Satellite > HughesNet Satellite > LNB focal point?

LNB focal point?

The focal point should be at the surface of the feedhorn window, I think (subjectively verified by the fried windows I've seen when a reflective paint was used on the dish and the sun passed behind the satellite).

After that the waves are "guided" to both LNB and transmitter. If you look again you will see a small slot in the side of the guide just in from the end, which is where the signal enters the LNB guide at a 90-degree angle to the main guide.
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reply to hcwiii

reply to hcwiii
You won't be able to use the waveguide or the feedhorn for your EVDO, the wavelengths are wrong. EVDO is in the 800MHz cellular (824-896MHz), and 1900MHz PCS (1850MHz-1990MHz) bands. The satellite feeds are cut for the 11-14GHz range (much shorter wavelengths).

That said, you can remove the electronics from the feedarm, and replace it with your EVDO antenna. If it's a dipole, you're going to lose the half of the signal that doesn't hit the dish. If it's a directional, obviously aim it in the direction of the dish - then aim the dish at the EVDO tower

//greg//
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HN7000S/98cm Prodelin/2w Osiris/ProPlus - G16/1250H/Germantown - NAT 66.82.187.152/Gateway 66.82.25.10/DNS 66.82.4.12 and 66.82.4.8 - Firefox 3 - AV/Firewalled by NIS2009

reply to dbirdman
aha, I guess I could have aimed it at the sun to figure it out...

Thanks dBirdman. I am fascinated by the technology, I suppose, but do I really have time to learn yet another....? Probably not.

But again, do I really have time to figure out this dish thing? We'll see.

Thanks again.
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Direcway - er Hughesnet Home Pro - DW7000 - AMC9-1290mHz - Win2K - Kerio firewall - Linksys WRT54GS-V7 wireless router
Soon, EVDO! USB727 w/ Cradlepoint MBR1000 wireless router. 1900MHz cellular Wilson roofmount yagi.

reply to tobicat
Thanks Tobicat, I'm getting the idea.

I'm glad you mentioned the offset of the dish. Can I picture it simply as a top section of the parabola?

I'm not sure if my setup will drop down enough. The top of the tower I'm aiming at is about 3.5 miles off, but probably at the same absolute altitude as my dish.

I may have to modify the mount to get it to adjust low enough.
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Direcway - er Hughesnet Home Pro - DW7000 - AMC9-1290mHz - Win2K - Kerio firewall - Linksys WRT54GS-V7 wireless router
Soon, EVDO! USB727 w/ Cradlepoint MBR1000 wireless router. 1900MHz cellular Wilson roofmount yagi.

reply to grohgreg
No Greg, I didn't expect to use the feedhorn, I just needed to know what the focal point is to know where to place the EVDO antenna.

I was thinking about putting together a biquad for it, and if the biquad by itself doesn't help my signal, then put it in front of the dish.

It'd be nice to make use of the Hughes investment somehow... Of course I put way too much time into tweaking the install, and the setup, to ever get much of my investment back.

Know anyone who wants to buy a DW7000 Hughes outfit, lacking only the dish? I'd hate to see that much silicon go to waste...
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Direcway - er Hughesnet Home Pro - DW7000 - AMC9-1290mHz - Win2K - Kerio firewall - Linksys WRT54GS-V7 wireless router
Soon, EVDO! USB727 w/ Cradlepoint MBR1000 wireless router. 1900MHz cellular Wilson roofmount yagi.

reply to hcwiii
If you're using the standard Direcway 74cm elliptical reflector, there is no offset to calculate. When the indicator on the side of the bracket says 0 degrees, it's focusing at 0 degrees. The problem you'll likely encounter is noise. Satellite dishes in general have enough parabolic gain to make elevations under ~8 degrees exceedingly noisy. But try anyway, the tower signal may be strong enough to where the S/N ratio is still acceptable to your modem.

