I don't think we should be asking the FCC for a specified bandwidth limit at
this time. Our actions should be geared toward getting
the FCC to dismiss the ARRL proposal.
Don AA5AU
-----Original Message-----
From: RTTY [mailto:rtty-bounces@contesting.com] On Behalf Of Kai
Sent: Saturday, November 23, 2013 10:01 AM
To: rtty@contesting.com
Subject: Re: [RTTY] ARRL attack on current RTTY users
Hi Joe,
I was referring to the future, not the past. We DO want to keep the door open
to innovation. That's why I agree that getting the
baud language out of the regs is good. But I also think that 2800 Hz BW is a
bit over the top, except perhaps up where "image" is
permitted. The number should be lower, but how low?
Perhaps this forum can home in on it.
Again, to keep what we can do today, (up to the 300 baud RTTY with up to
1000 Hz shift) would require a bandwidth of
300+1.2(1000) = 1500 Hz. THAT is the current RTTY teleprinter mode limit
So, the question boils down to: do we want more
restrictive regs?
My point about how we use PSK and JT modes was a bit more subtle. One has to
consider how those modes are used.
Each of the TRANSMISSIONS are indeed below at least 500 Hz. But PSK and JT were
designed to operating RECEIVING multiple users over
a 2-4 kHz band.
We all mostly cooperate and that system works. It is because of the need for
2-4 kHz "subbands" on RECEIVING the multiple PSK and JT
signals, that we would NOT want band-hogging 2800 Hz signals in the non-phone
non-image ranges.
Common practice for PSK and JT type modes is to operate at low transmit power.
It's an argument against 2800. And it is a argument that could be made to the
Commission.
Oh, while I think of it, the 60 m band channels are not a good example of where
2800 Hz
is now permitted because (1) they are channelized, and (2) modes like PSK and
JT (also
CW) can not be operated according to standard amateur practice, that is,
anywhere in the channel, with the efficiency of multiple
users.
Summary:
1- The argument for 2800 Hz is not substantiated by the ARRL, even with
reference to 60m.
2- Currently regs permit RTTY parameters for up to 1500 Hz BW ("Steam-RTTY" is
250 Hz).
3- Amateur practice must consider customary RECEIVE bandwidths for digital
modes (not just TX)
which may be impacted by wide-band transmissions
73
Kai, KE4PT
On 11/23/2013 12:10 AM, Joe Subich, W4TV wrote:
>
> > 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@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/rtty
>>>
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