davenn said:ok now that we have confirmed what you are talking about
just call it a TV tuner module ... can-tuner... had us all guessing
the majority of them are electronically tuned. 3 of the pins are for the 3 bands (VHF-L VHF-H and UHF) tuning voltage supply. The tuning voltage range is usually 0 - 30V ie. 0V = lowest freq in that band, to 30V = highest freq in that band
Other pins will be for IF out, B+ supply and AFC, maybe another couple of things
look on the tuner module or on the PCB the pin outs are usually labelled
cheers
Dave N
Added after 13 minutes:
further to my previous comments.....
on the much older TV's and VCR's there were individual trimpot resistors
say ~ 8 of them that you would individually adjust for each channel position.
they provided the set voltage for that channel that was switched to.
in the newer TV's etc.... those tuning voltage control settings for each tuned channel are stored in the processor/flash memory chip and when accessed switch the appropriate voltage to the appropriate band tuning input on the tuner module.
Dave
LNA said:Thanks, Dave. I feel better, but still a lot questions,
I think that you confirmed the LO tuning. There should be a RF tunable filter in the front for every channel, with ~5MHz bandwidth, right?
LNA said:How does the RF filter work in older TV? Are they mechaniclly tuned? Is there RF switch for channel switching?
FvM said:Because it's a superhet receiver, the adjacents channel rejection is mainly defined by the IF filter, not the tuner module.
The tuned input filter is responsible for the foreign channel large signal strength.
There are no "silicon tunable filters". Single chip receivers are either using tuned LC filters or operating as wideband
superhet receiver with IF selection only.
LNA said:
FvM said:The vendor says "wideband filter", most likely a variable active filter. The xceive products are different from common silicon tuner chips.
BigBoss said:LNA said:
It's a tracking filter.This filter select the desired channel and prevent the LNA from adjacent channel interference and other interefere sources.
It consists of a switched capacitor bank and probably bonding inductances.By digitally selecting proper capacitor value, inductance will be resonated with this capacitor at the center of the desired frequency.
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