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

A few years ago I inquired of John Johnston at the FCC about the issue of
ATV repeaters operating on 434.0 MHz.

His reply was short and to the point.  He quoted 97.205(b) which excludes
431.0 to 433.0 and 435.0 to 438.0.  He did not mention relative power levels
or potential interference possibilities.  He stated that the rules had not
changed on this in recent years and no further comment was needed.  I do not
still have the verbatim text of his message or I would attach it here.

The issue seems clear to me.  The FCC does not allow repeater pass bands to
include the stated frequencies.  No discussion needed.

Harold Reasoner, K5SXK

-----Original Message-----
From: Arthur H Feller <w4art@AMSAT.Org>
To: 07141939@msn.com <07141939@msn.com>
Cc: amsat-bb@AMSAT.Org <amsat-bb@AMSAT.Org>; amsat-officers@AMSAT.Org
<amsat-officers@AMSAT.Org>; ldanna@teamvideo.com <ldanna@teamvideo.com>;
ldanna@news.teamvideo.com <ldanna@news.teamvideo.com>; ldanna@home.com
Date: Monday, December 13, 1999 11:11 PM
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
>> >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,
>> >color) input frequency at 434.000 MHz. The local ATV activity with a 6
>> >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
>> >with no avail.
>> >
>> >I have heard that "ARRL or the FCC" has indicated a band-plan for 70 cm,
>> >no one here seems to be paying attention to my thoughts. The second ATV
>> >group is preparing to request "frequency coordination" from "T-MARC"
>> >local repeater coordinator). I have attended the annual T-MARC meeting
>> >and they indicated little or no objection to the requested 434.000 MHz
>> >frequency. I need some help here to convince all that "a bad choice is
>> >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
>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
>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.
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