Bob, Fred is wrong about 97.307(f)(2). It only applies in the subbands shown in 97.305(c) with “(2)” in the third column. It does not apply in the RTTY/data subbands. Understanding this is important because it’s why a bandwidth limit needs to be specified in 97.307(f)(3). Otherwise, exactly what some people fear would continue (and I emphasize continue) to be true: a data emission could be 6 kHz or 12 kHz wide and be legal as long as the symbol rate is no more than 300 baud, a condition that is easily met with OFDM.

Dave K1ZZ

From: arrl-odv-bounces@reflector.arrl.org [mailto:arrl-odv-bounces@reflector.arrl.org] On Behalf Of Vallio, Bob, W6RGG
Sent: Wednesday, December 11, 2013 11:56 PM
To: arrl-odv
Subject: [arrl-odv:22143] Fwd: Fw: [NCCC] FCC NRPM RM-11708

Greetings,

I have known Mr. Jensen for some time.  He is a learned man, and a gentle man, and can be relied upon to provide a careful evaluation for any problem which comes his way.  His explanation of RM-11708 is the first that I have seen which makes me feel like I really know where we are going.  Is there some way "we" can provide a similar, if not identical, explanation for all who have questions.  I believe Fred would authorize our use of this material, if he were but asked.  I'll be happy to do so.

Bob Vallio -- W6RGG

----- Forwarded Message -----
From: Fred Jensen <k6dgw@foothill.net>
To: nccc@contesting.com
Sent: Wednesday, December 11, 2013 4:30 PM
Subject: Re: [NCCC] FCC NRPM RM-11708

On 12/11/2013 10:30 AM, Jim Brown wrote:
> I am VERY concerned about ARRL's NPRM for several reasons. First, and
> most important, the proposed rule making would allow 2.8 kHz digital
> signals for our entire allocation.Allowing 2.8 kHz bandwidth in the CW
> bands would almost certainly result in the death of CW contesting, CW DX
> chasing, and even casual CW.
>
> Second, I agree with Steve's observation that 2.8 kHz is far too
> generous, and fails to challenge developers of systems to work with less
> bandwidth. Consider, for example, what can be done with PSK, and with
> K1JT's various protocols.
>
> Third, if you think we have a problem with the ATV crowd on 20M SSB now,
> just wait until hundreds of 2.8 kHz digital signals (and various
> modulation schemes) stake out their territory.
>
> The only good I can see with implementation of this proposal is that it
> could also spell the death of the mindless crap on our 75M and 20M phone
> bands.
>
> This NPRM filed by ARRL is a train wreck, and we ought to be filing
> comments against it. The deadline for doing so is Dec 21. Note the link
> below for AA5AU's guide on how to comment.

Hmmm ... trying out a new analysis technique ["actually find and read the ARRL petition" :-)], I *think* the following are facts:

1.  The petition removes the symbol rate limits from 97.307

2.  The petition does NOT change 97.305 which specifies the permitted emissions by band segment.

3.  PACTOR 3 has a symbol rate of 100 and an occupied bandwidth of 2.4KHz, and currently is a permitted emission type.  I'm pretty sure it's what I often see [on the P3] up in the regions where we tend to run RTTY contests.

4.  97.307(f)(2) now limits the BW of a non-phone emission to the bandwidth of a "communications quality phone emission of the same modulation type."  That's a tad obscure, but the ARRL petition does not address this paragraph.

5.  The ARRL petition modifies 97.307(f)(3) by removing the 300 baud symbol rate and the limitation for FSK to 1KHz shift or less.  It adds the 2.8KHz bandwidth limit.  [it does the same for the following paragraphs which deal with higher symbol rates on higher frequency bands]

I am fairly certain that #1 is true.  I can't find anything in the petition that suggests #2 is NOT true.  I know #3 and #4 is true.  #5 is true by inspection of the ARRL proposed changes.  Therefore, I conclude that:

A.  The petition does not change the band segments where RTTY/data emissions are permitted.  If RTTY/data emissions are permitted now, they still will be, and if they are not permitted now, they won't be if the petition is granted.

B.  97.307(f)(2) currently limits the bandwidth of a RTTY/data emission to the bandwidth of a comm quality phone emission of the same modulation type.  Nothing would change.

C.  PACTOR 3 with a symbol rate of 100 and a BW of 2.4KHz is a legal data mode.  The petition removes the symbol rate limit [and the 1KHz FSK limit] and replaces it with a 2.8KHz BW limit for HF.  The BW limits increase on VHF and UHF too.

So, it seems that the only real change is that a symbol rate limit is replaced by a specified BW limit, 400Hz greater than a currently permitted emission.  The phone BW limits in the 5 60m channels is 2.8KHz which is probably where that BW comes from.

Despite my initial fears that this was somehow a back door into "wideband digital signals everywhere," that doesn't seem to be the case, and "train wreck" may be a little bit of an over-statement.

What am I missing here?

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org


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