Just Sharing This Spotted last week.

[aceb]

Sat on the train last Friday heading through south London into St Pancreas and spotted a large, inverted offset on a rooftop somewhere near South Croydon and Purley. We were going too fast to get a photo of it but I've been looking at Google maps and have possibly found it. I say possibly because from memory I'm sure the one I saw was further away and higher up the other side of the valley but how many 3M inverted offsets can there be in that part of London?

 

[Channel Hopper]

Ahem, it's one of mine, a Prodelin 3.8m

 

[aceb]

What's it pointing at, presumably something low down to warrant you inverting it? It certainly stood out in the otherwise gloomy scenery!

 

[Channel Hopper]

I think it is currently pointing at 57 East and yes, the rear superstructure would be annoyingly close to the kingpost at much further than 48 degrees of south. It is sitting on a very nice Baird non-Pen mount by the way with loads of ballast, and five floors up.

 

[Channel Hopper]

Ah, it may have moved further east

Advice Needed - LNB Skew for 68.5e

Good thing it's inverted, but replacing the LNB is a pain ( I dit fit a quick release bolt and some rope to let the feedarm down gently though)

 

[blademedia]

I think it is currently pointing at 57 East and yes, the rear superstructure would be annoyingly close to the kingpost at much further than 48 degrees of south. It is sitting on a very nice Baird non-Pen mount by the way with loads of ballast, and five floors up.

Lovely dish, the baird mounts are very good, presumably this one was made for a smaller dish reason for inverting the dish.

 

[Channel Hopper]

Lovely dish, the baird mounts are very good, presumably this one was made for a smaller dish reason for inverting the dish.

Eh ?

 

[blademedia]

Only way a baird mount would clash with the dish if it was made for a smaller dish, there's no need to invert a dish 5 story up unless your in front of a mountain ?

 

[Channel Hopper]

What has a mountain got to do with the price of fish ?

 

[archive10]

Only way a baird mount would clash with the dish if it was made for a smaller dish, there's no need to invert a dish 5 story up unless your in front of a mountain ?

Yes, if it is an offset dish, and the target is very low on the horizon.
My Prodelin 2.4 was mounted inverted (on a Baird mount) on Greenland as the sat was very close to the horizon.
In fact, the bak structure is specifically manufactured for inversion, it has double set of anchors and holes for elevation bolts.
(No such problem with Prime Focus dishes.)

 

[blademedia]

My 1.2 is not inverted and not 5 stories up and I get 70.5E no problem they must have been after 74E.

 

[archive10]

My 1.2 is not inverted and not 5 stories up and I get 70.5E no problem they must have been after 74E.

...on a Baird mount?
I think your 1.2 is on a polar mount, and therefore does 70E without problem. the 3.8 on a Baird mount is upright, and therefore needs to be inverted.

 

[Channel Hopper]

Elevation from memory was 4.5 degrees at location meaning there was about -17 from the horizontal on any satellite of interest, and the chance of the lower part of the boom arm and reflector surround fouling the post.

Additionally the weight of the antenna in non inverted set-up is so far forward of the post, there is a need for further ballast at the rear of the mounting system.

 

[blademedia]

the boom arm and reflector surround fouling the post

Lovely dish, the baird mounts are very good, presumably this one was made for a smaller dish reason for inverting the dish.

Thank you Channel Hopper, thats what I said, you worked round the problem and installed it inverted, nice install the dish looks good inverted,

I might have a few jobs lined up for you in the near future, good installers of large dishes are hard to find, a few so called installers I've used in the past ive had to throw them of site and do the job myself.

 

[Channel Hopper]

Thank you Channel Hopper, thats what I said, you worked round the problem ....

What problem ?

ST1 has confirmed the reflector inversion is written into the manufacturer's design specification.