Amateur Radio Stack Exchange
Amateur Radio Stack Exchange

Questions tagged [lna]

Questions about low-noise amplifiers (LNAs) and their application in receiving antenna systems.

A low-noise amplifier (LNA) is an designed to amplify very weak signals while adding a minimum of noise to the output.

In antenna systems, a LNA may be placed between the antenna and feed line (as opposed to between the receiver and feed line) in order to improve the signal-to-noise ratio found at the receiver after losses in the feed line; this is particularly useful for higher frequencies where losses in transmission lines are significant.

If the same antenna is to be used for transmitting, a transmit/receive switch must be used to bypass the amplifier when transmitting.

Links:

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Digital transmission sounds

I'm playing with an RTL-SDR dongle and an LNA, on Linux Mint with GQRX and DSD A lot of frequencies show digital transmissions, which the DSD is not converting. I don't whether it is a format DSD cannot convert, encrypted, or just distorted. Is…
KP4MCG
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Use noise figure and gain to calculate weakest signal radio can receive?

An FM radio receiver, using a 1 kHz tone at 3 kHz deviation has a 12 dB SINAD (Signal To Noise and Distortion) of -116 dBm. I would like to increase the 12 dB SINAD sensitivity of the receiver to at least -121 dBm to increase the weak signal…
Skyler 440
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How to bypass LNA for TX in UHF Antenna?

I want to work with amateur, low power, and/or pico satellites. I would like to use an Eggbeater or Turnstile antenna with my UHF 433 MHz radio, since those antennas are very cheap and easy to build and I don't have to care about yagi rotors. The…
vz0
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What is unique about a Low Noise Amplifier (LNA)?

What is so special about a low noise amplifier? If I were to design an amplifier, I would always design an amplifier with low noise anyway. Why is it emphasised as being “Low Noise”? What are the design features that makes an amplifier “low…
user5349
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Generally, what happens when you power a GPS antenna or other RF amplifier with a low voltage?

I have a 5V active GPS antenna, and want to try using it on a device with a 3.3V bias provided. Obviously, operating at an over-voltage can damage or destroy the LNA. But what happens when the voltage is too low? Will it work with reduced gain,…
Paul
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What would happen if the low noise amplifier (LNA) is saturated?

Suppose that there is a 2 dBm interference signal and a -90 dBm signal of interest (SOI) at the input of LNA (Gain = 1, in linear region). Suppose that the P1dB of LNA is 1 dBm, so the LNA is saturated and can't amplify the input signal properly. My…
tyrela
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Lowest noise MMIC for HF? (160-20M)

I recently learned that these fancy modern ultra-low noise MMIC, while having <1dB noise figure around 1Ghz could be quite bad at low frequencies due to 1/f noise. What is lowest noise MMIC then for 160-20M bands? I am only aware of MAR-6 and…
BarsMonster - R2AYN
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Is there a technical reason to sell an LNA without advertising its gain?

I recently bought a couple SPF5189 low-noise amplifier boards via an online marketplace. One thing that struck me is that while nearly all the listings highlighted the LNA as having a noise figure of 0.6 dB, very few listings actually specified its…
natevw - AF7TB
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Strange Noise Floor observed in UHF Band

I have a tracking station for UHF band satellites which comprises of a cross yagi of 12 dBi and a wideband LNA of 40 dB Power Gain and 1.3 dB Noise Figure. I observe a Noise floor of about 300 kHz centered at the frequency of 436 MHz on the spectrum…
Vishal Desai
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Replace directional antenna by fixed antenna

Given the following specs of a directional antenna: VHF yagi antenna – 12dBic gain, switchable RHCP - LHCP VHF Low Noise Amplifier (NF: 0.8dB) Frequency range: 144-146MHz (Is this description enough to characterize the antenna?) What will be the…
KcFnMi
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How much dB gain do you need from an LNA in front of an antenna for great low-signal reception from satellites in the 2m and 70cm bands?

We are building a multi-stage LNA for a TR module we are building in the 144MHz and 440MHz range. This LNA we are considering (Qorvo QPL9547) provides about 22dB gain in the 2m and about 27dB in the 440MHz according to the Gain vs Frequency…
KJ7LNW
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Antenna + LNA Design Questions

I am trying to design and build an antenna + LNA board. Antenna: http://www.yageo.com/documents/recent/An_FR4_1690_2405_0.pdf LNA: http://www.avagotech.com/docs/AV02-1237EN The antenna is specced to run at 168 MHz. In the LNA documentation it…
PumpkinPie
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Design of an LNA housing box for a UHF/VHF satellite ground station

I'm currently designing a waterproof metallic case to house LNAs, power cables, and RF switches for a UHF/VHF satellite ground station. As shown in the diagram below, the antennas are connected to an absorptive RF switch by a 5-meter RF cable. The…
Moses Browne Mwakyanjala
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What is the point of using LNA if the SDR can increase the gain itself

Usually there is a LNA next to antenna, while SDR devices also have gain setting so we can increase the gain. As i know LNAs are amplifying all signals with same gain (Am I right?) So i wonder what is the point of LNA here? if the SDR device can…
Ariyan
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Is SSB and FM voice considered TDD or FDD (and what are TDD/FDD)?

We are looking at the Qorvo QPL9547 LNA and the datasheet notes: For TDD Applications: R1 = 0Ω & R2 = 100K For FDD Applications: R2 = 100K ‘OR’ Pin 6 tied to ground. R1 = DNP/Omitted This will be for SSB and FM voice in the 2m band. What are…
KJ7LNW
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