| People keep asking me what sort of LNB they have. It's easy to find out:
Tune to Sky news (vertical polarisation) Astra at 19.2'E.
Set your receiver LNB installation to 10.0 GHz (not adjustable in older receivers).
If Sky News is roughly 11.377 GHz then you have a standard 10.0 GHz LNB.
If it's roughly 11.627 GHz then you have a 9.75 GHz LNB. 1) Standard LNB 10.0 GHz L.O.
Often called a "Marconi switching LNB". Works in one band. Noise Figure usually 1.0 dB or better but older "Blue cap" types can be much worse. Integral feed horn, usually with 40mm neck but flange type available to special order and other neck sizes have been made (especially 22.5mm). Marconi also made a "Bullet" shape LNB of this type that used a PTFE insert instead of a horn. Polarisation switching is controlled by dc voltage supplied by the receiver. 12.5v to 14.5v gives vertical and 15.5 to 18v gives horizontal polarisation. A higher voltage than that can damage the LNB. A voltage that is too low will prevent the LNB from working correctly. 2) "Enhanced" LNB 9.75 GHz L.O.
Works 10.7-11.7 GHz. Noise Figure usually 1.0 dB or better. Integral feed horn with 40mm neck.
Normally used with later type receivers that have a 2GHz tuner but no 22kHz tone generator. Designed specifically for Astra satellite reception from satellites 1A, 1B, 1C and 1D. Polarisation switching is controlled by dc voltage supplied by the receiver. 12.5v to 14.5v gives vertical and 15.5 to 18v gives horizontal polarisation. A higher voltage than that can damage the LNB. A voltage that is too low will prevent the LNB from working correctly. 3) "Universal" LNB 9.75 and 10.60 GHz L.O.
Works in 2 bands* 10.7-11.8 and 11.6 - 12.7 GHz. (22 kHz tone switched). Noise Figure usually 1.0 dB or better. Integral feed horn with 40mm neck but flange type available to special order.
*If your receiver tuning range is less than 2.15GHz you will have a gap between high and low bands. Refer to calculations, below. In effect, this is a "Quad Band" LNB. A Universal LNB requires a 22kHz tone at 0.5v p-p to switch its Local Oscillator to 10.6GHz ("high band"). Otherwise it uses its 9.75GHz oscillator. Polarisation switching is controlled by dc voltage supplied by the receiver. 12.5v to 14.5v gives vertical and 15.5 to 18v gives horizontal polarisation. A higher voltage than that can damage the LNB. A voltage that is too low will prevent the LNB from working correctly. 4) "FSS" LNB 10.0 GHz L.O.
Normally bolted to separate polariser and feed horn. Works in one band: 10.9 - 11.7 GHz. Receiver with standard 0.95 - 1.75GHz tuner may be used. Noise figures vary. Very old ones can be 3.0 dB! 5) "DBS" LNB 10.75 GHz L.O.
Normally bolted to separate polariser and feed horn. Works in one band: 11.7 - 12.5 GHz. Receiver with standard 0.95 - 1.75GHz tuner may be used. Noise figures vary. 6) "Telecom" LNB 11.0 GHz L.O.
Normally bolted to separate polariser and feed horn. However, Marconi made a voltage-switching version with integral feed horn*. Works in one band: 11.95 - 12.75 GHz. Receiver with standard 0.95 - 1.75GHz tuner may be used. (* identified by a serial number label with a red corner, although some were incorrectly marked). Noise figures vary. 7) "Dual band" LNB
Normally bolted to separate polariser and feed horn. Works in 2 bands 10.9 - 11.7 and 11.7 - 12.5 GHz. Receiver with standard 0.95 - 1.75GHz tuner may be used. Band switching achieved by supply voltage of either 14 volts or 18 volts. Noise figures vary. 8) "Tripleband" LNB
Normally bolted to separate polariser and feed horn. Works in 2 bands 10.9-11.8 and 11.8-12.75 GHz. Receiver with 0.95 - 2.0 GHz tuner should be used. Noise figures vary. 9) "Quadband" LNB
Normally bolted to separate polariser and feed horn. Works in 2 bands 10.7-11.8 and 11.7-12.8 GHz. Receiver with 0.95 - 2.05 GHz tuner should be used. Noise figures vary. 10) "Twin output" LNB
Currently available in Standard, Enhanced and Universal form, the twin output LNB provides two outputs to feed two separate receivers. Each output can be switched by 13/17 volt input by the individual receiver to change polarisation. 11) "Dual output" LNB
