Torben

OK, thanks for the clarification!


Torben