Comments to Draft Version 2.0 by Sutron Corp. 7 July 2006

## 1) Reporting time accuracy (Section 2.1).

1200 BPS.

Currently the specification is 0.1 seconds. I see no valid reason to
loosen this to 0.25 seconds. All vendors are currently achieving 0.1
seconds. There could be future applications where 1200bps is placed in
less than 5 second windows.maybe even 2 or 3 second windows... If you
have +/- .25 second accuracy, that corresponds to .5 seconds wasted for
every window. Therefore, a 5 second window would waste 10% of the
available bandwidth just due to this wide specification. The previous 5
or so years of field experience have indicated that it is not a
challenge to achieve less than 0.1 second accuracy.

300 BPS.

The old spec is 15.0 seconds per year (or so). The proposed spec is now
+/- 0.25 seconds, period, under all conditions. I would make the same
argument that if the 0.1 second is ALREADY easily achievable, than we
should not settle for .25 second slop. In the last several TWG meetings,
it is now obvious that users are wishing to push more data in their 5
second window, and wasting more of the window to slop is
counterproductive. If anything, we should be looking at tightening the
requirement to .1 second or even better! While we know currently NESDIS
has 1 second timing resolution on the receive path, this may likely
change in the next generation DAPS in several years to support
millisecond receive timing accuracy. Finally, when down the road NESDIS
adopts a binary transmission only mode of operation (I think this would
be a good idea) then having in place the tighter (read hardware)
transmission accuracy will allow for easy and fast adoption without
having to create special channels, move DCPs around etc...

Final comment is that the .1 second is not challenging to achieve!
EVERYONE IS ACHIEVING IT NOW (maybe with a few exceptions...)

## RF POWER OUTPUT (Section 4.1.1).

While you have stated that this is under review currently, I believe
that the proposed limits are too tight if you consider all real world
contributions.

For example, if axial ratio is to be included in the EIRP limits, then
the +/- 1 dB is not a practical range. To cover the axial ratio, a +1/-3
dB limit may be used. ( or a larger range..).

If the power 'range' specification is to only reflect the RF power out
of the transmitter (i.e. not any antenna or cables), consider +1/-2 dB.

Given the satellite link budget improvements on the horizon, I do not
see any large problem with allowing for larger power variation as long
as the maximum is not exceeded.

Final comment, do we need the minimum spec at all? Allow operators to
judge benefits and risks for their program.

## RANDOM TRANSMISSION LENGTH (Section 2.2)

While we do not have any real concern about the 1.5 and 3 second
proposed limits on random transmissions from a manufacturer's
standpoint, have the users considered the impact of this on their
programs? Various governmental agencies might want to consider this
limit for their programs.

How did the 1.5 and 3 second recommendation come about and is there any
reasoning for choosing the value? The reason that this is asked is that
there is roughly twice the data amount allowed under the 1200 bps mode.

Finally, please clarify the "message length" to be either the entire
formatted message including carrier, etc vs. simply the DCP data field.
The terminology lacks a little clarity.

## RF POWER OUTPUT. (Section 4.1.1)

This section neither allows nor disallows the concept of users adjusting
the power of the transmitter in the field. A manufacturer could allow
the user to menu select the antenna, either a 11 dB gain, maybe a 7 dB
gain, or a 3 dB gain type, and the transmitter would put out the exact
power to achieve the correct uplink. Alternately, he could select
different power levels for different cable lengths, etc also uplinking
the correct power. One could even argue to put a physical knob on the
outside of the box to adjust things.

The problem with any of the above concepts is that users can either
accidentally select the wrong selection, or the user could willfully set
the power higher in hopes to 'come in stronger...' Not all field users
are completely aware of the consequences of too much uplink power.

I think the specification should make an effort to clearly define
whether this concept of adjustability is allowed. My thought is that it
would be better to have a fixed power output with a fixed antenna. Less
chance of errors.

## Sidebands (Section 4.5)

In the picture below, this simulates an adjacent 300 bps channel where
both are at 125 Hz error in the worst case sense drawn on the new 750 Hz
spacing. This clearly places some first sideband energy in the main lobe
of the second channel. The first question is will this either cause the
demod to lockup on the adjacent channel or potentially cause phase
errors with an active adjacent channel.

One recommendation is to drop the first sidebands by an additional 10 dB
instead of relying on the NTIA spec. The additional 10 dB should be
easily achievable with the new recommended filtering techniques (RRC).
Currently several manufacturers may already achieve this. There are not
any significant issues with power amplifiers and the necessary power
backoffs to achieve this as the costs and power are insignificant....

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