Currently available in Standard, Enhanced and Universal form, the dual output LNB provides two outputs to feed two separate receivers. Each output has a fixed polarisation; one horizontal and one vertical. This type of LNB should be used with switching boxes such as the "Mini Magic" which will feed four separate receivers. Explanation of (L.O.) Local Oscillator Frequency: Suppose a signal comes from the satellite at a microwave frequency of 12 GHz but your typical receiver tunes up only to 1.75 GHz? (Also bear in mind that most cable will NOT happily pass frequencies much above 2GHz). The function of the LNB is to reduce the frequency of the satellite signal. It does so by subtracting a frequency figure from the satellite signal frequency. This figure is called the "Local Oscillator" frequency ("LO") of the LNB. So an LNB with a LO of 10.25GHz will send a 12GHz satellite signal down the cable at 1.75GHz (just within range of your old receiver). 12GHz - 10.25GHz = 1.75GHz Working in reverse, if your highest satellite frequency is 12.6 GHz then you will need an LNB with a LO of at least 12.6 - 1.75 = 10.85GHz in order to reduce the satellite signal to a frequency that your receiver can "see" (1.75 GHz). Now let's reverse the process again: A "standard" LNB has a LO of 10.0GHz. So the highest satellite program frequency that your standard receiver can *see* is 1.75 + 10.0 = 11.75GHz An "enhanced" LNB has a LO of 9.75 GHz 1.75 + 9.75 = 11.50GHz A "universal LNB has TWO LOs. One is 9,75 (same as "enhanced") The other is 10.6 which is selected if it "hears" a 22kHz (just above audio) tone. 1.75 + 10.6 = 12.35GHz Of course, if your receiver can accept signals up to 2.0 GHz then the highest acceptable signal frequency becomes 2.00 + 10.6 = 12.60GHz And a receiver with a tuner that extends to 2.15GHz achieves 2.15 + 10.6 = 12.75GHz (which happens to be the top of the "Telecom" band!) Now, you are still puzzled about the DBS LNB This has a LO of (typically) 10.75GHz So an old 1.75GHz receiver will get up to 1.75 + 10.75 = 12.50GHz A final consideration has to be the LOWER limit on tuning: Most old receivers can tune no lower than 0950 MHz (= 0.95GHz) whereas later ones might go down to 0.70GHz. Check out the above calculations with these lower tuning range limits to see the overall tuning bandwidth for any receiver. This is all very basic "sums" - nothing complex - so once you have a "picture" of what is happening, you can sketch little band plans for any combination of receiver annd LNB. Once you know the value(s) of the LO(s) in the LNB and of the upper and lower tuning limits of the receiver in question, you can quickly figure out what can be received. NOTE:
Older receivers *expect" an LNB with a 10.0 LO and the frequency display is arranged just for this. However, you can use an LNB with a different value LO. It just means that the *displayed* frequency will be incorrect. Transponder - LNB Local = tuner frequency
Frequency Oscillator
12750 MHz
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| Telecom/Astra 1F
|
|
| DBS/Astra 1E
|
11700 MHz - 10000 MHz = 1700
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| Astra 1B |
| |
| Astra 1A Receiver tuning range without ADX
| |
| Astra 1C |
| 950 + 500 = 1450
| Astra 1D |
| Tuning range with ADX
| |
10700 MHz - 10000 MHz = 700 + 500 = 1200
An old standard receiver usually tunes from 950 to 1700 MHz.
The map above shows the limited tuning range of an old standard receiver with an old standard 10.0 GHz LNB. The addition of an ADX Channel Expander moves the Astra 1D frequencies up by 500 MHz into the tuning range of the receiver.
To receive all Astra channels from satellites D to B without using an ADX, a receiver would need a tuning range of 700 to 1700 MHz.
Transponder LNB Local
Frequency Oscillator
12750 MHz - 10600 MHz = 2150
| |
| |
| Telecom/Astra 1F |
| Receiver tuning range for Hi band (22kHz on)
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| DBS/Astra 1E |
| - 10600 MHz = 1100
11700 MHz - 9750 MHz = 1950
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| Astra 1B |
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| Astra 1A |
| Receiver tuning range for Lo band (22kHz off)
| Astra 1C |
| |
| Astra 1D |
| |
10700 MHz - 9750 MHz = 950
An Enhanced LNB has a local oscillator frequency of 9750 MHz.
The receiver now needs a tuning range of 950 to 1950 MHz as shown in the map above.
If a Universal LNB is used, its local oscillator can be switched from 9750 to 10600 MHz by sending a 22kHz tone up the cable. Some receivers have this facility built inside. Some will need an external tone-inserter box connected into the cable.
