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G8MNY > ATV 14.09.25 17:11l 155 Lines 8311 Bytes #25 (0) @ WW
BID : 40727_GB7CIP
Read: JH4XSY
Subj: 23cm ATV Repeater GB3HV System
Path: JH4XSY<N3HYM<GB7YEW<GB7CIP
Sent: 250914/0800Z @:GB7CIP.#32.GBR.EURO #:40727 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : ATV@WW
By G8MNY (Updated Jun 12)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Here is a run down of what the old closed down repeater was like (site rental
rocketed). A new one exists as a much simplified Rx only internet streaming
device near Reading.
The old one was very complex repeater, it was sited on the hill @ High Wycombe
IO91OO, that has grown & grown over many years, 1985 proposed 1987 on air.
It had ATV Rx on 3 bands, 2 with intercarrier sound & 1 band with a digital Rx.
It also has 2 comms Rx channels as well. All of these control the repeater or
output on the Analogue or Digital ATV Tx. As well as RF it had an expensive
internet side with 1 way video steaming @ www.gb3hv.com
(http::gb3vh.camstreams.com) where a few broadband visitors could see & hear
live ATV.
RX SIDE
4 Switched 90�
24cm Aerials @ 20m
\ｳ/ ___ \ｳ/ _______
ﾀﾄｴPreﾃﾄﾙ __________ｳDigitalﾃﾄ>Rx Dig Vid
ﾀﾄﾂﾄﾙ ___ ____ ｳ ｳ24cm Rxﾃﾄ>Rx Dig AF
mast ﾀﾄﾄﾄﾄﾄｴampｳ_ｳFiltｳ_ﾚﾁｿsplitter ｳ_______ﾃﾄ>Rx Dig ____________
ﾚﾄﾄﾄﾄﾄｴ___ｳ ｳ____ｳ ﾀﾂﾙ _________ ｳWEAK SIGNAL ｳ
\ｳ/ﾚﾄﾁﾄｿ\ｳ/ 5 pole ｳ__ｳNarrow ﾃﾄ>24 AF Rx ｳPAL TIMEBASEｳ Good
ﾀﾄｴ___ﾃﾄﾙ ________ ｳAnalog Rxﾃﾄﾄﾄﾂﾄﾄﾄ>ﾄﾄﾄﾄo ｳRESTORER & ﾃﾄﾄ>Analog
Preampｳ ｳLOGIC AEﾃ>VIC20 ~~~~~~~~~ ﾚﾄﾄﾁﾄﾄﾄﾄｿ ﾚo <ﾄﾄｴCONDITIONER ｳ Rx Vid
DC ﾀﾄﾄﾄｴselectorﾃﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄ<ﾄﾄﾄﾄﾄﾄｴRxSyncsｳ ｳ o ~~~~~~~~~~~~
~~~~~~~~ ﾀ<Rx Dig ~~~~~~~ ｳ ｳ DTMF
13cm Yagi @19m ______ ｳ ｳ Controlled
\ｳ/ ___ ｳ 13cmsﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ>ﾄﾄﾙ ｳ Switch
ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴPreﾃﾄｴATV Rxﾃﾄ>13cms RX AF ｳ
70cm Yagi @19m ~~~ ~~~~~~______ ｳ
\ｳ/ Cam Pan ___ ｳ 70cm ﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ>ﾄﾄﾄﾄﾙ
ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴPreﾃﾄﾄﾄﾄﾄﾄﾄﾄｴATV Rxｳ _______ _______ _____
2m & 70cm ~~~____ ~~~~~~ ｳComms ｳ 24 AF Rx>ｴDTMF ｳ_ｳMENU ｳptions
\ｳ/ Colinear ｳDuplﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴ70cm Rxﾃﾄﾂﾄﾄﾄ>ﾄﾄﾄﾄｴDecoderｳ ｳLOGICｳ�
ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴexerﾃｿ ___________ ~~~~~~~ ﾀ>70cm AF ~~~~~~~ ~~~~~
@ 19m ~~~~ ﾀｴComms 2m Rxﾃﾄ>2m AF
~~~~~~~~~~~
The four 24cm (6 loop & reflector) aerials are searched one at a time for the
best picture by measuring the picture noise during the frame sync, this took
several seconds if the radar is strong, as frame lock can be difficult. If you
selected all 4 aerials or use an omni Rx aerial you are RF worse off by 6dB S/N
+ reflections!
The 1248MHz FM ATV Rx, had a radar video clipper in it & the video feeds a PAL
conditioner that can handle very weak signals of just a few dB S/N. Software in
the controlling old VIC20 also allows for DX signals by holding in repeat mode
for up to 30 seconds if the signal is persistantly fading.
Milton keynes
GB3TG 10GHz
LUTON / GB3AD 23cm
GB3TV 23cms QRP
|
GB3BH 13cms
/ GB3EN 23cms Isle of Sheppy
NEWBURY GB3HV 23cm GB3KT 23cms
_ _ .- -'~~
GB3FT 13cm
(test only) L O N D O N
GB3AT 23cm
SOUTHAMPTON GB3VR 23cm GB3VX 23cm
BRIGHTON
The 13cm Rx system pointed at GB3BH, that can see 23cms ATV repeater GB3TV etc.
So manually controlled forward linking was possible, but active onward link
control was not possible.
The 2m & 70cm comms Rx could both be QSYed a few channels from DTMF menu.
