Es'hail-2 LNBs and Antennaes
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......