Tiny 20cm SMW dish (and an old BSB dish)

[Lazarus]

Is your garden big enough? 180ft is not inconsiderable.

 

[Captain Jack]

Yep, I have a number of presently empty fields behind my house.

 

[timo_w2s]

Here's what it looks like built with the original LNB. Haven't had a chance to test it yet.

Quick question, if the LNB is marked as 11.7-12.5GHz, what LO setting should be in the receiver? 10.60GHz?

 

[Lazarus]

Well it depends.

As you've got an 800MHz range, and you need to downshift it to L Band, which IIRC is from about 950MHz to around 2.2GHz, you have the scope to experiment a bit..

10.6GHZ would shift it nicely to between 1.1 and 1.9GHz, so is a suitable fit bang in the middle of L Band.

Of course, correlating the results against generic Channel listings will require a moments thought, but what the heck.

 

[Archive4]

Looks good! Shame about the watch, though the haircut is better
Oh yeah, the question, 10.6 should be OK

 

[Lazarus]

PS That LNB dwarfs the dish itself, even despite the foreshortening effect of the pic!

 

[timo_w2s]

Thanks guys, I'll try 10.6 and see how it goes. Mind you, it won't be easy, especially as it's a circular LNB but I'll see if I can get some 36E Russian channels on it as the signals are quite strong in Helsinki and they are the only circularly polarised stuff I can see from my location.

That SMW LNB is ridiculously big for the dish. I'm going to try an Alps LNB for the other satellites as it has the pointy head which fits the bracket and is a lot lighter and smaller.

 

[huve]

Try 56E if you can, it's much stronger than 36E. I get the wide beam fta channels with linear lnb. The dish is so small and light than you can temporarily tape it to broomstick or vacuum cleaner tube for testing.

 

[timo_w2s]

Try 56E if you can, it's much stronger than 36E. I get the wide beam fta channels with linear lnb. The dish is so small and light than you can temporarily tape it to broomstick or vacuum cleaner tube for testing.

No chance from my west facing balcony. I think I'll just about manage to see 36E. But this dish is so small I guess I can take it over to my parents place and see if I can see 56E from their roof.

 

[timo_w2s]

It's been a while since I started this thread but I finally managed to get some spare time to have a play with this 20cm SMW dish in Helsinki. It was a nice calm morning with just some light cloud to the south.

I haven't tried the original circular LNB yet but I found that a narrow Alps LNB fitted the best for linear reception on this unusual setup. Standard LNBs where simply too wide as the feed arm was in the way. You may also notice from the pictures that I used a rather crude way to hold the LNB to the arm using a safely arm band reflector that I had lying around which allowed for easy adjustment of the LNB to find the best signal.

Results were not brilliant, but I wasn't expecting too much on this size dish. I think one of the biggest issues is the beam width of the dish is so great it's too easy to pick up unwanted interference from nearby satellites. I could see as I moved the dish around how signal levels didn't vary much over a large area. It certainly made finding satellites easier...



First I tried 1°W. I could only lock one transponder, 11.421H at 8.3dB on the DrHD F15. Most of the other Nordic beam transponders where showing between 3-6dB but not locking due to the FEC used. The wide beams where under 2dB and Intelsat 10-02 beams were non-existent.

Next I swung the dish over to 5°E. Most Nordic beam transponders where under 4dB but I managed to get a lock on three transponders at this position:
11.727H 7.1dB
11.862V 5.7dB
12.476V 7.0dB

Moving further east, I couldn't find a recognisable signal from the Hotbird cluster at 13°E but I did manage to see the right pattern of transponders from Astra 1 at 19°E so I knew I was on target here. No luck with locking anything as most signals where under 2.5dB but 10.964H (3.9dB ) and 12.574H (4.2dB ) where the strongest two transponders according to the DrHD F15 receiver but sadly not enough to decode a signal.

Then I moved on to Astra 2 at 28°E. Unsurprisingly I could only see a pattern of signals from the Astra 2G Europe beam. 11.225V was coming in at 3.2dB but wasn't quite enough to lock it. Most of the other 2G Europe transponders where just under 2dB. Nothing from 2E/2F.

Finally, I also had a quick look at Astra 5B at 31.5°E. 11.954H was the strongest at 3.2dB but again no lock. I'm also reaching the limits of my view of the Clarke Belt to the east from this location.

So that was just four transponders that I could lock from two orbital locations using this dish in Helsinki and rather annoying nothing that I could watch as the transponders all contained encrypted stuff.

Next I'm going to take it to Maidenhead with me to see how it does in the UK. Hope to get slightly better results there. I'll report back once I've got some information to share.