What voltage for 18 inch satellite dishes?

DC. For simple LNB's, 13V for left hand circular polarization. 18V for right hand. That corresponds to the odd channels and the even channels (or the reverse in case I got it backwards). If you're using a DiSEqC switch, there's also a 22KHz control tone to switch outputs. Life gets really complexicated if you have a 5 LNB dish.

Ugh. I don't know how the VHF/UHF antenna is switched.

You can also build a wi-fi range extender with the dish:

Circular polarisation for US DBS, Jeff ? Over this side of the pond, it's vertical and horizontal polarisation for alternate channels or whatever, but with the same selection / LNB powering voltages, and additional switching by

22kHz tone, the same.

Arfa

9 - 13 VDC shud power it.

DirecTV and Dish are both circular polarization. HughesNet internet is linear (vertical or horizontal) polarization. FTA (free to air) transmissions are all linear polarization. Broadcast downlinks (FSS) are all linear polarization.

"Most North American DBS signals use circular polarization, instead of linear polarization, therefore requiring a different LNB type for proper reception. In this case, the polarization must be adjusted between clockwise and counterclockwise, rather than horizontal and vertical."

This explains it in detail:

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Wow. That's amazing.

Thanks to everyone. I should be able to get this working, plus I have

3 amplified antennas in my attic. One or two of them are broken, but I think I have enough for myself and a friend and his landlady, both of whom have had very little tv since digital.

BTW, I remember now I sold that thing in the center of the dish for one or two dollars BEFORE I saw it for sale at Radio Shack for 50 dollars, but that's still okay.

Dishes are passive devices; they are not powered by anything but incoming RF energy.

A good start would be to learn the difference between a dish, LNB, and receiver.

That's interesting. I wonder what the perceived advantage of using circular over linear polarisation is ? I can see that polarisation twist from passage of the signal through the atmosphere would be eliminated, and also skew caused by your E-W position with respect to the bird. Do you think that's the reason ? I didn't realise that a c.p, LNB was effectively just an l.p LNB with a signal 'de-spinner' (lump of ferrite ?) in the feed. As long as DBS has been going in Europe, which is quite a lot of years now if you go back to the old analogue birds, c.p. has never been used, which is why I'm not too familiar with it as applied to microwave signals.

Many of the LNBs here are now multis to allow use of receivers with dual independant tuners, and the multi-room service which allows two dual tuner receivers to be connected to the same dish. Do you have multis like this that still work with c,p, ?

Arfa

Perception is everything, except in this case.

There are some technical advantages to CP. With a single LNB, it's possible to install the dish with only elevation and azimuth, and no consideration for tilt. However, with 2 or more LNB's, it is necessary to align the dish tilt along the ecliptic. Similarly, with CP at the satellite end, the bird could theoretically not worry about alignment. However, none of the satellites are that crude. There's also an advantage when dealing with reflections. Odd order reflections change the sense of the signal, which then is ignored by the LNB. However, if the reflections are that bad, there's going to be some deterioration even with opposite sense cancellation.

However, that's not why the US has CP and the EU is linear polarization. The US has a long history of *NOT* doing whatever Europe is doing. EU uses CODFM for DTV, US uses 4VSB. Cellular is mostly GSM in EU, but a mix of CDMA and GSM in the US. Our cellular bands are 800/1900, while the EU is 900/1800. Europe is 220VAC 50Hz, US is 117VAC 60Hz. EU used PAL, US used NTSC. EU is metric, US is weird. Any semblence of a concerted effort to be different by both parties is probably intentional.

Incidentally, you can buy LNB's that do both linear and circular polarization.

That's Faraday rotation, which isn't much of a problem at 13GHz.

It's really bad at L-band, C-band, and lower frequency terrestrial point to point signals, but not for geosync birds at Ku band.

Incidentally, that's another reason why GPS systems (1.2-1.6GHz) are circularly polarized.

You're asking my opinion? Well, the current fashion is for political leaders and organization to make technical decisions, so my suspicion is that if there were an even more obscure polarization method, the US would have adopted it.

Dunno. I don't recall seeing anything of the sort when I looked inside. I'll see what I can find instead of guessing.

Yep. 3 and 5 LNB's per dish is quite common for the HDTV systems that need to hear 4 different slots on both Ka and Ku band. Here are some:

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Items sold as dishes include amplifers.

A good start on what?

I'm not really interested in an electronics lesson. I just want to know what voltage would power the amplifier on the VHF/UHF antenna that surrounds the dish. The manual says it uses the same voltage that dish does, or something like that. Maybe you can write the manual's author.

