Octagon Optima OTLSO PLL Slim Twin Review

In the previous post I reviewed a single output PLL LNB, the Sharp BS1K1EL100A. Today we are going to review a dual output universal PLL LNB, the Octagon Optima OTLSO PLL Slim Twin.

As the name implies, this is an LNB with two outputs, which means you can connect two receivers and tune the same or different transponders on the same or different polarity on the same or different band. This is the LNB type to buy if you want to feed two receivers from a single dish.

The product name says this is a slim LNB. Well, there is nothing particularly slim about this LNB. It uses a standard size feed horn. If you need to place two or more LNB's very closely, it may not be possible with this LNB. To get an idea of what true slim LNB's look like, please take a look at my Inverto Multiconnect LNB solution review.

Dual or twin output LNB's are naturally more complex than single output LNB's. After the low noise amplification stage for both polarities the signal is split and down-converted to individual outputs by two separate mixer, IF amplification and LO circuits. In the following picture one of this circuits is shown, the other one is located below, but the connection to both LNB's is visible. Being a PLL solution, the circuit is very simple with the usual crystal (27Mhz) and IC (RDA3565ES) which incorporates the mixer, IF amplification and  local oscillators. The first stage low noise amplification is done by NE3512S02 HJ-FET transistors which have a NF of 0,35 dB @ 12Ghz. Like most brands, Octagon claims this LNB has a NF of 0.1 dB which simply is impossible to obtain under normal operating conditions. Gain is claimed to be 60-65 dB.

Opening the feed horn I got a bad surprise. As it can be seen in the close-up image, it appears to be oxidation on the signal probes! The tear-down was done with a newly bought LNB shortly after performance tests where carried out. A perfectly sealed LNB should never exhibit signs oxidation. Usually the signal probes are gold coated to prevent any oxidation and signal degradation. After carefully cleaning the probes a new test was carried, but no significant performance difference was observed. This was not unexpected because it is very difficult to measure very small variations of NF.

Tests

The Octagon Optima OTLSO PLL Slim Twin is a good performer. It does not appear to favour a particular part of the Ku band. However, disassembly showed a potential weakness point in the probes. On can only guess if with time this could become a problem.