Fibo 1.2m v Channel master 1.2m

[Riverblue]

@Trust1 Dishes I checked for warpage (especially 90cm) all out of ideal shape. And, THB, I am afraid to string my Fibo120.:mad:

Are they very flimsy, is that due to being battered by the weather over the years or is that down to misuse or mishandling?

 

[Captain Jack]

They are not flimsy at all - in fact the 1.2m weighs more than the Channel Master (in my hands). It's that they are getting on being nearly 20 years old and took a lot of beating in their time.

 

[RimaNTSS]

The main test for warpage of antennas is to string them (put vertical and horizontal threads), and after that there is almost always couple of mm gap between threads, which indicates you will not get maximum performance of antenna till you make dish face ideally flat

 

[Riverblue]

They are not flimsy at all - in fact the 1.2m weighs more than the Channel Master (in my hands). It's that they are getting on being nearly 20 years old and took a lot of beating in their time.

I thought the reflector was made of aluminium? Is there a lot of bracing to them or something else to make them heavy? I know that a Channel Master is reasonably heavy, but you can see in the design of the ribbing on the back and SMC construction where the weight is.

 

[AndyX]

I remember, at the time, I was pleased with the useful signal gain, but you will understand that comparisons on signals would be not very meaningful now in the rapidly changing satellite broadcasting world.

So you've had both dishes, can you dispel/back up the "urban myth" about the phenomenal performance of the Fibo, in your experience did the Fibo massively outperform the Channel Master (assuming it was a 1.2m!) or were the differences a lot smaller?

 

[Riverblue]

I remember, at the time, I was pleased with the useful signal gain, but you will understand that comparisons on signals would be not very meaningful now in the rapidly changing satellite broadcasting world.

Surely though, if you were getting useful gains "back in the day", it would follow that the dishes would perform similarly today, assuming that they where both in good condition etc?

 

[Captain Jack]

I thought the reflector was made of aluminium? Is there a lot of bracing to them or something else to make them heavy? I know that a Channel Master is reasonably heavy, but you can see in the design of the ribbing on the back and SMC construction where the weight is.

There is a backplate on the dish, though I think that's aluminium too. Not sure why it's so heavy but I remember struggling getting the dish up the ladder far more than with the CM.

 

[AndyX]

Surely though, if you were getting useful gains "back in the day", it would follow that the dishes would perform similarly today, assuming that they where both in good condition etc?

What I was meaning was 2 compare 2 specific signals from then is meaningless as most of the satellites have been replaced since then.

 

[Riverblue]

There is a backplate on the dish, though I think that's aluminium too. Not sure why it's so heavy but I remember struggling getting the dish up the ladder far more than with the CM.

According to these;
Fibo Gregorian Dual Reflector Antenna Information




The 1.2m Channel Master weighs 15.2 kg (+ Az/El mount 5kg = 20.2kg)

The Fibo 1.2m weighs 11kg (no info about mount)

 

[archive10]

I was chatting to a guy the other day that was trying to sell his beaten up Fibo 1.2m dish and he reckoned that it had the performance of a 1.8m dish

Sure, if it is a Jonsa 1.8 meter petalised dish. Otherwise, no.

 

[archive10]

I've been doing a bit of research The gain on the CM 1.2m is stated as 42dBi @ 11.95 GHz (/http://www.skywareglobal.com/images/pdf/Prod.sheets 2012/Receive_Only/Type_120_VSR004.3.pdf)
The gain for the Fibo 1.2m is stated as 42.4dBi @ 11.7GHz (/http://www.satellite-calculations.com/Fibo/fibo.htm)
Looks like there is not a lot in it to me.

Also the CM 1.2m is 121cm x 132cm (my measurements), the Fibo is 120cm x 135cm (same source as above)
Yet again, not a lot in it!

The actual experienced gain depends on a range of other physical factors.

Including:

1) Illumination of the dish. The physical size of the dish is less relevant than the illuminated size of the dish (see RimanTSS detailed explorations elsewhere on this site for context). The illuminated size is smaller than the physical size, and will typically be an oval-ish portion of the entire dish, save a centimeter or two around the edges. Therefore you can't really compare the physical sizes of two dishes without knowing what part of the dish we are talking about. This depends on the "beam-width" of the LNB (roughly f/D ratio), and the accuracy of the placement of the LNB in the focal point (sweet spot) of the dish. This leads to:

2) Accuracy of LNB positioning. I.e. how well is the LNB chosen positioned when locked in the grip of the provided LNB holder?
This all depends on the mounting mechanics, and stability of the components used for the mount etc.
On larger (and often older) dishes, the LNB mount is designed to hold a specific feed-horn, ensuring a resonable good alignment of feed-horn, LNB and reflector. This is what people are trying to optimise when they go in search of original feed-horns etc.

