39" dish is possible to modify

[rodo2222]

hi i wonder is i can modify my 39" dish adding 9 more inches at the edge with aluminum to convert it to 48", if any one can give an advice i really apreciate for the help. thanks.

 

[navychop]

Interesting question. Brings up things like the curve of the dish, the precision needed to hit the exact focal point, and any differences in signal reflectivity based on different materials. Sounds like a really tough job. I can't say I've ever heard of someone doing this, but heck- I know so little about FTA.

Sent from my iPhone using SatelliteGuys

 

[Pi314]

This sounds familiar and I think there is a thread about this floating somewhere here. There is an equation to find out your focal length to diameter ratio.


f (focal length) = D squared divided by 16 times C
or D x D / 16 x C
where D is the diameter of the dish surface and C is the depth.






More about that here:
http://www.geo-orbit.org/sizepgs/tuningp4.html#anchor879461

 

[FaT Air]

If you can accurately, and I mean down to the mm, the parabolic shape of the reflector it would be worthwhile. Otherwise it's 'just for looks'. IMHO

 

[FaT Air]

Second thought - - - This must be an offset Ku dish(???)
The focal length wouldn't change, so the LNBF probably wouldn't see the added area anyway. (The F/D ratio is preset on a Ku LNBF) Larger dish requires longer focal length so the 'cone' the feed illuminates can 'grow' to see the additional area.
The focal length of my 1.2 meter is quite a bit more than the 1.0 meter, and a LOT more than the .7 meter.
So in retrospect, think it would all be just 'for looks'.

 

[navychop]

Second thought - - - This must be an offset Ku dish(???)
The focal length wouldn't change, so the LNBF probably wouldn't see the added area anyway. (The F/D ratio is preset on a Ku LNBF) Larger dish requires longer focal length so the 'cone' the feed illuminates can 'grow' to see the additional area.
The focal length of my 1.2 meter is quite a bit more than the 1.0 meter, and a LOT more than the .7 meter.
So in retrospect, think it would all be just 'for looks'.

Thank you for the post. I should have thought it thru and realized what you said. I suppose technically the outer addition could be "bent in" and force the signal in, but it would take Einstein to do it?

 

[KC9TIK]

Be sure to post pics when you're done.

 

[RimaNTSS]

2rodo2222: If this is your hobby, just to spend some time, than you can try. But, in reality, after spending time and money you will get 0-improvement in reception. Much easier and lot cheaper is to get bigger dish, even second-hand. I've seen PFA antennas with extension panels, for example to transfer 1,8m antenna to 2,4m., but nobody is extending offset dishes.... too difficult.

 

[rodo2222]

hi, guys thanks for all your replays thanks rimantss, kc9tik,navychop, fatair, pi314, i don't know much about dishes i was just thinking, i seen 1.20 dishes cheaper but the shipping is almost the same as the dish i think is to much, and the dish is model s900w and have a scale from 10 to 70 at the back and did not says offset, but you guys know more that i know thank you again to all of you and if i try to do something y will post pictures. good bless you guys. good night

 

[navychop]

Best to you!

Sent from my iPhone using SatelliteGuys

 

[FaT Air]

Keep on the look out for one that could be 're-purposed'. One may even show up in this thread Kijiji, eBay, and Craigslist dishes for you to take a look at