Use satelite dish as aerial

mp3ireland2

Possibly a stupid question but could a sky dish also be used as an aerial if you put a splitter on the cable? It's a lump of metal on the roof so though it could work? My sister has an indoor aerial at the min but reception not great but thinking that the dish could work? Anybody tried this?

The Cush

mp3ireland2 wrote: »

Possibly a stupid question but could a sky dish also be used as an aerial if you put a splitter on the cable? It's a lump of metal on the roof so though it could work?

The thing is the co-ax cable to the sat dish isn't connected directly to metal dish but to a little box of electronics, the LNB, at the end of the dish arm.

She could maybe fix an external aerial near the dish and combine the aerial feed down the sat co-ax cable and split it again before the sat receiver.

winston_1

mp3ireland2 wrote: »

Possibly a stupid question but could a sky dish also be used as an aerial if you put a splitter on the cable? It's a lump of metal on the roof so though it could work? My sister has an indoor aerial at the min but reception not great but thinking that the dish could work? Anybody tried this?

Nope, a TV needs an aerial not a lump of metal on the roof. As I've repeated to other posters only around 10% can use an indoor aerial. Your sister is one of them. She need to get a proper aerial put up.

mike65

Wire mesh works, but that's not a satellite dish either.

Ronnie Raygun

Mesh only works as a reflector.

reboot

mp3ireland2 wrote: »

Possibly a stupid question but could a sky dish also be used as an aerial if you put a splitter on the cable? It's a lump of metal on the roof so though it could work? My sister has an indoor aerial at the min but reception not great but thinking that the dish could work? Anybody tried this?

Have seen a sat dish used with a 3g phone placed at the focal point of the dish,instead of the LNB.So not a stupid question.I have no mobile service where I live(No masts in our area etc),but if I set the phone in an aluminium tray,left over from a rhubarb tart,hey presto.
May be way off thread here,apple tart not so good!

watty

You would need a UHF dipole where the LNB goes.

Satellite is 11GHz. A 3G data connection is 2.1 GHz. That is 5:1 ratio, 1/25th gain

UHF at 600MHz is 1/336th of the gain as at 11GHz. Assuming you have a UHF dipole at the focus instead of LNBF.

This is why at UHF dishes less than 4m diameter are not used. Even a small indoor Yagi aerial (sitting on a hedge) is much better than a 65cm dish.

At Ka band (22GHz, near Saorsat frequency) a good smooth solid dish gives FOUR times the signal as it does for Sky/Freesat.

If it was mirrored and optically smooth you could set stuff on fire.

(I have simplified the explanation by including effect of change of Free space path loss with frequency)

The small Mesh dishes work on MMDS because it's 2.5GHz to 2.6GHz band. About 16x better performance than UHF on such a dish.

Capt'n Midnight

Ronnie Raygun wrote: »

Mesh only works as a reflector.

only if pointed at the transmitter
and only if the tv aerial is positioned correctly relative to it

At best putting a small TV aerial on the bracket would save you some drilling, but it will increase the wind loading, and there is the likelyhood that you would upset the dish alignment (1cm at the lnb is enough to ruin your day)

You'd need to run a new cable too (yes you can buy combiners/splitters but they cause signal loss which is never a good thing)

reboot

watty wrote: »

You would need a UHF dipole where the LNB goes.

Satellite is 11GHz. A 3G data connection is 2.1 GHz. That is 5:1 ratio, 1/25th gain

UHF at 600MHz is 1/336th of the gain as at 11GHz. Assuming you have a UHF dipole at the focus instead of LNBF.

This is why at UHF dishes less than 4m diameter are not used. Even a small indoor Yagi aerial (sitting on a hedge) is much better than a 65cm dish.

At Ka band (22GHz, near Saorsat frequency) a good smooth solid dish gives FOUR times the signal as it does for Sky/Freesat.

If it was mirrored and optically smooth you could set stuff on fire.

(I have simplified the explanation by including effect of change of Free space path loss with frequency)

The small Mesh dishes work on MMDS because it's 2.5GHz to 2.6GHz band. About 16x better performance than UHF on such a dish.

Parabolic dishes have been used behind open fireplaces to focus and direct heat into the room,(Its all the same "Stuff,just at different freqs) One can be seen at Castleward,National Trust. 1830 ish?,and behind my wood burning stove.The dish at C/Ward goes one better than mine,it has a handle and pivots, to throw the heat to different parts of the room.
A good "Links" man could tell you how far away to sit by working out the focal point.

Capt'n Midnight

reboot wrote: »

Parabolic dishes have been used behind open fireplaces to focus and direct heat into the room,

Then again the dish is much bigger than the wavelength




Spherical or parabolic reflectors would of course lead to aberrant behavior.

reboot

Who said science wasn't sexy on Boards?