Birdview 8 1/2 foot scalar focal distance

[joe good]

I Have a 8 1/2 foot Birdview I want
to find the focal distance for the
scalar ring.

102" Diameter
16" Depth

F = 40.64"
F/D = .398
.398 = .32" feed horn opening to scalar
40.64" - .25" = 40.39" feed horn to Dish
40.39" + .32" = 40.71" scalar focal

The dish has all factory parts
installed and the scalar ring is
39.125" from the center of the dish.
Why is it not 40.71"?
Do I need to add extenders to
the rods? Please Help.

Thank you
Joe

 

[FaT Air]

We're not in a laboratory situation. so our measurements, could be a good percentage off. 102 inch dish, may be, but this is most likely an outside dia. But the actual dish does not extend to the perimeter. 100 inch dia gives us an fl of 39.0625, This would line up very close to the fl you measured, Being it is a BV dish, and is unmodified from when it was manufactured. And are known as a good performer. The only thing I would do is try tweaking the feed a little closer, then a little away, ( by just sliding the feed in/out of the scalar) and see if there is a noticeable improvement. If there is more improvement to be made by moving further, one way or the other, then it's time to add spacers.

 

[stogie5150]

I added length to my support rods, and improved signal. I don't remember the exact distance, but what you describe is close. I think the BV was setup for the "good enough" world of analog 25 years ago, and further tweaking CAN help with digital signals, even though the basic physics are the same...

Oh, and if you decide to remove the scalar, get ready to break one of those aluminum poles, the nuts that hold the scalar corrode themselves to the poles...before you start soak the nuts in some PB blaster for a few days, then get your ratchet and socket, say a Prayer to the Diety of your choice, and have at it. I broke 4 of mine I think...

 

[DWTexas]

My scalar ring had a very small lip about a half inch in side the scalar ring and that was the focal piont for that dish.

 

[flody1]

hi, I have 8.5 Birdview also, having trouble with QPSK S2 signals. I'm looking to modify my scalar and legs for adjustment. Have been told that the feed is not the correct F/L also. I measure 38.25 to feed and 39.25 to the scalar ( it is 11 inches in diameter ). Been told need 41 7/8 F/L and F/D .335 . Will try to check back in..

 

[Stefan2K8]

hi, I have 8.5 Birdview also, having trouble with QPSK S2 signals. I'm looking to modify my scalar and legs for adjustment. Have been told that the feed is not the correct F/L also. I measure 38.25 to feed and 39.25 to the scalar ( it is 11 inches in diameter ). Been told need 41 7/8 F/L and F/D .335 . Will try to check back in..

QPSK S2? I think you likely mean 8psk and not QPSK, because in theory QPSK S2 should be easier to lock than regular QPSK dvb-S because the FEC coding used with DVB-S2 works better. It's 8psk where the trouble begins and that's just because 8psk in general requires a much better signal. DVB-S2 8psk is easier to lock than the older Trellis 8psk which was used as an extension to the DVB-S spec until S2 came along, but Trellis 8psk was kind of rare as it wasn't part of DVB-S originally and required special equipment that few of us hobbyist could afford. Anyway, if I'm wrong and you really did mean QPSK, then I'd say it's likely a receiver issue and not a signal quality issue, because DVB-S2 QPSK shouldn't be that difficult to receive. Also, some of the earlier DVB-S2 receivers didn't properly support all of the DVB-S2 modes. This was probably because QPSK DVB-S2 was somewhat rare because most of the time the reason for switching to S2 was for the benefit provided by 8psk which is more bits for a given amount of bandwidth.

As for the focal point of your birdview, I'd say tweak it and see what results you get, but I'd be skeptical as to you seeing a huge improvement as I think it's likely the feed is already pretty close to correct as it is. Also, from my experience(I have the same dish as you), while the Birdview is a great dish and will manage to get a great deal of the DVB-S2 8psk feeds up there, you really need a larger dish for 8psk. Ultimately you may find that while the birdview is a great performer for it's size and tweaking may help some, you really want something better if you want to get all of the 8psk feeds. My recommendation would be to start looking for a good 12 foot or larger dish. Some people will recommend a 10 foot dish, but my opinion is you may be disappointed if you only upgraded to a 10' dish. I believe that my Birdview performs as well as many 10 footers do because surface accuracy is important also. So, simply upgrading to a 10 footer, unless it's a really good 10 footer like a patriot, might not yield the results you'd want. So, if you do go to the time, trouble, and expense of upgrading, make it worth the while and go all the way. Also, I'd keep the birdview, adapt one of those invacom c-120 prime focus feedhorns to it and have the ultimate ku only dish.

If you do find tweaking you feedhorn yields substantial results, be sure and report back your findings, as I'm sure many of us would like to hear about it.

 

[Lone Cloud]

This thread interests me, because I also don't have great luck with s2. My BV is a good performer otherwise.

After hearing about the broken aluminum strut issue, I ended up drilling my scalar out without taking it off. Now you guys have me wondering if I should be changing the strut length.

 

[flody1]

hi, I have 8.5 Birdview also, having trouble with QPSK S2 signals. I'm looking to modify my scalar and legs for adjustment. Have been told that the feed is not the correct F/L also. I measure 38.25 to feed and 39.25 to the scalar ( it is 11 inches in diameter ). Been told need 40 7/8 F/L and F/D .335 . Will try to check back in..

I corrected the F/L to 40 7/8 per Captain

 

[eltigre]

Need a dish

I have a second home in the Caribbean (Trinidad & Tobago). The TV programming is the pits sso I would like to get my Directv Service there..I am told that I need an 8ft dish minimum and I am toying with theidea of a 10 footer if it is within reach of my wallet.. where can I purchase dishes this size? What equipment would I need after dish purchase...Thanks Tiger

 

[flody1]

I added length to my support rods, and improved signal. I don't remember the exact distance, but what you describe is close. I think the BV was setup for the "good enough" world of analog 25 years ago, and further tweaking CAN help with digital signals, even though the basic physics are the same...

Oh, and if you decide to remove the scalar, get ready to break one of those aluminum poles, the nuts that hold the scalar corrode themselves to the poles...before you start soak the nuts in some PB blaster for a few days, then get your ratchet and socket, say a Prayer to the Diety of your choice, and have at it. I broke 4 of mine I think...

I added length to the rods on my 8.5 Birdview also. Added about 2 inches w/adjustment, put them on after work. I'll need to set them better this weekend, but signals are up. G1-3 from 100-65 to 100-75. 8PSK signals ( races ) will be on to test with this weekend.