My C Band experiment on a SOD (Small Offset Dish)

[sonnetpete]

Inspired by Vipersan and others to at least try with C Band, I bought an LNB, mount and scalar ring kit. The only appropriate spare dish was my 1M Gibertini and I threw this on an acrow (on which I was surprised it fit), supported in my battered workmate.

I lined it up on using a Ku band lnb on 39°E as I was aiming for 40°E, which I'm informed is the loudest C Band source in Europe. Swapped over to the C Band and was surprised to get a poor lock just holding the bare LNB at the end of the dish arm!

After fitting the clamp (not ideal for the Gibi), fitting the LNB and then the scalar rings. I got a pretty good lock and signal, without trying the peak up the dish finely. I think I'll try for a couple of others, probably 5°W, then fit it to my 1.2M motorised to see what I can get. I'm very much in the dark as to where the LNB should be in relation to the dish and the position of the scalar rings.

Photo's below are pretty much self explanatory (though I'd like to point out the man in one of them is on screen, and not hiding in my lens as it appears!)

Now, where's the cutting boards aisle in my supermarket?

 

[Llew]

A good first try Pete. Look forward to seeing some screencaps of any channels you get.

 

[aceb]

Excellent stuff Pete, I can't get any further east than 20° on my 1.2 but the Ku 1m Gibby can get passed 60° so I may well invest in an offset scalar ring and mount. I've just noticed you had it installed using the PF scalar ring to begin with, did it make much difference changing over to the offset scalar?

I can't help on the position of the scalar and LNB on an offset dish, on a PF the theory goes (according to a Chaparral site I found last night) you set the back edge of the scalar against the mark that corresponds to the f/D ratio of the dish and the front edge of the feedhorn is set to the focal distance. Not sure if that can be translated into anything useful on an offset?

 

[sonnetpete]

Excellent stuff Pete, I can't get any further east than 20° on my 1.2 but the Ku 1m Gibby can get passed 60° so I may well invest in an offset scalar ring and mount. I've just noticed you had it installed using the PF scalar ring to begin with, did it make much difference changing over to the offset scalar?

I can't help on the position of the scalar and LNB on an offset dish, on a PF the theory goes (according to a Chaparral site I found last night) you set the back edge of the scalar against the mark that corresponds to the f/D ratio of the dish and the front edge of the feedhorn is set to the focal distance. Not sure if that can be translated into anything useful on an offset?

Yes, it did make quite a difference when I put the scalar rings on. I'll have a look for F/D ratio and focal distance for the Gibertini. To be honest I set it up for best results with the meter but there are three variables to adjust. Actually, four if you include that funny Caramac looking thing in the LNB, all I know is it desn't work well without it.

 

[A nonymous]

What brand of LNB is that Pete?

I can see the Scalar ring is the same brand as the one i've purchased, but i don't think the lnb is.

I Purchased a cheepo Pauxis C band lnb to play with. No idea how good they are, but i thought it would be a good place to start before spending some serious money.

The Scalar ring arrived from the states in about 4 days. I think the lnb is coming by Rickshaw from Taiwan judging by how long its taking

Nano

 

[sonnetpete]

What brand of LNB is that Pete?

It's a DMS International BSC421. It was bundled together with the scalar rings and an offset dish LNB holder from one of the forum sponsors. I don't think I'll start swapping out LNB's to find out which is best!!

_www.dmsiusa.com

 

[Vipersan]

HI pete ...
You can also try Rascom/Chinasat @2.8 East ...
The recent find of a feed/promo loop ...details of which are in Acebs thread ..

Its so strong you should have no problems picking it up ..
It is actually linear ...so no plate required ...but stong enough to be logged with the plate inserted ..ie circular mode ..

Certainly imo ..another easy target to find.

...looking forward to your updates in due course.
rgds
VS

 

[sonnetpete]

It's one I could go for VS, but I'll have to see if I can add a new sat to my meter (which I haven't been able to yet) or somehow add that TP or find one on another sat which is the same. Other than that, I'd be back to the beeper. I haven't found out how to add a satellite to the F15, is that possible?

