[RTTY] ARRL attack on current RTTY users

[Joe Subich, W4TV]

 > Additionally, modes like PSK31 (63 Hz necessary BW on TX) and JT65
 > (170 Hz BW on TX) are actually practiced by hams as multiple users in
 > a 2-4 kHz BW subband. Individual TX BWs are small, but general usage
 > is for multiple simultaneous decodes in a contiguous BW. I guess that
 > this is the kind of innovation and usage that we don't want to shut
 > ourselves out of.

Asking for a 500 Hz bandwidth limit in the current "RTTY, data"
allocations below 30 MHz would not "shut out" any of the modes
like PSK31, JT65, JT9, WSPR or QRSS ... I doubt that 500 Hz would
shut out PSK63, PSK125 or some of the narrower MFSK modes either.
These narrow modes - traditional RTTY at 45.45 and 75 baud, PSK31,
JT65, JT9, WSPR and QRSS - represent well in excess of 90% of all
HF digital operators and QSOs over the course of a month or year.

300 Hz or 500 Hz is consistent with "traditional radiotelepriner
bandwidths" which is what the FCC, themselves, defined as the
criteria for establishing the 300 baud limit in 1980.  It is also
compatible with the overwhelming majority of *all* amateur activity
(including CW) in the spectrum allocated for "RTTY, data" operation.
I think it is incumbent on both the general digital operator and CW
operators to convince the FCC that we *still* want the bandwidth to
be consistent with "traditional teleprinter bandwidths" and that
there is no overwhelming need for wider bandwidth.

Again, if ARRL can justify a real need (which is doubtful due to
the overwhelming use of narrow bandwidth modes) for wider data
modes, they should petition the Commission to authorize "RTTY, data"
modes in the current "phone, image" portions 75, 40, 20, 17, 15, 12
and 10 meters with a bandwidth of "up to" 2.8 KHz - comparable to
the bandwidth of "phone, image" modes.

73,

    ... Joe, W4TV


On 11/22/2013 5:00 PM, Kai wrote:
> EXACTLY!  I've brought this up obliquely before, but in more detail
> here:
>
> BW limit means "occupied BW" defined as  less than 0.5% of power is
> below and less than 0.5% power is above the bandwidth. There is also
> necessary BW. See the regs, see 47 CFR 2.202 (a) and (b). In the case
> of two tone amateur RTTY (or using Chen's affectation "steam RTTY"),
> that means the BW=B+1.2S where B is the baud rate and S is the shift.
> The common 45.45B 170S works out to 249.45 = 250 Hz necessary BW.
>
> So 1000 S at 300 B works out to be 1500 Hz necessary BW. That is a
> nice possible limit since it parrots the current regs for RTTY as 300
> baud limit and max 1000 Hz shift. I won't debate whether that is
> needed or even used, but it is currently permitted.
>
> The lowest order  PACTOR-III SL1 mode has 100+1.2(840) = 1108 Hz
> necessary BW, the highest order PACTOR-III SL6 is 100+1.2(2040)= 2448
> Hz. There are four levels in between. The lowest order PACTOR fits in
> the 1500 BW.
>
> The FCC/NTIA and ITU-R publish guide lines on computing required BWs.
> See US 47 CFR 2.201-2.202-emission designators, modulations and
> necessary BW. Our 47 CFR 97 points to that.
>
> We indeed need to be careful about what we ask for!
>
> Additionally, modes like PSK31 (63 Hz necessary BW on TX) and JT65
> (170 Hz BW on TX) are actually practiced by hams as multiple users in
> a 2-4 kHz BW subband. Individual TX BWs are small, but general usage
> is for multiple simultaneous decodes in a contiguous BW. I guess that
> this is the kind of innovation and usage that we don't want to shut
> ourselves out of.
>
> 73 Kai, KE4PT
>
> On 11/22/2013 2:51 PM, Bill Turner wrote:
>> I am a little surprised that no one has brought up the question of
>>  measuring bandwidth. We need to be careful what we ask for - we
>> just might get it.
>>
>> If the FCC should establish a bandwidth limit of 500 Hz, what
>> exactly does that mean? Does that mean that all tones AND SIDEBANDS
>> must be within the 500 Hz? Or does it mean that the shift of a
>> signal must be within 500 Hz but the sidebands can be outside 500
>> Hz?  And if the latter, how many dB down must they be?
>>
>> You may recall that the "real" bandwidth of a 170 Hz shift RTTY
>> signal is approximately 300 Hz because of the sidebands.  Given
>> that, what is the real bandwidth of a mode that claims to occupy
>> 500 Hz, such as Olivia 500/16?
>>
>> This needs to be settled before the rule is made by the FCC,
>> otherwise chaos will surely follow.
>>
>> 73, Bill W6WRT _______________________________________________ RTTY
>> mailing list RTTY at contesting.com
>> http://lists.contesting.com/mailman/listinfo/rtty
>>
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