If the receiver has a range of 950 to 2150, it will be able to receive programmes on both Hi and Lo band.
Another possibility is to use an ADX-Plus. This has an internal switch which, when moved across, makes the ADX-Plus move the frequencies DOWN by 500 MHz instead of up.
So a channel at 12750 MHz is moved down like this:
12750 - 10600 - 500 = 1650 MHz (with an ADX-Plus)
which is well within the tuning range of an old standard receiver.
And the lowest channel receivable will be:
950 + 500 + 10600 = 12050 MHz (with tone ON and ADX-Plus)
By fiddling with the ADX-Plus switch and the tone inserter you can probably receive the full range of channels if you have a Universal LNB and a standard receiver!
Note: MHz (MegaHertz) = GHz (GigaHertz) x 1000
So 9750 MHz = 9.75 GHz
Please let me know if you have any other thoughts on this and maybe we can add it to the FAQs.
>Martin,
>
>Many thanks, I took your advice and sat down with a pen and post-it
>note, and went through your LNB FAQ. Very informative thanks.
>
>I think I've got it sussed! If you don't mind, I'd just like to clarify
>my understanding:
Sure. That's the idea.
>Having establish that I've got a "Universal" LNB it has two L.O. frequencies -
>9750 MHZ and 10600 Mhz. I now understand that these values represent the
>degree to which the received frequencies are shifted by (reduced by).
Yes.
>The tuning frequency of my receiver with it being an old Amstrad SRD400
>is probably: 950 Mhz to 1700 Mhz a range of 750Mhz.
Yes :o)
>Astra broadcast frequencies range from 10700 Mhz (Astra 1D) through to
>11700 Mhz (Astra 1B). So I need to calculate which of these frequencies
>each of the two L.O.s on the LNB in conjunction with the tuning range
>of the receiver, I can receive, thus:
>
>L.O. 1 of 9750 Mhz
>
>950 Mhz (lower tuning capabilities of receiver ) + 9750 Mhz (L.O. 1)
>= 10700 Mhz
>1700 Mhz (upper tuning cap. of receiver) + 9750 Mhz (L.O. 1) = 11450
>Mhz.
>
>Hence able to receive frequencies of 10700 Mhz to 11450 Mhz.
>
>L.O. 2 of 10600 Mhz
>
>950 Mhz (lower tuning capabilities of receiver ) + 10600 Mhz (L.O. 2)
>= 11550 Mhz
>1700 Mhz (upper tuning cap. of receiver) + 10600 Mhz (L.O. 2) = 12300
>Mhz.
>
>Hence able to receive frequencies of 11550 Mhz to 12300 Mhz.
>
>Being an old crappy Amstrad SRD400, I presume my receiver isn't able to
>signal the LNB to switch to the upper of the two L.O. frequencies, so I
>can't access anything above 11450 Mhz. With a tone inserter I should
>therefore be able to access 11550Mhz - 12300Mhz?
You are doing OK so far.
>However, this leaves a gap in the middle between 11450 and 11550 of
>frequencies which I can't access! Presumably with an ADX (and tone
>inserter) I can shift those frequencies into tunable ranges?
>
>Presumably, all I need now is an ADX and a tone inserter in order to
>receive all Astra frequencies (and then some ... )? Oh yes, and a Sky
>subscription :-)
You don't really need a tone inserter.
>Would I be better off buying an ADX plus, so that I shift the
>frequencies down rather than up? So as to ensure my receiver is happier
>about it?
Yes, I would think so. There's nothing on the higher frequencies for your Amstrad to receive from Astra at 19.2 degrees East.
Sky Sports 3 would be the highest useful channel, with a couple of foreign stations just above that.
>How much would I expect to pay for an ADX and tone inserter?
If you have a Sky subscription they will post you an ADX-Plus for just £9.99.
Otherwise you can buy one for £12.95 upwards.
>Many thanks for all your help. It all seems so much simpler now. Or have
>I missed something?
Nope. I told you it was simple. People become frightened because they think it's too technical. The truth is that you simply need to be able to add and subtract - roughly to primary school level or lower! You don't need *any* technical knowledge. Just realise that there are various ways to add or subtract the frequencies. Specifically: there are various fixed values that you can use - Typically 10.00 GHz, 9.75 Ghz, 10.6 Ghz etc. for an LNB. Also +0.5GHz and -0.5GHz for an ADX-Plus Channel Expander, dependent on its internal switch position. | 