Questions tagged [amplifier]

Questions about amplifiers, typically RF power amplifiers. For low-noise amplifiers (LNAs) consider using the "lna" tag.

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Looking for specifications for Wilson Electronics WAU 420 amplifier

Hey there helpful people I'm trying to track down some specifications on a Wilson Electronics WAU 420. I have no idea on its exact age but guessing its from the late 90's. It's likely UHF band and ...
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4 votes
1 answer
82 views

Really a Class C design?

In the March 2000 QST there was an article on the Tuna Tin QRP transmitter, which I thought I might build: The text describes Q2 as a C Class amplifier, but I just can't see how that can be true. &...
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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 ...
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2 votes
1 answer
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How can a low-impedance load can damage a FET final amplifier?

I believe I understand how an excessively high impedance can damage a final output power MOSFET (voltage rises until avalanche breakdown). But how does an excessively low impedance do that? If the ...
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How do you create a DC-blocking ground-shunt that looks inductive in an "L" match?

We are optimizing an impedance match with s2p models for an LNA and found that an "L" match with a serial cap and shunt inductor will optimize to provide +3 dB of output, versus using serial ...
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4 answers
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Does an RF amplifier allow us to receive a signal from further away?

From my understanding a RF amplifier boosts the transmission power of your antenna, this will in turn give you a higher gain. However I've read that this only will give you a further "...
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S-Parameters Power amplifier impedance matching

I recently decided to conceive a 10W class 446MHz amplifier. I want to be able to amplify a 100mW signal into a 10W, for that i'm going for a two stages amplifier : SKY65162 to amplify the signal to ...
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1 vote
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Need help in the fabrication of an UHF power amplifier

I recently decided to conceive a 10W class 446MHz amplifier. I want to be able to amplify a 100mW signal into a 10W, for that i'm going for a two stages amplifier : SKY65162 to amplify the signal to ...
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2 votes
2 answers
120 views

What safety procedures should be followed when developing and testing a high power amp?

I'm designing a 300W power amplifier using the MRF300AN from NXP targeting a center frequency of 146 MHz. Obviously I need to keep my fingers out of it and test into a dummy load, but generally ...
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6 votes
2 answers
150 views

Purpose and sizing of capacitors placed across RF push-pull power amplifier transformer windings

I keep finding RF push-pull power amplifier designs specified with a small(-ish) capacitor across the primary (or secondary) windings of the coupling transformers. Here's an example: This is one ...
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Is it beneficial to boost the transmit power from a transmitter past 2W around 2.4GHz?

I have a ready-made transmitter that outputs 2W of RF power at 2.4GHz carrier frequency (I'm trying to transmit TV using DVB-S2) into the antenna, and I was wondering if it made sense to add a power ...
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5 votes
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Using a Return Loss Bridge and Nano VNA to measure amplifier characteristics

One of the difficulties of measuring active devices like LNA and IF amplifiers with the Nano VNA is the care needed to avoid over-driving the amplifier input and, more importantly perhaps, to avoid ...
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Is it possible to boost WIFI signal? [closed]

Whilst strictly not radio ham question, it does fall in to the RF area so hopefully this is not too far off topic... I have BT broadband account which entitles me to use BT-WIFI hotspots. The trouble ...
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The amplifier does not work for hack rf one

Good day! I ask for help with repairing the hackrf one amplifier. Doesn't work at all. Accepts signals without amplifier, and LNA and VGA adjustment in SDR sharp works too! But when I put a tick on &...
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3 votes
1 answer
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Why is my experiment to produce 3rd order harmonics by saturating a receiver not working

I've been trying to devise an experiment to produce a third order harmonic in radio receiver that's been saturated, but I'm not seeing the expected results. My understanding of the theory is that when ...
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Circuit for RF Splitter [closed]

Does anyone know of any resources which describe how to design a circuit with one RF input and multiple (at least 6) RF outputs, whereby the signal strength of each output matches (does not exceed and ...
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4 votes
3 answers
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High-Z RF amplifier for magloop RX vs Q-factor

I've noticed that increasing load on magloop reduces it's Q-factor, it becomes less selective. Traditional way to approach this is reducing size of pickup loop, or alternatively, using transformer. ...
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3 votes
1 answer
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What is the difference between an RF amplifier's DC or quiescent operating point and the RF operating point?

