:: On Mon, 8 Mar 2021 10:41:05 +0100
:: (it.hobby.radioamatori)
Post by Arne SaknussemmHai usato un optoisolatore per ALC ? Non per altro, ma sospetto che i
voltaggi non siano esattamente compatibili :D
controllando il manuale dell'ampli
https://www.qsl.net/ea4bb/EA4BB/Old_Radios_files/L7.pdf
in riferimento all'AGC (ALC), si legge
======================================================================
"The transmitting AGC voltage, which controls the gain of the exciter,
is presented at a connector labeled XMTG AGC OUTPUT on the rear of the
L 7. Any power level can be run up to 2000 Watts PEP without peak
cliGping. A cable is furnished with the amplifier which provides a
connection to the R. L. DrakePS-7 or AC-4Power Supply. This connection
is routed through the power supply to the transmitter."
"The Drake TR 7 and some other exciters utilize transmitting AGC,
sometimes called ALC, during all modes of operation. During tune up,
transmit- ting AGC will have to be defeated either by un- plugging the
transmitting AGC connector, or by turning the AGC control fully
counterclockwise. All Drake Transmitters and Transceivers except the TR
7 and 2NT (which has no transmitting AGC) switch off AGC in TUNE, CW
and AM modes. It is not necessary to defeat AGC exter- nally on Drake
Transmitters, other than theTR-7"
"The AGC threshold needs to be set once on each band"
"When the negative-going peak RF voltage from the capacitor divider
C17 and C18 exceeds the positive bias set by R4, the transmitting AGC
threshold control, CR1 conducts and a negative voltage proportional to
the RF signal applied to the input appears at the transmitting AGC
output connector."
======================================================================
Ora, leggendo l'ultima nota, l'ALC fornisce un voltaggio negativo, ma
non è specificato il range di tale voltaggio e, sebbene si possa
ricavare, credo sia un'idea migliore usare un circuito "buffer" tra
l'amplificatore ed il trasmettitore, sia per isolare i due, sia perchè
tale circuito potrebbe prevedere un trimmer che permetta di aggiustare
i livelli ed eventualmente (vedasi la seconda nota) di escludere del
tutto l'ALC quando necessario