bsc-621 update

[truckracer]

well, I was going to give up on the 621. I thought I would give it one last try. I enjoy experimenting in this hobby but this thing has got the best of me.

With the lnbf on the dish pointed at g10r ku 11800V I got on a step ladder and took a screwdriver and removed the ku part. I removed the three screws and removed the o-ring.

With a tv out back next to the dish I had the on screen signal quality meter up on the pansat 9200Hd.

I skewed the ku part a little clockwise and held the ku lnb part in the hole and watched the singal - It went up from 70 to 84! Wow.

I already had c-band skew peaked (keep in mind) on the scrambled outdoor channel.

Now as it stands the ku and c-band probes are not lined up like they were.
Theoretically the skew should be wrong one way or the other. C or ku should be wrong.

I left the focal point as it was and skew of the c-band (main lnbf body)alone since any movement dropped the c-band signal quality.

Now-I have somewhat acceptable ku across the arc and pbs ku amc-3 is coming in at 58% quality (12138V 30000). Before I had virtually no signal on this one.

SBS-6 onn went up to 82% from 70%.

I now have isolation between H and V tp's when doing a blind scan.
Before, the strong ones would scan both polarities and no amount of skew would stop it without losing signal.

I am leaving it alone but am still going to replace it with a corotor.

I am happy it is working for now.

This has been a strange lnbf. My homemade frankenstein lnbf as one of the members called it-LOL, still gets much stronger ku on my 7.5' sami mesh.
Same exact antenna as my 10' except it is a 7.5'. Both antennas are fairly new.

No additional azimuth or elevation changes peak the signal from where it is now. I am confident I am tracking the arc.

 

[voomvoom]

Congratulations...! When I decide to play with mine again, I'll need to remember this and see if I can get better results on my 1.2m dish? I just went outside with my flashlight and took a long look at it, and I see the possibillity of 2 different positions for it? I would hope at least one of them would be better than what I previously achieved! Thanks for a new Trick to Try Out......

 

[truckracer]

Hope it works for you. It does not make sense that the skew between bands would be offset a little. In theory the satellite should send both bands in the same precision.

One theory could be that the isolation bar and c-band probes could be knocking the ku signal around a little causing a bending offset skew effect. I know the c-band probes are not resonate with ku band but they are still a reflective metallic obstruction to some degree just being physically located in the feedhorn.

 

[gabshere]

if you could get a couple of pictures on the way you have it set now would be great

do the screws holes align back up so the screws goback in and reattach the two lnb's ??

i never thought to try to adjust the two separately , i do get better signal with c-band tuned one way but looses a bit tuning ku in ...but like you my signal on AMC3 is poor but i attributed it to my center of arc being slightly off. i shall try to do some adjusting on it next week and see what i can come up with.

 

[truckracer]

I thought my center of the arc was off too. It seemed to be where I had the most trouble with this lnbf. I don't have a digital camera (I am going to buy one-I have needed one so many times).

But I have decent ku reception now. It still is not what my 7.5' dish is getting but its not far off.

I knew my arc could not be off because any pulling or pushing up on the dish killed the signal completely or dropped to 0-2% quality on amc-3. The patient channel is a strong one amc-3 that booms in at 100% quality.

This lnbf at the factory recommended setting (The dms technical service bulletin showing how the inside probes and isolation bars look) seems to have frequency dependent problems on my dish as the frequency on ku increases the signal progressively decreases.

a signal at 11.7xx was stronger than a signal near 12xxx on ku.
Their was also lack of isolation between H and V on ku when doing blind scans and on sbs-6, ONN would scan in both horizonat and vertical 11732V 6616. I knew there was something wrong that the lnbf was receiving the same tp on both polarities.

Now I seem to have good isolation.

I still think from what I read the polorotor will give me some points better signal quality.
One member on here I can't remember where I read it-claimed the polorotor did better.

I will miss the voltage switching convienience of an lnbf. It will slightly complicate doing blind scans as I will have to do H first and flip an analog channel then do V. As where now it is pretty automatic with the dish on a satellite.

I would like to build a servo circuit to take the 13v or 18v signal from the coax and turn the servo 90 degrees. I am going to experiment as one member gave me link to a servo schematic for robots or rc cars.

I guess all servos operate on the same principle. I did see on Dave's webshop website where he had a servo tester that would send pulses for "testing" servos. I guess you could leave that think connected all the time and manually switch the servo polarity.

 

[truckracer]

Sorry this is so long-

Point your dish on a ku satellite (I used G10R Ku) equity channels.
Peak your c-band skew and make sure your dish is on the arc doing the pull up and down test to see if your signal quality changes. If you cannot improve the signal by lifting or pushing down your are on.

Peak the signal East and West.

Now switch to KU band.
Watch your signal and get on a ladder or however you reach your dish and gently remove the three screws that hold the ku lnbf on the main body without disturbing the skew or f/d.

Keep the red rubber o-ring and if it is cold, it will be a pain to get back in the groove!

You may have to slightly loosen the nut on the coax connector so the ku lnbf will turn inside the housing.

Turn the ku lnbf just a little (I turned mine clockwise) and hold it back up there into the main body with the screw holes lined up and look at your signal.


Repeat this one direction or another and see it you get decent ku reception.

Let us know how it worked for you.
After you get it peaked, carefully snug down the nut on the coax connector making sure you don't turn the lnbf from its sweet spot.

 

[Mr Tony]

interesting...I might have to try that
I've has the same issues with the 621-2 and KU...but I usually use it for C-band but right now I have it on my Primestar dish for C-Band and 99 KU is at 45 on the Pansat 1500...I know it can be higher

 

[truckracer]

Ice,
After I peaked the c-band part, I did the above skewing the ku part of it and my ku isn't bad.
It is at a level I can live with. I will know more when we have a hard rain.

I have a 75cm patriot solid dish with an sg-2100 motor also for ku, So i will do a comparison during the next rainstorm.

Right now I have the 10 footer pointed at amc-4 ku on the 12060H 26700 (hotel cable service) scrambled channels getting 70% quality on the pansat 9200HD.

Before the skew, I couldn't even get that tp to register any quality.

what a difference.