DRO and PLL LNB

[Rizwan]

How can I compare DRO and PLL LNB ? Can I use PLL Lnb for fringe type reception ? any other advantage of PLL ?

[Tusker]

How can I compare DRO and PLL LNB ? Can I use PLL Lnb for fringe type reception ? any other advantage of PLL ?

PLL is supposed to be more stable and better than DRO, might keep a signal on weak/fringe reception channels when a DRO one is not getting stable lock.

[mahler]

How can I compare DRO and PLL LNB ? Can I use PLL Lnb for fringe type reception ? any other advantage of PLL ?

Hello Rizwan,
DRO (dielectric resonator oscillator) LNB types have very poor frequency stability and are suitable only for the reception of wide bandwidth carriers, such as a 27 Msps satellite TV or VSAT outlink carrier, where the receiver tuning circuits can lock onto the carrier despite frequency errors of up to +/-500 kHz or +/- 2 MHz and second's delay (or more) locking up is of no consequence.

PLL (phase lock loop) LNBs use an internal 10 MHz crystal oscillator (which has high stability) and a phase locked oscillator at say 10 GHz. Frequency accuracy is very good (say +/-25 kHz) and phase noise is low. Use this type for the reception of low symbol rate carriers and higher order modulation carrier like 8PSK and 16QAM. External reference PLL LNBs are also available. These need a 10 MHz supply up the cable from the indoor equipment. External reference PLL LNB accuracy can be extermely good if you use an atomic derived oscillator such as one based on GPS receiver. All teleport hub earth stations should use external reference PLL LNBs. The 10 MHz supply should have excellent phase noise characteristic so make sure its power supply is well smoothed and it is not located next to a motor (e.g. a fan which give out both vibration and an oscillating magnetic field).

I hope this helps a bit.
Regards mahler