L.O. Stablility

[franciscanfriars]

Please help! What is the best L.O. Stability, i.e, the Norsat uses the second number in the series to identify, i.e., 8115, 1 being plus or minus 100kHz. Is the higher number better or the lower?

 

[Lak7]

Lower is better.

 

[ZetaMale]

I wish they'd give stability specs on the LNBF's.

 

[Lak7]

I wish they'd give stability specs on the LNBF's.

Probably 'cause you'd be disappointed.

 

[Mr Tony]

agreed. Im always amazed how a LNB that is rated at 35K seems to be more stable than a LNBF rated at 17K or even 13K

Here in Minnesota where it can get COLD is when the stability really shows

 

[tvropro]

agreed. Im always amazed how a LNB that is rated at 35K seems to be more stable than a LNBF rated at 17K or even 13K

Here in Minnesota where it can get COLD is when the stability really shows

From what I know the colder it is outside the better the LNB likes it. There was an old guy Doug Dennert on the SkyStore back in the late 80's and early 90's. His sat business was out of Minnesota. He used to say that LNB's loved 20 below zero outside and performed great at the cold temps. I have seen back in analog days when noise temps were higher this really held true.

 

[Comptech]

From what I know the colder it is outside the better the LNB likes it. There was an old guy Doug Dennert on the SkyStore back in the late 80's and early 90's. His sat business was out of Minnesota. He used to say that LNB's loved 20 below zero outside and performed great at the cold temps. I have seen back in analog days when noise temps were higher this really held true.

Up until today I was running my vertical LNB[calamp minimag] Off the 13 volts from the recievers.It worked great when the weather was warm,as soon as the temps dropped so did my s2 signals on the vertical side,fixed it today with a power inserter!

 

[ZetaMale]

From what I know the colder it is outside the better the LNB likes it. There was an old guy Doug Dennert on the SkyStore back in the late 80's and early 90's. His sat business was out of Minnesota. He used to say that LNB's loved 20 below zero outside and performed great at the cold temps. I have seen back in analog days when noise temps were higher this really held true.

I've noticed that when it gets very cold that NETV on DCII comes in solidly.

 

[B.J.]

agreed. Im always amazed how a LNB that is rated at 35K seems to be more stable than a LNBF rated at 17K or even 13K

Here in Minnesota where it can get COLD is when the stability really shows

From what I know the colder it is outside the better the LNB likes it. There was an old guy Doug Dennert on the SkyStore back in the late 80's and early 90's. His sat business was out of Minnesota. He used to say that LNB's loved 20 below zero outside and performed great at the cold temps. I have seen back in analog days when noise temps were higher this really held true.

While some specs of LNBs might get better at low temperatures, I'm sure that other parameters will get significantly worse. And the LO freq stability is certainly one parameter that will suffer.

I used to test some military electronics at low (and high) temperature, and the mil spec (I think the one we used was something like 810e if I remember right) was very hard to meet. Something is always going to go wrong when you get down to -40.

LNBs might have less noise at low temp, but I've never seen an LNB that didn't drift significantly at even moderately low temperatures. If you look up the LO stability specs for LNBs, they usually quote them at only a relatively narrow temperature range. I have a Sadoun KUL1 that would drift 5 MHz when the temperature got down close to zero F, and that isn't really very cold. I've observed moderate quality LNBs rated in the .75 to 1.0 MHz range, and they would drift up above +/- 2MHz when it got cold, and an LNB rated down around 0.1 MHz drifts up close to a MHz when cold.

Back in the analog days, drift of these magnitudes wasn't important, and for high SR digital signals, it probably isn't important for many receivers, particularly for receivers with somewhat loose tuning. But for narrow, low SR signals with receivers with tight tuning, this much drift will mean that you can't lock the transponders unless you change the frequency, or it can mean that you lock the wrong signal. I've seen many times, when trying to lock either 3978 SR newsfeeds or those 4444 SR PBS SCPC transponders, that when the temperature gets cold, I'll either lock on the wrong signal or not be able to get to some of the signals at all.

So anyway, some aspects of LNBs might get better at low temperature, but the performance WILL get worse in some respects.

 

[ikki]

Time to build a cystal oven and hard lock the temp.

 

[pendragon]

You get what you pay for. A PLL LNB will normally be much more stable than a DRO, at quite a cost penalty. If you want your PLL to lock to an external reference, you can get down to fractions of a Hz. But it costs even more than a plain PLL. The point for the latter would be combining multiple apertures for higher CNR or interference mitigation. If we were dropping $500 apiece on LNBs, this hobby would look a little different.

 

[emuman100]

Actually, I know last year when it got gold in the winter here in Northeast Pennsylvania, I'd get excellent eb/no readings with the Weather Channel digital multiplex. Since the elevation of AMC 10 is so low up here, 14 degrees, I had a hard time getting a good signal trying to avoid the trees. But, the colder it got, the better performance I had.

Now, since I have the dish on a platform, I get the Weather Channel multiplex nice and strong, 6.8dB eb/no right now. 4 is the bare minimum to produce a stable picture, and most of last year I was a little over 4, kind of close to 5. The height that the platform adds really makes the difference. I use a Norsat 8115 and I love it.