[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: 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
> >
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home