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Re: Re: [bod] Fwd: 70 cm band plan???



The occupied bandwidth of a television signal on 434.000  violates BOTH
"protected segments" on 70cm.

73  Andy  N9AB




----- Original Message -----
From: Walter R. Jones, Jr. <wjonesjr@cdsnet.net>
To: Andrew Bachler <Andrew_Bachler@email.msn.com>
Cc: <07141939@msn.com>; Arthur H Feller <w4art@AMSAT.Org>;
<amsat-bb@AMSAT.Org>; <amsat-officers@AMSAT.Org>; <ldanna@teamvideo.com>;
<ldanna@news.teamvideo.com>; <ldanna@home.com>
Sent: Tuesday, December 14, 1999 5:42 AM
Subject: Re: [amsat-bb] Re: [bod] Fwd: 70 cm band plan???


> Andy,
>
> I read 97.205 Repeater Station subparagraph (b)
>
> " A repeater may receive and transmit only on the 10m and shorter
wavelength
> frequency bands except the . . . . . 431.0 ~ 433.0 MHz and 435.0 ~438.0
> segments."
>
> As I read it, it leaves the 434.0 MHz open for repeater operations, either
input
>
> or output.  I may be reading it wrong and open to inputs.
>
> 73
> Walt
> KC7HEX
>
> Andrew Bachler wrote:
>
> > This is actually a very easy problem to solve.  Look at  97.205 (b).
Any
> > ATV repeater with a receive input on 434.000 MHz  violates the FCC
rules.
> >
> > Andy  N9AB
> >
> > ----- Original Message -----
> > From: Arthur H Feller <w4art@AMSAT.Org>
> > To: <07141939@msn.com>
> > Cc: <amsat-bb@AMSAT.Org>; <amsat-officers@AMSAT.Org>;
> > <ldanna@teamvideo.com>; <ldanna@news.teamvideo.com>; <ldanna@home.com>
> > Sent: Tuesday, December 14, 1999 3:56 AM
> > Subject: [amsat-bb] Re: [bod] Fwd: 70 cm band plan???
> >
> > > Hi, Gene!
> > >
> > > Robin Haighton, VE3FRH, asked me to take a shot at answering your call
for
> > > help.  Let me see what I can do.
> > >
> > > As I understand it, the heart of the problem is summed up in these two
> > > paragraphs.
> > >
> > > > >The second group is proposing a second ATV repeater for 70 cm. They
> > have
> > > > >selected a frequency pair which includes a wide-band  TV
(fast-scan,
> > full
> > > > >color) input frequency at 434.000 MHz. The local ATV activity with
a 6
> > MHz
> > > > >bandwidth would/could prevent weak signal reception from
satellites. I
> > am in
> > > > >a turmoil here!!! I've asked the second group to change the input
> > frequency
> > > > >with no avail.
> > > > >
> > > > >I have heard that "ARRL or the FCC" has indicated a band-plan for
70
> > cm, but
> > > > >no one here seems to be paying attention to my thoughts. The second
ATV
> > > > >group is preparing to request "frequency coordination" from
"T-MARC"
> >  the
> > > > >local repeater coordinator). I have attended the annual T-MARC
meeting
> > today
> > > > >and they indicated little or no objection to the requested 434.000
MHz
> > input
> > > > >frequency. I need some help here to convince all that "a bad choice
is
> > in
> > > > >the making".
> > >
> > > Some thoughts for you.
> > >
> > > ARRL does have a suggested band plan which is published in several
places
> > > including the repeater directory, last I checked.  Within this band
plan
> > > are some local options which are considered by the frequency
coordinating
> > > committee.  And, there is the band from 435-438 MHz for the
> > > amateur-satellite service.
> > >
> > > FCC respects local frequency coordinators for repeaters and auxiliary
> > stations.
> > >
> > > However, every amateur radio operator signs away the right to any
specific
> > > frequency as a condition of application.  Sharing is the order of the
day.
> > >
> > > Now, there are some technical considerations.  First, is the ATV power
> > > spectrum.  While the total bandwidth of an ATV signal may be on the
order
> > > of 6 MHz, the power spectrum in not uniform.  Most of the energy in
common
> > > vestigial sideband NTSC color tranmissions is concentrated at three
> > > points.  One is at about 1.25 MHz from the bottom of the 6 MHz
"channel"
> > > for the visual carrier and it's most significant sidebands.  The vast
> > > majority of the sideband energy is most likely to occur within about
+/- 1
> > > MHz of the visual carrier.  The other two are the color subcarrier at
> > about
> > > 3.58 MHz above the visual carrier and the aural (sound) carrier at 4.5
MHz
> > > above the visual carrier.  What's important here is that, while the
power
> > > from an ATV station in the band 435-438 MHz is not zero, it may be low
> > > enough to be tolerable.
> > >
> > > How can you tell what will be tolerable?  This is a normal exercise in
> > > checking compatibility.  You'll have to look at your own station with
its
> > > directional antenna, where the antenna is likely to be pointing, and
the
> > > signal you'll be receiving and transmitting.  (Yes, transmitting!  You
may
> > > be a source of interference to the ATV repeater.)  Then, repeat the
> > > exercise for nearby ATV stations.  (You may have to go a ways to find
one
> > > as they're not all that common even in our neighborhood.)  Keeping in
mind
> > > the power within the bandwidth of your receiver, figure out how the
power
> > > received from the unwanted station will compare to the signal you want
to
> > > receive.
> > >
> > > Clearly, if you have an ATV station next door, you're much more likely
to
> > > have a problem.  But, as mentioned, that isn't too likely.
> > >
> > > Just run the numbers and see how it comes out.  The ATV repeater folks
> > > should be doing the same thing as they will have to deal with you as a
> > > source of interference as well.
> > >
> > > Then, there's the time factor.  Neither you nor nearby ATV stations
will
> > or
> > > should be on the air 100% of the time.  So, there may be more sharing
> > > opportunities here.
> > >
> > > Would it be wiser for the ATV'ers to look to wider bands like 902-928
MHz
> > > or 1240-1300 MHz or other bands?  Sure.  These bands could stand some
> > > heavier use to help justify their existence in the minds of those who
look
> > > at such things.  Probably so.  But, do the ATV'ers have to look beyond
the
> > > 420-450 MHz band?  No.  Not at all.
> > >
> > > The resolution of this problem is most likely to be by means of mutual
> > > enlightened self interest.  Both you and the ATV group need to find a
way
> > > to get along.  Technically, that may well be possible.  You'll both
have
> > to
> > > run the numbers taking into account frequency, power density, receive
> > > bandwidth, time, space, and other relevant factors.  T-MARC may be
able to
> > > lend a hand.  (I'm sending a copy of this to a friend who is a
member.)
> > >
> > > This may not be the answer you were seeking.  But, I believe it's
> > > realistic.  I hope it helps.
> > >
> > > 73, art.....
> > > ----
> > > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> > >
> >
> > ----
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>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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>



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