Es'hail-2 LNBs and Antennaes
Octagon LNB
References:
https://f5xg.jimdo.com/antennes/syst%C3%A8me-duo-bande-2-4ghz-10ghz/
http://www.hb9afo.ch/articles/pll-lnb/10ghz_pll-lnb.htm
https://www.oe7forum.at/viewtopic.php?f=7&t=284&start=135#p1519
https://www.qsl.net/zs6bte/LNB%20Test%20Results.htm
Frequency coverage and operating out of specification
G3YGF posted this on the UKmicrowave group forum:
I have measured a few of these. The earlier 27MHz dual version has about 1.2dB NF at 980MHz (bottom of tv satellite band) and at 618MHz (10368MHz), on both polarisations. Later ones are typically 1.5dB at 980MHz on either polarisation, and at 618MHz (10368MHz) about 1.5dB on the probe furthest from the backshort (V >15) and 2dB on the probe nearest the backshort (V <15v).
The 25MHz dual version is about 1.2dB at 980MHz on either polarisation, and at 618MHz 1.2dB on the probe furthest from the backshort and about 2.9dB on the probe nearest the backshort. (Measurements made using sky/ground noise). The main difference appears to be that the gain rolls off much more rapidly below the satellite band in the FET preamplifier on the probe nearest the backshort, so changing the IF makes no difference. The figures are approximate - they do vary somewhat between samples...
The measurements are on unmodified LNBs.
We use these LNBs on the FRARS EME system. Attempts to modify the LNB to interface to WG16 or different circular feeds usually lose about 0.3-0.4dB. We are currently trying to work out why... Matching screws do not improve it, so I don't think it is the Lambda-g......
Locking the Quad Octagon LNB to a 25 MHz Reference
The Octagon "Quad LNB Green" Model OQSLG Green HQ can easily be modified to run from an external 25 MHz reference fed in on one of its F-type sockets, while still providing 3 horizontal or vertical outputs. This LNB is available (Jan 2019) from Amazon UK for under £15. The item title is "Octagon 0.1db Quad High Gain HD Ready Universal LNB", but check carefully that you get the OQSLG model.
After prising off the white plastic cover (NOT the green cap on the feedhorn), and scraping away the sealant, 5 torx screws are exposed. Undo these screws and cut around the sealant at the edge of the cover. Then using a small screwdriver in the slot at the top of the unit, lever the cover off. The PCB looks like this:
The 25 MHz crystal is mounted on the reverse side of the board, just North of the West-most 78H06 regulator. The modification involves cutting the tracks leading to the West-most output and then coupling this to the East-most crystal connection, having cut the tracks to the crystal.