I'd suspect whoever could come up with something like t hat would be extremely rich in an extremely short amount of time... doubt it's possible, but new technology always pushes the limits... Who'd think circular+linear lnbfs would exit or cband+ku ? It's probably just a matter of time...
anyone anywhere working on a circular+linear+cband lnbf
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The new BSC621-2 C/KU LNBF comes with a dielectric plate that turns it into a circular LNB!
Have not tried it yet!
http://www.satelliteguys.us/showthread.php?t=60807
Have not tried it yet!
http://www.satelliteguys.us/showthread.php?t=60807
master, I haven't tried it, but I've given it a lot of thought as well as discussed it (or tried to) in this forum and come to the conclusion that the closest you might get to doing this would be using an ADL Dual C/ku feedhorn with a regular lnb for one and an lnb with dielectric plate for the other lnb. I don't know if it will work, but I don't know why it wouldn't. I've sort of been waiting for this (below), to see how well it works first. Although it has nothing to do with you question?
Al
Speaking of which, it's June are these ready for the consumer (me) yet?PSB said:
Al
Isolation is the ugly word that is going to come up with any such device.
A dielectric plate device on a C-band feedhorn, LNBF or polarizer is only a poor man's short-cut at achieving slight improvements in circular reception without
the use of a proper true circular feedhorn (such as the ADL CP-300, the former
CP-400 polarizer, or the two port CPOR-100 circular feed).
Look at the specifications for isolation between horizontal and vertical
polarization on a typical linear C-band feedhorn. Your average everyday
inexpensive C-band polarizers are typically 25 to 30 dB between H and V.
Look at a dual port orthomode feedhorn; 35 dB can be had on some models.
Then look at a circular feedhorn such as the ADL units mentioned above,
if you can find documentation, and you will sometimes struggle to get
isolation in the teens (15-17 dB) with an orthomode circular device.
A dielectric plate is lucky to provide isolation in the single digits of dB.
What this means is that unwanted signals from the other polarity may sometimes tend to overwhelm the desired signal. It's a balancing act that is best done with an oversized antenna for the job, unless you have a proper circular feed.
Leave a dielectric plate in the feed and then try looking at a linear C-band signal.
Try one of the transponders on PAS 9 at 58 West that happens to share the exact frequency on H and V, with only a minor difference in symbol rate. This will show you true effects of poor isolation. In many cases you will be lucky to resolve one of the two signals. In some situations, maybe unacceptable on either.
A true circular feedhorn will normally reduce one linear polarity by about 3 dB
(half power), while coming very close to full power on the other linear polarity.
This is all about mathematics, and numbers usually do not lie.
Which is probably the reason why nothing fully acceptable has hit the market
even in this day and age that combines circular and linear, and especially C and
Ku-band, in the same device. Something is always going to have to be compromised, and there will never be a "perfect" feed for all situations.
You have to decide what positive attributes are important, and hope that any negative performance does not overwhelm your desired result.
(Off the soap box)
Mike
A dielectric plate device on a C-band feedhorn, LNBF or polarizer is only a poor man's short-cut at achieving slight improvements in circular reception without
the use of a proper true circular feedhorn (such as the ADL CP-300, the former
CP-400 polarizer, or the two port CPOR-100 circular feed).
Look at the specifications for isolation between horizontal and vertical
polarization on a typical linear C-band feedhorn. Your average everyday
inexpensive C-band polarizers are typically 25 to 30 dB between H and V.
Look at a dual port orthomode feedhorn; 35 dB can be had on some models.
Then look at a circular feedhorn such as the ADL units mentioned above,
if you can find documentation, and you will sometimes struggle to get
isolation in the teens (15-17 dB) with an orthomode circular device.
A dielectric plate is lucky to provide isolation in the single digits of dB.
What this means is that unwanted signals from the other polarity may sometimes tend to overwhelm the desired signal. It's a balancing act that is best done with an oversized antenna for the job, unless you have a proper circular feed.
Leave a dielectric plate in the feed and then try looking at a linear C-band signal.
Try one of the transponders on PAS 9 at 58 West that happens to share the exact frequency on H and V, with only a minor difference in symbol rate. This will show you true effects of poor isolation. In many cases you will be lucky to resolve one of the two signals. In some situations, maybe unacceptable on either.
A true circular feedhorn will normally reduce one linear polarity by about 3 dB
(half power), while coming very close to full power on the other linear polarity.
This is all about mathematics, and numbers usually do not lie.
Which is probably the reason why nothing fully acceptable has hit the market
even in this day and age that combines circular and linear, and especially C and
Ku-band, in the same device. Something is always going to have to be compromised, and there will never be a "perfect" feed for all situations.
You have to decide what positive attributes are important, and hope that any negative performance does not overwhelm your desired result.
(Off the soap box)
Mike
So PSB, how's that testing going on the Primestar?
And what can you pick up with it? I'd just be interested in this sort of stuff if it worked on that since I have an old Primestar sitting in the basement that and some old Direct TV dishes just waiting to be torn apart to get Primestar working as a KU/Circular (and maybe C Band?) dish
And what can you pick up with it? I'd just be interested in this sort of stuff if it worked on that since I have an old Primestar sitting in the basement that and some old Direct TV dishes just waiting to be torn apart to get Primestar working as a KU/Circular (and maybe C Band?) dish
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