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[Ham-80211] HSMM: 420-430 MHz

Ron Olexa golexa at charter.net
Fri Mar 4 20:40:00 UTC 2011


Just a point of clarification,  ATSC does not use COFDM.  It uses 
8VSB  8 level vestigial sideband modulation.  The European DVB-T 
standard is OFDM based




At 03:12 PM 3/4/2011, Brian Webster wrote:
>While I would agree that it is nice to push the limits, I would further look
>at the rules to determine what modes or modulation formats are allowed for
>image communications just to make sure they don't specifically state them.
>
>Thank You,
>Brian N2KGC
>
>-----Original Message-----
>From: ham-80211-bounces at tapr.org [mailto:ham-80211-bounces at tapr.org] On
>Behalf Of kb9mwr at gmail.com
>Sent: Friday, March 04, 2011 2:01 PM
>To: ham-80211 at tapr.org
>Subject: Re: [Ham-80211] HSMM: 420-430 MHz
>
>You are correct there is a 56 kilobauds speed or maximum bandwidth of
>100 kHz for 222-450 MHz.  (On all frequencies 902 MHz and above there are no
>speed or bandwidth limits.)  However for 70 cm there is no bandwidth limit
>for image communications.
>
>Interestingly enough the ATSC digital TV standard uses Coded orthogonal
>frequency-division multiplex (COFDM)
>
>A 802.11a/g OFDM modem would be a J2C (fax) or J2F (video) emission.
>The word image encompasses both television and facsimile.  Basically the
>rules permits you to transmit images information using essentially any
>modulation method.
>
>John Stevensen, KD6OZH was the first that I know of to start development of
>a 70 cm OFDM Modem see:
>
>K8OCL & KD6OZH "28 kbps to 9 Mbps UHF Modems for Amateur Raio Stations," QEX
>Mar/Apr 2005
>
>Since I have a camera on my tower, I am willing to push the envelope on some
>rather antique rules and bandplans at the expense of helping show that some
>experimental uses can help bring new life to underutilized spectrum.
>
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