Best LNB with 80cm Triax Dish and Technomate 1500CI+

SimonMaher

Hello there,

Just a quick query. My old (lemon) LNB is giving me trouble so going to replace it. Any particular reccomendations? Online Ive seen very good reviews of the Invacom 0.3 ones.

Thanks in advance,

Pete

watty

Almost any will do..

As long as it intended for ordinary offset dish / integrated feed, Universal etc.

I don't have an Invacom, but I never heard anything bad.

Note than below 0.7dB the NF is not any longer a measure of quality.

ro2

I've had good results with the MTI Blue Line LNBs.

Why does the NF not make a difference below 0.7dB Watty?

Ronan|Raven

People give the Smart Titanium .2db edition good reviews and results and it is pretty cheap.

watty

ro2 wrote:

I've had good results with the MTI Blue Line LNBs.

Why does the NF not make a difference below 0.7dB Watty?

1) dB is a Log scale. 3dB is a huge variation compared with 0.4dB, slight variation in dish alignment is 1dB to 3dB. Weather in clear sky is up to 3dB variation. Rain a lot more.

2) flatter frequency response and performance of a weak signal in presence of a stronger one (i.e. 2D and other sats in Spain from Sky), can actually be poorer on a very low noise LNB.

3) Professional LNBs are mostly 1dB! Why not better? Because it makes no difference.

4) If you signal is marginal on an 0.8dB then you need a bigger dish, not a 0.4dB NF reduction, which might be imaginary on the desired transponder. Going even a slightly bigger dish can be 3dB to 6dB improvement.

5) An imperfect feed where LNB "sees" wider than the dish picks up more than 0.4dB of sky noise! Only professional Flanged feeds with horn / scaler rings etc recommended by dish maker typically match exactly.


So really important figures for a Modern LNB is NOT the nf of 0.2, or 0.3 or 0.6 etc but:
* Horn / Scaler rings of built in feed is for F/D of 0.6 (Typical domestic dish from 60cm to 110cm).

* Flat frequency response

* Good Group Delay (High SR transponders)

* Stable and accurate L.O. frequencies of 9.75 and 10.6 (low SR SCPC signals, ever had to enter an SR 2145 station 1MHz higher or lower?), from -10 to +30 (Winter night to Summer day?).

* Good lack of intermodulation (strong & weak transponders nearby)

* Accurate 90 degrees between H and V (accuracy and placement of the stubs in waveguide etc).

* 22KHz tone switch sensitivity. Some oversensitive ones stay on 10.6 L.O. with SMPSU noise of 35KHz etc... Some Panasonic Digibox owners have seen this, one LNB works and another won't do RTE/BBC/ITV! Satcure sells a filter.

* Immunity / rejection of Interference. What happens when a 10.2 / 10.6GHz wireless broadband link is nearby?

* IF level fed to cable. Is it too high for receiver on a short cable or too low on a longer coax cable? (If a little high, then the reciver will seem insensitiive to a week transponder as it will turn down AGC in response to strong signal or even reduce the BER (quality) due to intermodulation.

watty

The reason the Invacoms, MTI, Smart Titanium etc are regarded good is probabily nothing to do with the low NF.

I found a 0.7dB Philips costing €7 worked slightly better than a 0.6dB MTI Dual. I'm sure it is nothing to do with single vs dual or 0.1dB NF difference. I have no idea. Maybe even changing the LNB changed the dish alignment slightly?