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

[sonnetpete]

Oh, that sounds ok. Here's the bracket :

_http://www.2galli.fr/boutique/fiche_produit.cfm?ref=SUP2OFC&type=30&code_lg=lg_fr&num=21

I was thinking I might be able to get them closer than the 6° quoted with a bit of modification. I'll need to do something as obviously they are only 40mm holders. If there is problem with signal drop because the C band is off focus, I can always alter the sat's location slightly so that USALS will put it where it thinks it is. It's worth a punt I think.

 

[Huevos]

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.

Those numbers aren't related to an offset dish with a conical feed. I've found the feed works best adjusted to about 32.

makes the supplied offset conversion bracket 'challenging' to fit

It would probably be easier to make something from scratch.

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.

That will never work. You will be about 7º below the arc.

If there is problem with signal drop because the C band is off focus, I can always alter the sat's location slightly so that USALS will put it where it thinks it is. It's worth a punt I think.

I don't understand what you mean here. Best thing would be forget USALS for your C-band LNB and just set it up DiSEqC 1.2 on each satellite. With your Black Ultra for Ku band and the conical feed for C-band on the 1.2m dish you are going to need to move the dish about 7º when switching from Ku to C-band to still be aligned on the same satellite. And even though C-band alignment is not as critical as Ku, you still want to get as close as possible to perfect alignment especially when you are already using an undersize dish and an offset LNB.

 

[nelson_b]

Oh, that sounds ok. Here's the bracket :

_http://www.2galli.fr/boutique/fiche_produit.cfm?ref=SUP2OFC&type=30&code_lg=lg_fr&num=21

I was thinking I might be able to get them closer than the 6° quoted with a bit of modification. I'll need to do something as obviously they are only 40mm holders. If there is problem with signal drop because the C band is off focus, I can always alter the sat's location slightly so that USALS will put it where it thinks it is. It's worth a punt I think.

ah - yes that looks promising - with a bit of luck you will be able to keep the C band feed clear of the side support arms -- that was the biggest problem for me on the 1.8 ,
i had to lower the side arms a lot to get them out of the way of the blue feedhorn .

with 5 degree spacing i have to alter the positioner quite a bit from the k/u settings for the C band l.n.b,
and as i get further away from the centre of the arc -
elevation adjustment is needed too - so the home made incline adjusting jack setup, that i fitted years ago , is getting plenty of use recently

cheers -

 

[Huevos]

as i get further away from the centre of the arc - elevation adjustment is needed too

Is that just on the C-band LNB or on Ku-band too?

 

[nelson_b]

Is that just on the C-band LNB or on Ku-band too?

it seems just with weaker C band signals that i need to adjust a little,the further east or west i go
i havent noticed it with central k/u l.n.b.
do you think my setup could be slightly out of adjustment ?

regards.

 

[Huevos]

do you think my setup could be slightly out of adjustment ?

Sounds like it. My question is, if all three LNBs are aligned correctly at the centre of the arc how is it possible that the C-band LNBs go off track as you approach the extremes but the Ku-band LNB doesn't? If anything I would expect Ku to show any tracking error first due to the higher gain and narrower beamwidth.

 

[sonnetpete]

That will never work. You will be about 7º below the arc.

Yes, I do see your reasoning, it was me being (a) lazy, and (b) too eager to get the C Band fitted to the motorised set up. Obviously, there's no substitute for placing the LNB where it's designed to go. However, this is an experiment and unless you try, you can't learn from your mistakes.

I don't understand what you mean here. Best thing would be forget USALS for your C-band LNB and just set it up DiSEqC 1.2 on each satellite. With your Black Ultra for Ku band and the conical feed for C-band on the 1.2m dish you are going to need to move the dish about 7º when switching from Ku to C-band to still be aligned on the same satellite. And even though C-band alignment is not as critical as Ku, you still want to get as close as possible to perfect alignment especially when you are already using an undersize dish and an offset LNB.

I'm going to try and get the C-Band and Ku Band LNB's as close together physically as I can. I can't see this being any closer than a 4° seperation though. What I didn't realise was that you can mix USALS and DiSEqC 1.2 on the same receiver. I once tried this on my Vantage and made a complete horlicks of everything so I've avoided doing it again, hence the 'alternate'.

A little OT, but having tinkered with the DrHD for a few days, I'd say it's tuner is a little more sensitive than the VU+. The Vu+ was starting to break up on Badr6 last night and when I switched to the DrHD it was rock steady. There isn't much in it but I can see a difference.

