What's More Important?

[Whipskinny]

Hello all,
Will soon be getting a 36" or 90cm dish, an Invacom '031 Quad, and a Moteck SG2100.
I have spent weeks shopping different sponsor sites and following links from an endless list of posts. At this point I have succomb to complete information overload because of one problem that continues to bug me.
The Invacom LNB has an F/D of .65, all the dishs (36" and 90cm) that I've found won't match the LNB's .65. The closest I've come is a Fortec 90cm with a F/D of .60. I would like to find a perfect match, does anyone know of a supplier that carry's a matched dish?
This might be wishful thinking on my part, if so, could somebody tell me how to modify or adjust the focal length, or maybe set me straight on the actual importance of the F/D?
And as long as I'm asking questions about dishs. How important is db Gain of the dish as it relates to the F/D compatibility of the LNB and said dish?

I hope this post makes sense to someone (it's late, I'm tired, and my brain won't let me stop thinking about this).

Any help or guidance well be greatly appreciated.

Thanks!
Mark

P.S. I do recall seeing somewhere a 33" with a F/D of .65, maybe this would work better than the larger ones (see, can't stop thinking).

 

[Das Hammer]

The focal depth is based on the dish diameter and dish depth. Two dishes with the same diameter may not necessarily have the same focal depth becuase even though they have the same diameter, the depth of the dish could differ.

The 0.65 you mentioned is the "Ideal" depth. The LNBF holders will allow you manually adjust the location of your LNBF a little.

You're worrying about this too much. It'll work, just get it and have some fun.

 

[rainmaker]

I am using the QPH-031 with a fortec 90cm dish and it works just fine.just slide the lnbf all the way back in the holder and you won't have any problems.

 

[GreatNorth]

Having a winegard 1m dish with the qph-031. Don't know the ideal focal point.

But moving the lnb back and forth doesn't make any difference in both the strong and the weak transponder.

For me, it doesn't matter. It work anyway.

 

[Whipskinny]

Thanks!

Das Hammer,
Thanks for your encouragement, I do feel better!
I know I've over analyzed this whole setup that I want to put together. Been dreaming about it for more than a year now, and with the way my luck has run financially in the past few years I just want everything to be perfect right out of the gate. I may only get one shot at this with a small windfall that I will soon have.
I am completely new to this other than what I've read, never even seen any true FTA hardware other than my Direct TV equipment.
I want to DX the satellites the way I use to with shortwave, so a well tuned system is important to me for fringe, weak and marginal signals.

In the opinion of those here, in regards to my needs, how would you rank the importance for signal quality of the dishs db gain over a 'close' to matched LNB and dish F/D?

I can't go any larger with the dish, only received his permission to install nothing larger than 36"

Thanks again to those that responded.

Mark

Das Hammer - nobody is more entertaining than Dr. Scott

 

[SatAdam]

it doesn't matter.

buy what you want. It's close enough. The manufacturers measure it all with different meters, so it's all relative.

You're not gonna be able to aim the dish precise enough to worry about that minute focal length difference to matter.

 

[Hermitman]

You may have happened upon an ideal match and not realized it. According to the Invacom website, the QDH-031 LNB has an f/d of 0.6. The Fortec antenna model FC090CM has an f/d of 0.6. That may be what you're looking for.

In my opinion if you want to receive marginal signals, the biggest dish you can get away with the better. I believe you would want the maximum amount of signal reflected to the focal cloud in front of the LNB. I know my 60 foot longwire picks up a lot more that a coat hanger stuck in the antenna post (old SW utility listener). After you get the maximum signal at a reception point, then you can work on picking out the actual station you want to find. Have fun.

 

[SatelliteAV]

A slightly matched F/D will not be a factor in the performance of your system. I absolutely guaranty that you will not see any signal quality difference with a .10 or .15 mismatch in a hobbyist system! Sliding the LNBF towards or away from the reflector will usually provide a very close match and maximize the signal collection.

Go for the best LNBF, a dish that has a quality finish, the best efficiency ratings, gains, narrow beam widths and surface uniformity, pay attention to the reflector mounting, purchase the best coax cables, use quality fittings, properly ground the system, minimize switches, diplexers, multi-switches and barrels. These are the things that will quickly degrade your signals!

Choosing a DiSEqC switch with a lower insertion loss will certainly provide an improved signal more than a slight F/D mismatch.

 

[Whipskinny]

Decisions, decisions.

Thanks again for your replys,
Going to go with a Fortec 90, Moteck sg-2100, Invacom Quad, and a Traxis.
That's it, I'm done worrying about this anymore.
Now, what shipper is going to be the fastest, UPS, Fed-Ex or DHL.

 

[Tron]

Now, what shipper is going to be the fastest, UPS, Fed-Ex or DHL.

Oh, now we could start a whole new thread on this one

 

[mastermesh]

Having a winegard 1m dish with the qph-031. Don't know the ideal focal point.

But moving the lnb back and forth doesn't make any difference in both the strong and the weak transponder.

For me, it doesn't matter. It work anyway.

I have a Winegard setup like that too... and love it. Only thing to really mention is that you may have to do some tweaking with the lnb no matter what dish you use... The invacom quad is a bit heavier than some lnbs... as such, gavity can play a role. I have got mine tweaked as well as I could, spending a couple of weekends to tweak as much as I could, and then got it propped in to position via some electrical tape around the lnb from lnb to lnb holder, and a little wedge type stick down between the lnb and the holder... it works quite fine.....