[amsat-bb] Re: Two hundred 437 MHz satallites launch March 16 + WebSDR

Tue Mar 11 05:25:33 PDT 2014

Good Morning, Howie;

I don't believe there has been any limitation (in the US, anyway) on SS emission types on 70cm and above since at least the late 1990's.   I was hoping someone else would chime in since surely someone in this group knows more about that than I,  but I'm pretty sure you can use whatever DS technique you want provided that whatever other direction in part 97 is followed.  It seems things are pretty liberal to my reading, but I haven't had occasion to play in that space.

It's my understanding that RM-11708--the current petition you mentioned--deals only with HF and has nothing to do symbol rates or anything else that would affect 70cm.  That said, I do think it has everything to do with Wouter's concern about openness.  It makes little difference to my daughter and me if the transmissions in amateur bands--satellite or otherwise--are operating under part 97, part 5, or part 15 if they are by design unintelligible to all but a select few.   But that is only my picture of things.  An "HF only" petition may be relevant to this group in the sense that this group has in the past put quite a bit of thought into this particular subject.  The satellite community may have interesting perspective on some of this from its own experiences.  If this subject is important to you the ARRL is asking for your thoughts right now:

http://www.arrl.org/news/arrl-board-requests-member-comments-about-digital-modes

Enough of that digression....one other thing that *may* be an issue to the satellite community is that the current SS rules might have some limitations in regard to international communications, but that too may be history.  How that fits in with the *amateur satellite service* is not something I can answer, but if it is an impediment to a worthy project it would certainly have my support to change of needed, for whatever that is worth.

Andy K0SM/2

> On Mar 10, 2014, at 12:51 PM, Howie DeFelice <howied231 at hotmail.com> wrote:
> 
> Hi Wouter,
> 
> I personally agree with the ITU recommendations and think that CDMA/ spread spectrum techniques can be useful for amateur satellite communications. Unfortunately individual national regulatory entities (especially the U.S. FCC) can take a very long time to adopt ITU recommendations.  Current FCC rules define three spreading sequences based on defined tapped linear sequence generators; one 7 bit, one 13 bit and one 19 bit. That makes it difficult to deploy an effective CDMA system. I am sure provisions could be made for a STA ( special temporary authority) but I would anticipate this to be an involved process. 
> 
> I believe the current efforts by the ARRL to give amateurs more flexibility by adopting maximum bandwidth restrictions vs maximum symbol rate restrictions is a move in the right direction. If the purpose of amateur radio is to advance the state of the art, the rules need to be flexible enough to accommodate innovation. 
> 
> Of course, these are just the opinions of one person. I am sure there are as many opinions as there are subscribers to this list :) And yes, politics can be a great attenuator to progress... 
> 
> Howie, AB2S
> 
> Date: Sun, 9 Mar 2014 11:48:40 +0100
> Subject: Re: [amsat-bb] Re: Two hundred 437 MHz satallites launch March 16 + WebSDR
> From: wouterweg at gmail.com
> To: howied231 at hotmail.com
> CC: damonwa4hfn at gmail.com; amsat-bb at amsat.org
> 
> Howie,
> 
> CDMA is actually actively promoted by the ITU. Indeed all the details have to be published before launch, so everyone can demodulate it.
> 
> Citing from the ITU satellite-amateur
> handbook: 
> "Amateur
> and amateur-satellite systems should have technical characteristics
> that provide worldwide interoperability, and allow origination, relay
> and termination of communications independent of other radio
> services. Design emphasis should be placed on reliability, robustness
> and flexibility of reconfiguration for efficient emergency
> communications. Multiple access techniques (FDMA, TDMA and CDMA)
> should be selected for optimum spectrum efficiency and frequency
> reuse. The selection of modulation techniques should take into
> account resistance to interference and immunity to adverse
> propagation conditions."
> 
> 
> I have been researching this for the QB50 mission, but strong pressures (mainly from the US) within the project killed the idea early on.
> 
> The US is now actively putting satellites in 70cm with experimental licenses, which unfortunately means they could use CDMA without providing the spreading codes. The (majority of the) rest of the world is still using the amateur satellite service.
> 
> 
> Using CDMA would be beneficial for sharing the spectrum, but required coordination as well. I was trying to standardize the parameters (for QB50), so the IARU could be handing out orthogonal codes to satellite teams, so avoid clashes. But welcome to politics.....
> 
> 
> Wouter PA3WEG
> 
> 
> On Tue, Mar 4, 2014 at 10:16 PM, Howie DeFelice <howied231 at hotmail.com> wrote:
> 
> Yes, that is true, so are these licensed under an authority other than amateur radio ? If they aren't then my questions stand.
> 
> 
> 
> 
> Date: Tue, 4 Mar 2014 14:55:52 -0600
> 
> Subject: Re: [amsat-bb] Re: Two hundred 437 MHz satallites launch March 16 + WebSDR
> 
> From: damonwa4hfn at gmail.com
> 
> To: howied231 at hotmail.com
> 
> CC: amsat-bb at amsat.org
> 
> 
> 
> 70 CM is not just for the ham bands, it is a shared band check the ruleswa4hfn Damon
> 
> 
> 
> On Tue, Mar 4, 2014 at 2:30 PM, Howie DeFelice <howied231 at hotmail.com> wrote:
> 
> 
> 
> Is CDMA an authorized emission type for the Amateur service? What is the chipping rate/bandwidth of these? Don't the PRN sequences need to be made public so as not to be classified as "encryption" ? Detailed specs on the Sprites is in short supply. Has anyone done a link budget, seems like allot of spreading gain is required to hear 10mW form a 300km orbit which translates into allot of bandwidth in a part of the band usually reserved for narrow band modes. The lack of transparency on many of these projects that use the amateur bands seems to run against the spirit of amateur radio in my opinion.
> 
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> Howie
> 
> 
> 
> AB2S
> 
> 
> 
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