1.2M Fortec dish and a 621-2 C/Ku LNBf - success?

[Das Hammer]

Hi, just want to see if anyone else is having success with these for C/Ku on a 1.2 meter dish. I already have a BSC-621 for C band and it is working well. Wanted to give the 621-2 C/Ku a try, but have heard that the 621-2 has slightly worse C band performance. I'm most interested in C band AMC3 and IA13.

If you have a setup like that, could you please list your location and what you are able to receive?

Also, a quick question about the 621-2, do you have to use the internal switch and run one cable, or can you run an independant cable for each band?

Thanks!

 

[PSB]

Yes you can run an independent cable for each band!

Remember the focal distance will be slightly different from C to Ku, I peaked in the Ku the best I could and let C-Band take care of its self since there is no rain fade with C-band!

 

[Das Hammer]

And you used the "flat" scalar ring, correct?

 

[PSB]

I don't have a 1.2m (Ask me again after noon CST )

But I used the flat scalar on my 40" dish and BUD, flat scalar worded better than no scalar!

 

[caddata]

PSB:

Please elaborate on your " Remember the focal distance will be slightly different from C to Ku, ..." statement.

There should be no reason for C and Ku to have different focal lengths on the same dish. Parabolic dishes are not frequency dependant. They are simply reflectors and reflect microwaves, lightwaves, and soundwaves to the same focal point

If you are finding a "sweet spot" that peaks the C band at a different point than the Ku, the mount for the feedhorn and/or the feedhorn itself are not optimized to the dish. Is the feedhorn mount sized properly to fit the O.D. of the new feed? If not, then the focal point would not be correct.

I have noticed on some offset dishes (my Fortec .9M being an example) the feedhorn mount does not look directly towards the optical center of the dish. The slight amount of feedhorn adjustment allowed by the mount actually pases thru the focalpoint at an oblique angle. True adjustment (on a prime focus dish it would be towards the optical and physical center of the dish) should be towards where the feed arm intersects the rim of the dish.

Thanks for your posts and let's kick this idea around some.

Respectfully,
Harold

 

[PSB]

The C-Band and the Ku band LNB's are at different depths inside the BSC621-2 that's why they are different distances away from the reflector!

 

[VO1ONE]

I used this LNB with a Primestar fiberglass dish duct taped on and was able to receive all sorts of analog stuff! Didn't have too much luck with DVB and I don't have a 4DTV rcvr for DCII, but just watching the analog stuff using a receiver I bought from a hamfest for $1 was enough for me. I could pick up IA8 feeds, G11 (shop at home, a couple radio stations), W0KIE was quite weak but audible on IA6 but I had decent luck with the TV feeds, IA5 feeds, G16 (World Harvest, Shepards Chapel, probably the strongest 2 and sparkle free!, Buena Vista feeds), PBS on AMC4 very hard to see due to cosatellite interference, Anik F2 (Horse Racing, soap opera feeds), IA13 Jewelry TV, G10R the rcvr authorization box would come up on some transponders, G14 TBN and solid authorization screen on most transponders although last week TNT was coming through with a great picture but a little ghosting. I don't remember exactly what else I was able to pick up because I've since slapped back on the Invacom linear/circular LNB so I could get NASA TV off of dish for the shuttle activity. I've stepped up the search for a bigger dish though as this has really piqued my interest, although it was very fun experimenting with such a small dish on C-band!

 

[Das Hammer]

Thanks. I'm looking for DVB stuff, but it is worth noting what can be acheived on the Primestar for analog. Were you using the oval or one of the round ones?

 

[VO1ONE]

Sorry. I was using the oval. I could pick up some DVB but the quality was always about 35% or so, if at all. You'll probably have better luck with your 1.2m dish.

 

[rdel]

Hi Das Hammer
Let me know if you get the nets and how well they come in, I have a four foot dish and I was thinking about going after the nets on c-band with a 621.
thank
rdel
voione. were you able to get the nets with a primestar?

