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G8MNY > ATV 01.06.24 10:33l 44 Lines 1638 Bytes #999 (0) @ WW
BID : 8831_GB7CIP
Read: GAST
Subj: Hearing the ATV Buzz
Path: DB0FFL<DB0FHN<DB0RKB<DK0WUE<DK0WUE<N2NOV<K5DAT<PA8F<PI8LAP<PI8ZTM<
I0OJJ<GB7CIP
Sent: 240601/0915Z @:GB7CIP.#32.GBR.EURO #:8831 [Caterham Surrey GBR] $:8831_GB
From: G8MNY@GB7CIP.#32.GBR.EURO
To : ATV@WW
By G8MNY (New Jan 09)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Originally taken from my UK BATC's CQTV 163 "Tuning 70" of 8/93...
Trying to beam up on weak fast scan ATV signals with tight beams on a TV mon is
not that easy. Here is a way that greatly helps when you don't quiet know the
beam heading (e.g. /P). It is of no use for digital TV modes!
Take the recovered video and feed it to the TV audio stages (decent size LS or
HiFi headphones!) after some CR filtering to remove the line timebase & treble
noise.
FM SOUND >ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄo FM
SWITCH \oÄÄÄÄÄÄÄÄ>AF AMP
VIDEO >ÄÄ6K8ÄÄĀÄÄ6K8ÄÄÄĀÄÄÄo BUZZ Volume?
³ ³ BEAM UP
=== u1 === u1
________³________³________
This works by listening to the 50Hz buzz, as your ear/brain is a few dB better
than the TV sync stages. It also works on 10GHz/1255MHz FM TV just as well as
AM mode.
The extra 6k8 load on the 75ohm video line has no effect.
_
Tx ³_picture Rx °°°°°°°°°°°°°°°°° As /~\
___³ Info |_ _ °°°°±°°°°°°°±°°°° AF _ / 'ś._._./\_
Ž°°°°°°°°°°° Ž°°° ±°±±±±±±±±±±±±°±± \ / \ /
°±°°°°°°°°°°°°±°° ~-~ 50Hz BUZZ ~-~
<--- 20mS --> °°°°°°°°°°°°°°°°°Noise
This can work on any band including 70cms, although on AM a narrow band SSB/FM
phone Rx may even better if the exact carrier frequency is known!
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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