 

[Vipersan]

Hi Pete ...
The simple answer is No ...
A big bone of contention with F15 and F16 users ...
The satellite list is fixed ...and all are in use .... but for a couple ..
No problems though ..changing them ...
For example there is a list of HD and Adult transponders in a list ...plus some sats out of reach to us in the UK ..
These are easily edited to make space for something useful ..
I think the limit is around 60 sat positions ...but all mine are in use ..due to me wanting both ku and C in the list..
Just edit the ones you don't want ..to sat positions you do ..
rgds
VS

 

[Vipersan]

..Also ..
I'll be home from work in about 30 mins ..
I'll email you the editor ...
This will allow you to export your settings to a pen drive ...and open on a pc ...
Edit transponders sats etc ..then upload back to your F15

Easier than doing it through the on screen menus

rgds
VS

 

[Vipersan]

you have a PM reply Pete..

rgds

 

[sonnetpete]

A good first try Pete. Look forward to seeing some screencaps of any channels you get.

Here you go Llew.

 

[Llew]

Ah yes - they're the ones I had on my Triax 88. Need a larger dish if propose to try other satellites. No spare cash unfortunately after buying the TBS 6925 PC card O-no

 

[sonnetpete]

I might experiment a little more this week but it's a less than practical arrangement I've got at the moment. (and I really need to make progress with other things!) Mounting the C Band on the motorised dish is something I need to look into, though it will require some thought, as the Laminas has three support legs more like a prime focus dish, which makes the supplied offset conversion bracket 'challenging' to fit. I could actually lash it on top of the Black Ultra, as I suspect it would make little performance difference. Margins for error with C Band seem a lot greater than Ku.

 

[nelson_b]

as the Laminas has three support legs more like a prime focus dish, which makes the supplied offset conversion bracket 'challenging' to fit. I could actually lash it on top of the Black Ultra, as I suspect it would make little performance difference. Margins for error with C Band seem a lot greater than Ku.

hi - sonnetpete -

i had the problem of the support legs being in the way of the feed etc on the channel master 1 metre and 1,2 metre -- and made a simple support bracket which has done the job nicely , i dont know if a similar type would do for your laminas dish but here,s some pics anyway, hope they help -- just a mention, the difference in the reception from a 1.2 dish compared to a 1 metre is massive -- 1 metre gave a handfull of channels over 3 sats - the 1.2 gave well over 100 over 8 or 9 sats

cheers nelson.b.

 

[Vipersan]

...Go on then Nelson ...
I'll be the one to ask ..
Wots wiv the wedge shaped plate ...mate..
;)
rgds
VS

 

[nelson_b]

...Go on then Nelson ...
I'll be the one to ask ..
Wots wiv the wedge shaped plate ...mate..
;)
rgds
VS

just something i read about on a satellite forum
it definately - helps reception on the channel masters

cheers

 

[Vipersan]

just something i read about on a satellite forum
it definately - helps reception on the channel masters

cheers

Useful info Nelson ..
It might make all the difference to Channel master/cband users

rgds
VS

 

[sonnetpete]

That looks a useful mod Nelson, but the support legs on the Laminas are a lot thinner and less 'robust' than those on a Channel Master. I think it requires some pre planning as I don't want to make permanant alterations to the dish as I'll still use it for Ku band as well. Laminas do a offset bracket and I wonder if I can get one and modify it to take the C Band and leave it on the dish with the Black Ultra.

 

[nelson_b]

Laminas do a offset bracket and I wonder if I can get one and modify it to take the C Band and leave it on the dish with the Black Ultra.

yes maybe that will be ok -- the permanent arrangement i have on the 1.8 CM , is with the k/u in the centre and the C band offset by 5- 6 degrees -- and i did not notice any loss of signal to speak of, from when i had it in a central position.

cheers