The C-band Tin-Dish challenge

A

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So size matters, even more on C-band.
Unfortunately, good 180cm dishes are not cheap, and the used ones only comes up occasionally.
Also, they require much sturdier mounting poles and polar mounts == more hassle, and more expense.

Then perhaps the heretic question:

If you just want to dabble into C-band, to see what it's like, perhaps there is a low-cost alternative as a try-out? Could it be ... gasp ... a 6-petal tin dish?

If size is everything, and C-band is much less intolerable of surface inaccuracies, then one of the Chinese or Taiwanese tin-dishes might do the job for a season's worth of experimentation.
Notwithstanding the manufacturing quality (or lack thereof), these dishes are very likely designed for C-band operation. At least they are often marketed as such, if judging by the Asian web sites.

Can't quite make out who is manufacturing for whom, and which are originals and which are blatant copies. But there a lot of them about! (Furniture land seems to be trying to peddle them.)

The sheer size will, however, put off a sizable portion of our members - they live in/near city, where 180 cm dishes are not readily, erm, erectable. Nevertheless, some of us have less such problems, some may choose to put them in the back yard, some have understanding neighbors etc.

Now, the mount (pedestal/pillar type) that come with these things are sh*te, so we need some form of polar mount. Some (Fortec Stars in the US at least), can be ordered with a polar mount.
Those are scarcer here in Europe. But as the dish does not present a lot of weight, perhaps it can be grafted onto any other "normal" prime focus polar mount - these seem to be available postal order from china. Or re-used, I have one here for a 140 cm dish - it could probably do the 180 without too much stress.

Yes, I know I have lambasted these dishes in the past; but that's when they're marketed and sold as Ku-band dishes for fringe reception. Does not work.
But as a single-season, or a-few-season C-band dish, it just might work??

So there you have it: a challenge to go forth, low-cost, into C-band land with a crappy tin-dish, which might just work for C-band only reception!


PS: I think I managed a triple negation in one of the sentence above - not everyday you commit one of those!
 
rob12770

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useful post thanks,
yes a tin petal dish might do for experimenting, also easy to get delivery due to its construction.
I am thinking also of setting up a mobile outfit, so i can go out up a hillside with no obstructions and do some feed hunting etc, sounds a bit mad i know, but i do this sort of thing with radio quite often, might be fun with satellite tv gear :D

thanks Rob :)
 
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rob12770

rob12770

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yes, that looks pretty great, not sure if the trailer is totally necessary in my case , ( given i have a big enough vehicle) i could possibly mount it straight onto the a frame of my tow bar..ive done it with a 25ft vertical antenna.. so should be ok
cheers rob
 
aceb

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1.25m Gibertini + Inverto B.Ultra/C1W, Moteck H180, 68.5E-67W Ku/C-Band /
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I say go for it, I've seen so many people slag off the Fortec Star/Jonsa dishes for performance often due to their inability to construct it to a good enough standard, because they're using it on Ku and comparing it to a similar sized dish costing ten times the price or because they've never had one but have read what everyone else says. Obviously you get what you pay for but if a £150 dish is a dB down on £1500 dish then it's probably worth experimenting with.

I've found very few (read none) tests of the 1.8 or 2.4 being compared to a similar sized dish on C Band so one needs doing! I've got a 2.4m FS here that I keep meaning to test on C Band but it's finding the time to construct, align and compare it against my 1.8m Precision.

The fixed mount is very poor quality indeed and the base ring is rusted quite badly but I was surprised how heavy the petals are, I can't lift them all together when they're stacked inside each so they're not exactly wafer thin. As you say with some home construction I'm sure an adaption could be made so the reflector would bolt onto a polar mount and to that end I've been looking for a mount to come up on Ebay but so far no luck.
 
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I cant find the thread but someone recently installed one pointing 50ish west it was roughly aligned and he was doing ok, hope he sees this thread and gives his reports.
 
S

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B

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Thanks G, that not the one I was thinking about but good results, the one was very recently the chap has a 1.8 channel master and lives in Scotland,

I say go for it, I've seen so many people slag off the Fortec Star/Jonsa dishes for performance often due to their inability to construct it to a good enough standard,
You might have hit the nail on the head, I might try one at some point fixed around 68,5e
 
aceb

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1.25m Gibertini + Inverto B.Ultra/C1W, Moteck H180, 68.5E-67W Ku/C-Band /
1.8m Precision PF + ESX241/Inverto Black Pro, 66E-63W Ku/C-band /
2.4m Fortec Star+Titanium C1W/Pride plate, 49E-58W
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I'm playing with a 2.4m FS on C Band at the moment and so far I'm impressed. Once I've got a selection of signal readings across the arc I'll move the ESX241 onto the 1.8 and repeat the test so I can compare results, happy to write up the comparison if anyone is interested?

If anyone in the southern part of the UK has a few marginal signals they could check and post the SNR I could try a comparison from here, ta!
 
lovelyperson

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..........I'll move the ESX241 onto the 1.8 and repeat the test so I can compare results, happy to write up the comparison if anyone is interested?
Def interested as I know most here will be...thanks. respect-048.gif
 
John

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Def interested as I know most here will be...thanks. View attachment 98505


.... Certainly food for thought for spending a few more quid on it as a D.I.Y upgrade path, if it were constructed accurately i would like to see pics of it "strung" to get some idea of it's accuracy to see if it would be a viable exercise. Fabricate more support structures from nearer to the edge of dish to circular back ring to more of a "hub" type fixing for a stronger installation. Change to Inox nuts, bolts & washers etc .... Apply decent coats of paint or varnish / laquer to panels for more weather resistance etc etc . would make a nice little project if your into tinkering ;)
 
Captain Jack

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@aceb had some interesting results on his FS 2.4 .. outperforms my 1.8m CM in C...
 