I'll go with one of the helpful answers.

Why don't you just go away? You gave no brand or model number, or anything else that would let anyone help you.

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You can\'t have a sense of humor, if you have no sense!

Not completely true - the UK's old BSB satellite service used circular plolarisation (quoted as right hand circular which I'm assuming means clockwise) until the system was killed off by SKY's dodgy dealings - they persuaded the UK government that BSB would need 2 satellites so there would be a backup and that they'd need to use the more expensive D-MAC standard to get good enough picture quality.

The result being it cost a fortune to get new box hardware designed and put

2 satellites up just to broadcast 5 channels (which couldn't be expanded without launching another 2 satellites) when at the same time SKY were exempt from UK satellite broadcast restrictions due to uplinking from Luxembourg and were allowed to rent space on an Astra satellite with space for 16 channels and using cheaper PAL receivers that were already designed and available.

When BSB closed down (after only 6 months of broadcasting) the 2 satellites were sold to Scandinavian broadcasters who switched to D2-MAC and used them until 2003.

US DTV HD dishes are now tilted but I don't recall this in the beginning of their HD offering. Single/dual LNB are not tilted, at least mine isn't and there is no aiming spec for it. US DISH network has always tilted even with one LNB IIRC.

Yes, all quite true. I'd forgotten about the BSB service, it's active life being so short ...

And to Jeff. The 'multi' LNBs that I was asking you about are not multiple singles on a bracket on one dish, but all inside one standard sized LNB package, so it's one lump with either two or four F connectors on its back.

Arfa

In order to get helpful answers, you first need to have a little respect for the people who are trying to guide you. Your question doesn't even relate to any kind of "repair" - read the name of the group, so you are doing well to elicit any kind of sensible responses at all. If you are not interested in learning in order to help yourself to arrive at answers, why should we waste our time doing your research for you ? I would suggest that you try 110v AC "or something like that". If it works, you won't need to ask any more, and if it doesn't, you may learn a valuable lesson in both electronics, and life ...

Arfa

Dual LNB is a single LNB with two front end sections. It is aimed at a single satellite and can feed two receivers, or a dual front end receiver (i.e. DVR). A dish with two seperate LNB's, each with 2 outputs or 1 output going to a DISEqC switch, is a different animal as it's designed to hear two satellites. I try to avoid using the term dual LNB because it's ambiguous.

I've installed a few single LNB dishes. The dish alignment instructions and web pages didn't have any provisions for tilt. Only when multiple LNB dishes appeared was there any consideration for tilt. It might also be useful to note that the single LNB dishes do not have any mechanism for adjusting tilt.

With HD, one must see more than one satellite. As usual, Europe does it with a mechanical DISEqC protocol rotator, while the US does it with multiple LNB's. Each has their benefits and problems. I wasn't paying much attention when HD first appeared, but I do recall that it required a new dish because the feed came from a different bird.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

See my comment to Mr Meat Plow about the ambiguous term "dual LNB".

There are dishes with 5 LNB's and a built in switch. For example, the DirecTV AU9 Slimline dish:

They have 4 outputs, each of which can be switched to one LNB and pickup a satellite. The assumption is that there will be a maximum of

4 receivers attached, so that there's no need for a 5th output.

I haven't noticed a 5 LNB dish with only 2 outputs.

Things get rather messy with 7 satellites and 4 receivers:

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

I have great respect for and gratitude to the people who are trying to help or guide me. I don't believe the previous poster was.

OTOH, two posters gave me helpful answers. One was simple, and much of the other was above me, but it was still quite helpful. Thank you, both.

I don't remember how the manual phrased it, but it said it used the OTA antenna, that is the amplifier, used the same voltage as the dish, an 18 inch dish used either for Dish network or Direct TV, probably the first one.

I already know that lesson, and I didn't have to burn anything out to learn it.

Thanks for the explanation Jeff. I thought a dual LNB was actually two LNBs with different polarizations. But as far back as I was paying attention, the DISH discs were always tilted even before they offered HD and it's always been a question floating around inside my head as to why DTV were not tilted and DISH were way before HD. Maybe DISH has two LNB devices anyway and looks at two different birds? Or is it linier vs polarization circular at issue?

Your free antenna was designed to use the Sat feedline to not only power it but to also transfer the broadcast signal to either a Multi Switch with an antenna output or a splitter provided by the antenna manufacturer. My old Multi Switch had an antenna output IIRC. This would block standard brodcast frequencies with the downlink, control signals and voltages from your set.

If you just have the antenna itself and nothing else you may not have enough of it to work. What brand/model is it?