Replies to This Discussion

Permalink Reply by Grips on April 12, 2012 at 10:00am

The Si4432 IS certified by the FCC.. The problem is the FCC certification does not apply outside of the USA.

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Permalink Reply by Jake Stew on April 14, 2012 at 2:37pm

   The chip is designed and tested to comply with FCC standards.  It's not "certified".  Complying with the standard and actually being certified are two different things.

   There are all sorts of parts to a "radio".  The Si1000 has all the radio parts inside one chip, with the exception of the external clock crystal and the PA matching network.  The PA (power amplifier) matching network is the key part of the radio that determines if it will meet the specs.  The PA matching network is the low-pass filtering between the power output and the antenna.  It filters out the harmonics generated by the chip and creates the proper impedance for the antenna you're using.

   The HopeRF module contains the entire "radio" the only thing the 3DR carrier does on the radio side is attach an antenna connector to the TX/RX pin of the module.  The chip can't be FCC certified because a lot of what will make or break the specs is between the chip and the antenna.  If you tied the chip directly to an antenna it would not even be close to meeting FCC specs.

   The module doesn't have a case and doesn't have a RF shield covering any of the TX/RX path.  So I don't have any idea if the uncased, unshielded 3DR radio unit is going to meet FCC specs.  I certainly wouldn't bet on it.  So before too much time is wasted trying to get it certified we need to first find out if the unit is meeting the FCC specs.

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Permalink Reply by Allen Bishop on April 16, 2012 at 5:09pm

Before anyone gets too carried away with the 433 MHz radio. You might want to consider what the FCC has to say about the 70 cm band.   First of all, 420 MHz to 450 MHz is assigned to the U.S. Amateur Radio spectrum by the FCC and also in concert with the ITU (International Telecommunications Union).  Use of any portion of the 70 cm band between 420 and 450 MHz requires an FCC Amateur radio license.  The second issue is production and sale of transmitters that emit RF in the Amateur Radio spectrum (including 70 cm) requires compliance and conformance with PART 97 of the FCC rules and specifically Sub Part "D" Technical Standards.  There are issues regarding interference and the need for components like interstitial filters to esure that signals do not bleed beyond the frequency chosen for the specific transmitter.  I would recommend you also go to the followng website:

http://kh6htv.com/

Jim Andrews background is technically based. He holds a Ph.D. in electrical engineering from the University of Kansas. He is a Fellow of the IEEE. In 1980, he founded Picosecond Pulse Labs (PSPL) and served as the chief design engineer and president for twenty years.

He builds video transmitters in the 70 cm spectrum and knows what the issues are.  The FCC has quite a list of individuals and companies that have been fined significant $$$ for violation of these rules.

Just a heads up.  The first offense is $10,000. (US) and it goes up from there.  Fines can include not only the confiscation of equipment but the fines can be assessed by the number of transmitters sold and the user is not exempt from the fines either. 

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Permalink Reply by Jake Stew on April 16, 2012 at 5:17pm

Lots of stuff operates in the 433 mhz ISM band without requiring any license.

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DeveloperPermalink Reply by Andrew Tridgell on April 16, 2012 at 6:13pm

Hi Jake,

I'm not sure how the terminology works in the US, but at least in Australia there is really no such thing as a band that doesn't require a license. The bands that people commonly refer to as "unlicensed" are really "class license" bands, which means that a license is automatically granted as long as you follow the rules for that band.

I suspect its similar in other countries, but I haven't looked into it in detail.

Cheers, Tridge

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ModeratorPermalink Reply by Mark Harrison on April 17, 2012 at 9:20am

Here's a nice writeup on what's allowed in that band.  It includes the FCC verbiage and a flowchart to determine if your application is legal in that range.

http://www.linxtechnologies.com/resources/documents/an-00125.pdf

There's a "no toys" clause, so you had better hope my wife is not consulting with the FCC on this matter!

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DeveloperPermalink Reply by Andrew Tridgell on April 16, 2012 at 6:11pm

Hi Allen,

Not everyone on this site is from the USA :-)

On the documentation page for these radios we list which frequency to use for different countries. You may notice that 433 is not listed for the US.

In Australia (where I live), you can transmit on 433 up to 25mW under the LIPD-2000 class license rules. In some countries (such as Australia) both 433 and 915 are allowed, although with different power levels and channel rules.

Cheers, Tridge

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Permalink Reply by Allen Bishop on April 16, 2012 at 7:35pm

Understood.  My comments only referenced the FCC (which is US).  No reference was made regarding usage outside the US.  Just to clarify, the 70 cm band between 420 MHz and 450 MHz is not available to ANYONE in the US without an FCC issued Amateur license regardless of power levels.  I run 1 watt, 5 watt, and 10 watt transmitters for video and with vestigial filters to keep the analog signal within the bandwidth requirements.  The following image shows the video with adjacent audio with vestigial sidebands suppressed.

