Large Dish

peliroco

Hi All,

I had a scan through the various forums but couldn't find anything to help me out. I am looking for a large sat dish (2.3m prefferably) and i am wondering does anyone know of where i could purchase one?
There are plenty available in the US and Australia but they dont' ship to Ireland.

Thanks for the help

peliroco

watty

Maplin (overpriced), HMsat.de maybe.

Can we ask what you hope to do with it?

Zaphod

Try emailing Satworld. http://www.satworld.ie/

peliroco

yeah cheers ill try emailing Satworld but i'm apprehensive.

The dish itself won't be used for TV much. I have tried in the science section but there is nothing there either. It'll mainly be used for educational purposes. Mapping H-alpha lines and sunspots etc for local schools and astro clubs. There are one or two already available in the US but have a 9 month waiting list and i was hoping to get one sooner.

Zaphod

peliroco wrote: »

Mapping H-alpha lines and sunspots etc for local schools and astro clubs.

How do you map H-alpha lines and sunspots with a dish?

peliroco

Well technically it would be the distribution of Hydrogen within the plane of our solar system, rather than the specific H-alpha line but with the correct LNB (Hydrogen emits at 1420MHz) and a spectrum analyzer then PC feedback results in a spectral analysis of the milky way.
Spectrum analyzers don't need to be that expense (I've witnessed first hand a bunch 17yr olds building a circuit to do basic radio spectrum analysis).

Sun spots would be similar in that depending upon the freq then the particles emitted during a flare could be viewed (I've never tried this one so i can't say for sure but i am aware of others doing it).

watty

Then a cheaper mesh C-band dish would do.
You can get a 3.7m flatpack, the frame of ribs is assembled and mesh petals screwed on.

Or cut a parabola.
Make mound of sand with pole in middle
run plywood parabola arround the sand heap to get parabaloid shape
spray with paint
lay fibre glass mats and spray with polyester or epoxy.
glue on al foil or fine mesk
more mats and polyester/epoxy
Make more ribs and fibre glass around it.
Remove from sand and smooth / paint front

Mount.

Not easy to make accurate for 10GHz. But for L-Band 1.4 to 1.5GHz, a very cheap way to do 2m to 6m dish.

mesh hole size or (dish surface has to be accurate) to better than 1/10th wave length.
1GHz = 3cm (Just below L-Band)
3GHz = 1cm (Below C-Band)
10GHz = 3mm (X-Band, just below Ku Band).

So you can see for 1450MHz, fine chicken wire would do to make your dish.

A second hand HP141T with the correct plug in is best value spectrum analyser.

Or else a 28MHz bandwidth L-Band radio (your custom LNB) downcoverting to 100kHz to 28MHz and a USB socpe/ spectrum analyser (120 Euro) that samples at 60MHz.

A tuner of a very old voltage tuned Analogue satellite receiver will work as a primitive spectrum analyser from 950MHz to 1700MHz. Old 16 ch memory Alba has a suitable tuner. You can use a Vellman 50 Euro USB controller to control a 1V to 25V regulator from its 0V to 5V 256 step analogue output and peak detect the tuner IF out and feed to Vellman Analogue in. A simple program in VB, C++ or C# can slowly tune the Satellite Analogue tuner and display graph of level. The slower you tune the narrower an IF filter you can use to reject noise. The filter bandwidth wants to be about 1/500th of your sweep span.

If the Vellman 0 to 5V feeds a suitable regulator circuit, you can adjust (gain) span of frequncey to sweep and (offset voltage) start frequency. Thus your 256 steps could be 1390MHz to 1480MHz instead of 950MHz to 1700Mhz.



Old spectrum analysers like the HP141T had very expensive storage tubes, the PC program does that better and cheaper.

peliroco

Cheers Watty.

First of all i'd like to correct myself. I noticed that i said

distribution of Hydrogen within the plane of our solar system

. That should obviously have said Galaxy.

The flatpack 3.7m sounds interesting. Do you know where i can get this??

I have a few spectrum analyzers in mind (mainly USB but one or two through a NI DAQ card for fun really). I plan, as you say, to do a C# program then as a GUI.

I do like the idea of using some of the more primitive tools as well as it really gets those doing it to think about what they are doing on a number of levels and not just that "a computer does it" type approach. you've given me food for thought.

Cheers again

Zaphod

peliroco wrote: »

The flatpack 3.7m sounds interesting. Do you know where i can get this??

http://www.satshop24.de/satshop24_s/meshantennen_mesh_kti_antennen_ab_2_10m_.html

What's your budget like? It would give us an idea of what's feasible.