Help me put these dish sizes in order

[Mr Tony]

Need some help guys...I have a few dishes laying around and now that its warm enough to do stuff outside,

Now I started thinking of these dishes I have and trying to get the biggest ones mounted, but sicne some are round and some are oblong, I get confused. I think oblong you just tak the average of the 2 dimensions, right?

Here's what I have to work with

30" Winegard (currently on motorized)
36" Fortec (currently on G10)

Here's what I have left
37x27" StarChoice dish (I assume this is the equivalent of a 32")?
40x30" Primestar (assume its the equivalent of a 35")?
32x18" DirecPC dish (24")?
39x23" DirecPC dish (31")?

I was going to replace the 30" Winegard with the SC dish, but if its only an inch or more bigger, it may be more work to retrofit the dish then to get good results.

So I assume it goes (from smallest to biggest)
32x18 SC
30" Winegard
39x23 DPC
37x27 SC
40x30 P*
36" Fortec

or are the oblong ones measured differently? Only reason I ask is I use to have the 39x23 DPC dish for G3 (for NoDak Hockey) and I would get a strong signal on that but my 30" I'd get squat.

 

[dishMIKE]

Ice I have the same question. Would I really see that much of a difference with a 90cm or a 1 meter primestar over my current 40 x 30 ? Thanks, Mike

 

[Mr Tony]

Obviusly a 40x30 would be better than a 30" but between that and a 37x27 I dont think much (if any)

 

[dishMIKE]

Thanks Ice . I thought that would be the answer but I didn't know for sure. Mike

 

[mwgiii]

Hopefully one of the engineers will jump in here soon.

If I remember my math, which I doubt, aren't the formulas for area:

Circle Area = pi (3.14) x radius squared

Oblong Area = edge length x edge width

So 36" Fortec area is 3.14 x (18x18) = 1017.36

I may be way off base, since I haven't had to use these in years

 

[Mr Tony]

so using your math

37x27 is 999
32x18 is 576
30" round is 706.5
40x30 is 1200
39x23 is 897

 

[WyrTwister]

so using your math

37x27 is 999
32x18 is 576
30" round is 706.5
40x30 is 1200
39x23 is 897

Some how , in the back of my mind , the oblong formula does not sound right ?

Anyway , I am thinking , the average Ku linear LNBF is going to work better on a dish with the major axis vertical , as oppose to horizontal .

( The " eye " of the PrimeStar LNBF's looked flatten horizontally , kind of a " cat's eye " ? )

Wyr

 

[charlie123]

math on dish size

the length times width will only result in the correct sq inches if the dish was perfectly rectangular. With the eliptical shape obviously the sqi's will be far less than length times width.

 

[Mr Tony]

D'OH...thats right

 

[techpuppy]

Somewhat of a solution

Hi Everyone, (that should get Iceberg's attention)

The formula for area of an ellipse is pi*a*b. You take the radius of the long axis times the radius of the short axis and then multiply that by pi. Now with that said this formula is for a flat ellipse. The forumula for a dish shape is much more complex and involves symbols that would mean I would fail the class. You can find that formula at https://ewhdbks.mugu.navy.mil/ANTENNAS.HTM

If we go for just the flat elliptical area of the antennas mentioned here's the order of effective size in square inches.

32x18 Direcpc dish 452 sq in
39x23 Direcpc dish 704 sq in
30" Winegard dish 706 sq in
37x27 Starchoice dish 784 sq in
40x30 Primestar dish 942 sq in
36" Fortec dish 1017 sq in

Of course the performance could vary due to the efficiency of the dish. And you should keep in mind I did these calculations with a solar calculator in a dark room.

Using the same calculation on my .9 m Primestar elliptical means that it has about 678 sq in which supposedely would be a little less powerful than a 30" round. I think I'm getting dish envy.

 

[Mr Tony]

that is weird that the 40x30 has a fair amount less than the 36" round

But whats weird is last year I needed the 39x23 dish aimed at G3 to get the hockey games..the 30" gave me 0 quality (maybe 15 max) when the 39x23 gave me a 50 quality...this was due to the satellite interference at IA5 on same transponder

 

[techpuppy]

That's the problem with going by square inches only. It leaves out so many factors.

The Fortec reflects 75% of what it sees to the lnb, the Winegard 73%. I couldn't find information on the others. Likewise precision of focus, etc.

I tried to find the gain specifications on the dishes you mentioned, but only found 2 of them and I don't think anyone would have trouble deciding between a 30 or 36 inch dish.

Perhaps one of the fine sponsors of this site could someday do a reception test using various dishes, both new and commonly found used and publish the results using the same transponder, receiver, cable, lnb. That would be very useful.

 

[Larry1]

Does the Fortec really outperform the Winegard? or is this just overly aggressive specs. I do see that the 1m Fortec advertises more gain than the 1m Winegard and is actually about 4-5cm smaller.

 

[Larry1]

I finally came across the specs for the ChannelMaster dish, model 610029301:
(A little late, but maybe someone else will need them)
Reflector Dimensions 35.3" x 26.2"
Antenna Gain 35.7 dB, offset LNB's