 

[Huevos]

I'm going to try and get the C-Band and Ku Band LNB's as close together physically as I can.

Pete, mine are as close together as possible too (see picture below), but with the size of the C-band feed that is still far enough apart that I need to move the dish 5º to move from Ku-band to C-band. With a 1.2m dish you are going to need to move the dish even more, probably about 7º. At the dish sizes we are using C-band is pretty forgiving of slight misalignments but you still need to be within about 0.5º, or 1º on a strong satellite. And strapping an LNB above the Ku LNB is a no-no because that LNB will never be on the arc whatever you do with the motor. Also, you can't see from the picture but the LNBs are turned in so they face the centre of the dish.

On my next project I am going to move the LNBs in and out of position as I need them. That way all the LNBs will be in perfect focus and I won't need to move the dish when changing from C-band to Ku.

I didn't realise was that you can mix USALS and DiSEqC 1.2 on the same receiver.

On the Solo you just set up the C-band and Ku-band satellites as two different satellites in the satellites.xml file. Any combination of DiSEqC 1.0/1.1/1.2 and USALS is possible on each individual satellite.

 

[sonnetpete]

Yes, I've had another close up look at the Laminas this morning and I don't think that it will be easy to modify a (Laminas) multi bracket to fit both LNB's. Or even go to the trouble of zip tying a C Band above the Ku band. I've no doubt you're right and it would be a pointless exercise to do so. However, I'm sure it would be fairly simple to remove the Ku band LNB and the top half of it's holder and temporarily fix the C Band in it's place though.

My VU+ already has Ku and C Band sat's listed seperately. Looking at the arc I can presently cover, there are 10 C Band sats whose footprints 'appear' to be within reach. I realise that the reality is I'll be lucky to catch any transmissions from a third of them, but I'll have fun trying!!

 

[Huevos]

Pete, I'm sure you can make a bracket. All you need is a drill, hacksaw, file, and any bit of aluminium extrusion out of the local DIY store, and a bit of lateral thought. And in the end custom built stuff always looks better than something designed for something else and shoehorned to fit.

Also you can probably still use USALS. All you would need to do is fudge the C-band satellite positions in satellites.xml by whatever amount the C-band LNB is offset.

I think you are being conservative with your estimate that you will only be able to lock transponders on 3 or 4 satellites. I've got screenshots from 19 satellites using the 1.5m dish. And there are plenty more I can't lock.

 

[sonnetpete]

Pete, I'm sure you can make a bracket. All you need is a drill, hacksaw, file, and any bit of aluminium extrusion out of the local DIY store, and a bit of lateral thought. And in the end custom built stuff always looks better than something designed for something else and shoehorned to fit.

Also you can probably still use USALS. All you would need to do is fudge the C-band satellite positions in satellites.xml by whatever amount the C-band LNB is offset.

I think you are being conservative with your estimate that you will only be able to lock transponders on 3 or 4 satellites. I've got screenshots from 19 satellites using the 1.5m dish. And there are plenty more I can't lock.

Hmm, well I do happen to have a bit of aluminium angle bar lying about. The 'fudge' was what I meant in my earlier post.

I've managed to get the C-Band zip tied onto the Ku Band holder (after removing the top bracket). It's not any better on 40°E than on the Gibi, but it's not adjusted properly or pointing anywhere near the centre of the dish. A home made bracket sounds a good idea, but it's all on hold for a while as I have visitors for a few days.

 

[Huevos]

Pete, what would be interesting to know is which gets the better signal, the 1m dish with the C-band LNB central, or the 1.2m with the C-band LNB offset.

 

[sonnetpete]

At the moment, the 1.2M is better but only by about 5% on the Quality reading (I haven't discovered how to make the DrHD display db).The C-Band LNB is mounted in the middle as I removed the Ku band LNB, but because it's only zip tied, I can see it's pointing marginally away from the dish centre. It doesn't explain why, having tried a few other sats last night, I can't get a lock on anything other than 40°E. Any suggestions as to the 'next best' source for C-Band? (bearing in mind LOS stops my arc at 22°W) I've left the plate in the same position as it is for 40°E, should I be scanning for other sats with it out or turned through 90°?

I can't get the C-Band LNB working on the VU+ either. It must be the setup menu, as it seems to be turning the LNB off but for the life of me, I can't remember how to get into the basic setup.

 

[Huevos]

The C-Band LNB is mounted in the middle as I removed the Ku band LNB, but because it's only zip tied, I can see it's pointing marginally away from the dish centre. It doesn't explain why, having tried a few other sats last night, I can't get a lock on anything other than 40°E.