 

[Eastcoast]

Hi Das

I tried the 621-2 with my 1.2M Andrew fiberglass dish and did have some success with the C band but did not record or list what I could get at that time but did see some TP's on most of the popular sats.I was a little fustrated with it as the KU section was not at all as good as my single ku lnbf as alot of the Quality was around 63% on the coolsat and there you may or may not get a picture, my single lnb would show 80-90%.So this was a couple of months ago and have not gotten back to it since.I may try again soon.

Dave

 

[sikma]

I've tried my 621 on a 4' offset solid CM dish and terrible ku results. The c-band side seems to work fine. I then tried it on my 5' mesh, again ku is terrible (unwatchable) but the c-band is fine....including the 'nets.'

 

[PSB]

You have to setup the Ku Band side FIRST, the focal distance, skew and azimuth are slightly different from Ku to C-Band.

Optimise the Ku signals, you may notice a slight decrease in C-Band signal quality but there is no rain fade with C-Band.

I also found that the C-Band and Ku Band signals are NOT at exactly the same place in the sky (Even on the same satellite), so you will have to move you dish in azimuth slightly for best results!

 

[rdel]

GREAT, Thanks Guys. I think I'll give it a shot.
rdel

 

[Das Hammer]

Thanks for all the comments.

I can get everything (DVB, analog, and otherwise) off of the 10 footer which is nice. However, since that is almost always in use for subscription programming (wife and kids watching it) it is difficult to attain any "playtime" with it.

So, I wound up with this 1.2 meter dish that I'm going to use for fta. Adjusting the dual band LNBf for Ku first does degrade the C band readings slightly as PSB said. I think I'll just end up using this dish for C band and setup the Primestar oval again for Ku fta.

Unless, maybe someone has been successful using a C band LNBf and a separate Ku LNBf? Probably not.

 

[MrTim]

PSB:

Please elaborate on your " Remember the focal distance will be slightly different from C to Ku, ..." statement.

Take a look at http://www.dmsiusa.com/documents/c-ku focal point.pdf for a better understanding.

 

[PSB]

THANKS Tim! That's a great link! Will save me a LOT of typing

 

[Stefan]

I also found that the C-Band and Ku Band signals are NOT at exactly the same place in the sky (Even on the same satellite), so you will have to move you dish in azimuth slightly for best results!

The reason your experiencing this phenomenon is because your dish is too small and it's beamwidth too wide on C band thus your getting interference from adjacent satellites. This creates a situation where sometimes you don't get a good signal when you point directly at a satellite because there's another signal at overlapping frequencies on another satellite on one side of the satellite your aiming at and your dish is seeing both. Therefore sometimes you can get a better signal by actually aiming away to the opposite side of the satellite that the interfereing signal is coming from. I have a small 6' dish I use for AMC 1 that I expereince the same thing on. The 2 nearest satellites with C band signals on them are AMC4 to the east and anik F1 to the west. AMC 4 is 2 degrees east of AMC1, but Anik F1 is slightly over 4 degrees to the west of AMC 1. Therefore to null out the interference from AMC 4 instead of aiming directly at AMC 1, I aim about 1 degree to the west of it. Since Anif F1 is over 4 degrees west of AMC 1 this works and gives me a useable signal on AMC 1.

If you had a 2 degree compliant dish you wouldn't experience this. On my big dish , I don't experience this. In fact on my big dish I always use Ku to tweak my aim as I know that if I'm aligned on Ku, the C band signals will be fine. So, this clearly demonstrates the interference problems on undersized reflectors.

 

[PSB]

My "undersize" 6' dish works GREAT for me

Moving a fraction in azimuth to peak signals on the same satellite is no biggie !

I was also talking about Ku band in the above statment !

 

[rdel]

I have a couple of c-band feedhorns laying around the house, What do you think of using a standard c-band lnb on a four foot dish? Has anyone tried it yet?
Thanks
rdel