____________________
DTMF > Keyboard wires >ﾄｴ VIC20 ﾃﾄ>Vic Vid
Joystick input (Pmeter)>ﾄｴ Computer ﾃﾄ>Vic AF
ﾀﾂﾄﾄﾄﾄﾂﾄﾄﾄﾂﾄﾄﾄﾂﾄﾄﾄﾄﾂﾂﾙ
Parallel I/F VCR TX Rx Test AE
Timeout Sync card info
The very old but highly reliable VIC20 runs things (PCs crash, VIC 20 not!), &
provides a carousel of 12 pages when in beacon mode, including control of the
seperate the testcard generator. The DTMF menus were all in hardware & menus
seen were from the testcard generator multiple EPROM system. DTMF menu options
have sound confirmation was by G8MNY's voice recorded in EPROMs.
An old V2000 format VCR had been wire up to record the 1st 10 mins of ATV
activity, unless it is a SUNDAY RSGB news time, when the 10 min limit was
suppressed.
All video sources were DTMF controlled from hardware menus. The video switcher
had all inputs DC clamped so there was no DC thumps & Tx PLL off lock when
switching sources.
VIDEO SOURCES MATCHING AF1 SOUND SOURCE AF2
VIC20 Computer ﾄo o- VIC20 ID + Rx Sync Tones 2m AF
Test card gen ﾄo <ﾄﾄTxﾄﾄ> o- VIC20 ID + Rx Sync Tones 2m AF
Analog Rx (23) ﾄo o- VIC20 ID + 24 AF Rx 2m AF
" " (13BH) -o o- VIC20 ID + 13 AF Rx 2m AF
" " (13FT) -o o- " " " " " " "
" " (70) -o o- VIC20 ID + 70cm AF 2m AF
Digital 23cm Rx -o o- VIC20 ID + Dig Rx AF 2m AF
V2000 VCR Replay -o o- VIC20 ID + VCR AF 2m AF
Shack Camera -o o- VIC20 ID + Shack Mic 2m AF
Security " " -o o- VIC20 BERP + Shack Mic Shack Mic
Mast Camera @ 20m -o o- VIC20 ID + 70cm AF 2m AF
Internet Video PC -o o- VIC20 ID + Internet PC AF 2m AF
TX SIDE
This was on 1308MHz which was the only frequency available 27km away fro
London Heathrow 530MW ERP 4 channel Radar (Primary User).
4 90� 23cms
Aerials @ 22m
\ｳ/ \ｳ/ ______ ___ 1308 _____ 70 ___ PQ _____
ﾀﾄﾄ[]ﾄｴFilterﾃｴPA1ﾃｿ ______ MHz ﾚｴXvertﾃﾄﾄﾄｴModﾆﾍﾍｵMPEG ﾃﾄ<AF1
~~~~~~ ~~~ﾚﾁｿ_ｳDriverｳDigital oﾙ ~~~~~ MHz~~~ ｳCODERﾃﾄ<AF2
\ｳ/ \ｳ/ ______ ___ﾀﾂﾙ ｳ PA ﾃﾄﾄﾄﾄﾄﾄﾄ/oｿｳ~~~~~ﾃﾄ<AF1 ｳ_____ﾃｿ ______
ﾀﾄﾄ[]ﾄｴFilterﾃｴPA2ﾃﾙ ~~~~~~ Analog ﾀｴFM Txﾃﾄ<AF2 ________ ﾃｴT.B.C.ﾃ<VID
mast ~~~~~~ ~~~ DTMF MENU ｳ_____ﾃﾄﾄﾄ<ﾄﾄｴTELETEXTﾃﾄｴ ~~~~~~
splitters ________ ~~~~~~~~ ｳ
Broadband link <ﾄｴInternetﾃﾄﾄ<ﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾙ
ｳ PC ﾃﾄ<AF1&2
~~~~~~~~
Two FET PAs were used, & were linear enough to handle QPSK digital Tx at only
a couple of dB down on the satuated FM output. As the MPEG coder can only
encode full spec video a Time Base Corrector is used to clean up all the Tx
sources to full TV spec. The encoder generates P & Q data streams that drove
the 70MHz QPSK modulator, its output was transverted to 1308MHz. As the main
mode is FM, users had to DTMF to digital mode, which lasts until 1 or 2 of 15
min testcard idents were done.
Only the analog Tx system could handle the 7Mb/s 100 page Teletext signal so
that is inserted into that path only. Two sound carriers were used, a HiFi one
@ 6MHz @ -17dBc & a comms quality one @ 5.5MHz @ -20dBc (not Sat Rx freq). As
there was potential with a 1308MHz FM Tx with 6MHz sub-carrier to generate
significant -12MHz (1296MHz) noise, a cleaver 2nd harmonic subcarrier (both for
5.5 & 6MHz) phasing system is introduced to null out much of the 1296MHz
products, this was in addition to the 3 pole Tx filters.
________ __________
RF /_ｳ UHF FM ｳ_______________________ﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂｴ 6MHz Mod ﾃﾄ<AF1
Buffer\ ｳModultorｳ ｳ _ｳ____________ ｳ ___________ ｳ ~~~~~~~~~~
~~~~~~~~ DC^ ｳVideo Filter &ｳ ﾃ<ﾄｴ12MHz Phaseﾃﾄﾙ
from PLL ｳ Pre emphisis ｳ ｳ ~~~~~~~~~~~ __________
~ｳ~~~~~~~~~~~~ ﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂｴ5.5MHz Modﾃﾄ<AF2
ﾀ<Video ｳ ___________ ｳ ~~~~~~~~~~
ﾀ<ﾄｴ11MHz Phaseﾃﾄﾙ
~~~~~~~~~~~
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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