DVB HDTV / Ready to Give Up

[Anole]

Brand XXX
Gold label series
Noise Figure 17K

Online specs from satellite supplier for brand XXX as follows:
* 65 db gain
* +/- 2.0 MHz stability
* Excellent 80 db@1 KHz phase noise reduction
* Frequency input 3.7 to 4.2 GHz
* Frequency output 950 to 1450 MHz

Interesting. And by comparison, here are more specs on the Norsat 8115:

conversion gain: 64db
noise temp: 15º Kelvin
LO offset: +/- 5khz
LO stability: +/- 100khz
phase noise:
-65 dBc/Hz at 1kHz
-80 dBc/Hz at 10kHz
-95 dBc/Hz at 100kHz

Less differences than I would have expected.
Yet still enough to have the big affect.

Only significant parameter that jumps out at me, is the phase noise.
I don't think the LO stability with temp should be a contributing factor.

Do we have any TV station engineers with a clearer view?

 

[barret]

Anole.
I don't really understand the numbers but brand xxx stability is listed as 2.0 MHz. Wouldn't this convert to 2000 KHz and if so be a major difference from the 100 KHz stability of the Norsat?

 

[Anole]

test case

Well, if I didn't drown in the spec-soup, I think that means +/- 2mhz overall frequency drift with temperature.

So, if you are actually interested in a test, put the LNB back on.
Set your receiver to +1 mhz and see if you get a stable picture.
Set your receiver to -1 mhz and check again.
Whichever side of nominal you got the better signal, go in additional 1 mhz steps , trying each time.
So, if +1 is good but -1 is bad, then go to +2, +3, and maybe +4mhz, testing for signal breakup.

I'm not going to bet a lot of money that you'll find a point at which you have a good picture.
I sort of think it might be the phase noise, but... I just don't know.


AND, it might be the dish alignment.
So, putting back the original and finding that it just works, might lend support to that theory.

 

[barret]

I guess I am finished testing at this point. As I'm posting this I am running DVBViewer on both cores with Skystar 2 (which according to earlier post should not work) watching ESPN HD College Football. I am connected to the internet, and have AVG running all this with the task manager up showing a steady cpu usage of 20 to 27%. I am pushing all of this through a 46" LCD with a rock solid picture. I could not be happier. I hope the information that came out here can be helpful to others in the future.
Many thanks for all the help
barret

 

[updatelee]

remember too, specs lie. lol.

Ive seen cheap ebay nock off lnb's claim 0.4db noise that were 10x worse then my 0.3db and probably 2x worse then other 0.5db ones Ive used.

a spectrum analyzer shows all that nasty noise the other claim isnt there, but it really is.

2mhz stability if true isnt to bad, you can be off a little on your tp freq and most dvb ird's will automatically move a mhz up or down to get the center, but 0.1mhz is better, means the ird doesnt have to move its freq, its just automatically correct.

I would suspect where the lie is is in the 15k vs 17k. I would bet ya the norsat isnt lieing and the xxx no-name is fudging the numbers.

 

[Anole]

thanks for the info

If you are happy, that's great.
If you are done, no one can complain!
Thanks for the fine feedback.

As for who's lying, I might bet the Norsat exceeds its spec - :up
And, as to whether XXX LNB lives up to its spec... well... ?
(maybe it got dropped on its head when it was just an L)

 

[voomvoom]

I don't think the LO stability with temp should be a contributing factor.

I would have to disagree with this, at least from my stand point. If I'm comparing lnb's and lnbf's and I look at the very alluring cheap price of the lnbf and the maybe 5 degree better temperature rating than the lnb I'm comparing it with. And then I notice the lnb at least gives a Stability rating while the lnbf usually doesn't. I will go for the lnb even though it may cost 5-10 times more. I firmly believe in the Stability Rating and it is what ultimately makes me decide which I will get. The lower the Rating, the Better! Just my 2 cents?

Al

 

[barret]

voomvoom
Your not far off on the price being 5 to 10 times more. Brand XXX sells for $20.00 to $30. from most major sat suppliers. The Norsat 8115 goes for $130 to $189. from most sat suppliers. Again I don't claim to understand all of the technical specs on these units but I do no there is no comparing them physically ( size and weight) the Norsat being at least three times the size and weight of brand xxx. Also Norsat doesn't hold back on providing the specs right on the unit. Brand xxx gives nothing with the unit. All of these things combined tell me there is a major difference somewhere in these units although as Anole stated the specs alone don't support any major differences. I do know I would not hesitate on spending the extra dollars the next time around if ever needed.