The suppression of sidebands ensures that the signal does not spread into adjacent cable channels.  In the US on the 70 cm band, we use cable channels 57, 58, 59 and 60 for broadcasting amateur TV (ATV).  It is critical that the transmitter output does not spread into any adjacent channel.  The example image above clearly shows the narrow signal produced by a well architected transmitter.

Regards, Allen

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Permalink Reply by Jake Stew on April 17, 2012 at 8:52am

Just to clarify, you're wrong.

   433 mhz, 900mhz, and 2.4 ghz are all unlicensed ISM bands in the US.  You need to check out part 18 and reread part 15.

   Ham operators do NOT have exclusive use of the 70cm band.  This is shared spectrum.

   Low power, frequency hopping, narrow bandwidth transmitters are ENTIRELY different from video, audio, and ham transmitters.  The rules are also entirely different for these devices.  They don't transmit on any given frequency for more than a fraction of a second and they use only a tiny, narrow fraction of the spectrum.  They're not subject to the rules for higher power devices that continuously use a large chunk of the spectrum like you're talking about.

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DeveloperPermalink Reply by Andrew Tridgell on April 17, 2012 at 4:36pm

433 mhz, 900mhz, and 2.4 ghz are all unlicensed ISM bands in the US.  You need to check out part 18 and reread part 15.

I'm not an expert on the FCC rules, but I have read part 18, and I don't see the 433 band listed. Subpart C, 18.301 lists all the frequencies allocated to ISM use in the USA, and 433 isn't one of them.

Can you point me at the specific document and paragraph number you are basing this statement on?

Here is the table from my copy of FCC part 18:

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Permalink Reply by Allen Bishop on April 17, 2012 at 5:06pm

Just to re-clarify further.

The 70 cm band is "technically" shared - however.  ISM devices can only transmit RF at such a low power that the device range is genrally only 500 to 700 feet.  This includes garage door openers, remote control switches, etc.  You cannot transmit video or long duration controls on the ISM "unlicensed" bands.  I made my initial comment to ensure that no one intends to market a transmitter for use as a FPV solution or as a telemetry solution for UAS systems.  One of the issus that the FAA and FCC have is the proliferation of these small market solutions that hobbyists build in their basements and then go out and broadcast video for 10 miles at 25 watts ERP.  The FAA doesn't like the idea that a hobbyist is flying his homebuilt UAV beyond line of site and the FCC doesn't like a high powered transmitter flying over homes and businesses transmitting high power in a band that has medical, emergeny and industrial controls in legal operation and in conformance with the ISM "unlicensed" frequencies.  Every solution that you can purchase in the US that is intended to transport video or telemetry requires at least 100 mwatts to have any effective range. Unless your only sending video from a model airplane field for 100 to 300 feet.  In which case you might be able to use a transmitter that is spec'd for the ISM band.  Telling people they can use the unlicnesed ISM portion of 23 cm, 33 cm and 70 cm bands is not an entirely true statement.  Anyone who wants to transmit video and/or telemetry and/or control signals to any reasonable distance such as the distances most UAS pilots will be doing requires transmitter power that puts the device outside of ISM "unlicensed" specifications.  If all you want to do is operate your garage door from your Quad-Copter - GREAT!  Have fun.  If you want to transmit a FPV signal from a mile away and you are using 433 MHz and are not licensed - good luck there too.  It is you that will pay the $10,000 fine for first offense and loose all the associated hardware related to the violation.  The good news is on a first offense you will not get more than probation so you can rebuild your system from scratch all over again.

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DeveloperPermalink Reply by Andrew Tridgell on April 17, 2012 at 8:23pm

Hi Allen,

I know we are in basic agreement, but there are a few parts of your comments that puzzle me.

First off, you now seem to be saying that the FCC rules allow for low power telemetry transmission in the 433 band under ISM class license rules. Can you tell me exactly which part of the FCC rules allow for that? I couldn't find 433 listed at all at any power level. Is there some general low power exception you are perhaps referring to? If so, what is that power level? (I am most familiar with the Australian rules, so I may well have missed some parts of the US FCC rules).

Secondly, the comment that telemetry "requires at least 100 mWatt to have any effective range" is not correct. In the 433 band 10mW is fine for well over a mile range, as is demonstrated by the graphs I posted in the thread on the 433MHz radios recently. The high receive sensitivity of the 3DR radios means that 10mW can give you quite long range, even if you use a very small omni antenna at the receiving end (I was testing with a 2dBi antenna). The lower path loss in the 433 band means that 10mW is equivalent to about 40mW in the 915 band.

If you want to do the calculations yourself using a link budget calculator, then these parameters are a good place to start for the 3DR 433 radios:

• receive sensitivity -115dBm at 64 kbit
• need 6dB signal to noise ratio for good reception
• assume you need another 6dB of fade margin for safety

The theoretical range is quite good given those parameters. In practice I think people will see about a 2km range, depending on the local noise floor. I got a bit more than that, but I wouldn't want to promise that everyone will get the same result.

Cheers, Tridge

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