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Re: ATV + Missed sked(s) on AO-27

A couple of points to your question about ATV.  ATV simplex in the San
Francisco Bay area is on 434.0.  I dont know of anyone in the country on 433.1
except for maybe some bootleggers (and there are a lot of them if you see the
ads in the security magazines and they have gotten into our repeaters).
Simplex ATV or any other mode is not prohibited in the 431.0-433.0 and
435.0-438.0 but not a good idea and none of the local band plans in the USA
that I know of would do that.
There are ATV repeaters that use 434.0 for input only and rarely interfere
with satellite operation due to the low spectrum power density +/- 1 MHz from
the video carrier - see ARRL Handbook ch12 pg 48 spectrum analyzer pix.  While
a video channel is 6 MHz wide, 95% of the AM video modulated power is within
this 1st MHz around the carrier.  The energy within the satellite and weak
signal segment when using 434.0 is typically below 40 dBc and therefore below
the FCC definition of bandwidth which is 26 dB below mean transmitted power.
A TV receiver on the other hand has to have the instantaneous response time of
around 3 MHz for lumenance video components.
What you may be hearing in your area is the Pave Paws Radar from Beal AFB.  I
suggest getting on the Mt. Diablo two meter repeater on 147.06 and asking if
there are any ATVers on in your area that might be on 434 at the time that you
experience the interference.  I dont know of any problems with ATVers on 434
here in So. Calif. interfering with some one receiving satellites on 436
except once when the two people were less than 1/2 mile apart.  I suggest
contacting the person if it is indeed a ham near you and working out an
operating time arrangement like they did here - each mode knows the others 2
meter calling frequency and work it out.
Tom O'Hara W6ORG
ARRL Technical Advisor for Spectrum Management and ATV

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