I chose the resistor values in the following schematic to set the DC bias point of VCE=6V and IC=5mA because the transistor data sheet gave the S-parameters at 162MHz for these values. I learned how ...
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1 answer
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How effectively do modern transmitters protect against high SWR?

The following are fairly common knowledge: Transmitting at full power with too much of an impedance mismatch can damage your finals. If we do so inadvertently, modern radios drop the power ...
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2 votes
1 answer
118 views

Hypothetical question: Repeater with power amplifier

This is my first time ever asking a question on stack exchange or any stack site, so please be gentle if I missed something here. I am currently working on building a UHF (GMRS) repeater, and while ...
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1 vote
2 answers
146 views

Increasing communication range by boosting output and input power

ORIGINAL QUESTION I am trying to increase the range of communication between two SDRs to simulate near space communication. The output power of TX is 10dBm but I would need 37dBm for near space ...
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Simple minimum component RF Amplifier Design

Looking for advice/assistance in Retrofitting sans Cabinet Antique 2 and 3 Dialer 1920's TRF tube radios to operate with low safe Plate voltages.Both Hollow State and Solid State. The plan is to ...
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4 votes
2 answers
392 views

Reduction in transceiver power output into high SWR

How much do transceivers drop their output power, when the SWR is high? Most amateur solid state amplifiers or transceivers are (fully?) protected against high SWR, by a circuit which reduces the ...
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4 votes
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Checklist for QRO remote setup

In a few weeks I'm hoping to set up a solid state linear amplifier at a remote shack that I've set up at the house of a friend who lives in a rural area. I've been connecting to this shack remotely ...
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4 votes
3 answers
131 views

Coax braid acting as power supply ground between radio and amplifier connected to the same supply, is this a problem?

I have a Kenwood TH-D72 and I just got an old Radio Shack HTA-20 2m amplifier to use with it. They're both powered from a sizeable 3S2P Li-Ion battery pack and they work great together for the most ...
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4 answers
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Building an AM Radio receiver

I am making an AM radio with the specifications of: Part 1. Design a circuit with an antenna for tuning your receiver to a signal of a specific carrier radio frequency so that you can select a certain ...
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1 vote
1 answer
190 views

Signal power measurement

I have a radio with a nominal output of 1-30mW (frequency dependent) and amplify this with a 21.8dB capable amplifier (frequency dependent, but should be ~150mW). The signal output then passes through ...
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sdr as watts and amps [closed]

Thanks to rclocher3 for helping edit more to English why closed so my struggle to get thought to English thank rclocher3 I round back too best I put in avuenue what I was asking why closed i tryed ...
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What is an optimal amplifier arrangement with ham radios?

As I am settling on a design for a radio I need to figure out one thing: Should I modulate on low power and boost it up with a post amp, or should I go on full power right out of the gate?
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4 votes
1 answer
148 views

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 ...
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How to calculate combined power of two amplifiers

If I have 1 amplifier running at 95%, and another identical one running at 60%, how may I calculate the output power of the combiner? I believe this combiner is a "Magic T", but if there is a ...
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2 votes
3 answers
476 views

Under what circumstances does intermodulation become an issue in a filter after LNA setup?

I'm reading about using software-defined radio for picking up ADS-B signals at 1090MHz. There is this blog which considers (among others) a setup as follows: ...
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1 vote
3 answers
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How does the Maximum Power Transfer Theorem relate to RF power amplifiers?

The Maximum Power Transfer Theorem says that maximum power transfer occurs when the source impedance equals the load impedance, when the power transferred to the load is 50%, the other 50% being ...
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4 votes
4 answers
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Why does an RF Amplifier fail when the SWR is high?

Exactly why does an RF output transistor fail if the SWR is bad ? Is it A because the impedance mismatch between the transmission line and the antenna results in maximum power not being transferred ...
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0 votes
3 answers
324 views

How to make simple AM detector using an LED?

