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Old 11-Sep-2013, 11:55 AM   #5
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 172
Winegard LNA-200 Components

Hi Pete,

The following is some guesswork based on your images and information.

It appears that the LNA-200 has two active amplifier devices.

The UHF portion is amplified by Q2, an ATF-54143. The ATF-54143 is an industry-standard pHEMT transistor. As a broadband amplifier, at TV frequencies it can readily achieve noise figures below 1 dB. It and most other pHEMT devices are very susceptible to transients Voltage (ESD or atmospheric discharge). It, or a very similar device, was used in the Kitz KT-200, and another low noise pHEMT-based TV preamplifier.

Q3 is a part of the bias regulator (current mirror) for the ATF-54143.

The VHF portion is amplified by Q1, probably an NPN transistor.

The TZx are Tranzorbs. Fairly sure TranZorb is a trademark name of the company that originated them. They are transient voltage suppression diodes. Tranzorbs are similar to Zener diodes, with some special characteristics for particular applications (probably low capacitance and such). These help protect the transistors (especially the ATF-54143).

D1 and D2 are signal diodes, one or both, could be involved in protecting the transistor Q1 from transients.

The component L15 is an inductor, Coilcraft makes similar, the dots indicate the amount of inductance. It is probably part of the power supply circuitry.

Some of the spiral PCB inductors are associated with the input and output diplexers. Like UVSJ, the diplexers separate VHF and UHF for amplification then recombine at output. Also, some spiral inductors are associated with the FM Trap.

Relating to the noise figure and signal handling capabilities:

- The spiral inductors used in the FM trap and the diplexers have lower Q than open-air wound inductors. Thus, they have more signal loss.
- The Tranzorbs and the diodes used for input protection also introduce losses.

Losses at the input contribute directly to the noise figure of the unit.

- The nonlinearities of the diodes and Tranzorbs may generate intermodulation products from very strong signals.

As evident in this preamplifier:

Preamplifier design often involves tradeoffs between low noise figure, ESD susceptibility, and signal handling capability.
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