Primestar 84E/BSC621-2 LNBF Experiment

[satcom1]

Out on a limb

With the DREAMFOX dish and LNBF setup you get the perfect storm. This dish and focal distances come into play here. The wavelengths for KU and C Band on this dish create an interesting result. The C-band signals are exactly 90 degrees phase shifted.


so with his Panorama LNBF set at zero skew he is actually 90 degrees skewed to the true C-Band signal on this 1 Meter dish. If he rotated the LNBF 90 degrees he would have normal V and H in his receiver.

It is likely that you would have to use this exact same dish and LNBF setup to duplicate his C-Band performance.

When I go to do what he has done here on my P* dish, it likely won't work the same.

 

[satcom1]

Earlier in this thread I was told that I was not getting strong V channels in my C-Band scan of 121. If my C-Band polarity was 90 degrees off that would explain poor scan results. I have noticed that a really strong transponder can be scanned either V or H.

 

[satcom1]

DREAMFOX1,

Please measure from the center of your dish to the center of your Panorama C-Band LNBF. Right to the Plastic lens cap.

This will help me to test my dish.

Thank You


.DWD-90C-BKB
39" Offset Dish w/Single Linear LNB

Is this your dish?

 

[DREAMFOX1]

Lnbf is 23 1/2 inches away from dish.

Dish is...

34 1/2 wide

36 1/2 tall

 

[DREAMFOX1]

Best way to get the most gain.

 

[voomvoom]

I've never tried an in-line amp on a satellite feed cable, but my experience for an in-line amp on a terrestrial cable was fine, for a few days, then they would blow-out. It got to be to expensive. Of course that was 30 years ago, and I hope the electronics have improved since then? I still couldn't recommend one to anyone though, maybe you can though?

 

[satcom1]

DREANFOX1,

Please place a string across your dish face horizontally and measure the depth to the dish face at the center. Then place the string vertically and measure that depth.

What receiver are you using?

Did cutting away the Scalar Ring like that improve the C-Band signal or did you just do that so you can get it in closer to the dish arm?

That skyline view of downtown Los Angeles gives me a good idea of where you are.


Thanks

 

[satcom1]

LOS ANGELES

I would say you are within 5 miles East of downtown LA in a two to three story apartment building.

You have added the Line Amplifier to make up for a long cable run to your receiver. This does add alot of noise and loss to your signal. Guess you will get lower SQ because of insertion loss and noise of this amplifier. Not much problem with static or lightening surges in LA.

You raised your LNBF in ths last picture so you should have changed your dish elevation.

By the way, the best performance on C-Band from your dish ????? would be achieved by following the LNBF back from your KU LNBF on the same line but further back. The C-Band LNBF will look directly into the back side of your KU LNBF but because the C- Band wavelength is longer "FOCAL" distance is greater.

Thank you for your "help" on this project!

 

[satcom1]

East Los Angeles

DREAMFOX1


About here, right?

 

[DREAMFOX1]

Its more north near olympic.

 

[satcom1]

Dish Calculations

OK, enough of that diversion, back to work.

I have done some wavelength calculations for C-Band and KU-Band.

The P* dish has 2.2 wavelengths from the center of the dish to the LNBF lens.
In order for the C-Band LNBF to "focus" it should be a wavelength from the dish. This would produce a properly polarized signal to the lens of the LNBF. It should also produce a better SQ then if it were closer.

So the f/d calculation for the KU band dish may not work for the best C-Band reception on the same dish. The data attached is for the focal point inside the LNBF and not the lens face. Obviously, the C-Band LNBF will be compromised f/d on the dish, but the in phase signal may make up for that.

 

[cracklincrotch]

And for those that aren't interested in doing the math:

Frequency to Wavelength Calculator - Wavelength to Frequency Calculator

Has a form where you key in the wavelength and it spits out the frequency and vice versa.

Also has the conversion chart that goes above 3GHz.

 

[satcom1]

Minimum C-Band dish

So lets look at this wavelength issue backwards. A C-Band wave at one cycle or one wavelength sets the minimum focal distance for the dish.

If 75 cm is one wavelength then what dish has a focal point about one wavelength?

The FortecStar 120cm dish has a focal distance of -

 

[satcom1]

New Pictures

Thanks for the pictures, you did a very nice looking modification. When it's attached, it looks store bought. Have you got a picture of the BSC631-2 with it in the feedhorn and on the dish? Or have you already posted it in an earlier post? I guess I'll go back and look. Thanks again, great work..!!

Edit: OK, I went back and looked at your other pictures and don't see both lnb's on at the same time in any of them. So, a picture of the BSC631-2 inside the modified feedhorn and next to the P* lnbf, would be nice to see...!

Here are todays setup for testing and show the BSC-621-2 back together and on the P*

 

[Anole]

how long?

I believe a wavelength at C-band is about three inches.
The Ku band is about an inch.

This site was in agreement with another site I checked:
www.onlineconversion

 

[satcom1]

How big is it?

Maybe that should have been 2.9 inches and not 29 inches. LOL
dam decimal points.

Hats off to brother Anole for catching that.

 

[satcom1]

Side mount lnbf

Well, disappointing resullts today. The side mount LNBF did not work at all.

I got the B1 Stack and it tested 37%SQ against the BSC-621-2 which yielded 41% SQ. The BSC-621-2 was much easier to tune.

I assume I have to move the dish East to get 121 to look into the side mount LNBF. I moved the LNBF 10 degrees East and West but got no signal.

Appreciate any suggestions.

 

[PopcornNMore]

Very interesting thread.

My Channel Master 1.2m receives C band rather well.

 

[satcom1]

Very interesting thread.

My Channel Master 1.2m receives C band rather well.

Was this a dish that was made for some commercial service?

How long ago did Channel Master get bought up by Andrews?

I really like these dishes, they work great!

 

[linuxman]

Was this a dish that was made for some commercial service?

How long ago did Channel Master get bought up by Andrews?

I really like these dishes, they work great!

To answer the question about Channel Master getting bought out, I talked to a young lady at ASC Signal Corporation today, and got the lowdown on the series of buy-outs.

Channel Master was bought by Andrews Corporation, but don't know when. Andrews was bought out by Commscope within the last couple of years, and Commscope sold the Andrews line to their subsidiary ASC Signal Corp.

So if you want anything on a Channel Master/Andrews dish, ASC is where you go for the answer.