I'm new to amateur radio, and as a beginner project, I wanted to use some of the basic components I have to create an AM receiver. Anyway, what I'm trying to do is create a simple AM receiver that ...
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4 votes
2 answers
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Pi Matching circut for tube PA - what values?

I am working on my 80m and 40m CW transmitter and ran into a problem: I need to match the high impedance of PL504 to 50ohm coax, a Pi match seems to be the best, but I don't know how to calculate ...
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7 votes
1 answer
853 views

Double power-handling ability of RF amplifier output transformer

I want to base the output network for a 500W push-pull HF amplifier on "A 250W Broadband Linear Amplifier" described in Chapter 17 of the 2014 ARRL Handbook. I need advice on whether and/or how the 1:...
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1 vote
0 answers
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Parasitic inductance of relay contacts

I need to switch a bank of filters operating on bands from about 2MHz to 30MHz. The parasitic series inductance of the relay contact system will have an effect on the performance of my system. ...
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1 vote
2 answers
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Toroid Coupling Issue in Common-base Amplifier

I'm working on an old school VFO for the 15 meter band based on a JFET Hartley oscillator. The plan is to follow the oscillator section with a JFET buffer, then a CB amplifier (for increased reverse ...
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0 votes
3 answers
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Voltage Converter for Amp

I have a chance to get a 1 kW amplifier with a 220V plug dirt cheap from a friend of mine, but I only have a 110 outlet. The 110 outlet is on its very own 20A breaker with no other outlets. Could I ...
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2GFSK 9600bps Transmitter and amplifier for 433 MHz

I'm looking for a reliable, however cheap solution for ground-space communication. I need at least 50W of transmitted power with 2GFSK modulation at 70cm band (433 MHz). Transmission will be done ...
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1 vote
1 answer
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is KPA100 a good amplifier for Yaesu Vx-8Dr

I am interested to explore what a Yaesu VX-8DR radio can do and would like to add an amplifier to it. One of the AMPs that seems to work with a 5W input is KPA100, I am still doubtful how the Yaesu ...
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7 votes
2 answers
350 views

Water cooling a GS-35B in lieu of air cooling?

Does anyone know how to --or have any experience with-- water or oil-cooling the anode? Since forced-air cooling is required, the sound from the blower and the exhaust air would be too noisy for my ...
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2 votes
2 answers
2k views

Why does a Class-C non-linear power amp distort SSB but does not distort AM?

Can someone tell me why exactly a transistor non-linear power amplifier will amplify an AM signal without noticeable distortion, but will distort an SSB signal, giving the familiar scratchy sound ...
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  • 3,492
13 votes
3 answers
305 views

UHF FM power amplifier design without expensive software

I'm designing a small UHF data transceiver for the 70cm band, based on a Silicon Labs EZRadioPro Si4463 IC. Modulation is FM, 12.5kHz channel step. The concept is similar to SiLabs' AN656 application ...
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2 votes
2 answers
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How to supply high voltage to an amplifier in a safe way?

The grounded-grid amplifier that I am looking at requires 1100 volts Max. How do I safely deliver this rated voltage without getting hurt? Should I consider a alternative amplifier? By request here ...
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7 votes
3 answers
1k views

Impedance Matching between RF Amplifier Stages

I'm in the process of building a RF buffer-amplifier chain for a VFO and I'm experiencing a design issue trying to impedance match between the sections. The issue I'm having is that many (most) of ...
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3 votes
1 answer
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Power Amplifier Balun Question

Second (and last hopefully) question on the classic Solid State Design for the Radio Amateurs (SSDRA) book by Hayward et al. Again it's a power amplifier circuit (Chapter 4, pg. 66), and again it's ...
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9 votes
2 answers
900 views

What is the purpose of the transformer at the input (and output) of this RF push-pull amplifier

Firstly, feel free to move this to Electronics SE if it's not on-topic, but it's strongly related to ham radio and RF circuitry. Reading Hayward's classic "Solid State Design for the Radio Amateur" ...
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  • 937
1 vote
2 answers
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HackRF + Amplifier = HF/VHF QRP Radio?

Do you think it would work to combine a HackRF One and an amp like the following to create a QRP SDR? Link to eBay Output of HackRF is approximately 10dBm, which fit's this amp nicely... What is ...
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