What kind of wear I should expect for 10 year old large fiberglass dish?

[BombedOne]

One international organisation is shutting down their office here, and selling their equipment for a low price. One of the items on sale is big VSAT dish. The information that I've gathered about it so far is:

1. Size is somewhere in range of 3-4 meters (google earth says 4 meters).

2. According to ribs and fins it has (I can see only back side from the ground), it looks more like to be Prodelin product, rather than channel master.

3. It was installed around 1998-99 and haven't been painted or otherwise serviced starting from that date to today.

4. We have moderate weather here, rarely going above +30C in summer and below -5C in winter, climat is medium-dry, continental. But we have DAMN HEAVY winds in place where that dish is located, so there are high chances that this is special, wind reinforced model. According to prodelin website, one dish falls into such category - 3.8m, high wind resistant dish: _ttp://www.gdsatcom.com/Antennas/Data_Sheets/2383.pdf

5. It haven't being used for last 3-4 years (not due to damage or malfunction, but because cable connection available, delivering same speed for much much less price).

According to that data, is it worth to go up and inspect that dish more closely? How do you think, will it be still usable as it is now, or only minor repairs will be needed?

 

[Topper]

My only comment would be for a fibreglass dish, if it is in a coastal or desert region then it will have been subjected to many sandblast episodes. Although in reality if the blasting has not reached the metal reflector it would not be a problem, just something to look for

 

[BombedOne]

Nearest seaside is about 400km away, and nearest desert - about 4000km so these hazards can be omitted.

 

[Channel Hopper]

Without a picture of the rear structure, it could be one of about ten designs.

Is it a receive only, or receive transmit dish ?
Does it have actuators to move it ?

What are the maximum / minimum temperatures over a year in the area ?

Prodelin uses SMC compound, (not quite fibreglass) that is heated in a press with the metal mesh to form the reflector panels. After a few years in the field, the three main issues that can affect the dish are

1)Delamination of the mesh away from the backing compound
2)Brittleness of the reflector edges (taking it apart without causing fin/hole enlargement is going to be your main priority)
3) Distortion of the reflector due to weight and temperature changes.

A picture would be very handy, and any idea on whats bolted to the focal point.

 

[BombedOne]

Today I went there, trough we had no access to that building (guy who had keys was at another city), but I was able to closely check another dishes, which were installed together with that ones. They are in very good condition, and also for sale for a very low price, but they are too huge...

There's one 4.5m andrews dual mirror primefocus dish (model ES45MP), equipped with C band BUC and automatic defrost system, and russian (SOVIET! with dual axis sat tracking system) 5 meter dish, also C band.

Surface of both is I can say in almost perfect condition. If no bird poo trace, you may think they are just brand new. So I hope my small ones are also in good condition.

My friend took photos, so I'll have them at hand at the evening, will post then.

 

[BombedOne]

(sorry, the soviet one was installed in early 90s, and as technican said, worked only 3 monthes, then something happened, then ussr disbanded, so dish stands without use since these times. Currently the tracking mechanism is broken, feedhorn screws missing, otherwise dish surface looks nice. And construction is many many times stronger than any commercial dishes)

Also, which company makes offset dishes for VSAT, with the following specs?:

Material also fiberglass-like,
Two piece model, but these pieces are vertical, not horisontal as in case of channel
2.4m size, master.

 

[BombedOne]

here they are. Anyone can help me guessing the manufacturer? One was used for receive only (you still can see LNB attached), and 2nd one was used for vsat...

 

[Channel Hopper]

Definitely a 1251 in the centre

_http://www.gdsatcom.com/Prodelin/Technical_Docs/assembly_manuals/4096-476.pdf

The other could be the earlier version - 1250 ?
or an Indian copy, there are plenty of them about .

 

[BombedOne]

That vsat one is relatively fresh - only about 5 years as installed. and it has little cracks around one of the side bolts. Looks like it was overtightened when assembled.

 

[Channel Hopper]

You will require two visits, one to apply fluid to penetrate the bolts, and generally clean off the corrosion, second will be a careful disassembly of everything from the top down.

the 1251 was not a good performer at Ku band frequencies even when new, but will provide you with quite a bit of entertainment in the setting up. Be very careful when touching the main metal components behind the dish, edges can be very sharp.

 

[BombedOne]

The 1st thing is to agree on price These two dishes are from another supplier, so I'll know the price for them only at next week...

bolts and metallic parts look absolutely corrosion-free.

 

[BombedOne]

But what you mean under "bad performer"? I'm planning to use (if will buy it) for Ku band reception only.

 

[Channel Hopper]

The design of the 1251 does not lend itself well to Ku band, once it has been sitting in the field for a few years.

The weight of the reflector parts supported only in the vertical plane by metal, means the wind forces and temperature changes over five years have an impact on the reflector surface integrity.

Additionally the weight of anything heavy on the front (a C band feed and amplifier ?) is supported by the support arms only when set up in the non-inverted way , and this pulls on the reflector sides, causing either distortion, and/or damage to the reflector at the bolt points.

 

[BombedOne]

Thanks for information, but most dishes have such construction, just some models have LNB holder attached to base plate. So this means, ALL dishes of such construction become bad in a several years?

 

[Channel Hopper]

Thanks for information, but most dishes have such construction, just some models have LNB holder attached to base plate. So this means, ALL dishes of such construction become bad in a several years?

No, when it comes to VSAT dishes , most have the front components supported by the metal behind the dish, or the reflector is reinforced all the way round.

The 1251 is a cheap design, not bad at all for C band use, but Prodelin have other designs for Ku band reception (1252) or Ku receive / Transmit (1244)

 

[BombedOne]

So it won't work for Ku reception now, so I should not care about price/purchase of it?

 

[Channel Hopper]

Depends on the price. It is a solid and heavy dish (and a 2.4m) which is an advantage, it does not lend itself well to motorising though.

Have you got a vehicle able to fit the two panels in ? They are 2.7m x 1.2m.

 

[BombedOne]

I'd have to hire one, and some workers too, but this is not a great financial load, I'll fit with both workers and truck under $50 mark.

 

[BombedOne]

And also, it will be interesting to estimate, what gain loss I will face, and what advantages this dish in general will give to me...

For example,

by having 1.2m dish with 42db gain, I can ONLY receive wide beam of Astra 1M.

Using 1.5m dish with 43db gain I can receive almost all european TPs from 1M, and even some TPs from 1H, but with quite low level, absolutely no space for bad weather.

The declared gain of 1251 is 47.6db. Say, due to deformation and aging it had lost 2.6db and now has 45db.

Currently, when comparing 42db and 43db dishes, I achieve average 15% increase in signal Q. If follow that methodics, I should expect 45% more Q on 1251, compared to 1.2m one or not? I mean, is actual signal increase linear, or logaritmhic, or any other formula?

 

[Channel Hopper]

If you are using the screen graphics of the receiver then it is unlikely to have much bearing on the overall incoming signal, as this is not just down to the dish area (the gain of the LNB can also vary by a factor of two or three).

Effectively the dish will have a surface area four times that of the 1.2, and so you should be expecting an improvement of some 6dB. The beamwidth will also be much narrower, allowing you to easily differentiate between satellite positions as small as 0.2 of a degree.