Which C-band lnb for DSR922 would be best?

[Desertnight]

My c-band lnb fried. It was about 22 years old. A good ole General Instrument lnb bought back in 1987. I do not know what degree range it was or any other details.

Now, I see that vendors selling c-band lnbs with 20 degree, or a 17 degree, or a 13 degree and probably others.

What would be the best degree to use with the 4dtv system? I have both a DSR920 and 922 with a Sonicview 360 elite slaved to the 922. The DSr920 is not being used right now (it's plugged in, though).


Then what would you suggest as the best lnb or most reasonably priced cband lnb compatible with the 4dtv system? Would the lnb you suggest then be compatible with any other receiver or Gbox I may use in the future as my dish mover?

I have a Chaparral c-band feedhorn.

Thanks.

 

[pendragon]

There is a big difference in price between the best and reasonably priced alternatives. All should work with your 4DTV and DVB receivers. If you want to continue using your current C-band feed, you can probably find a decent replacement C-band LNB in the $20-40 range. I can't recommend anything specifically because I haven't tried one. A high-end C-band LNB is more like $100 (I like the Norsat 8115).

You could replace your feed with an integrated LNBF unit, which has the advantage of eliminating the servo motor. People on this forum have used Geosatpro, DMX and BSC units with varying, but generally good success. Those are mostly under $50. The best would be something like a Chaparral single ortho feed for around $60, plus a couple of LNBs like the 8115 above. Only in this last case would you need a switch and a power inserter to make it work with your receivers.

The best units are only necessary for those who are looking to squeak every last ounce of performance out of their systems. Reasonably priced units are a better option for most people.

 

[tvropro]

A cheepie DMS would work with your original feedhorn but if you want quality I would use a California Amplifier or a Norsat.

 

[servoman]

Dont expect the Norsat to last as long as the GI. I don't know about anyone else, but I can't get 10 years out of the Norsat. 5 years of the the Norsat ku, 6 years out of the C-Band.

 

[tvropro]

My Cal Amp is on almost 20 years old

 

[Desertnight]

Thanks. All interesting answers.

What I have also found out is that the c-band lnb recommended by Motorola should be a 17 degree dB for the DSR922 and 920.

The Chaparral c-band lnb (part number 11-7100-1) is a 20 degree Noise Figure.
It's a $40.00 lnb. Reasonably priced, I think.

But, I have not made a decision yet which one to get. But I am leaning towards the c-band lnbs that are at least 17 degrees.

Let's hope that my local ota antenna stations stay powered up for a few more days til I finally get an lnb. Since they are low powered and transmitting analog, I did not have to buy the converter box. The county technician here has had such problems in keeping the translators up and running. Sometimes, I just don't think he knows what he is doing!

Ooops! Babbling.

 

[mikekohl]

I think that you have missed some of the points expressed above.
15 to 20 degrees Kelvin would be a good noise temperature range to look at.
There are some consumer LNBs out there that claim 13 degrees, but whether that is realistic is up to contentious debate. What is more important than a noise temperature rating is the local oscillator stability. Your average consumer unit is anywhere from 2000 to 3000 KHz (2 to 3 MHz) allowable drift. Hard to believe that manufacturers can get away with using the term DIGITAL on such units, but they are out there. I prefer the terms "consumer digital" and "commercial" or "professional" digital. High Stability units are available from NORSAT in 500 KHz (model 8515), 250 KHz (model 8215), and 100 KHz (model 8115), the latter being the best. Any of the last three, and you will not go wrong; if you are comparing a 40 dollar consumer unit that claims 15 or 17 degrees, that is only part of the picture....digital signals are finicky and LNBs do drift after years in the weather. Don't expect a miracle with a low dollar unit; High Stability gives you some insurance that things won't fall apart on weaker digital signals.

 

[Desertnight]

Thanks, Mike.

The more I learn, the better. It's all in the little details. Understanding how all these frequencies work together is a new playing field for me. That's great!

The Chaparral lnb has a LO frequency of 5.15 GHz and LO stability of +/-2.5 MHz.

How does that translate and compare to the Norsat 8115? (I guess I better go read on that myself, huh?)

 

[pendragon]

For LO stability, the smaller the number the better. If your Chaparral is +/- 2.5 MHz, a Norsat 8115 would be +/- 0.1 MHz. A lot better, and probably even more than it sounds because many LNBs are not specified over a full temperature range.

However I have to respectfully disagree a little with Mike. Good frequency stability is always helpful, but most modern receivers can lock over a fairly broad range. When I've tested mine, I can almost always lock +/- 5 MHz and some will do +/- 10 MHz. That means they will not be much affected by a LNB that is off frequency. I bought 8115s specifically because I wanted to read signals directly off my bench spectrum analyzer which is very accurate. I might have saved some if I wasn't going to do this and suffered very little.

But this does point out a weakness in specs that would allow a shady vendor to put out a crappy LNB and make it look much better than it really is. The vernacular for frequency stability specs in FTA is usually intended to describe a clean LO whose frequency is dependent on temperature. As temperature normally changes relatively slowly, as long as the LO drifts along with temperature change there shouldn't be any cause for concern. I still don't like this and domains that care about frequency stability don't specify it this way. Regardless it isn't going to hurt to have a tighter LO stability.

However a crummy LO might be unstable over short periods of time, unrelated to temperature, and that will cause terrible losses in reception quality. Unfortunately a frequency stability spec could be used to cover this fact and such a LNB might have the same stability specs as an excellent one.

What is generally more instructive is to look at phase noise. An unstable LO cannot hide from this. Phase noise specs are normally given for several frequency offsets. The more negative the number for a given offset the better. A quick glance at these will normally distinguish the good from the bad or even ugly LNBs. Unfortunately vendors often omit these specs for very good reasons. The Norsats score very well on these specs and this is a primary reason why they perform so well.

Sorry for the long answer to a simple question. My sister has castigated me for this her entire life and neither one of us is young

 

[ZetaMale]

My c-band lnb fried. It was about 22 years old. A good ole General Instrument lnb bought back in 1987. I do not know what degree range it was or any other details.

Now, I see that vendors selling c-band lnbs with 20 degree, or a 17 degree, or a 13 degree and probably others.

What would be the best degree to use with the 4dtv system? I have both a DSR920 and 922 with a Sonicview 360 elite slaved to the 922. The DSr920 is not being used right now (it's plugged in, though).


Then what would you suggest as the best lnb or most reasonably priced cband lnb compatible with the 4dtv system? Would the lnb you suggest then be compatible with any other receiver or Gbox I may use in the future as my dish mover?

I have a Chaparral c-band feedhorn.

Thanks.

A 13 degree with a high stability oscillator would be best but may be overkill. The high stability oscillator is recommended for the DCII stuff but you could slide by without it but you may have trouble getting some DCII stuff to come in without a lot of fiddling. Ultimately, the best you can afford is always the best way to go, IMHO.

 

[Desertnight]

Thanks everyone.

Pendragon--as long as you do not repeat yourself several times in a long-winded explanation, a long-winded explanation to a question is perfect.

A neigbor has let me borrow a California Amplifier c-band lnb until I get a new one. It is working okay.