And if the modem has a signal strength indicator, use it to optimize your Az/El settings. The point of max receive signal strength should coincide with your strongest signal hitting the tower. Otherwise, you're pointing blind.

//greg//
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HN7000S/98cm Prodelin/2w Osiris/ProPlus - G16/1250H/Germantown - NAT 66.82.187.152/Gateway 66.82.25.10/DNS 66.82.4.12 and 66.82.4.8 - Firefox 3 - AV/Firewalled by NIS2009

Yes, the azimuth scale is there, but it's a pole mount, and only drops down to +10 degrees.

By my calculations, I should need an angle of .3333 degrees or so. (Tower is 6.5 miles distant, and the top of it is 200 feet higher than my dish altitude.)

I did a little experimenting, putting the modem on an extension cable and placing it at the focal point (although not quite - now I know where the focal point really is). I never found any 'sweet spot' that was any better than hanging the modem on the wall indoors.

I'll have to try it again with the antenna in the correct place of focus, and see if I can modify the mount a bit to aim it lower.

Do you know if it's necessary to set up a small shield between the modem and the tower, so it's mainly getting signal that's reflected from the dish? And should this shield be grounded, or signal-grounded (the laptop is obviously not grounded...)?
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Direcway - er Hughesnet Home Pro - DW7000 - AMC9-1290mHz - Win2K - Kerio firewall - Linksys WRT54GS-V7 wireless router
Soon, EVDO! USB727 w/ Cradlepoint MBR1000 wireless router. 1900MHz cellular Wilson roofmount yagi.

Fabricate a 10 degree wedge and insert it between the dish and the top of the bracket - with the pointy end down. That will get the dish in the vicinity of the horizon when the EL scale says +10. But the reason the scale stops at +10 in the first place, is that noise below 8 degrees I mentioned above.

You are correct in assuming that simply placing the EVDO antenna on the Direcway feedarm will render you vulnerable to multi-path distortion. But in this case a sub-reflector can cause multi-path as well. The trick is to negate any RF - transmit and receive - that is in a direct line between your EVDO antenna and the tower. Grounding the shield should do this. But make sure that it's the shield only that's grounded - you don't want parasitic grounding of the main reflector. I'd electrically isolate the shield from the feedarm and THEN ground the shield. RF from the tower couldn't then hit the EVDO antenna except on the bounce from the dish and RF from the EVDO antenna would only reach the tower on a bounce from the dish.

But this assumes you can actually get a good "focus" between the parabola and the tower. The alternative may be simply to put up with the multi-path distortion and the ground noise.

//greg//
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HN7000S/98cm Prodelin/2w Osiris/ProPlus - G16/1250H/Germantown - NAT 66.82.187.152/Gateway 66.82.25.10/DNS 66.82.4.12 and 66.82.4.8 - Firefox 3 - AV/Firewalled by NIS2009

Excellent Greg, I sure appreciate your input.

I'll work on it, and post any results here....

The nice thing is that Verizon has recently acquired a permit to install a tower about a mile down the hill from my house. I'm hoping that they'll get it up this spring or summer, though I don't really know how long it takes these things to happen. When that's in, I hope to get 5 bars with no outside antenna. Then I can mount the dish on top of my car and use it for travel ....

Thanks for your help!
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No longer Hughesnet Home Pro - DW7000 - AMC9-1290mHz -
Now EVDO! Verizon USB727 w/ Cradlepoint MBR1000 wireless router.
Win2K - Kerio/Sunbelt firewall

reply to hcwiii
Something else for you to consider when aiming your antenna. Certainly, having a better dBm reading will benefit you, but if your EVDO modem has a DRC (Data Rate Control) reading (would be found in diagnostic menu perhaps) then you would also want to get the highest DRC reading you can get. Sometimes this means using a lower dBm reading.

I've found with my Franklin that I can go to 3 bars, but with a higher DRC and get faster downloads than I can with 6 bars (yes, Franklin modem has 6 bars) and lower DRC.
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