Upside down offset dish

[RimaNTSS]

Finally, we see some light at the end of the tunnel! I have some data in this collage

 

[John]

Finally, we see some light at the end of the tunnel! I have some data in this collage

I have used the data that Rima provided on my two 1.2 CM's and a 1.8 CM using the stock CM scalar feedhorns - for me the data measurements supplied and implemented on my CM reflectors gave a performance increase over the factory feed position of approx 1.5dB at least.

 

[Channel Hopper]

The dish is an offset CM 2.4m (Andrew, Raven, Skyware yet.... but it is always the same I believe).
Please note it is the receive-only version, not receive-trasmit one.
As I mentioned, I would like to test Viking 2-ports Ku-band motorised feedhorn that was originally designed for a Prodelin offset 1.8m dish but I hope in a good matching with such similar dishes.
Anyone can tell me the exact focal distance of this CM?

Somebody will be along soon to claim such a dimension does not exist on an offset dish.

 

[7mdish]

Interesting. 1.5 dB is a significant increase!
So, is it true that CM is very similar to Prodelin? If so, maybe no matching issues would occur. What do you think? Thanks.

 

[RimaNTSS]

What do you think?

I am pretty sure that 1,8m offset Prodelin and 2,4m CM have exactly the same opening angle, so what was designed for Prodelin will perfectly fit to your CM. Good luck.

 

[Channel Hopper]

Both models (if you have the correct Prodelin model) have f/d ratios of 0.8

 

[7mdish]

Thank you Rimantss and Channel Hopper. Good news. Yes Viking designed this motorised feedhorn to match the Prodelin 1.8m offset dish, so new arms and feed support was built based on the original CM one to fit the feed on the 2.4m dish in the same position as the original feed.
But your suggesion in post 61 could be very useful for fine tuning.
I hope to complete my installation in June. Thanks.

 

[RimaNTSS]

fit the feed on the 2.4m dish in the same position as the original feed

Actually, you only have to place the new feed in such a way that it's phase center is co-located with the antenna's focal point. And, to perform that, the new feedarms should have some adjustment possibilities.

 

[7mdish]

Actually, you only have to place the new feed in such a way that it's phase center is co-located with the antenna's focal point. And, to perform that, the new feedarms should have some adjustment possibilities.

Yes, the arms are adjustable, so the feed can be moved forward and backward for the strongest signal. Also, I believe that the scalar feed has such adjustment too.
I will tell you as soon as I will get all parts but I believe that the feed is adjustable, many tweaks and fine tuning with the meter.

 

[Channel Hopper]

The clamping arrangement of the Prodelin r/o feed is quite different to the CM version, what exactly has Viking provided for your new dish ?

 

[7mdish]

The clamping arrangement of the Prodelin r/o feed is quite different to the CM version, what exactly has Viking provided for your new dish ?

Nothing. Viking provided only the feed. The additional arms and feed support are provided by SSS after examining the feed and having all dish specs and measurements. Don't believe they made a real test on the field, but the arms are largely adjustable, so I believe it is a good starting point for a fine adjustment when the feed will be positioned on the dish. Maybe an entire day tweaking the feed with the meter?

 

[Channel Hopper]

I'll ask again, what exactly has Viking provided for your new dish ?

 

[John]

Nothing. Viking provided only the feed. The additional arms and feed support are provided by SSS after examining the feed and having all dish specs and measurements. Don't believe they made a real test on the field, but the arms are largely adjustable, so I believe it is a good starting point for a fine adjustment when the feed will be positioned on the dish. Maybe an entire day tweaking the feed with the meter?

This drawing was part of a project but it shows and illustrates the different feed position from the CM stock position to the position obtained using the data sheet. The new higher elevated position from the original CM stock position also gives correct dish rim illumination tracking. There's not a whole lot of movement difference but the new data dimensions have to be applied accurately to benefit from them if you want your reflector to perform as a well set up 2.4mtr instead of a 2.4 performing as a 2.2
Good luck with it, look forward to your results.
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[RimaNTSS]

I think that is about feed like this

 

[Channel Hopper]

I think that is about feed like this

If that was directed at me then unless I have misread the particular posts the o/p has confirmed Viking is supplying two port receive only components. Illustrated is a receive/ transmit feedhorn / OMT combination with filter.

 

[7mdish]

Here you can find all information about this feed. It is a motorised 2-port, Ku-band, receive-only feed.
They provided only this feed. In addition, looking at this feed, SSS provided a complete kit including arms, support, all bolts and nuts to position the feed in the right way, and this arms are adjustable to find the best position obviously based on the best signal.
As soon as we begin the installation I will post pictures. Thanks.

 

[Channel Hopper]

The 1184 is/was a reflector with 0.6 f/d ratio. If Viking is correct with their sale then the CM 2.4 single optics design is actually 0.6 f/d.

 

[7mdish]

I don't know.... The dish will be delivered during this week, so I will check all specs. Have you these specs and do you know if f/d is the same for both dishes? As Rimantss mentioned, Prodelin and CM seem the same, so I believe (hope) this feed can be installed without any additional issue.

 

[Channel Hopper]

I don't know.... The dish will be delivered during this week, so I will check all specs. Have you these specs and do you know if f/d is the same for both dishes? As Rimantss mentioned, Prodelin and CM seem the same, so I believe (hope) this feed can be installed without any additional issue.

I've not ordered a Channel Master for years from any supplier willing to back up their product.

The actual f/d ratio should be in a Raven or Global Skyware catalogue somewhere

 

[a33]

For the 2.4m CM from RimaNTSS's picture I'd come to f/D=0.60.

Opening angle of the CM-dish would be about 79.5 degrees (assumed inputs H/W/dcenter about 2630?/2425?/232.1, leading to BF=1460, AF=2471 and FG=1651 as indicated in the picture).
That 79.5 degree would be equivalent to a prime focus f/D-equivalent of 0.69.

Greetz,
A33