RF transceiver chips with low-kHz bandwidth?

Hi Joerg,

Look for the ADF7021-N from our dear friends Analog Device... IF bandwidth down to 9KHz, 2,88$.

Friendly yours, Robert Lacoste www.alciom;com

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Merci beaucoup, Robert. It won't get to the single digit kilohertzes but does go down to 12.5kHz. That's a lot better than all the others with

50kHz. The price is a bit high and it has a stiff package which isn't so great if gear gets banged around but it sure beats all the other chips in performance so far.

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Regards, Joerg

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Any idea how well it does detecting Amplitudinous Modulation (true AM)?

Jim

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No, sorry, we used it only for FSK Robert

Robert, what kind of range did you get with it? And what sort of antenna (length)?

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Regards, Joerg

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Well, we used an ADF7021-N for a VHF system (169MHz telemetry band), so range was, well, long (around 20km open field, some km in urban environments), so I guess this experience will not be transposable to yours... By we way we wrote a small white paper on advantages of 169Mhz for telemetry, in case someone is interested :

Yours, Robertt

Thanks. I've been following the discussions in this thread and learning from them. The paper connected some things I learned about elsewhere (Friis formula, though in somewhat different form from eetimes and mpdigest in 2007 authored by ADI employees) and anticipated would come up in your paper as I read it. And they did! The worked details were nice, too.

thanks, Jon

Excellent paper, Robert. Unfortunately we can't do 500mW. Well, on

900MHz and inside the US we can and sometime do but that won't fly at all in Europe. Especially not in France ;-)

I like VHF just like you do, much better for longer range communications. That is why I completely fail to understand why many of our TV stations gave up their VHF channel for a UHF channel, without putting up a fight.

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Regards, Joerg

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Nobody lets you use external filters any more? Or does that blow the budget?

Sometimes I wonder about the transceiver chip market -- mostly it's "Are those guys really that much smarter than me? Or are they that much dumber?" (It's got to be one or the other).

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Tim Wescott
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Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

They don't let you. I guess that designing external filters is expecting too much these days so they poured it into the silicon. Or maybe engineers just don't want to fuss around with this and rather treat it as a digital building block. Probably for the same reason many people won't or can't drive a stick shift anymore.

It's like with TV set, things are being dumbed down. Heck, ours won't even let you add channels. You can only run a clean slate scan and there are few days when more than 95% of channels will "stick".

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Regards, Joerg

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You should run the channel scan after dark - propagation conditions are much better then. :-)

Cheers! Rich

Not out here. We even stopped taping movies if they do not run during the day. After 7:00pm numerous channels begin to pixelate. Sometimes we were sure a movie stuck, only to discover that it froze into a Picasso painting 1h into the movie #@&*!!

Our TV consumption has dropped significantly since DTV was foisted upon our nation. Same for many neighbors. Analog was better, much better. OTOH it had some good effects, more real socializing among neighbors.

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Regards, Joerg

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You're thinking HF -- at VHF, and especially at UHF, there's not enough ionization in the upper atmosphere to bend (or bounce) the radio waves.

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Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Unless a slew of little meteorites hisses out up there :-)

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Regards, Joerg

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Maybe it's just here then. During the day, channel 50.x doesn't come in worth beans, but at night it's about the strongest one in the range.

How about tropospheric bending by the thermocline? :-)

Thanks! Rich

Maybe it's the smog?

DTV reception quality does not have much to do with field strength. The ATSC protocol appear to be so shakey that the slightest multipath reflection can toss it off the rocker. Sometimes when my wife says that we probably can't watch or tape anything because the stations all blue-screen I look at the spectrum in my lab. And sure enough, they're all there, nice and strong. But undecipherable :-(

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Ah, the Friss formula for free space path loss, which states bluntly that this path loss is proportional to frequency... If that were true, then light wouldn't ever get anywhere, now would it?

Of course, free space path loss simply goes as r^2. No frequency term in there. No one ever seems to notice that Friss defines his effective antenna apertures as a fixed number of wavelengths! In fact, he's supposing smaller and smaller antennas as the frequency goes up. No wonder the amount of received power drops!

Jeroen Belleman

Feds prolly bribed them with tax breaks...

No, it is because OTA transmissions don't bring in any money, while cable and sattelite rebroadcast does. You just need to broadcast anywhere to get the rebroadcasters to give you money...

Charlie