Black Ultra LNBF to C120 Conversion

The Invacom - Inverto match is a draw.

Adding up the differences on horisontal/vertical and low/high band
gives a number smaller than the accuracy of the S/N measurements.

The Inverto BU is still on the dish and the next heavy rain/snow will
show if the dropout-level also is similar.
 
Waveguide said:
The Invacom - Inverto match is a draw.

Adding up the differences on horisontal/vertical and low/high band
gives a number smaller than the accuracy of the S/N measurements.

The Inverto BU is still on the dish and the next heavy rain/snow will
show if the dropout-level also is similar.
Click to expand...


So, looks like my new BlackUltra will either do the business as it stands, or not. Will know next week when I get back home.
 
I found that too much machining on a black ultra is detrimental to the DRO stability. Although picture one looks great, sadly the LNB didn't work very well - the DRO was very unstable so it was scrapped in favour of v2 seen in the second picture where no machining was carried out on the actual LNB. These are for direct fit to a Fibo feedhorn so not quite the same as a C120 flange but you get the idea. Interestingly I have a modified Octagon PLL LNB and although it's not quite as sensitive as the IBU it does lock low symbol rates much quicker than the IBU and exhibits much better stability overall. I mailed Inverto to ask when they might consider producing PLL units but sadly no reply as yet :-(
 

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Ahhh... nothing like pictures of Actual Reality!
After opening a few old LNB's and seeing the DRO hardware like the
adjustable plungers for frequency I never did any mashining at all on
the LNB itself. There are small pieces of microwave absorbant glued
to strategic places in most old LNB's and I would not think they would
survive spinning in a lathe even at low speeds. The rest of the hardware
will take a few tens or hundreds of G's but why thake any chances.

My own C120 flange adapter looks much like your second picture.
It's held to the front rim of the old feed horn on the LNB and can be rotated
and removed. No pictures unfortunately, I was too keen to see the results of
the measurements.
 
The short story:
Invacom SNF-031 is better than Inverto Black Ultra with C120 flange!

The long story:
Saturday evening the "Evening Sickness" (daily signal variation) gave
a total signal loss on BBC News HD between 21 to 23 CET. BBC 1 HD had
no problems. (10847V tp50 & 11023H tp61 were used in all tests)
This was with the Inverto LNB and on sunday it was replaced with the
Invacom LNB and signal strength was measured between 16 to 24 CET.
The threshold was 7,0 to 7,1 dB SNR with the Inverto and the Invacom
never went below 7,6 dB so there were no dropouts at all with Invacom.
The total daily variation was around 1,5 dB.

The Inverto has a larger difference in SNR between H and V polarisation
and I suspect the cross polarisation isolation is the real culprit.
It is lower in the specs for Inverto, 22 dB compared to >= 25 dB.
The E-field probes inside the LNB's (signal pickups for H & V) look
much "nicer" engineeringwise in the Invacom. The Inverto looks less
accurate with the probes beeing slightly off from perpendicular.
Mistake on the production line or shoddy tweaking procedure?
Anyway, adjusting one polarisation makes the other less than optimal.

Only the LNB's were swapped, the dish was fine-tuned before the test
and never moved during the test. The polarisation angle was the only
thing adjusted individually for each LNB.

Me Mythbuster - Inverto Black Ultra is not for prime focus dishes!
 
The LNB C120 flange:
C120c.webp

The feedhorn flange:
C120d.webp

The everything:
LNB-II.webp
(The bird is an optional Zwittermaschine)
 
thank you
I use a stripped down from plastics Inverto BU twin - It has a long neck with cut down front end then fitted machined pfa feedhorn
In that way you do not need to add additionl feedhorn which adds attenuation - for me It Is much better than Invacom QDF
 
Samoloko - look again, only one feedhorn! There is a
round waveguide going straight through the old one (the feedhorn that is).
No additional attenuation from a short piece of additional
waveguide that matches the bottom part of the LNB exactly.
 
why do you want additional round waveguide
try to remove It and mount just Inverto BU without ofset feedhorn
you have to find a way to mount pfa scalar rings feedhorn without thread
 
FRINGE said:
So, looks like my new BlackUltra will either do the business as it stands, or not. Will know next week when I get back home.
Click to expand...
And it didn't. My existing Invacom Quad came out on top. You live and learn.
 
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