Questions tagged [amplifier]

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

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4
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2answers
88 views

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 ...
7
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1answer
71 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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0answers
59 views

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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2answers
60 views

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 ...
0
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3answers
68 views

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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0answers
74 views

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 ...
1
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1answer
67 views

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 ...
7
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2answers
113 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 ...
1
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2answers
312 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 ...
7
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0answers
94 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 ...
2
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2answers
206 views

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 ...
5
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3answers
244 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 ...
2
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1answer
122 views

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 ...
7
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2answers
164 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" ...
0
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2answers
1k views

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 ...
1
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3answers
103 views

I just got this RF equipment but i don't know what's for

I got some RF equipment for free (it was going to the trash and I 'rescued' it). It's almost new, and seems expensive, but i don't know it's purpose. Googling the model numbers yields very little ...
0
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1answer
66 views

RF Coverage range doesn't improve inspite of increased Tx power

I built an RF power amplifier with about 10 to 13 dB gain operating at about 100 MHz. It amplifies signal from about 50 to 100mW to about 1W. Inspite of the amplification, I don't see a real ...
1
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1answer
191 views

building a relay for 5.8Ghz?

I'm interested in building a relay for analog video sent from an R/C aircaft. The idea is to get around obstacles like hills and increase distance a bit. Rather than just applying more power, I ...
1
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1answer
82 views

Parallel tube amplifier power supply using 6DE4 tubes [closed]

I’m looking to build a vacuum-tube based linear amplifier. I’d like to do it all tube based, including the power supply. The original ARRL design I’m looking at (from the 60s) has two paralleled 807s ...
8
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1answer
211 views

How can I do direct digital synthesis of a 630m WSPR signal?

I want to do direct digital synthesis of a 630m band WSPR signal. Specifically I'd like to use an Atmega 328 chip running at 20 MHz to produce such a signal. I will use standard phase accumulator ...
2
votes
1answer
185 views

FET for low voltage class E amplifier

I'm building a small APRS radio for a high altitude balloon, and I'm thinking of using an Si570 (3.3 V CMOS) at 144 MHz to drive a small class E amplifier. I'm looking for about 1W output power. I'm ...
2
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3answers
1k views

Will an Internal Antenna Tuner work with an external HF amplifier?

I am a new General and don't quite understand how Antenna Tuners work other than changing the impedance ratio between the radio and the antenna. So my question is - Do I need to buy a new tuner if ...
0
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2answers
616 views

what are the alternatives to LM387 and SA602AN?

I am building a 20 Mhz RF receiver out of the NASA radio JOVE instruction manual and they have recommended the use of LM387 as an audio amplifier. SA602AN as mixer IC:
1
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1answer
127 views

UHF Into VHF Power Amplifier

What would be the result of accidentally applying a UHF signal to a VHF power amplifier? Say a 70cm transmission from a dual-band 2 meter / 70 cm radio into a 2 meter PA, assuming the input power is ...
2
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1answer
876 views

33cm 5W(effective output power) tx amplifier for ATV (HamTV)

I am searching for a 5W effective output power TX amplifier that I can use with my BladeRF to send DVB-T Signals for ATV (33cm band). Can someone tell me on what things I have to look for when buying ...
5
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4answers
456 views

Recommended way to analyze spectrum output of a high-power amplifier?

I have a small collection of "software defined RF lab" equipment, notably a HackRF and a VNWA3. I am almost done building a 35W HF amplifier and once I've done some other testing, would like to look ...
6
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2answers
407 views

How to calculate if low-pass filtering is sufficient?

An answer on this question Suggested method for boosting 0.05 watt transmitter up to 10+ watts? suggests putting a filterless 19dB amplifier between the HackRF (or similar general-purpose SDR) and a ...
9
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3answers
2k views

Why does “high SWR” damage transmitters, instead of “impedance mismatch”?

In the audio realm, where cable lengths are insignificant compared to the signal wavelength, I would understand an impedance mismatch damaging an amplifier as follows: Take an audio amplifier that ...
1
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2answers
244 views

RF6886 high power amplifier maximum reverse power

I'm designing a circuit which uses the RF6886 amplifier IC. What is the maximum reverse power that the amplifier can sustain? At what reverse power will the amplifier die?
2
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1answer
208 views

AN762 Amplifier Transistors

According to the MRF421 or MRF454 transistor datasheets, used in the AN762 HF amplifiers say that the transistors are "100% tested for load mismatch at all phase angles with 30:1 VSWR". Further, in ...
0
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1answer
185 views

How can I reduce power consumption and thermal dissipation in power amp?

I am designing a Class-E power amplifier in UHF band using ADS. Now I have 20dBm fundamental output power with 13% PAE, which is low for this class of PA. The problem is that I have thermal ...
3
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1answer
430 views

Receiving through a linear amplifier

I want to build a simple amplifier using those Mitsubishi modules (like the RA30H1317M or other RA parts). I know this might seem like a very obvious question, but I am unable to find the answer after ...
1
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1answer
84 views

Is preheating required before replacing an old valve?

I have a Drake transceiver. I want to replace the valves in the final output stage. The valve in question is a 6jb6. I was told by elmers that the valves need to be preheated (cooked) before ...
3
votes
2answers
87 views

Link margin calculations with two antennas and two low noise preamplifiers

Background - UHF - 434-438MHz Two identical crossed Yagi's mounted on rotator. Currently, I have a low noise preamplifier after combining cables from the two antennas (T connector + matching stub). ...
0
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1answer
128 views

audio amplifier as fm amplifier possible?

Is it possible? I know it depends on legal issues; it is just for testing. I will "transmit" from RPI (Raspberry pi as fm transmitter).
6
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1answer
924 views

Suggested method for boosting 0.05 watt transmitter up to 10+ watts?

Long time ham operator here, new to this particular challenge - I have a software defined radio transceiver that I'd like to try and use to make contacts on HF, in particular 20-meters. Tuning ...
6
votes
1answer
119 views

Efficient BPSK31 amplification

I'm looking at making a portable system that can transmit BPSK31. I have a limited power budget, so I'm looking at trying to make my final power amplifier as efficient as possible. From my ...
2
votes
2answers
220 views

What is the difference between Rf Gain Blocks & IF Gain Blocks?

As advertised on websites of large manufacturers like Analog Devices And Texas Instruments I am aware of the difference between an IF stage and an RF stage, however, I was curious if there was any ...
4
votes
1answer
290 views

What is the average fade margin required for proper operation at 2.4 GHz?

I have two radios. Sensitivity is -84 dBm and transmitting EIRP is +30 dBm. How much distance should I expect? I want it to be somewhere near about 2-3 km. Is it possible?
8
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3answers
6k views

What is dBm and why is it used rather than watts?

Reading through an RF power amplifier datasheet, I found the sheet only referenced dBm output power, rather than watts. What is dBm? How do I convert it to watts? Why, or when, would you use dBm to ...
1
vote
1answer
1k views

Is transmission wattage calculated using RMS?

I understand (and correct me if I'm wrong) that transmission power follows Ohm's law ($I = \frac{V}{R}$), that is that if I have a 50 Ω antenna that I know is transmitting at 1 W, then the current is: ...
13
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3answers
2k views

What is a linear RF amplifier?

Most of the RF amplifiers advertised, and most of the questions about amplifiers, are "linear" amplifiers. What is a linear amplifier, and what other common amplifier type(s) exist that requires ...