In effect trying to catch C-band with a small dish is like like trying to catch Nilesat on a minidish. To have any hope at all everything is going to need to be perfect. Looking at your picture the centreline of the C-band LNB is 2cm higher than where it should be, maybe more. So you are easily aligned at least 1º below the arc. Have you checked with your meter and adjusted for maximum signal before trying a scan?

Any suggestions as to the 'next best' source for C-Band?

Not sure really. 20ºE JSC transponder is pretty strong.

I've left the plate in the same position as it is for 40°E, should I be scanning for other sats with it out or turned through 90°?

Leave the plate in (if the satellite is polarised right or left circular). Skew setting is not important for circular polarised signals.

I can't get the C-Band LNB working on the VU+ either. It must be the setup menu, as it seems to be turning the LNB off but for the life of me, I can't remember how to get into the basic setup.

What do you mean "it is turning the LNB off"?

 

[sonnetpete]

Yes, I peaked the LNB as best I could on the meter whilst at the dish. I knew it wouldn't be perfect, but I was expecting to at least achieve a lock on one other C-Band sat. It doesn't matter too much right now, as I've taken the C-Band LNB off and replaced the Ku. My stepdaughter arrives on Thursday and she will neither appreciate the nuances of C-Band or trying to get her head round the Dr.HD. I'll be changing back to the VU+ on Thursday morning, that one she can work easily.

Talking of the VU+, I'm wondering if, in the basic initial set up there's a setting to enable the power to a C-Band LNB. That's what I meant by 'turning the LNB off'. I couldn't get a peep on the VU+ last night, nor could I when I tried at the receiver end of the cable with my meter. When I connected back up to the Dr.HD it worked perfectly. However, I can't remember seeing a setting to turn the LNB power on or off.

 

[aceb]

Any suggestions as to the 'next best' source for C-Band? (bearing in mind LOS stops my arc at 22°W) I've left the plate in the same position as it is for 40°E, should I be scanning for other sats with it out or turned through 90°?

I'd say 5W and try 4114L 2143-5/6 Télé Africa It sits around 93/100 S/Q with me and is probably the strongest signal I get on C band. On my ESX241 there are two sets of slots for the plate to sit in, if yours has the same arrangement it's worth trying it in the other set and switching polarity, I'm not sure if it *should* make a difference but it certainly does on mine.

 

[Huevos]

You need to post some screenshots of your tuner config. Is the cable to that dish going through any switches? You need your tuner config set to advanced otherwise the LOF is going to be wrong on C-band. It should be "Universal" on all the Ku satellites and and "C-band" for the C-band satellites. If you don't set that right the receiver is going to know what you are asking it to do is out of range so it will just shut down the power to the LNB.

 

[sonnetpete]

@ aceb : yes it does have the two slots as you've described and I'll give it all another go when the C-Band LNB is mounted up again.

@ Heuvos : There's no switches wired up in the motorised setup. However, there's no need for screen shots. From your explanation I know that my tuner set up is not in advanced mode, so although it's 'universal' for the Ku band it's not set up on the C-Band and it'll have been shutting off the LNB power. Another thing to sort out in due course. Once again this forum has proved to be a fount of knowledge!!

 

[nelson_b]

Quote Originally Posted by nelson_b View Post

do you think my setup could be slightly out of adjustment ?

Sounds like it. My question is, if all three LNBs are aligned correctly at the centre of the arc how is it possible that the C-band LNBs go off track as you approach the extremes but the Ku-band LNB doesn't? If anything I would expect Ku to show any tracking error first due to the higher gain and narrower beamwidth.

hi -Huevos -

on close inspection of everything and a few test on weak signals C and K/u -
i discovered that the mounting post was no longer quite vertical -

( the foundations have sunk slightly at one side - a long and complicated story - which i wont go into here )

Anyway it was leaning a fraction , directly west - i suppose i had just got used to compensating for it by adjusting the incline jack , without giving it much thought -
and had assumed wrongly that it was a feature of the offset C band l.n.b,s .U-zzz
so slackend off the groundstand bolts and inserted a thin spacer under the west edge and all is fine again for now

there are one or two other features of my recent setup that i dont quite understand - but i will start a new thread sometime , for those
as this thread is for "sonnetpete,s" setup .

cheers -

 

[Huevos]

there are one or two other features of my recent setup that i dont quite understand - but i will start a new thread sometime , for those

That's good. Can you post a link to the other thread when you start it.