BSC-621 dissapointment-new plan

[truckracer]

KU band has really sucked on this bsc-621 lnbf. I have a 10 foot dish and ku is weird. I will have on ku one tp booming in and another at 10% quality.
I have setup and tuned a lot of dishes and the C-band side of this thing works great but ku just is not right. Dish is tracking arc
F/D is at it's best and focal point.


I like voltage switched polarity but the combo lnbf's just don't seem to be great.

Here's my plan:

Buy an orthomode c and ku feedhorn. (dual ku and c lnbs)
4 coaxes down to a weatherproof grey plastic electrical box from home depot

coax 1 KU V
coax 2 KU H
coax 3 C V
coax 4 C H

buy two passive multiswitches: (dedicate one for C-band and one for KU band)

Connect the 13V port to the Vertical lnb
Connect the 18V port to the Horizontal lnb

connect the two cables from my 2x1 diseqc switch (one for C-band and one for KU) through my dsr-905 sidecar and out to the dish to each appropriate multiswitch.

When either receiver sends 13v dc It will switch to the vertical lnb
Same for horizontal.

It would require two passive multiswitches. One for c and one for ku

will lnb's for feedhorns that normally run 18v still operate at 13v?


Here's the horn I am thinking about:High Performance Dual C/Ku Band Feedhorn - PM-C/KU-OR2+2

 

[tvropro]

will lnb's for feedhorns that normally run 18v still operate at 13v?

I have heard that some LNB's won't fire up or aren't stable with 13v. You can use a power inserter in line so the V LNB's get a full 18v. You would have to use a DC block on the 13 vdc line feeding the V LNB after the switch and use the PI to inject 18 v to the V LNB.

 

[truckracer]

after thinking, that's a lot of hardware to perform voltage switching functions. I wonder how much signal loss there would be by the time the signal passes through the multiswiches and power inserters?

I think I will just order a corotor pack. I don't know yet.

 

[Hermitman]

I've been reading your trials and tribulations with the BSC621. I'm running 2 BSC621s and haven't had any problems. So here's my 2 cents worth. If you're still using the lnb with that ku scalar ring modification, I'd remove that tape without touching anything else in the throat and make sure its clean. An oily finger on the probe is bad news. That scalar ring doesn't choke the signal you want, its choking off those signals you don't want like cross-polarization from dish signal bending. It also helps place the focal cloud directly in front of the ku lnb. Please remember, the way that feedhorn works is the large scalar ring that the entire BSC621 sits in focuses the signal from the dish reflection and rejects the cross-polarization. That radio energy is sent down the feedhorn which is really a c-band waveguide. The c-band probes pick up the signal they're designed to receive and then the signal travels further down the throat. Now there needs to be a transition from a c-band waveguide to a ku-band waveguide. The small scalar ring helps there since its rejecting unwanted signals. That tape on the ring sets up all kinds of signal reflections in the waveguide that may augment some signals, decrease some signals and have no effect on others. The BSC621 technical bulletin also talks about the KU probe and isolation bar being in alignment with the polarity marking on the case. Have you checked that? I also noticed that on one of the scalar rings I received with the BSC621, there was a small metal slag piece on a landing causing the feedhorn not to set perpendicular with the ring. A little filing fixed that problem. Good luck.

 

[Stefan]

will lnb's for feedhorns that normally run 18v still operate at 13v?

It depends. Some will and some won't and some will be marginal meaning they'll work sometimes but probably provide a weaker output due to reduced gain as a result of being undervolted. In my expereince PLL LNBs won't work on 13v whereas DRO types often will but of course that's not etched in stone as technically any of these type LNBs are being operated out of spec when you run them at only 13v. My advice would be to use power inserters outside at the LNBs. You'll have to put them inside an enclosure of some sort and you'll need to run DC voltage out to them (or run 110 AC and have power adapters out there as well). I'd probably just run DC out on an additional coaxial cable. I'd maybe use an 18-20v switch mode power supply inside to supply this voltage. Most of them probably have short circuit protection built-in in case anything should go wrong.

You would have to use a DC block on the 13 vdc line feeding the V LNB after the switch and use the PI to inject 18 v to the V LNB.

Usually power inserters have a capacitor to block DC going back to the receiver. That's all a "DC block" is anyway. So, an additional DC block shouldn't be needed. Of course youd need to check the specs of the power inserters used.