In the end, a 1.2m high-quality shaped dish will perform as another 1.2m high-quality shaped dish, when it comes to gain, or *signal strength*.

Then there is the matter of signal quality, which is a different kettle of fish. Signal quality depends on noise floor of the LNB electronics, the background noise seeping into the feed-horn, the polarisation dispersion introduced by the reflector, any signal distortion introduced in calbles, connectors, amplifiers etc (if used at all), and of course non-linear issues like irradiated noise (DECT phones, microwaves etc) before the signal gets to the analogue-to-digital converter of the STB. Plus a range of other stuff.

But there is (of course) a link between size and quality, in that signal quality is usually easier to get from a high-gain dish than a lower gain dish. Thus, a 1.8m dish gives better results than a 1.2m one when boh are aimed correctly.

I tend to agree wth RimanTSS and others here, it really comes down to a hands-on comparison.

 

[archive10]

My 120cm Echostar is in fact a channel master.

Sure it's not a Prodelin? My 120cm Echostar is definitely a Prodelin (significantly different from my CM120s), but I know there was a(n early) time when Channel Masters where very Prodelin-like...

 

[Riverblue]

The actual experienced gain depends on a range of other physical factors.

Including:

1) Illumination of the dish. The physical size of the dish is less relevant than the illuminated size of the dish (see RimanTSS detailed explorations elsewhere on this site for context). The illuminated size is smaller than the physical size, and will typically be an oval-ish portion of the entire dish, save a centimeter or two around the edges. Therefore you can't really compare the physical sizes of two dishes without knowing what part of the dish we are talking about. This depends on the "beam-width" of the LNB (roughly f/D ratio), and the accuracy of the placement of the LNB in the focal point (sweet spot) of the dish. This leads to:

2) Accuracy of LNB positioning. I.e. how well is the LNB chosen positioned when locked in the grip of the provided LNB holder?
This all depends on the mounting mechanics, and stability of the components used for the mount etc.
On larger (and often older) dishes, the LNB mount is designed to hold a specific feed-horn, ensuring a resonable good alignment of feed-horn, LNB and reflector. This is what people are trying to optimise when they go in search of original feed-horns etc.

In the end, a 1.2m high-quality shaped dish will perform as another 1.2m high-quality shaped dish, when it comes to gain, or *signal strength*.

Then there is the matter of signal quality, which is a different kettle of fish. Signal quality depends on noise floor of the LNB electronics, the background noise seeping into the feed-horn, the polarisation dispersion introduced by the reflector, any signal distortion introduced in calbles, connectors, amplifiers etc (if used at all), and of course non-linear issues like irradiated noise (DECT phones, microwaves etc) before the signal gets to the analogue-to-digital converter of the STB. Plus a range of other stuff.

But there is (of course) a link between size and quality, in that signal quality is usually easier to get from a high-gain dish than a lower gain dish. Thus, a 1.8m dish gives better results than a 1.2m one when boh are aimed correctly.

I tend to agree wth RimanTSS and others here, it really comes down to a hands-on comparison.

Thanks for that st1, basically dispelling this "urban myth" crap, which was part of my original question.

 

[archive10]

... the polarisation dispersion introduced by the reflector...

Forgot to mention, this is where the Gregorian advantage comes into play.

The H and V separation is enforced with the dual-reflector design ("dual optics"), where the sub-reflector will re-instate most of the polarisation separation (rectifying mainly the dispersion that is due to the circular main reflector). In other words: Even though the signal may be weak, it is a very very good signal!

Interestingly enough, I had a similar experience the other day with having a CM100 at the other end of at least 100m of cable before coming to the receiver. The signal strength was 10%, but the quality was 70%! While not quite the same situation as with a Gregorian, it shows that a weak but good signal may outperform a strong but not-so-hight-quality signal.

SO, if you can get your hans on a pristine-condition 120cm Fibo with original feedhorn etc, it will probably outperform a CM120 with a standard LNB mounted, when it comes to fringe reception.

The alternative is: Get a used CM120 (which will be good unless is has been damaged - I do have a couple of cracked-rim CMs), then check if it does the job, and if not, get a CM180.

 

[Captain Jack]

Very interesting information here. And, of course, CMs are much easier to find than Fibos.

Or you can convert your CM to Gregorian design, like Rimant did with his Prodelin.

 

[Trust]

Sure it's not a Prodelin? My 120cm Echostar is definitely a Prodelin (significantly different from my CM120s), but I know there was a(n early) time when Channel Masters where very Prodelin-like...

Is y Echostar also a Prodelin ? Don't pay attention to the strange mount .

 

[archive10]

Is y Echostar also a Prodelin ? Don't pay attention to the strange mount .

Yes, it looks very much like a Prodelin series 112x (at least the reflector does. Feed arms varied with specific application.)
I think the Echostars where a rebadged version with a polar mount.