L-band, local oscilators, and receiver settings.

[ynnedibanez]

hey guys, a question for anyone in-the-know,
why does a receiver need to know what the local oscillator frequency is?
the output of the lnb or lnbf (for normal applications) is always in the L-band, so why does the receiver not just scan L-band and work with that?
Thanks,

Denny

 

[qwert1515]

The receiver scans the L-Band, the receiver uses the LO frequency for the users convenience to display the satellite frequency.
It also allows the user to enter a satellite frequency instead of entering L-Band frequencies.

Example:
A L-Band frequency of 955 MHz is equivalent to 11705 MHz using a Ku band LNB with a LO of 10750 MHz or it could be equal to 4195 MHz using a C-band LNB with a LO of 5150 MHz.

If I post that I am picking up a transponder at a L-Band frequency of 955 MHz, but you don't know my LNB's LO frequency you would not know what transponder I am picking up.
If I tell you that I am picking up 11705 MHz you know the exact transponder I am picking up and you or your receiver can calculate the proper L-Band frequency that it must use.

 

[ynnedibanez]

so, in theory, i should be able to enter a lo frequency of 0 and blindscan in everything that i could with the correct lo frequency, the receiver would just display the L-band frequency in place of the transponder frequency.
for some reason, that has not worked for me
when i put in a lo frequency of 0 the receiver will not blindscan in anything.
has anyone else tried this?
with success or failure?

 

[cracklincrotch]

On a number of receivers, you can set the LO to zero and it will work.

Next thing I'd try is setting the LO to one and see what that does for you. Then you'll be 1MHz off the L-Band frequency.

 

[Smith P.]

Published info for all sats describe down-link frequencies, like for OTA transmitters; all sites like Lyngsat or SatcoDX listed down-link freqs in Ku and Ka standardized (approved by ITU and FCC) ranges.
So you must know what sat/freq your tuning your receiver; knowing L-band freq is not usual for viewing sat channels.
Also, you must know LOF(s) of your LNBF(s) to correctly setup your receiver/card. It's like work with a car parts - maker, model, year, etc - to tune and fix it. Mocking instead of possession real info is not productive and don't lead to stable functioning devices like receivers or cars.

 

[ynnedibanez]

Published info for all sats describe down-link frequencies, like for OTA transmitters; all sites like Lyngsat or SatcoDX listed down-link freqs in Ku and Ka standardized (approved by ITU and FCC) ranges.
So you must know what sat/freq your tuning your receiver; knowing L-band freq is not usual for viewing sat channels.
Also, you must know LOF(s) of your LNBF(s) to correctly setup your receiver/card. It's like work with a car parts - maker, model, year, etc - to tune and fix it. Mocking instead of possession real info is not productive and don't lead to stable functioning devices like receivers or cars.

ya????,,,,
not all of us do things the usual way.
if i find an old lnb and dont know the specs, i want to hook it up and see how it performs, and maybe add it on to my setup, not just say, oh well, i dont know what it is and throw it away.
sure, i could buy a new lnb, bolt it up, and call it good.
but to tell you the truth, i watch very little tv, the fun for me and what seems like most of the people into fta is the hunt and the experimentation.
with great modern features in a receiver like blindscan, if you could enter a lo frequency of 0, blindscan a bird that you know transponder frequencies on, and do a little math, you could use it as a tool to find out what the lo frequency is (or frequencies, if stacked or universal) of a lnb that you dont know the settings on.
and trust me, my setup works GREAT
maybe i didnt buy it all new and get the specs from the manufacturer, but with the right test equipment, measurement, a little math, patience, and experience, its amazing what you can do.

 

[ynnedibanez]

On a number of receivers, you can set the LO to zero and it will work.

Next thing I'd try is setting the LO to one and see what that does for you. Then you'll be 1MHz off the L-Band frequency.

good idea, thanks, i'll try that,

 

[Smith P.]

Useful method of define the unknown LOF ... Yeah, researching blank LNBFs would be need it.
My impression was using the method for regular satDXing. As the converting L-band to Ku/kA bands for each tpn's freq would be boring. Especially using for reference Internet sites.