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The technical side of broadcasting. Think IBOC is a sham? Talk about it here! How about HDTV? Post DX reports here as well.
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Kennelly Heaviside
- Posts: 145
- Joined: Fri Jun 11, 2021 12:06 am
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by Kennelly Heaviside » Sun Oct 03, 2021 2:00 pm
They used to use FM BCB Transmitters for tracking animals. The transmitters were detectable for miles, using multielement Yagis. Are these still legal in the United States? They can't be within legal radiation limits, unless there are exceptions for research of this type.
It used to be no problem finding vacant channels. Now the band is jammed. I imagine you could use 87.75 MHz in some areas. The researcher I knew used the receiver as an FM radio in his office when not tracking animals.
![Image](https://defenders.org/sites/default/files/2020-07/4841247207_268eb60af7_k.jpg)
Kennelly Heaviside. The best Technical Consultant no money can buy.
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bosco
- Posts: 17
- Joined: Sat Dec 04, 2004 10:43 am
- Location: Grand Rapids, MI
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by bosco » Mon Oct 04, 2021 9:13 am
Someone somewhere may have used the BCB FM frequencies, but for the last 30 years, there are dozens of 160-170 MHz freqs that are used. And the signals only transmit for 10 ms every 5 or 10 minutes for birds, much more often for really large and dangerous animals.
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Kennelly Heaviside
- Posts: 145
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by Kennelly Heaviside » Mon Oct 04, 2021 9:41 am
bosco wrote: ↑Mon Oct 04, 2021 9:13 am
Someone somewhere may have used the BCB FM frequencies, but for the last 30 years, there are dozens of 160-170 MHz freqs that are used. And the signals only transmit for 10 ms every 5 or 10 minutes for birds, much more often for really large and dangerous animals.
Mecosta County, circa 1980. Granted, this is 40 years ago. But in China, they track Pandas with FM BC antennas and receivers. I've seen pictures in National Geographic, more recently than 30 years ago. The size of the Yagi elements were too long for the 160-170 MHz band, as elements were almost as tall as they were.
Kennelly Heaviside. The best Technical Consultant no money can buy.
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Plate Cap
- Posts: 222
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- Location: After the rectifier stack
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by Plate Cap » Wed Oct 06, 2021 8:43 am
Hmm.
I guess the equipment would be cheap, but 72-75 mHz would be a lot better choice.
The box that many broadcasters won’t look outside of was made in 1969 and hasn’t changed significantly since.
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k8jd
- Posts: 617
- Joined: Fri Jun 28, 2013 3:35 pm
- Location: Commerce, MI
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by k8jd » Wed Oct 06, 2021 5:11 pm
The ranger in the photo posted, sure is holding a 150-170 MHz Yagi antenna !
If you went to 72-75 MHz, the Yagi antennas would be roughly twice that size.
Not so good for tracking in the field.
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WOHO
- Posts: 821
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- Location: 2965 Pickle Rd.
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by WOHO » Thu Oct 07, 2021 8:48 am
If the movie "Star Trek IV" has any accuracy, the humpback whales were fitted with transmitters for 406MHz IIRC? Funny thing about that movie is when Scotty was trying to use an Apple Computer, it had a 1986 wired mouse on it, and used the mouse like a microphone for voice recognition and everyone in the theater laughed; now we do talk to our computers/phones/'communicators' (and it never gets the damn voice to text correct).