Hi there. I'm looking for a portable FM radio that can be used for listening to miniature bug transmitters. I was wondering if anybody has bought one that worked well for them. These are the things that I am looking for in one:

1. Must have headphones and be small, like fit in my pocket
2. Must be one that is tuned by turning a dial, not one that scans for a signal. The reason for this is that i want to be able to modify it to go lower than 88-108MHZ.

I've built a transmitter that is supposed to have a range of 300 meters, but @ the most i can only get about 20 meters. Thanx

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I have a nice FM receiver but it was a free promotional gift, so that won't help you. I bought a 433mHz transmitter and receiver for about $10 each, got the antennas from Mouser and used a parabolic reflector to get 300 meters range, so it can be done. Getting that kind of range below 88 mHz will require a very large antenna.

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yeah, im prepared for a large receiving antenna.

is a license required for 433mhz operation? and could a small bug be built at that frequency? i'm sure that a crystal would have to be used cuz the good ol' lc circuit would be very unstable.

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I hate to be pedantic (actually I love it), but that statement doesn't make much sense to me. I think the concept of range is only valid for a transmitter/receiver pair. The signal from your transmitter has an infinite range, it's governed by an inverse square law. Given a sensitive and selective enough receiver (and lack of interference) you should be able to detect it on the moon.
Who or what are you bugging, anyway?

 

Hi JohnBrown,
Good point. I'll bet that NASA can detect the reflection of Zach's transmitter signal bouncing off the moon! Since Zach's receiver and antenna aren't nearly as good as NASA's, may be he should cool his radio in liquid nitrogen to get its noise level down.
As for gain, he can cascade a bunch of current-feedback ICs. They must be cooled too.
Bandwidth and interference rejection? Just a bunch of LCs, but difficult to tune simultaneously.

Someone must make a good "walkman" FM radio, but how does Zach rate them without listening to the exagerated claims by their manufacturers?

Hi Zach,
Did you Google for "walkman radio sensitivity test"? Consumer Reports mag?

 

good idea audio :lol: . ill try taht.

not sure yet, but im sure it'll come in handy one of these days. if nothing else i can inspire fear in people by telling them that i can eavsdrop :twisted:

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ya no, i was just thinking that a radio telescope hardly seems portable duz it? :wink:

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You don't have to carry the thing. Just hack into NASA's website and gain control of their biggest dish.

Remember when they landed 2 rovers on Mars 10 months ago? They said they would last maybe 3 months. They still work fine! That's far away, mighty good range. The rovers' site is here:
http://marsrovers.jpl.nasa.gov/home/index.html

 

3 posts in a row :roll: lol. well i tried consumer reports and needed to pay for the reports. Then i tried walkman radio sensitivity test and the results were so wide and varied. Tried a couple of websites like sony, panasonic, phillips. i couldn't really find anything like specs or data sheets, just "how many presets there are, how sleek it looks . . ."

That's kind of the reason i started this thread was because I knew it would be rather hard to find a sensitive radio on the internet, i was just wondering if anyone could recommend one that they have.

I'm also up for building one. I built a TDA7000 receiver, but didn't have very good results with it.

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