Modulation in FM?
10-21-2006, 03:39 PM
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Modulation in FM?
Can somebody clarify the modulation standards used in our RC in the
72/75MHz band? I tried to look up FCC documents, but could only find
they specifying that "The authorized bandwidth for any emission type
transmitted by an R/C transmitter is 8 kHz." Nothing about "ultra
narrow band" as seen on Hitec receivers, for example. I have a
recollection seeing something about 2.5kHz, but can't find it anymore.
What is the actual bandwidth used here? What is the maximal deviation
frequency in these transmitters? What is the actual bandwidth of
quality receivers? Is there the url to the "new" rules by FCC of 1991
often referred to?
Nick
72/75MHz band? I tried to look up FCC documents, but could only find
they specifying that "The authorized bandwidth for any emission type
transmitted by an R/C transmitter is 8 kHz." Nothing about "ultra
narrow band" as seen on Hitec receivers, for example. I have a
recollection seeing something about 2.5kHz, but can't find it anymore.
What is the actual bandwidth used here? What is the maximal deviation
frequency in these transmitters? What is the actual bandwidth of
quality receivers? Is there the url to the "new" rules by FCC of 1991
often referred to?
Nick
10-21-2006, 07:37 PM
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RE: Modulation in FM?
ORIGINAL: BarracudaHockey
CFR 47 Part 95 covers R/C
http://www.fcc.gov click on rules and regulations
CFR 47 Part 95 covers R/C
http://www.fcc.gov click on rules and regulations
Ok, I finally could get there the FCC rules formulations. Yet again no
more said than 8kHz of authorized bandwidth. That is a legal
limitation. What is the actual peak deviation frequency for the FM RC
transmitters on 72-76MHz band?
Some receivers state "ultra narrow band", some mention only "narrow
band". Is there an actual difference?
I also recall seeing some requirements for the receivers. The FCC Sec. 95
seemingly does not contain anything of this sort. Where this can be found?
I have the recent receivers from Hitec like RCD3500, and their old
"Platinum RCD" which both state "ultra narrow band" and look very
similar; the design seems nearly the same, alethough the circuit and used
chips are somewhat different, evidently in the decoder part. Otherwise,
should they perform similarly? I have an impression
that the old one has less sensitivity leading to a shorter range in
the absence of any interference. Should this be so, or it is a
consequence of aging?
Nick
10-21-2006, 07:42 PM
#4
RE: Modulation in FM?
While I dont know the specific answer to your question other than to say this. The FCC doesnt care about recievers, the only regs are on the transmitter end.
Also, I suspect, but Mike Mayberry could probably answer better than I could, that "ultra narrow band" is nothing more than marketing hype much like "high performance" or "competition special" often means nothing more than whats printed on the packaging, think of it as high tech fishing lure for geeks.
Also, I suspect, but Mike Mayberry could probably answer better than I could, that "ultra narrow band" is nothing more than marketing hype much like "high performance" or "competition special" often means nothing more than whats printed on the packaging, think of it as high tech fishing lure for geeks.
