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G8MNY > ATV 13.08.25 17:08l 43 Lines 1637 Bytes #15 (0) @ WW
BID : 38621_GB7CIP
Read: JH4XSY
Subj: Hearing the ATV Buzz
Path: JH4XSY<IW0QNL<HB9ON<DK0WUE<ZL2BAU<VK3AT<K5DAT<W0ARP<VK2RZ<GB7CIP
Sent: 250813/0805Z @:GB7CIP.#32.GBR.EURO #:38621 [Caterham Surrey GBR]
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 >ﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄo FM
SWITCH \oﾄﾄﾄﾄﾄﾄﾄﾄ>AF AMP
VIDEO >ﾄﾄ6K8ﾄﾄﾂﾄﾄ6K8ﾄﾄﾄﾂﾄﾄﾄo BUZZ Volume?
ｳ ｳ BEAM UP
=== u1 === u1
________ｳ________ｳ________
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 ｳ_picture Rx ｰｰｰｰｰｰｰｰｰｰｰｰｰｰｰｰｰ As /~\
___ｳ Info |_ _ ｰｰｰｰｱｰｰｰｰｰｰｰｱｰｰｰｰ AF _ / '�._._./\_
ﾞｰｰｰｰｰｰｰｰｰｰｰ ﾞｰｰｰ ｱｰｱｱｱｱｱｱｱｱｱｱｱｱｰｱｱ \ / \ /
ｰｱｰｰｰｰｰｰｰｰｰｰｰｰｱｰｰ ~-~ 50Hz BUZZ ~-~
<--- 20mS --> ｰｰｰｰｰｰｰｰｰｰｰｰｰｰｰｰｰ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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