John

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.... Certainly food for thought for spending a few more quid on it as a D.I.Y upgrade path, if it were constructed accurately i would like to see pics of it "strung" to get some idea of it's accuracy to see if it would be a viable exercise. Fabricate more support structures from nearer to the edge of dish to circular back ring to more of a "hub" type fixing for a stronger installation. Change to Inox nuts, bolts & washers etc .... Apply decent coats of paint or varnish / laquer to panels for more weather resistance etc etc . would make a nice little project if your into tinkering ;)


Edit: also .... stringing is one thing, i wonder how accurate the pressings are for accurate parabola shape of the panels ?
 
aceb

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The panels probably aren't as accurate as a dish costing thousands but if anyone wants a cheap dabble with C Band then this looks like a go-er, I was given this one FOC so it doesn't owe me anything but I was suprised how heavy it is, I can't lift all six panels and it doesn't deform as I push it around. The base is shocking, it's really cheap and nasty with quite a bit of rust and some holes forming in the bottom ring but it quite well balanced, I'm weighting it all down with bags of ballast but it doesn't attempt to fall over if I remove them.

Each of the petals eventually lined up within half a mil of the adjacent one and I strung it using cotton, two pieces per petal, end result were all lengths just touching with no obvious gap. I'm using a scalar that was shipped with my C1 bolted onto the FS arms and the ESX is set where it gave best SNR on the BBC mux on 1W, that equated to 905MM focal distance. I've got another scalar so at some point I'll fix further back on the arms, set the correct FD and then use the other scaler to peak SNR but this was a rough and ready test to see what these are like on C band.

I'm more than happy with the results today with quite a few firsts across the sky. I'm just about to test it on 38E then I'll move it round onto 58W, once I've checked that one I'll stick the ESX on the 1.8 and see how it compares.
 
A

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Fabricate more support structures from nearer to the edge of dish to circular back ring to more of a "hub" type fixing for a stronger installation.
Yes, that's more like it!
Keeping @Analoguesat 's and other's wheel--based-mounts in mind, maybe here a new proper use for steel rims?

Quite strong, and can be fitted with angle-iron bits by drilling and bolting (or welding for @RimaNTSS), they would be great "hub structures" for the back of these dishes. Then 6 pieces of angle iron to make support struts, and you're ready for gale force winds.

...but a whole different class of polar mount to support the weight :(
The 180cm would probably require one of those Precision polar mounts like the ones @Spiff and @Captain Jack has...
 
RimaNTSS

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or welding
Friend of mine is saying that welding is only one of the ways of joining metal. And I agree with that. Moreover, welding might not be best option in some cases. ;)
 
aceb

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Foiled by the weather. was hoping to re-measure some of the signals on 38E this morning, swap the ESX onto the 1.8 then compare results. These are some of the signals I recorded yesterday.

40E (partially obscured by trees)
NTV0 3675V 15.3dB
Dagestan 3561V 12.3dB
TB 3740V 13.3dB
P1 3743V 9.7dB

38E My go to satellite for testing, locked a total of 14 transponders from this yesterday.
Capital 4184V 8.8dB
Waseb 4114V4.7dB

30E
data 4106L 8.8dB

20E
AFTV 3884R 13.8dB
data 4110R 7.1dB

10E
NWTV 3664R 11.1dB
RTV 3701L 9.4dB

5E
MFM 3693L 11.1dB
TV001 3844R 6.1dB
C3 3924L 6.3dB

3E
Clouds 3668R 11.3dB
QFM 3785L 5.2dB

1W
BBC 3985 11.3dB
BBC 4032 8.6dB

8W
Channels 3840L 9.4dB
Star 1 4135R 8.3dB
Star+ 4171R 8.2dB

11W
Russia 3662R 8.6dB

18W
Racing 3961H 10.6dB
ZBC 4018R 4.3dB

24W
RTS1 3653R 6.7dB
ORTM 4120R 4.1dB

Waseb TV 38E
WASEB_TV_0380 4114_V_5700_20160930_174929.jpg

QTV Zambia 3E
QTV Zambia_0030 3795_H_1570_20160930_133129.jpg

Star One 8W
Star One_3520 4135_V_30000_20160930_110052.jpg

Pointing at 50W
24fs.jpg
 
A

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Friend of mine is saying that welding is only one of the ways of joining metal. And I agree with that. Moreover, welding might not be best option in some cases. ;)
Welding, bolting, rivetting, gluing...
what else - clamps? magnets? Suction air pumps? The Force?
 
Channel Hopper

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Welding, bolting, rivetting, gluing...
what else - clamps? magnets? Suction air pumps? The Force?
Add soldering and brazing to the list
 
A

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Hmm... if the tin-dish concept means worse focus, would it then be possible to adapt to this by using technology similar to thos flat square dishes?
I.e. an LNB that does not have a feed-horn, but rather a flat, probably round, front-end?
This would probably be mounted slightly closer to the dish, to achived illumination of more of the surface.
And if things got really up-to-date, we'd use DSP power to amplify and combine different parts of the "LNB", giving maximum aggregate signal...

I seem to have problems finding documentation on how flat, square dishes work.
Can some-one here enlighten me on how those square dishes really work as antennas?
 
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