I think I will just order a corotor pack. I don't know yet.

As for a signal quality, that may be your best route to go. A polar servo does have the ability to fine tune the skew which can be helpful to signal quality sometimes. This is especially true on satellites like AMC1 which has odd skew on Ku.

 

[truckracer]

bsc621

what size dish are you running the 621's on?
Just curious.

My homemade feed works like a champ on my 7.5' sami.
Ku amc pbs tp's boom in at 82% quality on amc-3ku.

This 10 footer is not even coming close. Even with hours of tuning and tracking the arc.

String test did not indicate any warpage.

even with low signal I cannot pull up or down on the dish to improve the ku signal on any satellite. It just goes completely away.

I measure four points from the edge of the dish and the scalar is centered.
I have fine tuned the skew and focal depth.

I am stumped here.

 

[truckracer]

OK,
After tinkering further, I have G17 ONN locked in at 72% quality on the pansat 9200.
Given that- I cannot push or pull the dish and get better signal. I the f/d is at it's peak, focal point is peaked.

Theoretically I should get every ku satellite like this right?

Amc-3 is still pretty bad.
amc-4 is weak except one tp (ku) that is booming in at 87% quality. No others will lock.

G10r ku 11800v 72%
11720v 62%

Amc-6ku 12143H 2573 72% quality
12143V 2573 90% quality *same tp lighting up both polarities -(Here's the problem). What is causing this?

Are those numbers in line?

I cannot pull or push the dish to improve reception. It goes away if I pull up or push down.
C-band is phenomenal!

AMC-8 v 100% on nasa and one other tp.
G-15 HBO/max tp's 85% and 99% 4dtv.


Inside the bsc621 when looking down the feedhorn throat, should the isolation bars be in line or crossed. The big one inside the c-band part is opposite of the ku isolation bar.

 

[voomvoom]

Inside the bsc621 when looking down the feedhorn throat, should the isolation bars be in line or crossed. The big one inside the c-band part is opposite of the ku isolation bar.

Not sure if I'm reading (or thinking) right, but mine has 2 probes for C-Band and 2 probes for Ku-Band, and another 2 bars going all the way across (one inside the Ku section and one inside the C section, and they are opposite/crossed with each other). If you think of a 180 degree Arc, or half of a circle, they are lined up with the C on one 90 degree and the Ku on the other 90 degree (or each in one half of the 180 degree). Each has a probe that lines up and each has a probe that's 180 degree opposite, or lined up but pointing at each other. The probes that are 180 degree opposite are also lined up with the bar that goes across the C section. And the probes that line up are lined with the bar in the Ku section.
On another note, when I played with mine on a 1.2m dish. I could not get the C-Band to work at the same time as the Ku-Band. I have not tried this lnbf with any other dish. I could get the C-Band to work with very few C-Band signals, but it worked. Also, I could get the Ku-Band to work about as well as any Ku lnbf I have. I just couldn't get the C-Band and Ku-Band signals to work at the same time. I would hope that if I ever tried a 10' dish with it, I would have much better results?
It's probably something simple, like maybe you've got the lnbf inverted, or if not, maybe you need to invert it? Meaning, try to turn the SKEW 90 degrees and see if the ku will get better? Then maybe go another 90 degrees and see if it helps? Bottom line (I think?) is there is a Sweet Spot, you just need to find it? Good Luck!

 

[truckracer]

lnbf

See that is the problem I have- I can get ku to come in good on most of the sats but my c-band is down. I checked the alignment of the probes and they are as you described.

I know have the skew peaked so that's not it.
It does seem that I can change the f/d point and bring either band in better.
If I go almost even with the scalar ring (opening of the feedhorn)Ku gets good, but c-band goes way down and vice versa.

I have not really found a sweet spot where they both work.
When I get to the top of the arc-it seems that sometimes my receiver will scan the same tp on both v and h and still have a very strong signal on both polarities.

I believe this thing is getting the best of me. I have never had this much work involved in setting a big dish for c and ku.

 

[truckracer]

I give up

Just ordered a chaperal corotor and lnbs from ebay.

 

[Hermitman]

Here is a url for the BSC621 Technical Bulletin with pictures showing how the probes should look down the throat. Good luck.

dmsiusa.com/technical/bsc621t1.html

 

[truckracer]

please see my post here in the c band section "bsc-621 update"