The 8000 series is definitely better than the 8900, and more expensive. The $65 quote from Satmall is for an 8915, -not- an 8515. They want around $200 for an 8515 (didn't have exact quote).

Here's a summary of the differences between models:

The 8900s is physically different from the rest of the 8000 series. Some say it is really a 5200 (consumer analog) LNB that has passed a screening for low phase noise.

Again, here is how you read a Norsat part #:

1st digit = LNB series #. The "8" in 8515 denotes 8000 series.
2nd digit = LO stability, in hundred KHz. The "5" in 8515
means LO stability is +/-500KHz. "9" means +/-900,
"2" means +/-250Khz.
3rd and 4th digits = noise temp. for C-band, its in Kelvin. The "15" in 8515 means a noise temp of 15K.

LO stability: Remember, this is a measure of how much the LNB LO frequency drifts as a function of temperature. If you can receive a signal during the day, but not at night, then you may have a LO stability problem. The amount of LO stability you need depends on your climate. For example, you will need more if you live in the midwest where the temperature changes dramatically from day to night and season to season than if you live in say sunny San Diego where the temperature is always around 80F (and the locals wear winter coats when it dips much below 70F ;-). A better LO stability number will -not- pull in more signals, assuming a constant ambient temperature. Also, most modern receivers, including the 4DTV, have forgiving tuners that will compensate for an LNB that is slightly off frequency. I think 4DTVDUDE stated here that the 4DTV will lock a signal that is within a few MHz of the target.

The rest of the 8000 series has better numbers than the 8900; it's not just a question of LO stability. For example, the 8900 has an input VSWR of 2.5:1. The rest of the 8000s have a 2:1 VSWR (lower is better, with 1:1 being perfect). Simply put, that means the 8000s do a better job of gathering the signal from the feedhorn. The input VSWR of the 8900 will add 51K (!) of noise to total system noise (in addition to the 15K from the LNB circuitry). The input VSWR of the 8000 will only add 39K to total system noise. In other words, an 8515 will outperform an 8915 by an additional 12K. Both add a maximum of 15K of noise from their circuitry, but the 8515 adds 12K less at the interface with the feedhorn. Another way of looking at this is to think of the 15K 8515 as being the equivalent of a 3K 8900.

Both the 8000 series and the 8900 have the same phase noise figure: -65dBc/Hz@1Khz. This is 10X lower than the number for the 5200 series of analog LNBs. The amount of phase noise will have a large impact on the reception of digital signals. Higher phase noise translates directly into higher bit error rates, and higher bit error rates lead to pixelation and picture freezing, or no lock at all.

Here are the prices I was quoted:

8915 - $65
8515 - $166
8215 - $233

My recommendations are:

8915: excellent choice for 4DTV with a proper size dish, casual mpeg2/dvb
8515: 4DTV with an undersized dish or in extreme climates, serious mpeg2/dvb.
8215: probably overkill, even in extreme climates, except maybe for SCPC mpeg2/dvb.

The Ku LNBs follow the same pattern as the C-band LNBs, with the equivalencies as follows:

Ku series C series
--------- --------

6600 ~ 5200
7000 ~ 8900
4000 ~ 8000

The 6600A is -not- their premium Ku LNB; it is their least expensive Ku LNB. I would recommend at least the 7000 for the 4DTV.

btw, The letter at the end of the Ku LNB model number denotes the frequency band (e.g."6600A"). "A" means N. American FSS band (11.7-12.2).

The numbering system works the same. A 4706A is a 4000 series, with 700KHz LO stability, .06dB noise temp, and intended for N. America.

hth,

Tom